add a readme

.gitignore

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 /target
 **/*.rs.bk
 .idea/
-*.srt

README.md

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+# srtune 0.2.0
+
+'srtune' helps you edit a .srt file to match a video. Input and output can be either a file, or a stream, so you can
+pipe multiple invocations to create more complex operations. However, a single invocation should suffice in most cases.
+
+An example invocation, used to adapt a full-length subtitle track to a shorter version of "Whisper of the Heart", looks
+like this:
+
+```
+srtune source.srt -o whisper.srt -M235=15:06.7 -M309=24:15 -M412=32:12 \
+  -M411=32:01 -M762=58:51 -M895=1:08:33 -M1125=1:26:28 -M01:44:22=01:41:37.3
+```
+
+Times are specified with colons (required) and always include seconds (HH:MM:SS, MM:SS, 0:SS, :SS). Decimal point in the
+seconds part, if needed, can be either a period or a comma; times can be copied from the .srt file. Numbers without
+colons are assumed to be subtitle indices.
+
+The tool can be used iteratively, adjusting the invocation until the generated subtitle file matches the audio track.
+You can reload the file in VLC by dragging it onto the player window. To make this work, subtitle times specified in
+arguments are the ones seen in the output file (after shifts and moving), while entry indices are those from the input
+file.
+
+Using indices makes it easier to specify a subtitle to alter, but it is tied to the one .srt file. Times are harder to
+write, but the one configuration will work for any locatization or variant of the file,so long as it is intended for the
+same version of the movie. Enable debug logging with '-v' to see times you can use in place of indices.
+            
+Indices are normally not renumbered, so the output file can be used as a reference for both times and indices when you
+work out the right set of arguments. The flag '--renumber' will give each output entry a new sequential number. Please
+note that, once renumbered, the indices in the output file should no longer be used in the command invocation, as there
+can be (and often will be) differences from the original file.
+
+```
+USAGE:
+    srtune [FLAGS] [OPTIONS] [--] [INFILE]
+
+FLAGS:
+    -h, --help        Prints help information
+    -r, --renumber    Renumber all emitted entries with sequential 1-based numbers.
+    -v                Increase the logging verbosity; can be used multiple times
+    -V, --version     Prints version information
+
+OPTIONS:
+    -M, --automove <ENTRY=VIDEOTIME>...    Move subtitles starting at a given time or index to align with a matching
+                                           audio track time. This argument can be given multiple times. Some subtitles
+                                           may be dropped if they fall outside the timeline after the move.
+    -S, --autoscale <SUBTIME=VIDEOTIME>    Calculate scaling based on a perceived difference. The scaling is related to
+                                           the first emitted subtitle; align it with '--move'. This overrides '--scale'.
+    -d, --durscale <RATIO>                 Scale durations, can be combined with '--scale' or '--autoscale'. The given
+                                           value will always be multiplied by the absolute time scale. 1 means identity,
+                                           1.1 makes all times 10% longer.
+    -m, --move <OFFSET>                    Move all subtitles in time (e.g 12:00.15 or -0:44)
+    -o, --output <OUTFILE>                 Output file, defaults to stdout
+    -s, --scale <RATIO>                    Scale all subtitle times and durations to compensate for bitrate differences.
+                                           1 means identity, 1.1 makes all times 10% longer. Scaling is relative to the
+                                           first emitted subtitle; align it with '--move'. This option has no effect if
+                                           '--autoscale' is used.
+
+ARGS:
+    <INFILE>    Input file, leave out for stdin
+```

test/sample.srt

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+20
+00:00:12,838 --> 00:00:20,762
+♪♪～　Ｃｏｕｎｔｒｙ　Ｒｏａｄｓ　ｔａｋｅ　ｍｅ　ｈｏｍｅ
+
+21
+00:00:20,762 --> 00:00:28,770
+♪♪～　Ｔｏ　ｔｈｅ　ｐｌａｃｅ　Ｉ　ｂｅｌｏｎｇ
+
+22
+00:00:28,770 --> 00:00:32,758
+♪♪～　Ｗｅｓｔ　Ｖｉｒｇｉｎｉａ
+
+23
+00:00:32,758 --> 00:00:36,812
+♪♪～　ｍｏｕｎｔａｉｎ　ｍｏｍｍａ
+
+24
+00:00:36,812 --> 00:00:40,766
+♪♪～　Ｔａｋｅ　ｍｅ　ｈｏｍｅ
+
+25
+00:00:40,766 --> 00:00:46,772
+♪♪～　Ｃｏｕｎｔｒｙ　Ｒｏａｄｓ
+
+26
+00:00:46,772 --> 00:00:49,775
+♪♪～