FFmpeg doesn't auto-select subtitle codec for MP4

[slhck]

FFmpeg doesn't seem to be able to auto-select the proper subtitle codec for MP4, which would be mov_text.

I expect FFmpeg to automatically choose the codec, similar to how it does with libx264 and libfaac.

ffmpeg -i in.mp4 -i subs.srt -c:v copy -c:a copy -map 0 -map 1 out.mp4
ffmpeg version 1.1.2 Copyright (c) 2000-2013 the FFmpeg developers
  built on Feb  8 2013 22:55:29 with Apple LLVM version 4.2 (clang-425.0.24) (based on LLVM 3.2svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/1.1.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --cc=cc --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid --enable-libfreetype --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvo-aacenc --enable-ffplay --enable-libfdk-aac --enable-libopus --enable-libopenjpeg --extra-cflags='-I/usr/local/Cellar/openjpeg/1.5.1/include/openjpeg-1.5 '
  libavutil      52. 13.100 / 52. 13.100
  libavcodec     54. 86.100 / 54. 86.100
  libavformat    54. 59.106 / 54. 59.106
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 32.100 /  3. 32.100
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'in.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 2012-01-08 11:16:19
    encoder         : Lavf53.24.0
  Duration: 00:03:31.58, start: 0.000000, bitrate: 2359 kb/s
    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 2229 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
    Metadata:
      creation_time   : 2012-01-08 11:16:19
      handler_name    : VideoHandler
    Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 125 kb/s
    Metadata:
      creation_time   : 2012-01-08 11:16:19
      handler_name    : SoundHandler
[srt @ 0x7fb8ea843c00] Estimating duration from bitrate, this may be inaccurate
Input #1, srt, from 'subs.srt':
  Duration: N/A, bitrate: N/A
    Stream #1:0: Subtitle: subrip
File 'out.mp4' already exists. Overwrite ? [y/N] y
Output #0, mp4, to 'out.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf53.24.0
    Stream #0:0(eng): Video: h264, yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 2229 kb/s, 25 fps, 90k tbn, 25 tbc
    Metadata:
      creation_time   : 2012-01-08 11:16:19
      handler_name    : VideoHandler
    Stream #0:1(eng): Audio: aac, 48000 Hz, stereo, 125 kb/s
    Metadata:
      creation_time   : 2012-01-08 11:16:19
      handler_name    : SoundHandler
    Stream #0:2: Subtitle: none
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
  Stream #1:0 -> #0:2 (subrip -> ?)
Encoder (codec none) not found for output stream #0:2

Encoding with -c:s mov_text works fine.

[slhck]

Also broken in Git Master (git-2013-02-10-3acaea2)

[Carl Eugen Hoyos]

Replying to slhck:

Encoding with -c:s mov_text works fine.

Are you sure? Ticket #1845 indicates it does not work.

[slhck]

Oh, you're correct. The subtitle file had at the beginning of the video, and playing the file resulted in a black screen in QuickTime player (and crashed VLC).

Feel free to close this issue then.

(Any workaround for subtitles in MP4?)

[llogan]

Instead of closing I'm going to consider this being blocked by #1845.

[Carl Eugen Hoyos]

Replying to llogan:

Instead of closing I'm going to consider this being blocked by #1845.

I wonder if it isn't actually a bug that FFmpeg auto-selects ass for mkv if the input file contains subtitles: Many input files have subtitles that are not text based, trying to convert them (as is done by default) breaks re-encoding.
I am therefore mildly against changing the current mov behaviour.

[llogan]

Replying to cehoyos:

I wonder if it isn't actually a bug that FFmpeg auto-selects ass for mkv if the input file contains subtitles: Many input files have subtitles that are not text based, trying to convert them (as is done by default) breaks re-encoding.

I did not consider that. Thanks for pointing it out.

I am therefore mildly against changing the current mov behaviour.

I have no ideas/suggestions for now. Feel free to manage however you think is best.

[domifm]

I'm having a similar issue when trying to convert mkv container to mp4 without re-encoding.

An example file has the following streams:

Input #0, matroska,webm, from 'input.mkv':
  Metadata:
    CREATION_TIME   : 2017-04-08T10:54:24Z
    ENCODER         : Lavf57.7.2
  Duration: 00:22:23.34, start: 0.000000, bitrate: 964 kb/s
    Chapter #0:0: start 0.033000, end 1343.300000
    Metadata:
      title           : Chapter 1
    Stream #0:0: Video: h264 (High), yuv420p(tv, smpte170m/smpte170m/bt709, progressive), 704x480 [SAR 8:9 DAR 176:135], SAR 182:205 DAR 4004:3075, 23.98 fps, 23.98 tbr, 1k tbn, 180k tbc (default)
    Stream #0:1(eng): Audio: aac (LC), 48000 Hz, stereo, fltp (default)
    Metadata:
      title           : English
    Stream #0:2(eng): Subtitle: dvd_subtitle, 720x480
    Stream #0:3(eng): Subtitle: ass

The command line I'd like to use fails with the following error:

ffmpeg -i input.mkv -map 0 -codec copy output.mp4
...
[mp4 @ 0x7fae14deed60] Could not find tag for codec ass in stream #3, codec not currently supported in container
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument

It seems to work mostly with the following command line, but I have to manually specify the codec for that stream:

ffmpeg -i input.mkv -map 0 -codec copy -codec:3 mov_text output.mp4

It would be nice if ffmpeg would realize that the appropriate output codec for that subtitle track is mov_text.

[slhck]

Replying to domifm:

I'm having a similar issue when trying to convert mkv container to mp4 without re-encoding.

When you specify -c copy, you tell ffmpeg to copy the input file streams. It's therefore not ffmpeg's fault if those streams are not applicable for the output file.

This bug relates to what would happen if you did -c:v copy -c:a copy, having ffmpeg figure out how to convert the subtitle stream.

[Cigaes]

You are explicitly telling it not to automatically select codecs by writing -c copy.

[slhck]

With recent ffmpeg (testing 3.2.4 here), the error message now says:

$ ffmpeg -i video.mp4 -i subtitles.srt -c:v copy -c:a copy -map 0 -map 1 output.mp4
…
Automatic encoder selection failed for output stream #0:2. Default encoder for format mp4 (codec none) is probably disabled. Please choose an encoder manually. Error selecting an encoder for stream 0:2

When using -c:s mov_text, the encoded video plays fine in QuickTime now. And #1845 seems to be fixed anyway.

So the mov_text codec autoselection for MOV/MP4 could now be implemented.

[domifm]

It's not as simple as using -c:s mov_text because there are other subtitle streams of other types that I want to keep.

If it could autoselect the codec when using -map 0 -c:v copy -c:a copy that would be great. Otherwise it is hard to batch convert files that have different numbering of the streams since each file has to be inspected and the stream numbers tailored.

[slhck]

If it could autoselect the codec when using -map 0 -c:v copy -c:a copy that would be great.

That's what it would do anyway.

If you do not specify -map 0 it will only take the first subtitle stream and re-encode it. (Or as currently implemented, not re-encode it, but fail.)

there are other subtitle streams of other types that I want to keep.

Then you need to specify -c:s:1 copy or whatever the stream index of the subtitle stream you want copied is.

[colemarc]

Six years after this issue is still present.

ffmpeg -i vidaud.mp4 -i subs.srt -map 0 -map 1 -c:v copy -c:a copy output.mp4
ffmpeg version 2022-11-28-git-becbb22eb0-full_build-www.gyan.dev Copyright (c) 2000-2022 the FFmpeg developers
[...]
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'vidaud.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf59.34.102
  Duration: 00:00:47.51, start: 0.000000, bitrate: 11153 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 1620x1080 [SAR 1:1 DAR 3:2], 11020 kb/s, 24 fps, 24 tbr, 90k tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
  Stream #0:2[0x3](und): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s (default)
    Metadata:
      handler_name    : SubtitleHandler
Input #1, srt, from 'subs.srt':
  Duration: N/A, bitrate: N/A
  Stream #1:0: Subtitle: subrip
Automatic encoder selection failed for output stream #0:2. Default encoder for format mp4 (codec none) is probably disabled. Please choose an encoder manually.
Error selecting an encoder for stream 0:2