diff --git a/src/audio/CMakeLists.txt b/src/audio/CMakeLists.txt
index a7dda8fd..de6c9b64 100644
--- a/src/audio/CMakeLists.txt
+++ b/src/audio/CMakeLists.txt
@@ -3,9 +3,8 @@
 # SPDX-License-Identifier: GPL-3.0-only
 
 idf_component_register(
-  SRCS "audio_task.cpp" "chunk.cpp" "fatfs_audio_input.cpp"
-  "stream_message.cpp" "i2s_audio_output.cpp" "stream_buffer.cpp" "track_queue.cpp"
-  "stream_event.cpp" "stream_info.cpp" "audio_fsm.cpp" "sink_mixer.cpp" "resample.cpp"
+  SRCS "audio_task.cpp" "fatfs_audio_input.cpp" "i2s_audio_output.cpp"
+  "track_queue.cpp" "audio_fsm.cpp" "sink_mixer.cpp" "resample.cpp"
   "fatfs_source.cpp" "bt_audio_output.cpp"
   INCLUDE_DIRS "include"
   REQUIRES "codecs" "drivers" "cbor" "result" "tasks" "span" "memory" "tinyfsm"
diff --git a/src/audio/audio_decoder.cpp b/src/audio/audio_decoder.cpp
deleted file mode 100644
index b8054574..00000000
--- a/src/audio/audio_decoder.cpp
+++ /dev/null
@@ -1,208 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#include "audio_decoder.hpp"
-
-#include <string.h>
-
-#include <algorithm>
-#include <cstddef>
-#include <cstdint>
-#include <memory>
-#include <variant>
-
-#include "codec.hpp"
-#include "freertos/FreeRTOS.h"
-
-#include "esp_heap_caps.h"
-#include "esp_log.h"
-#include "freertos/message_buffer.h"
-#include "freertos/portmacro.h"
-
-#include "audio_element.hpp"
-#include "chunk.hpp"
-#include "fatfs_audio_input.hpp"
-#include "stream_info.hpp"
-
-namespace audio {
-
-static const char* kTag = "DEC";
-
-AudioDecoder::AudioDecoder()
-    : IAudioElement(),
-      current_codec_(),
-      current_input_format_(),
-      current_output_format_(),
-      has_prepared_output_(false),
-      has_samples_to_send_(false),
-      has_input_remaining_(false) {}
-
-AudioDecoder::~AudioDecoder() {}
-
-auto AudioDecoder::ProcessStreamInfo(const StreamInfo& info) -> bool {
-  has_prepared_output_ = false;
-  current_codec_.reset();
-  current_input_format_.reset();
-  current_output_format_.reset();
-
-  if (!std::holds_alternative<StreamInfo::Encoded>(info.format)) {
-    return false;
-  }
-
-  const auto& new_format = std::get<StreamInfo::Encoded>(info.format);
-  current_input_format_ = new_format;
-
-  ESP_LOGI(kTag, "creating new decoder");
-  auto result = codecs::CreateCodecForType(new_format.type);
-  if (result.has_value()) {
-    current_codec_.reset(result.value());
-  } else {
-    ESP_LOGE(kTag, "no codec for this file");
-    return false;
-  }
-
-  return true;
-}
-
-auto AudioDecoder::NeedsToProcess() const -> bool {
-  return has_samples_to_send_ || has_input_remaining_;
-}
-
-auto AudioDecoder::Process(const std::vector<InputStream>& inputs,
-                           OutputStream* output) -> void {
-  auto input = inputs.begin();
-  const StreamInfo& info = input->info();
-
-  // Is this a completely new stream?
-  if (!current_input_format_) {
-    if (!ProcessStreamInfo(info)) {
-      // We couldn't handle the new stream. Signal to the producer that we don't
-      // have anything to do.
-      input->mark_consumer_finished();
-      return;
-    }
-  }
-
-  // Have we determined what kind of samples this stream decodes to?
-  if (!current_output_format_) {
-    auto res = current_codec_->BeginStream(input->data());
-    input->consume(res.first);
-
-    if (res.second.has_error()) {
-      auto err = res.second.error();
-      if (err == codecs::ICodec::Error::kOutOfInput) {
-        // We didn't manage to clear whatever front matter is before this
-        // stream's header. We need to call BeginStream again with more data.
-        return;
-      }
-      // Somthing about the stream's header was malformed. Skip it.
-      ESP_LOGE(kTag, "error beginning stream");
-      input->mark_consumer_finished();
-      return;
-    }
-
-    // The stream started successfully. Record what format the samples are in.
-    codecs::ICodec::OutputFormat format = res.second.value();
-    current_output_format_ = StreamInfo::Pcm{
-        .channels = format.num_channels,
-        .bits_per_sample = format.bits_per_sample,
-        .sample_rate = format.sample_rate_hz,
-    };
-
-    if (format.duration_seconds) {
-      duration_seconds_from_decoder_ = format.duration_seconds;
-    } else if (format.bits_per_second &&
-               current_input_format_->duration_bytes) {
-      duration_seconds_from_decoder_ =
-          (current_input_format_->duration_bytes.value() - res.first) * 8 /
-          format.bits_per_second.value() / format.num_channels;
-    }
-
-    if (info.seek_to_seconds) {
-      seek_to_sample_ = *info.seek_to_seconds * format.sample_rate_hz;
-    } else {
-      seek_to_sample_.reset();
-    }
-  }
-
-  if (seek_to_sample_) {
-    ESP_LOGI(kTag, "seeking forwards...");
-    auto res = current_codec_->SeekStream(input->data(), *seek_to_sample_);
-    input->consume(res.first);
-
-    if (res.second.has_error()) {
-      auto err = res.second.error();
-      if (err == codecs::ICodec::Error::kOutOfInput) {
-        return;
-      } else {
-        // TODO(jacqueline): Handle errors.
-      }
-    }
-
-    seek_to_sample_.reset();
-  }
-
-  has_input_remaining_ = true;
-  while (true) {
-    // Make sure the output buffer is ready to receive samples in our format
-    // before starting to process data.
-    // TODO(jacqueline): Pass through seek info here?
-    if (!has_prepared_output_ && !output->prepare(*current_output_format_)) {
-      return;
-    }
-    if (duration_seconds_from_decoder_) {
-      output->set_duration(*duration_seconds_from_decoder_);
-    }
-    has_prepared_output_ = true;
-
-    // Parse frames and produce samples.
-    auto res = current_codec_->ContinueStream(input->data(), output->data());
-    input->consume(res.first);
-
-    // Handle any errors during processing.
-    if (res.second.has_error()) {
-      // The codec ran out of input during processing. This is expected to
-      // happen throughout the stream.
-      if (res.second.error() == codecs::ICodec::Error::kOutOfInput) {
-        has_input_remaining_ = false;
-        has_samples_to_send_ = false;
-        if (input->is_producer_finished()) {
-          // We're out of data, and so is the producer. Nothing left to be done
-          // with the input stream.
-          input->mark_consumer_finished();
-
-          // Upstream isn't going to give us any more data. Tell downstream
-          // that they shouldn't expact any more samples from this stream.
-          output->mark_producer_finished();
-          break;
-        }
-      } else {
-        // TODO(jacqueline): Handle errors.
-        ESP_LOGE(kTag, "codec returned fatal error");
-      }
-      // Note that a codec that returns an error is not allowed to write
-      // samples. So it's safe to skip the latter part of the loop.
-      return;
-    } else {
-      // Some samples were written! Ensure the downstream element knows about
-      // them.
-      codecs::ICodec::OutputInfo out_info = res.second.value();
-      output->add(out_info.bytes_written);
-      has_samples_to_send_ = !out_info.is_finished_writing;
-
-      if (has_samples_to_send_) {
-        // The codec wasn't able to finish writing all of its samples into the
-        // output buffer. We need to return so that we can get a new buffer.
-        return;
-      }
-    }
-  }
-
-  current_codec_.reset();
-  current_input_format_.reset();
-}
-
-}  // namespace audio
diff --git a/src/audio/audio_fsm.cpp b/src/audio/audio_fsm.cpp
index 9558d778..87fbbda2 100644
--- a/src/audio/audio_fsm.cpp
+++ b/src/audio/audio_fsm.cpp
@@ -5,23 +5,24 @@
  */
 
 #include "audio_fsm.hpp"
+
 #include <future>
 #include <memory>
 #include <variant>
-#include "audio_decoder.hpp"
+
+#include "esp_log.h"
+#include "freertos/portmacro.h"
+#include "freertos/projdefs.h"
+
 #include "audio_events.hpp"
 #include "audio_task.hpp"
 #include "bluetooth.hpp"
 #include "bt_audio_output.hpp"
-#include "esp_log.h"
 #include "event_queue.hpp"
 #include "fatfs_audio_input.hpp"
-#include "freertos/portmacro.h"
-#include "freertos/projdefs.h"
 #include "future_fetcher.hpp"
 #include "i2s_audio_output.hpp"
 #include "i2s_dac.hpp"
-#include "pipeline.hpp"
 #include "system_events.hpp"
 #include "track.hpp"
 #include "track_queue.hpp"
diff --git a/src/audio/audio_task.cpp b/src/audio/audio_task.cpp
index d1432007..1ebd4e46 100644
--- a/src/audio/audio_task.cpp
+++ b/src/audio/audio_task.cpp
@@ -6,8 +6,8 @@
 
 #include "audio_task.hpp"
 
-#include <stdlib.h>
-#include <sys/_stdint.h>
+#include <cstdint>
+#include <cstdlib>
 
 #include <algorithm>
 #include <cmath>
@@ -28,13 +28,10 @@
 #include "freertos/ringbuf.h"
 #include "span.hpp"
 
-#include "audio_decoder.hpp"
-#include "audio_element.hpp"
 #include "audio_events.hpp"
 #include "audio_fsm.hpp"
 #include "audio_sink.hpp"
 #include "audio_source.hpp"
-#include "chunk.hpp"
 #include "codec.hpp"
 #include "event_queue.hpp"
 #include "fatfs_audio_input.hpp"
diff --git a/src/audio/bt_audio_output.cpp b/src/audio/bt_audio_output.cpp
index 71e40d02..641bea21 100644
--- a/src/audio/bt_audio_output.cpp
+++ b/src/audio/bt_audio_output.cpp
@@ -5,8 +5,6 @@
  */
 
 #include "bt_audio_output.hpp"
-#include <stdint.h>
-#include <sys/_stdint.h>
 
 #include <algorithm>
 #include <cstddef>
@@ -17,14 +15,12 @@
 #include "esp_err.h"
 #include "esp_heap_caps.h"
 #include "freertos/portmacro.h"
-
-#include "audio_element.hpp"
 #include "freertos/projdefs.h"
+
 #include "gpios.hpp"
 #include "i2c.hpp"
 #include "i2s_dac.hpp"
 #include "result.hpp"
-#include "stream_info.hpp"
 #include "wm8523.hpp"
 
 static const char* kTag = "BTOUT";
diff --git a/src/audio/chunk.cpp b/src/audio/chunk.cpp
deleted file mode 100644
index 11503b2b..00000000
--- a/src/audio/chunk.cpp
+++ /dev/null
@@ -1,71 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#include "chunk.hpp"
-
-#include <algorithm>
-#include <cstddef>
-#include <cstdint>
-#include <cstring>
-#include <optional>
-
-#include "cbor.h"
-#include "esp_log.h"
-
-#include "stream_buffer.hpp"
-#include "stream_message.hpp"
-
-namespace audio {
-
-static const std::size_t kWorkingBufferMultiple = 2;
-
-ChunkReader::ChunkReader(std::size_t chunk_size)
-    : raw_working_buffer_(static_cast<std::byte*>(
-          heap_caps_malloc(chunk_size * kWorkingBufferMultiple,
-                           MALLOC_CAP_SPIRAM))),
-      working_buffer_(raw_working_buffer_,
-                      chunk_size * kWorkingBufferMultiple) {}
-
-ChunkReader::~ChunkReader() {
-  free(raw_working_buffer_);
-}
-
-auto ChunkReader::HandleNewData(cpp::span<std::byte> data)
-    -> cpp::span<std::byte> {
-  assert(leftover_bytes_ + data.size() <= working_buffer_.size());
-  // Copy the new data onto the front for anything that was left over from the
-  // last portion. Note: this could be optimised for the '0 leftover bytes'
-  // case, which technically shouldn't need a copy.
-  std::copy(data.begin(), data.end(),
-            working_buffer_.begin() + leftover_bytes_);
-  last_data_in_working_buffer_ =
-      working_buffer_.first(leftover_bytes_ + data.size());
-  leftover_bytes_ = 0;
-  return last_data_in_working_buffer_;
-}
-
-auto ChunkReader::HandleBytesUsed(std::size_t bytes_used) -> void {
-  HandleBytesLeftOver(last_data_in_working_buffer_.size() - bytes_used);
-}
-auto ChunkReader::HandleBytesLeftOver(std::size_t bytes_left) -> void {
-  leftover_bytes_ = bytes_left;
-
-  // Ensure that we don't have more than a chunk of leftever bytes. This is
-  // bad, because we probably won't have enough data to store the next chunk.
-  assert(leftover_bytes_ <= working_buffer_.size() / kWorkingBufferMultiple);
-
-  if (leftover_bytes_ > 0) {
-    auto data_to_keep = last_data_in_working_buffer_.last(leftover_bytes_);
-    std::copy(data_to_keep.begin(), data_to_keep.end(),
-              working_buffer_.begin());
-  }
-}
-
-auto ChunkReader::GetLeftovers() -> cpp::span<std::byte> {
-  return working_buffer_.first(leftover_bytes_);
-}
-
-}  // namespace audio
diff --git a/src/audio/fatfs_audio_input.cpp b/src/audio/fatfs_audio_input.cpp
index cae552db..44653624 100644
--- a/src/audio/fatfs_audio_input.cpp
+++ b/src/audio/fatfs_audio_input.cpp
@@ -6,8 +6,6 @@
 
 #include "fatfs_audio_input.hpp"
 
-#include <stdint.h>
-
 #include <algorithm>
 #include <climits>
 #include <cstddef>
@@ -19,22 +17,21 @@
 #include <string>
 #include <variant>
 
-#include "codec.hpp"
 #include "esp_heap_caps.h"
 #include "esp_log.h"
-#include "fatfs_source.hpp"
 #include "ff.h"
+#include "freertos/portmacro.h"
+#include "freertos/projdefs.h"
+#include "idf_additions.h"
+#include "span.hpp"
 
 #include "audio_events.hpp"
 #include "audio_fsm.hpp"
 #include "audio_source.hpp"
+#include "codec.hpp"
 #include "event_queue.hpp"
-#include "freertos/portmacro.h"
-#include "freertos/projdefs.h"
+#include "fatfs_source.hpp"
 #include "future_fetcher.hpp"
-#include "idf_additions.h"
-#include "span.hpp"
-#include "stream_info.hpp"
 #include "tag_parser.hpp"
 #include "tasks.hpp"
 #include "types.hpp"
diff --git a/src/audio/fatfs_source.cpp b/src/audio/fatfs_source.cpp
index 58986648..7fe4adf9 100644
--- a/src/audio/fatfs_source.cpp
+++ b/src/audio/fatfs_source.cpp
@@ -5,7 +5,6 @@
  */
 
 #include "fatfs_source.hpp"
-#include <sys/_stdint.h>
 
 #include <cstddef>
 #include <cstdint>
diff --git a/src/audio/i2s_audio_output.cpp b/src/audio/i2s_audio_output.cpp
index 8b7d130f..8c779e15 100644
--- a/src/audio/i2s_audio_output.cpp
+++ b/src/audio/i2s_audio_output.cpp
@@ -5,8 +5,6 @@
  */
 
 #include "i2s_audio_output.hpp"
-#include <stdint.h>
-#include <sys/_stdint.h>
 
 #include <algorithm>
 #include <cstddef>
@@ -14,18 +12,16 @@
 #include <memory>
 #include <variant>
 
-#include "audio_sink.hpp"
 #include "esp_err.h"
 #include "esp_heap_caps.h"
 #include "freertos/portmacro.h"
-
-#include "audio_element.hpp"
 #include "freertos/projdefs.h"
+
+#include "audio_sink.hpp"
 #include "gpios.hpp"
 #include "i2c.hpp"
 #include "i2s_dac.hpp"
 #include "result.hpp"
-#include "stream_info.hpp"
 #include "wm8523.hpp"
 
 static const char* kTag = "I2SOUT";
diff --git a/src/audio/include/audio_backend.hpp b/src/audio/include/audio_backend.hpp
deleted file mode 100644
index 86d90d25..00000000
--- a/src/audio/include/audio_backend.hpp
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstdint>
-namespace drivers {
-
-class IAudioBackend {
- public:
-  virtual ~IAudioBackend() {}
-
-  enum SampleRate {};
-  enum BitDepth {};
-
-  virtual auto Configure(SampleRate sample_rate, BitDepth bit_depth)
-      -> bool = 0;
-  virtual auto WritePcmData(uint8_t* data, size_t length) -> bool = 0;
-
-  virtual auto SetVolume(uint8_t percent) -> void = 0;
-};
-
-}  // namespace drivers
diff --git a/src/audio/include/audio_decoder.hpp b/src/audio/include/audio_decoder.hpp
deleted file mode 100644
index e8da415e..00000000
--- a/src/audio/include/audio_decoder.hpp
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstddef>
-#include <cstdint>
-#include <memory>
-#include <vector>
-
-#include "chunk.hpp"
-#include "ff.h"
-#include "span.hpp"
-
-#include "audio_element.hpp"
-#include "codec.hpp"
-#include "stream_info.hpp"
-
-namespace audio {
-
-/*
- * An audio element that accepts various kinds of encoded audio streams as
- * input, and converts them to uncompressed PCM output.
- */
-class AudioDecoder {
- public:
-  AudioDecoder();
-  ~AudioDecoder();
-
-  auto Process(const InputStream& input, OutputStream* output) -> void;
-
-  AudioDecoder(const AudioDecoder&) = delete;
-  AudioDecoder& operator=(const AudioDecoder&) = delete;
-
- private:
-  std::unique_ptr<codecs::ICodec> current_codec_;
-  std::optional<StreamInfo::Encoded> current_input_format_;
-  std::optional<StreamInfo::Format> current_output_format_;
-  std::optional<std::size_t> duration_seconds_from_decoder_;
-  std::optional<std::size_t> seek_to_sample_;
-  bool has_prepared_output_;
-  bool has_samples_to_send_;
-  bool has_input_remaining_;
-
-  auto ProcessStreamInfo(const StreamInfo& info) -> bool;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/audio_element.hpp b/src/audio/include/audio_element.hpp
deleted file mode 100644
index 7e3d9d7d..00000000
--- a/src/audio/include/audio_element.hpp
+++ /dev/null
@@ -1,56 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <atomic>
-#include <cstdint>
-#include <deque>
-#include <memory>
-#include <vector>
-
-#include "freertos/FreeRTOS.h"
-
-#include "chunk.hpp"
-#include "freertos/message_buffer.h"
-#include "freertos/portmacro.h"
-#include "result.hpp"
-#include "span.hpp"
-
-#include "stream_buffer.hpp"
-#include "stream_event.hpp"
-#include "stream_info.hpp"
-#include "types.hpp"
-
-namespace audio {
-
-static const size_t kEventQueueSize = 8;
-
-/*
- * One indepedentent part of an audio pipeline. Each element has an input and
- * output message stream, and is responsible for taking data from the input
- * stream, applying some kind of transformation to it, then sending the result
- * out via the output stream. All communication with an element should be done
- * over these streams, as an element's methods are only safe to call from the
- * task that owns it.
- *
- * Each element implementation will have its input stream automatically parsed
- * by its owning task, and its various Process* methods will be invoked
- * accordingly. Element implementations are responsible for managing their own
- * writes to their output streams.
- */
-class IAudioElement {
- public:
-  IAudioElement() {}
-  virtual ~IAudioElement() {}
-
-  virtual auto NeedsToProcess() const -> bool = 0;
-
-  virtual auto Process(const std::vector<InputStream>& inputs,
-                       OutputStream* output) -> void = 0;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/audio_events.hpp b/src/audio/include/audio_events.hpp
index 9c945f33..28e29863 100644
--- a/src/audio/include/audio_events.hpp
+++ b/src/audio/include/audio_events.hpp
@@ -6,7 +6,6 @@
 
 #pragma once
 
-#include <stdint.h>
 #include <cstdint>
 #include <string>
 
diff --git a/src/audio/include/audio_fsm.hpp b/src/audio/include/audio_fsm.hpp
index 5d44fcda..cb307e68 100644
--- a/src/audio/include/audio_fsm.hpp
+++ b/src/audio/include/audio_fsm.hpp
@@ -10,6 +10,8 @@
 #include <memory>
 #include <vector>
 
+#include "tinyfsm.hpp"
+
 #include "audio_events.hpp"
 #include "audio_task.hpp"
 #include "bt_audio_output.hpp"
@@ -20,11 +22,9 @@
 #include "i2s_audio_output.hpp"
 #include "i2s_dac.hpp"
 #include "storage.hpp"
+#include "system_events.hpp"
 #include "tag_parser.hpp"
-#include "tinyfsm.hpp"
 #include "track.hpp"
-
-#include "system_events.hpp"
 #include "track_queue.hpp"
 
 namespace audio {
diff --git a/src/audio/include/audio_output.hpp b/src/audio/include/audio_output.hpp
deleted file mode 100644
index 074f21d4..00000000
--- a/src/audio/include/audio_output.hpp
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstdint>
-#include <memory>
-
-#include "audio_common.h"
-#include "audio_element.h"
-#include "audio_element.hpp"
-
-namespace audio {
-
-class AudioOutput : IAudioElement {
- public:
-  AudioOutput();
-  ~AudioOutput();
-
-  auto GetAudioElement() -> audio_element_handle_t { return element_; }
-
-  auto SetInputBuffer(StreamBufferHandle_t buffer) -> void;
-
-  virtual auto Configure(audio_element_info_t& info) -> void = 0;
-  virtual auto SetSoftMute(bool enabled) -> void = 0;
-
- private:
-  audio_element_handle_t element_;
-  uint8_t volume_;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/audio_sink.hpp b/src/audio/include/audio_sink.hpp
index b5d6ef57..cce14242 100644
--- a/src/audio/include/audio_sink.hpp
+++ b/src/audio/include/audio_sink.hpp
@@ -8,11 +8,10 @@
 
 #include <stdint.h>
 #include <cstdint>
-#include "audio_element.hpp"
+
 #include "esp_heap_caps.h"
 #include "freertos/FreeRTOS.h"
 #include "idf_additions.h"
-#include "stream_info.hpp"
 
 namespace audio {
 
diff --git a/src/audio/include/audio_source.hpp b/src/audio/include/audio_source.hpp
index 6c54a882..a0d690a6 100644
--- a/src/audio/include/audio_source.hpp
+++ b/src/audio/include/audio_source.hpp
@@ -6,19 +6,7 @@
 
 #pragma once
 
-#include <stdint.h>
-
-#include <bitset>
-#include <memory>
-
-#include "freertos/FreeRTOS.h"
-#include "freertos/portmacro.h"
-#include "freertos/semphr.h"
-
 #include "codec.hpp"
-#include "stream_info.hpp"
-#include "track.hpp"
-#include "types.hpp"
 
 namespace audio {
 
diff --git a/src/audio/include/audio_task.hpp b/src/audio/include/audio_task.hpp
index cd79b708..d2c25add 100644
--- a/src/audio/include/audio_task.hpp
+++ b/src/audio/include/audio_task.hpp
@@ -6,12 +6,9 @@
 
 #pragma once
 
-#include <sys/_stdint.h>
-
 #include <cstdint>
 #include <memory>
 
-#include "audio_decoder.hpp"
 #include "audio_sink.hpp"
 #include "audio_source.hpp"
 #include "codec.hpp"
diff --git a/src/audio/include/bt_audio_output.hpp b/src/audio/include/bt_audio_output.hpp
index e11a5d44..d762bab6 100644
--- a/src/audio/include/bt_audio_output.hpp
+++ b/src/audio/include/bt_audio_output.hpp
@@ -6,20 +6,16 @@
 
 #pragma once
 
-#include <sys/_stdint.h>
 #include <cstdint>
 #include <memory>
 #include <vector>
 
-#include "audio_element.hpp"
-#include "audio_sink.hpp"
-#include "bluetooth.hpp"
-#include "chunk.hpp"
 #include "result.hpp"
 
+#include "audio_sink.hpp"
+#include "bluetooth.hpp"
 #include "gpios.hpp"
 #include "i2s_dac.hpp"
-#include "stream_info.hpp"
 
 namespace audio {
 
diff --git a/src/audio/include/chunk.hpp b/src/audio/include/chunk.hpp
deleted file mode 100644
index f5ba6654..00000000
--- a/src/audio/include/chunk.hpp
+++ /dev/null
@@ -1,65 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstddef>
-#include <cstdint>
-#include <memory>
-#include <optional>
-#include <string>
-
-#include "freertos/FreeRTOS.h"
-
-#include "cbor.h"
-#include "freertos/message_buffer.h"
-#include "freertos/portmacro.h"
-#include "freertos/queue.h"
-#include "result.hpp"
-#include "span.hpp"
-#include "stream_buffer.hpp"
-
-namespace audio {
-
-/**
- * Utility for handling an input stream of chunk data, which simplifies needing
- * access to blocks of data spanning two chunks.
- */
-class ChunkReader {
- public:
-  explicit ChunkReader(std::size_t chunk_size);
-  ~ChunkReader();
-
-  auto HandleBytesLeftOver(std::size_t bytes_left) -> void;
-  auto HandleBytesUsed(std::size_t bytes_used) -> void;
-
-  /*
-   * Reads chunks of data from the given input stream, and invokes the given
-   * callback to process each of them in turn.
-   *
-   * The callback will be invoked with a byte buffer and its size. The callback
-   * should process as much data as it can from this buffer, and then return the
-   * number of bytes it was able to read. Any leftover bytes will be added as a
-   * prefix to the next chunk.
-   *
-   * If this function encounters a message in the stream that is not a chunk, it
-   * will place the message at the start of the working_buffer and then return.
-   */
-  auto HandleNewData(cpp::span<std::byte> data) -> cpp::span<std::byte>;
-
-  auto GetLeftovers() -> cpp::span<std::byte>;
-
-  ChunkReader(const ChunkReader&) = delete;
-  ChunkReader& operator=(const ChunkReader&) = delete;
-
- private:
-  std::byte* raw_working_buffer_;
-  cpp::span<std::byte> working_buffer_;
-  cpp::span<std::byte> last_data_in_working_buffer_;
-  std::size_t leftover_bytes_ = 0;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/fatfs_audio_input.hpp b/src/audio/include/fatfs_audio_input.hpp
index df40696a..da44d2ec 100644
--- a/src/audio/include/fatfs_audio_input.hpp
+++ b/src/audio/include/fatfs_audio_input.hpp
@@ -12,13 +12,12 @@
 #include <memory>
 #include <string>
 
-#include "codec.hpp"
 #include "ff.h"
+#include "freertos/portmacro.h"
 
 #include "audio_source.hpp"
-#include "freertos/portmacro.h"
+#include "codec.hpp"
 #include "future_fetcher.hpp"
-#include "stream_info.hpp"
 #include "tag_parser.hpp"
 #include "types.hpp"
 
diff --git a/src/audio/fatfs_source.hpp b/src/audio/include/fatfs_source.hpp
similarity index 100%
rename from src/audio/fatfs_source.hpp
rename to src/audio/include/fatfs_source.hpp
diff --git a/src/audio/include/fir.h b/src/audio/include/fir.h
deleted file mode 100644
index e50c3eff..00000000
--- a/src/audio/include/fir.h
+++ /dev/null
@@ -1,131 +0,0 @@
-/*
- * FIR filter coefficients from resample-1.x smallfilter.h 
- * see Digital Audio Resampling Home Page located at
- * http://ccrma.stanford.edu/~jos/resample/
- */
-32767, 32766, 32764, 32760, 32755, 32749, 32741, 32731, 32721, 32708,
-32695, 32679, 32663, 32645, 32625, 32604, 32582, 32558, 32533, 32506,
-32478, 32448, 32417, 32385, 32351, 32316, 32279, 32241, 32202, 32161,
-32119, 32075, 32030, 31984, 31936, 31887, 31836, 31784, 31731, 31676,
-31620, 31563, 31504, 31444, 31383, 31320, 31256, 31191, 31124, 31056,
-30987, 30916, 30845, 30771, 30697, 30621, 30544, 30466, 30387, 30306,
-30224, 30141, 30057, 29971, 29884, 29796, 29707, 29617, 29525, 29433,
-29339, 29244, 29148, 29050, 28952, 28852, 28752, 28650, 28547, 28443,
-28338, 28232, 28125, 28017, 27908, 27797, 27686, 27574, 27461, 27346,
-27231, 27115, 26998, 26879, 26760, 26640, 26519, 26398, 26275, 26151,
-26027, 25901, 25775, 25648, 25520, 25391, 25262, 25131, 25000, 24868,
-24735, 24602, 24467, 24332, 24197, 24060, 23923, 23785, 23647, 23507,
-23368, 23227, 23086, 22944, 22802, 22659, 22515, 22371, 22226, 22081,
-21935, 21789, 21642, 21494, 21346, 21198, 21049, 20900, 20750, 20600,
-20449, 20298, 20146, 19995, 19842, 19690, 19537, 19383, 19230, 19076,
-18922, 18767, 18612, 18457, 18302, 18146, 17990, 17834, 17678, 17521,
-17365, 17208, 17051, 16894, 16737, 16579, 16422, 16264, 16106, 15949,
-15791, 15633, 15475, 15317, 15159, 15001, 14843, 14685, 14527, 14369,
-14212, 14054, 13896, 13739, 13581, 13424, 13266, 13109, 12952, 12795,
-12639, 12482, 12326, 12170, 12014, 11858, 11703, 11548, 11393, 11238,
-11084, 10929, 10776, 10622, 10469, 10316, 10164, 10011, 9860, 9708,
-9557, 9407, 9256, 9106, 8957, 8808, 8659, 8511, 8364, 8216, 8070,
-7924, 7778, 7633, 7488, 7344, 7200, 7057, 6914, 6773, 6631, 6490,
-6350, 6210, 6071, 5933, 5795, 5658, 5521, 5385, 5250, 5115, 4981,
-4848, 4716, 4584, 4452, 4322, 4192, 4063, 3935, 3807, 3680, 3554,
-3429, 3304, 3180, 3057, 2935, 2813, 2692, 2572, 2453, 2335, 2217,
-2101, 1985, 1870, 1755, 1642, 1529, 1418, 1307, 1197, 1088, 979, 872,
-765, 660, 555, 451, 348, 246, 145, 44, -54, -153, -250, -347, -443,
--537, -631, -724, -816, -908, -998, -1087, -1175, -1263, -1349, -1435,
--1519, -1603, -1685, -1767, -1848, -1928, -2006, -2084, -2161, -2237,
--2312, -2386, -2459, -2531, -2603, -2673, -2742, -2810, -2878, -2944,
--3009, -3074, -3137, -3200, -3261, -3322, -3381, -3440, -3498, -3554,
--3610, -3665, -3719, -3772, -3824, -3875, -3925, -3974, -4022, -4069,
--4116, -4161, -4205, -4249, -4291, -4333, -4374, -4413, -4452, -4490,
--4527, -4563, -4599, -4633, -4666, -4699, -4730, -4761, -4791, -4820,
--4848, -4875, -4901, -4926, -4951, -4974, -4997, -5019, -5040, -5060,
--5080, -5098, -5116, -5133, -5149, -5164, -5178, -5192, -5205, -5217,
--5228, -5238, -5248, -5257, -5265, -5272, -5278, -5284, -5289, -5293,
--5297, -5299, -5301, -5303, -5303, -5303, -5302, -5300, -5298, -5295,
--5291, -5287, -5282, -5276, -5270, -5263, -5255, -5246, -5237, -5228,
--5217, -5206, -5195, -5183, -5170, -5157, -5143, -5128, -5113, -5097,
--5081, -5064, -5047, -5029, -5010, -4991, -4972, -4952, -4931, -4910,
--4889, -4867, -4844, -4821, -4797, -4774, -4749, -4724, -4699, -4673,
--4647, -4620, -4593, -4566, -4538, -4510, -4481, -4452, -4422, -4393,
--4363, -4332, -4301, -4270, -4238, -4206, -4174, -4142, -4109, -4076,
--4042, -4009, -3975, -3940, -3906, -3871, -3836, -3801, -3765, -3729,
--3693, -3657, -3620, -3584, -3547, -3510, -3472, -3435, -3397, -3360,
--3322, -3283, -3245, -3207, -3168, -3129, -3091, -3052, -3013, -2973,
--2934, -2895, -2855, -2816, -2776, -2736, -2697, -2657, -2617, -2577,
--2537, -2497, -2457, -2417, -2377, -2337, -2297, -2256, -2216, -2176,
--2136, -2096, -2056, -2016, -1976, -1936, -1896, -1856, -1817, -1777,
--1737, -1698, -1658, -1619, -1579, -1540, -1501, -1462, -1423, -1384,
--1345, -1306, -1268, -1230, -1191, -1153, -1115, -1077, -1040, -1002,
--965, -927, -890, -854, -817, -780, -744, -708, -672, -636, -600,
--565, -530, -494, -460, -425, -391, -356, -322, -289, -255, -222,
--189, -156, -123, -91, -59, -27, 4, 35, 66, 97, 127, 158, 188, 218,
-247, 277, 306, 334, 363, 391, 419, 447, 474, 501, 528, 554, 581, 606,
-632, 657, 683, 707, 732, 756, 780, 803, 827, 850, 872, 895, 917, 939,
-960, 981, 1002, 1023, 1043, 1063, 1082, 1102, 1121, 1139, 1158, 1176,
-1194, 1211, 1228, 1245, 1262, 1278, 1294, 1309, 1325, 1340, 1354,
-1369, 1383, 1397, 1410, 1423, 1436, 1448, 1461, 1473, 1484, 1496,
-1507, 1517, 1528, 1538, 1548, 1557, 1566, 1575, 1584, 1592, 1600,
-1608, 1616, 1623, 1630, 1636, 1643, 1649, 1654, 1660, 1665, 1670,
-1675, 1679, 1683, 1687, 1690, 1694, 1697, 1700, 1702, 1704, 1706,
-1708, 1709, 1711, 1712, 1712, 1713, 1713, 1713, 1713, 1712, 1711,
-1710, 1709, 1708, 1706, 1704, 1702, 1700, 1697, 1694, 1691, 1688,
-1685, 1681, 1677, 1673, 1669, 1664, 1660, 1655, 1650, 1644, 1639,
-1633, 1627, 1621, 1615, 1609, 1602, 1596, 1589, 1582, 1575, 1567,
-1560, 1552, 1544, 1536, 1528, 1520, 1511, 1503, 1494, 1485, 1476,
-1467, 1458, 1448, 1439, 1429, 1419, 1409, 1399, 1389, 1379, 1368,
-1358, 1347, 1337, 1326, 1315, 1304, 1293, 1282, 1271, 1260, 1248,
-1237, 1225, 1213, 1202, 1190, 1178, 1166, 1154, 1142, 1130, 1118,
-1106, 1094, 1081, 1069, 1057, 1044, 1032, 1019, 1007, 994, 981, 969,
-956, 943, 931, 918, 905, 892, 879, 867, 854, 841, 828, 815, 802, 790,
-777, 764, 751, 738, 725, 713, 700, 687, 674, 662, 649, 636, 623, 611,
-598, 585, 573, 560, 548, 535, 523, 510, 498, 486, 473, 461, 449, 437,
-425, 413, 401, 389, 377, 365, 353, 341, 330, 318, 307, 295, 284, 272,
-261, 250, 239, 228, 217, 206, 195, 184, 173, 163, 152, 141, 131, 121,
-110, 100, 90, 80, 70, 60, 51, 41, 31, 22, 12, 3, -5, -14, -23, -32,
--41, -50, -59, -67, -76, -84, -93, -101, -109, -117, -125, -133, -140,
--148, -156, -163, -170, -178, -185, -192, -199, -206, -212, -219,
--226, -232, -239, -245, -251, -257, -263, -269, -275, -280, -286,
--291, -297, -302, -307, -312, -317, -322, -327, -332, -336, -341,
--345, -349, -354, -358, -362, -366, -369, -373, -377, -380, -384,
--387, -390, -394, -397, -400, -402, -405, -408, -411, -413, -416,
--418, -420, -422, -424, -426, -428, -430, -432, -433, -435, -436,
--438, -439, -440, -442, -443, -444, -445, -445, -446, -447, -447,
--448, -448, -449, -449, -449, -449, -449, -449, -449, -449, -449,
--449, -449, -448, -448, -447, -447, -446, -445, -444, -443, -443,
--442, -441, -440, -438, -437, -436, -435, -433, -432, -430, -429,
--427, -426, -424, -422, -420, -419, -417, -415, -413, -411, -409,
--407, -405, -403, -400, -398, -396, -393, -391, -389, -386, -384,
--381, -379, -376, -374, -371, -368, -366, -363, -360, -357, -355,
--352, -349, -346, -343, -340, -337, -334, -331, -328, -325, -322,
--319, -316, -313, -310, -307, -304, -301, -298, -294, -291, -288,
--285, -282, -278, -275, -272, -269, -265, -262, -259, -256, -252,
--249, -246, -243, -239, -236, -233, -230, -226, -223, -220, -217,
--213, -210, -207, -204, -200, -197, -194, -191, -187, -184, -181,
--178, -175, -172, -168, -165, -162, -159, -156, -153, -150, -147,
--143, -140, -137, -134, -131, -128, -125, -122, -120, -117, -114,
--111, -108, -105, -102, -99, -97, -94, -91, -88, -86, -83, -80, -78,
--75, -72, -70, -67, -65, -62, -59, -57, -55, -52, -50, -47, -45, -43,
--40, -38, -36, -33, -31, -29, -27, -25, -22, -20, -18, -16, -14, -12,
--10, -8, -6, -4, -2, 0, 0, 2, 4, 6, 8, 9, 11, 13, 14, 16, 17, 19, 21,
-22, 24, 25, 27, 28, 29, 31, 32, 33, 35, 36, 37, 38, 40, 41, 42, 43,
-44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 58, 59,
-59, 60, 61, 62, 62, 63, 63, 64, 64, 65, 66, 66, 66, 67, 67, 68, 68,
-69, 69, 69, 70, 70, 70, 70, 71, 71, 71, 71, 71, 72, 72, 72, 72, 72,
-72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72,
-72, 71, 71, 71, 71, 71, 70, 70, 70, 70, 69, 69, 69, 69, 68, 68, 68,
-67, 67, 67, 66, 66, 66, 65, 65, 64, 64, 64, 63, 63, 62, 62, 62, 61,
-61, 60, 60, 59, 59, 58, 58, 58, 57, 57, 56, 56, 55, 55, 54, 54, 53,
-53, 52, 52, 51, 51, 50, 50, 49, 48, 48, 47, 47, 46, 46, 45, 45, 44,
-44, 43, 43, 42, 42, 41, 41, 40, 39, 39, 38, 38, 37, 37, 36, 36, 35,
-35, 34, 34, 33, 33, 32, 32, 31, 31, 30, 30, 29, 29, 28, 28, 27, 27,
-26, 26, 25, 25, 24, 24, 23, 23, 23, 22, 22, 21, 21, 20, 20, 20, 19,
-19, 18, 18, 17, 17, 17, 16, 16, 15, 15, 15, 14, 14, 14, 13, 13, 12,
-12, 12, 11, 11, 11, 10, 10, 10, 9, 9, 9, 9, 8, 8, 8, 7, 7, 7, 7, 6, 6,
-6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 1, 1, 1,
-1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, -1, -1,
--1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2, -2, -2,
--2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
--2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
--2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
--2, -2, -2, -2, -2, -2, -2, -2, -1, -1, -1, -1, -1, -1, -1, -1, -1,
--1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
diff --git a/src/audio/include/i2s_audio_output.hpp b/src/audio/include/i2s_audio_output.hpp
index 717e6519..13cb183f 100644
--- a/src/audio/include/i2s_audio_output.hpp
+++ b/src/audio/include/i2s_audio_output.hpp
@@ -6,19 +6,14 @@
 
 #pragma once
 
-#include <sys/_stdint.h>
 #include <cstdint>
 #include <memory>
 #include <vector>
 
-#include "audio_element.hpp"
 #include "audio_sink.hpp"
-#include "chunk.hpp"
-#include "result.hpp"
-
 #include "gpios.hpp"
 #include "i2s_dac.hpp"
-#include "stream_info.hpp"
+#include "result.hpp"
 
 namespace audio {
 
diff --git a/src/audio/include/pipeline.hpp b/src/audio/include/pipeline.hpp
deleted file mode 100644
index bb773006..00000000
--- a/src/audio/include/pipeline.hpp
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <memory>
-#include <optional>
-#include <string>
-#include <vector>
-
-#include "freertos/portmacro.h"
-
-#include "audio_element.hpp"
-#include "stream_info.hpp"
-
-namespace audio {
-
-static const std::size_t kPipelineBufferSize = 64 * 1024;
-
-class Pipeline {
- public:
-  explicit Pipeline(IAudioElement* output);
-  ~Pipeline();
-  auto AddInput(IAudioElement* input) -> Pipeline*;
-
-  auto OutputElement() const -> IAudioElement*;
-
-  auto NumInputs() const -> std::size_t;
-
-  auto InStreams(std::vector<RawStream>*) -> void;
-
-  auto OutStream() -> RawStream;
-
-  auto GetIterationOrder() -> std::vector<Pipeline*>;
-
-  // Not copyable or movable.
-  Pipeline(const Pipeline&) = delete;
-  Pipeline& operator=(const Pipeline&) = delete;
-
- private:
-  IAudioElement* root_;
-  std::vector<std::unique_ptr<Pipeline>> subtrees_;
-
-  std::array<std::byte, kPipelineBufferSize> output_buffer_;
-  StreamInfo output_info_;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/resample.hpp b/src/audio/include/resample.hpp
index 7b114f59..a9464cb1 100644
--- a/src/audio/include/resample.hpp
+++ b/src/audio/include/resample.hpp
@@ -1,6 +1,12 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
 #pragma once
 
-#include <sys/_stdint.h>
+#include <cstdint>
 #include <vector>
 
 #include "span.hpp"
diff --git a/src/audio/include/sink_mixer.hpp b/src/audio/include/sink_mixer.hpp
index 4a7627e8..37143439 100644
--- a/src/audio/include/sink_mixer.hpp
+++ b/src/audio/include/sink_mixer.hpp
@@ -6,19 +6,15 @@
 
 #pragma once
 
-#include <sys/_stdint.h>
 #include <cstdint>
 #include <memory>
 
 #include "resample.hpp"
 #include "sample.hpp"
 
-#include "audio_decoder.hpp"
 #include "audio_sink.hpp"
 #include "audio_source.hpp"
 #include "codec.hpp"
-#include "pipeline.hpp"
-#include "stream_info.hpp"
 
 namespace audio {
 
@@ -38,7 +34,7 @@ class SinkMixer {
  private:
   auto Main() -> void;
 
-  auto SetTargetFormat(const StreamInfo::Pcm& format) -> void;
+  auto SetTargetFormat(const IAudioSink::Format& format) -> void;
   auto HandleSamples(cpp::span<sample::Sample>, bool) -> size_t;
 
   struct Args {
diff --git a/src/audio/include/stream_buffer.hpp b/src/audio/include/stream_buffer.hpp
deleted file mode 100644
index 06fe8af5..00000000
--- a/src/audio/include/stream_buffer.hpp
+++ /dev/null
@@ -1,65 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstddef>
-#include <cstdint>
-
-#include "freertos/FreeRTOS.h"
-
-#include "freertos/message_buffer.h"
-#include "span.hpp"
-
-namespace audio {
-
-/*
- * A collection of the buffers required for two IAudioElement implementations to
- * stream data between each other.
- *
- * Currently, we use a FreeRTOS MessageBuffer to hold the byte stream, and also
- * maintain two chunk-sized buffers for the elements to stage their read and
- * write operations (as MessageBuffer copies the given data into its memory
- * space). A future optimisation here could be to instead post himem memory
- * addresses to the message buffer, and then maintain address spaces into which
- * we map these messages, rather than 'real' allocated buffers as we do now.
- */
-class StreamBuffer {
- public:
-  explicit StreamBuffer(std::size_t chunk_size, std::size_t buffer_size);
-  ~StreamBuffer();
-
-  /* Returns the handle for the underlying message buffer. */
-  auto Handle() -> MessageBufferHandle_t* { return &handle_; }
-
-  /*
-   * Returns a chunk-sized staging buffer that should be used *only* by the
-   * reader (sink) element.
-   */
-  auto ReadBuffer() -> cpp::span<std::byte> { return input_chunk_; }
-
-  /*
-   * Returns a chunk-sized staging buffer that should be used *only* by the
-   * writer (source) element.
-   */
-  auto WriteBuffer() -> cpp::span<std::byte> { return output_chunk_; }
-
-  StreamBuffer(const StreamBuffer&) = delete;
-  StreamBuffer& operator=(const StreamBuffer&) = delete;
-
- private:
-  std::byte* raw_memory_;
-  StaticMessageBuffer_t metadata_;
-  MessageBufferHandle_t handle_;
-
-  std::byte* raw_input_chunk_;
-  cpp::span<std::byte> input_chunk_;
-
-  std::byte* raw_output_chunk_;
-  cpp::span<std::byte> output_chunk_;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/stream_event.hpp b/src/audio/include/stream_event.hpp
deleted file mode 100644
index d98d9baa..00000000
--- a/src/audio/include/stream_event.hpp
+++ /dev/null
@@ -1,57 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <memory>
-
-#include "arena.hpp"
-#include "freertos/FreeRTOS.h"
-#include "freertos/queue.h"
-
-#include "span.hpp"
-#include "stream_info.hpp"
-
-namespace audio {
-
-struct StreamEvent {
-  static auto CreateStreamInfo(QueueHandle_t source, const StreamInfo& payload)
-      -> StreamEvent*;
-  static auto CreateArenaChunk(QueueHandle_t source, memory::ArenaPtr ptr)
-      -> StreamEvent*;
-  static auto CreateChunkNotification(QueueHandle_t source) -> StreamEvent*;
-  static auto CreateEndOfStream(QueueHandle_t source) -> StreamEvent*;
-  static auto CreateLogStatus() -> StreamEvent*;
-
-  StreamEvent();
-  ~StreamEvent();
-  StreamEvent(StreamEvent&&);
-
-  QueueHandle_t source;
-
-  enum {
-    UNINITIALISED,
-    STREAM_INFO,
-    ARENA_CHUNK,
-    CHUNK_NOTIFICATION,
-    END_OF_STREAM,
-    LOG_STATUS,
-  } tag;
-
-  union {
-    StreamInfo* stream_info;
-
-    memory::ArenaPtr arena_chunk;
-
-    // FIXME: It would be nice to also support a pointer to himem data here, to
-    // save a little ordinary heap space.
-  };
-
-  StreamEvent(const StreamEvent&) = delete;
-  StreamEvent& operator=(const StreamEvent&) = delete;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/stream_info.hpp b/src/audio/include/stream_info.hpp
deleted file mode 100644
index 01dd282a..00000000
--- a/src/audio/include/stream_info.hpp
+++ /dev/null
@@ -1,174 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <stdint.h>
-#include <sys/_stdint.h>
-#include <cstdint>
-#include <optional>
-#include <string>
-#include <string_view>
-#include <type_traits>
-#include <utility>
-#include <variant>
-
-#include "esp_heap_caps.h"
-#include "freertos/FreeRTOS.h"
-#include "freertos/ringbuf.h"
-#include "freertos/stream_buffer.h"
-
-#include "result.hpp"
-#include "span.hpp"
-#include "types.hpp"
-
-namespace audio {
-
-class StreamInfo {
- public:
-  StreamInfo() : bytes_in_stream_(0), total_length_bytes_(), format_() {}
-
-  // The number of bytes that are available for consumption within this
-  // stream's buffer.
-  auto bytes_in_stream() -> std::size_t& { return bytes_in_stream_; }
-  auto bytes_in_stream() const -> std::size_t { return bytes_in_stream_; }
-
-  auto total_length_bytes() -> std::optional<std::uint32_t>& {
-    return total_length_bytes_;
-  }
-  auto total_length_bytes() const -> std::optional<std::uint32_t> {
-    return total_length_bytes_;
-  }
-
-  auto total_length_seconds() -> std::optional<std::uint32_t>& {
-    return total_length_seconds_;
-  }
-  auto total_length_seconds() const -> std::optional<std::uint32_t> {
-    return total_length_seconds_;
-  }
-
-  struct Encoded {
-    // The codec that this stream is associated with.
-    codecs::StreamType type;
-
-    bool operator==(const Encoded&) const = default;
-  };
-
-  /*
-   * Two-channel, interleaved, 32-bit floating point pcm samples.
-   */
-  struct FloatingPointPcm {
-    // Number of channels in this stream.
-    uint8_t channels;
-    // The sample rate.
-    uint32_t sample_rate;
-
-    bool operator==(const FloatingPointPcm&) const = default;
-  };
-
-  struct Pcm {
-    // Number of channels in this stream.
-    uint8_t channels;
-    // Number of bits per sample.
-    uint8_t bits_per_sample;
-    // The sample rate.
-    uint32_t sample_rate;
-
-    auto bytes_per_sample() const -> uint8_t {
-      return bits_per_sample == 16 ? 2 : 4;
-    }
-
-    bool operator==(const Pcm&) const = default;
-  };
-
-  typedef std::variant<std::monostate, Encoded, FloatingPointPcm, Pcm> Format;
-  auto format() const -> const Format& { return format_; }
-  auto set_format(Format f) -> void { format_ = f; }
-
-  template <typename T>
-  auto format_as() const -> std::optional<T> {
-    if (std::holds_alternative<T>(format_)) {
-      return std::get<T>(format_);
-    }
-    return {};
-  }
-
-  bool operator==(const StreamInfo&) const = default;
-
- private:
-  std::size_t bytes_in_stream_;
-  std::optional<std::uint32_t> total_length_bytes_;
-  std::optional<std::uint32_t> total_length_seconds_;
-  Format format_{};
-};
-
-class InputStream;
-class OutputStream;
-
-class RawStream {
- public:
-  explicit RawStream(std::size_t size);
-  RawStream(std::size_t size, uint32_t);
-  ~RawStream();
-
-  auto info() -> StreamInfo& { return info_; }
-  auto data() -> cpp::span<std::byte>;
-  template <typename T>
-  auto data_as() -> cpp::span<T> {
-    auto orig = data();
-    return {reinterpret_cast<T*>(orig.data()), orig.size_bytes() / sizeof(T)};
-  }
-  auto empty() const -> bool { return info_.bytes_in_stream() == 0; }
-
- private:
-  StreamInfo info_;
-  std::size_t buffer_size_;
-  std::byte* buffer_;
-};
-
-class InputStream {
- public:
-  explicit InputStream(RawStream* s) : raw_(s) {}
-
-  void consume(std::size_t bytes) const;
-
-  const StreamInfo& info() const;
-
-  cpp::span<const std::byte> data() const;
-  template <typename T>
-  auto data_as() const -> cpp::span<const T> {
-    auto orig = data();
-    return {reinterpret_cast<const T*>(orig.data()),
-            orig.size_bytes() / sizeof(T)};
-  }
-
- private:
-  RawStream* raw_;
-};
-
-class OutputStream {
- public:
-  explicit OutputStream(RawStream* s) : raw_(s) {}
-
-  void add(std::size_t bytes) const;
-
-  void prepare(const StreamInfo::Format& new_format,
-               std::optional<uint32_t> length);
-
-  const StreamInfo& info() const;
-
-  cpp::span<std::byte> data() const;
-  template <typename T>
-  auto data_as() const -> cpp::span<T> {
-    auto orig = data();
-    return {reinterpret_cast<T*>(orig.data()), orig.size_bytes() / sizeof(T)};
-  }
-
- private:
-  RawStream* raw_;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/stream_message.hpp b/src/audio/include/stream_message.hpp
deleted file mode 100644
index cf9ba39c..00000000
--- a/src/audio/include/stream_message.hpp
+++ /dev/null
@@ -1,69 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstdint>
-#include <functional>
-#include <optional>
-
-#include "cbor.h"
-#include "result.hpp"
-#include "span.hpp"
-
-namespace audio {
-
-extern const int kEncoderFlags;
-extern const int kDecoderFlags;
-
-enum MessageType {
-  TYPE_UNKNOWN,
-  TYPE_CHUNK_HEADER,
-  TYPE_STREAM_INFO,
-};
-
-template <typename Writer>
-auto WriteMessage(MessageType type, Writer&& writer, cpp::span<std::byte> data)
-    -> cpp::result<size_t, CborError> {
-  CborEncoder root;
-  CborEncoder container;
-  uint8_t* cast_data = reinterpret_cast<uint8_t*>(data.data());
-
-  cbor_encoder_init(&root, cast_data, data.size(), kEncoderFlags);
-  cbor_encoder_create_array(&root, &container, 2);
-  cbor_encode_uint(&container, type);
-
-  std::optional<CborError> inner_err = std::invoke(writer, container);
-  if (inner_err) {
-    return cpp::fail(inner_err.value());
-  }
-
-  cbor_encoder_close_container(&root, &container);
-  return cbor_encoder_get_buffer_size(&root, cast_data);
-}
-
-template <typename Result, typename Reader>
-auto ReadMessage(Reader&& reader, cpp::span<std::byte> data)
-    -> cpp::result<Result, CborError> {
-  CborParser parser;
-  CborValue root;
-  CborValue container;
-
-  cbor_parser_init(reinterpret_cast<uint8_t*>(data.data()), data.size(),
-                   kDecoderFlags, &parser, &root);
-  cbor_value_enter_container(&root, &container);
-  // Skip the type header
-  cbor_value_advance_fixed(&container);
-
-  return std::invoke(reader, container);
-}
-
-auto WriteTypeOnlyMessage(MessageType type, cpp::span<std::byte> data)
-    -> cpp::result<size_t, CborError>;
-auto ReadMessageType(cpp::span<std::byte> msg) -> MessageType;
-auto GetAdditionalData(cpp::span<std::byte> msg) -> cpp::span<std::byte>;
-
-}  // namespace audio
diff --git a/src/audio/pipeline.cpp b/src/audio/pipeline.cpp
deleted file mode 100644
index f54f8d11..00000000
--- a/src/audio/pipeline.cpp
+++ /dev/null
@@ -1,61 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#include "pipeline.hpp"
-#include <algorithm>
-#include <memory>
-#include "stream_info.hpp"
-
-namespace audio {
-
-Pipeline::Pipeline(IAudioElement* output) : root_(output), subtrees_() {
-  assert(output != nullptr);
-}
-
-Pipeline::~Pipeline() {}
-
-auto Pipeline::AddInput(IAudioElement* input) -> Pipeline* {
-  subtrees_.push_back(std::make_unique<Pipeline>(input));
-  return subtrees_.back().get();
-}
-
-auto Pipeline::OutputElement() const -> IAudioElement* {
-  return root_;
-}
-
-auto Pipeline::NumInputs() const -> std::size_t {
-  return subtrees_.size();
-}
-
-auto Pipeline::InStreams(std::vector<RawStream>* out) -> void {
-  for (int i = 0; i < subtrees_.size(); i++) {
-    out->push_back(subtrees_[i]->OutStream());
-  }
-}
-
-auto Pipeline::OutStream() -> RawStream {
-  return {&output_info_, output_buffer_};
-}
-
-auto Pipeline::GetIterationOrder() -> std::vector<Pipeline*> {
-  std::vector<Pipeline*> to_search{this};
-  std::vector<Pipeline*> found;
-
-  while (!to_search.empty()) {
-    Pipeline* current = to_search.back();
-    to_search.pop_back();
-    found.push_back(current);
-
-    for (const auto& i : current->subtrees_) {
-      to_search.push_back(i.get());
-    }
-  }
-
-  std::reverse(found.begin(), found.end());
-  return found;
-}
-
-}  // namespace audio
diff --git a/src/audio/resample.cpp b/src/audio/resample.cpp
index bc2c7c51..a3a34ee7 100644
--- a/src/audio/resample.cpp
+++ b/src/audio/resample.cpp
@@ -4,27 +4,18 @@
  * SPDX-License-Identifier: GPL-3.0-only
  */
 #include "resample.hpp"
-/*
- * This file contains the implementation for a 32-bit floating point resampler.
- * It is largely based on David Bryant's ART resampler, which is BSD-licensed,
- * and available at https://github.com/dbry/audio-resampler/.
- *
- * This resampler uses windowed sinc interpolation filters, with an additional
- * lowpass filter to reduce aliasing.
- */
 
-#include <stdint.h>
-#include <stdlib.h>
-#include <string.h>
 #include <algorithm>
 #include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
 #include <numeric>
 
 #include "esp_log.h"
+#include "speex/speex_resampler.h"
 
 #include "sample.hpp"
-#include "speex/speex_resampler.h"
-#include "stream_info.hpp"
 
 namespace audio {
 
diff --git a/src/audio/sink_mixer.cpp b/src/audio/sink_mixer.cpp
index 79ff4fb7..c6cb886f 100644
--- a/src/audio/sink_mixer.cpp
+++ b/src/audio/sink_mixer.cpp
@@ -6,19 +6,18 @@
 
 #include "sink_mixer.hpp"
 
-#include <stdint.h>
 #include <algorithm>
 #include <cmath>
+#include <cstdint>
 
 #include "esp_heap_caps.h"
 #include "esp_log.h"
 #include "freertos/portmacro.h"
 #include "freertos/projdefs.h"
 #include "idf_additions.h"
+
 #include "resample.hpp"
 #include "sample.hpp"
-
-#include "stream_info.hpp"
 #include "tasks.hpp"
 
 static constexpr char kTag[] = "mixer";
diff --git a/src/audio/stream_buffer.cpp b/src/audio/stream_buffer.cpp
deleted file mode 100644
index 569c9189..00000000
--- a/src/audio/stream_buffer.cpp
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#include "stream_buffer.hpp"
-#include "assert.h"
-#include "esp_log.h"
-
-namespace audio {
-
-StreamBuffer::StreamBuffer(std::size_t chunk_size, std::size_t buffer_size)
-    : raw_memory_(static_cast<std::byte*>(
-          heap_caps_malloc(buffer_size, MALLOC_CAP_SPIRAM))),
-      handle_(
-          xMessageBufferCreateStatic(buffer_size,
-                                     reinterpret_cast<uint8_t*>(raw_memory_),
-                                     &metadata_)),
-      raw_input_chunk_(static_cast<std::byte*>(
-          heap_caps_malloc(chunk_size * 1.5, MALLOC_CAP_SPIRAM))),
-      input_chunk_(raw_input_chunk_, chunk_size * 1.5),
-      raw_output_chunk_(static_cast<std::byte*>(
-          heap_caps_malloc(chunk_size, MALLOC_CAP_SPIRAM))),
-      output_chunk_(raw_output_chunk_, chunk_size) {
-  assert(input_chunk_.size() <= buffer_size);
-  assert(output_chunk_.size() <= buffer_size);
-  ESP_LOGI("streambuf", "created buffer of chunk size %d, total size %d",
-           chunk_size, buffer_size);
-}
-
-StreamBuffer::~StreamBuffer() {
-  vMessageBufferDelete(handle_);
-  free(raw_memory_);
-  free(raw_input_chunk_);
-  free(raw_output_chunk_);
-}
-
-}  // namespace audio
diff --git a/src/audio/stream_event.cpp b/src/audio/stream_event.cpp
deleted file mode 100644
index d7533ea2..00000000
--- a/src/audio/stream_event.cpp
+++ /dev/null
@@ -1,101 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#include "stream_event.hpp"
-#include <cstddef>
-#include <memory>
-#include "arena.hpp"
-#include "stream_info.hpp"
-
-namespace audio {
-
-auto StreamEvent::CreateStreamInfo(QueueHandle_t source,
-                                   const StreamInfo& payload) -> StreamEvent* {
-  auto event = new StreamEvent;
-  event->tag = StreamEvent::STREAM_INFO;
-  event->source = source;
-  event->stream_info = new StreamInfo(payload);
-  return event;
-}
-
-auto StreamEvent::CreateArenaChunk(QueueHandle_t source, memory::ArenaPtr ptr)
-    -> StreamEvent* {
-  auto event = new StreamEvent;
-  event->tag = StreamEvent::ARENA_CHUNK;
-  event->source = source;
-  event->arena_chunk = ptr;
-
-  return event;
-}
-
-auto StreamEvent::CreateChunkNotification(QueueHandle_t source)
-    -> StreamEvent* {
-  auto event = new StreamEvent;
-  event->tag = StreamEvent::CHUNK_NOTIFICATION;
-  event->source = source;
-  return event;
-}
-
-auto StreamEvent::CreateEndOfStream(QueueHandle_t source) -> StreamEvent* {
-  auto event = new StreamEvent;
-  event->tag = StreamEvent::END_OF_STREAM;
-  event->source = source;
-  return event;
-}
-
-auto StreamEvent::CreateLogStatus() -> StreamEvent* {
-  auto event = new StreamEvent;
-  event->tag = StreamEvent::LOG_STATUS;
-  return event;
-}
-
-StreamEvent::StreamEvent() : tag(StreamEvent::UNINITIALISED) {}
-
-StreamEvent::~StreamEvent() {
-  switch (tag) {
-    case UNINITIALISED:
-      break;
-    case STREAM_INFO:
-      delete stream_info;
-      break;
-    case ARENA_CHUNK:
-      arena_chunk.owner->Return(arena_chunk);
-      break;
-    case CHUNK_NOTIFICATION:
-      break;
-    case END_OF_STREAM:
-      break;
-    case LOG_STATUS:
-      break;
-  }
-}
-
-StreamEvent::StreamEvent(StreamEvent&& other) {
-  tag = other.tag;
-  source = other.source;
-  switch (tag) {
-    case UNINITIALISED:
-      break;
-    case STREAM_INFO:
-      stream_info = other.stream_info;
-      other.stream_info = nullptr;
-      break;
-    case ARENA_CHUNK:
-      arena_chunk = other.arena_chunk;
-      other.arena_chunk = {
-          .owner = nullptr, .start = nullptr, .size = 0, .used_size = 0};
-      break;
-    case CHUNK_NOTIFICATION:
-      break;
-    case END_OF_STREAM:
-      break;
-    case LOG_STATUS:
-      break;
-  }
-  other.tag = StreamEvent::UNINITIALISED;
-}
-
-}  // namespace audio
diff --git a/src/audio/stream_info.cpp b/src/audio/stream_info.cpp
deleted file mode 100644
index 73dbf91b..00000000
--- a/src/audio/stream_info.cpp
+++ /dev/null
@@ -1,84 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#include "stream_info.hpp"
-#include <sys/_stdint.h>
-
-#include <cstdint>
-#include <optional>
-#include <string>
-#include <string_view>
-#include <type_traits>
-#include <utility>
-#include <variant>
-
-#include "esp_heap_caps.h"
-#include "result.hpp"
-#include "span.hpp"
-#include "types.hpp"
-
-namespace audio {
-
-RawStream::RawStream(std::size_t size)
-    : info_(),
-      buffer_size_(size),
-      buffer_(reinterpret_cast<std::byte*>(
-          heap_caps_malloc(size, MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT))) {
-  assert(buffer_ != NULL);
-}
-
-RawStream::RawStream(std::size_t size, uint32_t caps)
-    : info_(),
-      buffer_size_(size),
-      buffer_(reinterpret_cast<std::byte*>(heap_caps_malloc(size, caps))) {
-  assert(buffer_ != NULL);
-}
-
-RawStream::~RawStream() {
-  heap_caps_free(buffer_);
-}
-
-auto RawStream::data() -> cpp::span<std::byte> {
-  return {buffer_, buffer_size_};
-}
-
-void InputStream::consume(std::size_t bytes) const {
-  assert(raw_->info().bytes_in_stream() >= bytes);
-  auto new_data =
-      raw_->data().subspan(bytes, raw_->info().bytes_in_stream() - bytes);
-  std::move(new_data.begin(), new_data.end(), raw_->data().begin());
-  raw_->info().bytes_in_stream() = new_data.size_bytes();
-}
-
-const StreamInfo& InputStream::info() const {
-  return raw_->info();
-}
-
-cpp::span<const std::byte> InputStream::data() const {
-  return raw_->data().first(raw_->info().bytes_in_stream());
-}
-
-void OutputStream::add(std::size_t bytes) const {
-  assert(raw_->info().bytes_in_stream() + bytes <= raw_->data().size_bytes());
-  raw_->info().bytes_in_stream() += bytes;
-}
-
-void OutputStream::prepare(const StreamInfo::Format& new_format,
-                           std::optional<uint32_t> length) {
-  raw_->info().set_format(new_format);
-  raw_->info().bytes_in_stream() = 0;
-  raw_->info().total_length_bytes() = length;
-}
-
-const StreamInfo& OutputStream::info() const {
-  return raw_->info();
-}
-
-cpp::span<std::byte> OutputStream::data() const {
-  return raw_->data().subspan(raw_->info().bytes_in_stream());
-}
-
-}  // namespace audio
diff --git a/src/audio/stream_message.cpp b/src/audio/stream_message.cpp
deleted file mode 100644
index a7b8901a..00000000
--- a/src/audio/stream_message.cpp
+++ /dev/null
@@ -1,68 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#include "stream_message.hpp"
-
-#include <cstdint>
-
-#include "cbor.h"
-#include "span.hpp"
-
-namespace audio {
-
-const int kEncoderFlags = 0;
-const int kDecoderFlags = 0;
-
-auto WriteTypeOnlyMessage(MessageType type, cpp::span<std::byte> data)
-    -> cpp::result<size_t, CborError> {
-  CborEncoder root;
-  CborEncoder container;
-  uint8_t* cast_data = reinterpret_cast<uint8_t*>(data.data());
-
-  cbor_encoder_init(&root, cast_data, data.size(), kEncoderFlags);
-  cbor_encode_uint(&container, type);
-
-  return cbor_encoder_get_buffer_size(&root, cast_data);
-}
-
-auto ReadMessageType(cpp::span<std::byte> msg) -> MessageType {
-  CborParser parser;
-  CborValue root;
-  CborValue container;
-
-  cbor_parser_init(reinterpret_cast<uint8_t*>(msg.data()), msg.size(),
-                   kDecoderFlags, &parser, &root);
-
-  uint64_t header = 0;
-  if (cbor_value_is_container(&root)) {
-    cbor_value_enter_container(&root, &container);
-    cbor_value_get_uint64(&container, &header);
-  } else {
-    cbor_value_get_uint64(&root, &header);
-  }
-
-  return static_cast<MessageType>(header);
-}
-
-auto GetAdditionalData(cpp::span<std::byte> msg) -> cpp::span<std::byte> {
-  CborParser parser;
-  CborValue root;
-  uint8_t* cast_data = reinterpret_cast<uint8_t*>(msg.data());
-
-  cbor_parser_init(cast_data, msg.size(), kDecoderFlags, &parser, &root);
-
-  while (!cbor_value_at_end(&root)) {
-    cbor_value_advance(&root);
-  }
-
-  const uint8_t* remaining = cbor_value_get_next_byte(&root);
-  size_t header_size = remaining - cast_data;
-
-  return cpp::span<std::byte>(msg.data() + header_size,
-                              msg.size() - header_size);
-}
-
-}  // namespace audio