Added isRangeAllowed() function for transcoded sources

This isn't a perfect solution, but it should help increase confidence
that the transcoder in use is likely to produce an approximately
correct-sized stream.

airsonic-main/src/main/java/org/airsonic/player/controller/StreamController.java

@@ -159,13 +159,13 @@ public class StreamController {
 
                 // Wrangle response length and ranges.
                 //
-                // Support ranges as long as we're not transcoding; video is always assumed to transcode
-                if (file.isVideo()) {
+                // Support ranges as long as we're not transcoding blindly; video is always assumed to transcode
+                if (file.isVideo() || ! parameters.isRangeAllowed()) {
                     // Use chunked transfer; do not accept range requests
                     response.setStatus(HttpServletResponse.SC_OK);
                     response.setHeader("Accept-Ranges", "none");
                 } else {
-                    // Not transcoding, partial content permitted because we know the final size
+                    // Partial content permitted because either know or expect to be able to predict the final size
                     long contentLength;
                     // If range was requested, respond in kind
                     range = getRange(request, file.getDurationSeconds(), fileLengthExpected);

airsonic-main/src/main/java/org/airsonic/player/service/TranscodingService.java

@@ -216,6 +216,7 @@ public class TranscodingService {
         }
 
         parameters.setMaxBitRate(maxBitRate);
+        parameters.setRangeAllowed(isRangeAllowed(parameters));
         return parameters;
     }
 
@@ -487,6 +488,28 @@ public class TranscodingService {
         return matches != null && matches.length > 0;
     }
 
+    private boolean isRangeAllowed(Parameters parameters) {
+        Transcoding transcoding = parameters.getTranscoding();
+        List<String> steps = Arrays.asList();
+        if (transcoding != null) {
+            steps = Arrays.asList(transcoding.getStep3(), transcoding.getStep2(), transcoding.getStep1());
+        }
+        else if (parameters.isDownsample()) {
+            steps = Arrays.asList(settingsService.getDownsamplingCommand());
+        }
+        else {
+            return true;  // neither transcoding or downsampling
+        }
+
+        // Check if last configured step uses the bitrate, if so, range should be pretty safe
+        for (String step : steps) {
+            if (step != null) {
+                return step.contains("%b");
+            }
+        }
+        return false;
+    }
+
     /**
      * Returns the directory in which all transcoders are installed.
      */
@@ -517,6 +540,7 @@ public class TranscodingService {
 
     public static class Parameters {
         private boolean downsample;
+        private boolean rangeAllowed;
         private final MediaFile mediaFile;
         private final VideoTranscodingSettings videoTranscodingSettings;
         private Integer maxBitRate;
@@ -543,6 +567,14 @@ public class TranscodingService {
             return transcoding != null;
         }
 
+        public boolean isRangeAllowed() {
+            return this.rangeAllowed;
+        }
+
+        public void setRangeAllowed(boolean rangeAllowed) {
+            this.rangeAllowed = rangeAllowed;
+        }
+
         public void setTranscoding(Transcoding transcoding) {
             this.transcoding = transcoding;
         }