ffprobe identifies caption track as subtitle

[Jerry Scoggins]

When I run the latest ffprobe on a QuickTime movie that contains a track of type 'clcp' the output from ffprobe says it's a subtitle track, which is incorrect. In QuickTime, Closed Captioning tracks have the type 'clcp', and Subtitle tracks have a type of 'sbtl' as documented in two sections of this page: ​https://developer.apple.com/library/mac/documentation/QuickTime/qtff/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-SW87

The terms Closed Captioning and Subtitles are often used interchangeable, probably due to the way they're presented to the user but they are actually quite different in most every other aspect.

For a good explanation of the differences between closed captioning and subtitle's, I would suggest Jason's overview at this URL: ​https://cpcweb.zendesk.com/entries/25142571-Closed-Captions-vs-Subtitles

If you need sample media, or additional details, please ask.

Thank you,
Jerry Scoggins

[Carl Eugen Hoyos]

Please provide a sample and the complete, uncut console output of ffmpeg -i yoursample to make this a valid ticket.

[Jerry Scoggins]

Was this an automated response? It's a little odd my keywords and component were cleared. Okay, I'll go make a movie for you.

[gjdfgh]

He always does this.

Is the issue here that ffmpeg usually always calls both subtitles and captions just "subtitles"?

[Carl Eugen Hoyos]

Did you find any ticket with your keywords?

[Jerry Scoggins]

Sorry, I didn't search for previous keywords. This is my first bug report to ffmpeg, so I didn't know what to expect.
It's certainly the case that caption tracks are called subtitles, but I don't know what subtitle tracks are called. I don't have a clip handy with a sbtl track, but I'll create a movie with both a caption and subtitle track, test with ffprobe, report and upload. Thank you.

[Carl Eugen Hoyos]

Please test with ffmpeg, only report ffprobe issues if they are unreproducible with ffmpeg.

The keyword for closed captions is cc, the keyword for subtitles is sub but you don't have to worry about it, I will set them once more information is available.

[Carl Eugen Hoyos]

Please reopen this ticket if you can provide a sample.

[Jerry Scoggins]

QT movie with c708 caption track

[Jerry Scoggins]

Caption file extracted from provided movie.

[Jerry Scoggins]

ffmpeg version N-64012-g61df081 Copyright (c) 2000-2014 the FFmpeg developers

built on Jun 16 2014 22:01:59 with gcc 4.8.3 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfi

g --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
e --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --
enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsox
r --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrw
benc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-
libxavs --enable-libxvid --enable-decklink --enable-zlib

libavutil 52. 89.100 / 52. 89.100
libavcodec 55. 67.100 / 55. 67.100
libavformat 55. 43.100 / 55. 43.100
libavdevice 55. 13.101 / 55. 13.101
libavfilter 4. 8.100 / 4. 8.100
libswscale 2. 6.100 / 2. 6.100
libswresample 0. 19.100 / 0. 19.100
libpostproc 52. 3.100 / 52. 3.100

[mov,mp4,m4a,3gp,3g2,mj2 @ 02d29100] Could not find codec parameters for stream 3 (Subtitle: none (c708 / 0x38303763), 7
20x480, 19 kb/s): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'ShortCaption.mov':

Metadata:

major_brand : qt
minor_version : 537199360
compatible_brands: qt
creation_time : 2014-06-17 20:21:29

Duration: 00:00:10.01, start: 0.000000, bitrate: 31164 kb/s

Stream #0:0(eng): Video: dvvideo (dvc / 0x20637664), yuv411p, 720x480 [SAR 8:9 DAR 4:3], 28771 kb/s, SAR 654:720 DA

R 109:80, 29.97 fps, 29.97 tbr, 2997 tbn, 29.97 tbc (default)

Metadata:

creation_time : 2014-06-17 20:21:29
handler_name : Apple Alias Data Handler
encoder : DV25 NTSC
timecode : 00:00:00:00

Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s (default)
Metadata:

creation_time : 2014-06-17 20:21:29
handler_name : Apple Alias Data Handler
timecode : 00:00:00:00

Stream #0:2(eng): Data: none (tmcd / 0x64636D74), 0 kb/s (default)
Metadata:

creation_time : 2014-06-17 20:21:29
handler_name : Apple Alias Data Handler
timecode : 00:00:00:00

Stream #0:3(eng): Subtitle: none (c708 / 0x38303763), 720x480, 19 kb/s (default)
Metadata:

creation_time : 2014-06-17 21:22:04
handler_name : Apple Alias Data Handler

At least one output file must be specified

[Jerry Scoggins]

Sorry, here's the output from ffmpeg (instead of ffprobe). BTW, movie is now attached.
Jerry

ffmpeg version N-64012-g61df081 Copyright (c) 2000-2014 the FFmpeg developers

built on Jun 16 2014 22:01:59 with gcc 4.8.3 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfi

g --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
e --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --
enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsox
r --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrw
benc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-
libxavs --enable-libxvid --enable-decklink --enable-zlib

libavutil 52. 89.100 / 52. 89.100
libavcodec 55. 67.100 / 55. 67.100
libavformat 55. 43.100 / 55. 43.100
libavdevice 55. 13.101 / 55. 13.101
libavfilter 4. 8.100 / 4. 8.100
libswscale 2. 6.100 / 2. 6.100
libswresample 0. 19.100 / 0. 19.100
libpostproc 52. 3.100 / 52. 3.100

[mov,mp4,m4a,3gp,3g2,mj2 @ 02d29100] Could not find codec parameters for stream 3 (Subtitle: none (c708 / 0x38303763), 7
20x480, 19 kb/s): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'ShortCaption.mov':

Metadata:

major_brand : qt
minor_version : 537199360
compatible_brands: qt
creation_time : 2014-06-17 20:21:29

Duration: 00:00:10.01, start: 0.000000, bitrate: 31164 kb/s

Stream #0:0(eng): Video: dvvideo (dvc / 0x20637664), yuv411p, 720x480 [SAR 8:9 DAR 4:3], 28771 kb/s, SAR 654:720 DA

R 109:80, 29.97 fps, 29.97 tbr, 2997 tbn, 29.97 tbc (default)

Metadata:

creation_time : 2014-06-17 20:21:29
handler_name : Apple Alias Data Handler
encoder : DV25 NTSC
timecode : 00:00:00:00

Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s (default)
Metadata:

creation_time : 2014-06-17 20:21:29
handler_name : Apple Alias Data Handler
timecode : 00:00:00:00

Stream #0:2(eng): Data: none (tmcd / 0x64636D74), 0 kb/s (default)
Metadata:

creation_time : 2014-06-17 20:21:29
handler_name : Apple Alias Data Handler
timecode : 00:00:00:00

Stream #0:3(eng): Subtitle: none (c708 / 0x38303763), 720x480, 19 kb/s (default)
Metadata:

creation_time : 2014-06-17 21:22:04
handler_name : Apple Alias Data Handler

At least one output file must be specified

[Timothy Gu]

FFmpeg does not distinguish subtitles from captioning internally. Therefore, in real life caption may be not = subtitles, in FFmpeg the handling for captions = handling for subtitles.

For example, EIA/CEA-608 has a dedicated CODEC_ID assigned to it, and it is considered a subtitle in the ​codec descriptions. We do not have a dedicated CODEC_ID for CEA-708 yet, but we will not distinguish it from subtitles either.