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README.md

@@ -8,3 +8,47 @@ I don't know if the ffmpeg code is immature,
 or if I just don't understand ffmpeg,
 but this codec demands some special treatment,
 which this shell script provides.
+
+# Special Treatment
+
+Here are the quirks I've identified
+(February 2023):
+
+* The codec will not write into a `.mkv` container,
+  but it will write into a `.mp4` or `.nut` container.
+* The codec does not play well with subrip subtitles,
+  making it look like you don't have enough capture buffers.
+  You will never have enough capture buffers:
+  you have to stop trying to copy over subtitles.
+
+The solution this script uses is to
+transcode video and audio
+into an intermediate `.nut` file.
+Then it combines the `.nut` file,
+and any subtitles from the original file,
+into a new `.mkv` file.
+Since the "copy" video codec is used in the second step,
+everything works properly.
+
+# Thanks
+
+Thank you to Will Usher,
+who figured out how to get the codec working at all.
+Without Will's
+[helpful blog post](https://www.willusher.io/general/2020/11/15/hw-accel-encoding-rpi4)
+I would still be fighting with ffmpeg trying to make it use hardware acceleration.
+Will also wrote the
+[FBED](https://github.com/Twinklebear/fbed) batch transcoder,
+very similar to this.
+You might try it out if you don't like this script.
+
+I created this simpler shell script mainly
+to avoid Python package dependencies:
+FBED needed an ffmpeg library that I had to patch
+before it would run.
+I wound up having to fiddle with ffmpeg so much
+dealing with the codec quirks,
+that working in Bourne shell
+made things much simpler
+as I chased down the subtitle problems.
+

h264

@@ -120,11 +120,9 @@ for fn in "$@"; do
     -i "$intermediate" \
     -i "$fn" \
     -map 0:v \
-    -c:v copy \
     -map 0:a \
-    -c:a copy \
     -map 1:s? \
-    -c:s copy \
+    -c copy \
     -y \
     "$out"