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• How does FFmpeg determine the dispositions of an MP4 track ?

  5 mars, par obskyr

  The Issue

  


  FFmpeg has a concept of “dispositions” – a property that describes the purpose of a stream in a media file. For example, here are the streams in a file I have lying around, with the dispositions emphasized :

  


    Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo,&#xA;fltp, 251 kb/s <strong><em>(default)</em></strong>&#xA;      Metadata:&#xA;        creation_time   : 2021-11-10T20:14:06.000000Z&#xA;        handler_name    : Core Media Audio&#xA;        vendor_id       : [0][0][0][0]&#xA;&#xA;  Stream #0:1[0x2](und): Video: mjpeg (Baseline) (jpeg / 0x6765706A),&#xA;yuvj420p(pc, bt470bg/unknown/unknown), 1024x1024, 0 kb/s, 0.0006 fps, 3.08 tbr,&#xA;600 tbn <strong><em>(default) (attached pic) (timed thumbnails)</em></strong>&#xA;      Metadata:&#xA;        creation_time   : 2021-11-10T20:14:06.000000Z&#xA;        handler_name    : Core Media Video&#xA;        vendor_id       : [0][0][0][0]&#xA;&#xA;  Stream #0:2[0x3](und): Data: bin_data (text / 0x74786574)&#xA;      Metadata:&#xA;        creation_time   : 2021-11-10T20:14:06.000000Z&#xA;        handler_name    : Core Media Text&#xA;&#xA;  Stream #0:3[0x0]: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/&#xA;unknown), 1024x1024 [SAR 144:144 DAR 1:1], 90k tbr, 90k tbn <strong><em>(attached pic)</em></strong>

  


  However, if I make any modification to this file’s chapter markers using the C++ library MP4v2 (even just re-saving the existing ones : auto f = MP4Modify("test.m4a"); MP4Chapter_t* chapterList; uint32_t chapterCount; MP4GetChapters(f, &chapterList, &chapterCount); MP4SetChapters(f, chapterList, chapterCount); MP4Close(f);), some of these dispositions are removed :

  


    Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo,&#xA;fltp, 251 kb/s <strong><em>(default)</em></strong>&#xA;      Metadata:&#xA;        creation_time   : 2021-11-10T20:14:06.000000Z&#xA;        handler_name    : Core Media Audio&#xA;        vendor_id       : [0][0][0][0]&#xA;&#xA;  Stream #0:1[0x2](und): Video: mjpeg (Baseline) (jpeg / 0x6765706A),&#xA;yuvj420p(pc, bt470bg/unknown/unknown), 1024x1024, 0 kb/s, 0.0006 fps, 3.08 tbr,&#xA;600 tbn <strong><em>(default)</em></strong> <kbd>← “attached pic” and “timed thumbnails” removed!</kbd>&#xA;      Metadata:&#xA;        creation_time   : 2021-11-10T20:14:06.000000Z&#xA;        handler_name    : Core Media Video&#xA;        vendor_id       : [0][0][0][0]&#xA;&#xA;  Stream #0:2[0x0]: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/&#xA;unknown), 1024x1024 [SAR 144:144 DAR 1:1], 90k tbr, 90k tbn <strong><em>(attached pic)</em></strong>&#xA;&#xA;  Stream #0:3[0x4](und): Data: bin_data (text / 0x74786574)&#xA;  <kbd>This stream was moved to the end, but that’s intended behavior. It contains chapter titles, and we just edited the chapters.</kbd>&#xA;      Metadata:&#xA;        creation_time   : 2025-03-05T09:56:31.000000Z

  


  It also renders the file unplayable in MPC-HC (but not in VLC !), which is apparently a bug in MP4v2. I’m currently investigating that bug to report and potentially fix it, but that’s a separate issue – in my journey there, I’m wracking my brain trying to understand what it is that MP4v2 changes to make FFmpeg stop reporting the “attached pic” and “timed thumbnails” dispositions. I’ve explored the before-and-afters in MP4 Box, and I can’t for the life of me find which atom it is that differs in a relevant way.

  


  (I’d love to share the files, but unfortunately the contents are under copyright – if anyone knows of a way to remove the audio from an MP4 file without changing anything else, let me know and I’ll upload dummied-out versions. Without them, I can’t really ask about the issue directly. I can at least show you the files’ respective atom trees, but I’m not sure how relevant that is.)

  


  The Question

  


  I thought I’d read FFmpeg’s source code to find out how it determines dispositions for MP4 streams, but of course, FFmpeg is very complex. Could someone who’s more familiar with C and/or FFmpeg’s codebase help me sleuth out how FFmpeg determines dispositions for MP4 files (in particular, “attached pic” and “timed thumbnails”) ?

  


  Some Thoughts…

  


  

  • I figure searching for “attached_pic” might be a good start ?

  


  • Could the MP4 muxer movenc.c be helpful ?

  


  • I’d imagine what we’d really like to look at is the MP4 demuxing process, as it’s during demuxing that FFmpeg determines dispositions from the data in the file. After poring over the code for hours, however, I’ve been utterly unable to find where that happens.

  


  


• flutter_ffmpeg is discontinued with no alternatives ?

  13 mars, par Rageh Azzazy

  Based on this article by Taner Sener
https://tanersener.medium.com/saying-goodbye-to-ffmpegkit-33ae939767e1

  


  and after the discontinuation of flutter_ffmpeg and ffmpeg_kit_flutter packages.

  


  most packages for executing video editing commands were built depending on them and so won't work After April 1, 2025 as mentioned in the package documentation and Taner's article.

  


  example of packages depending on flutter_ffmpeg or ffmpeg_kit_flutter like

  


  

  • video_trimmer

  


  • zero_video_trimmer

  


  • flutter_video_trimmer

  


  • video_trim

  


  • bemeli_compress

  


  • video_trimmer_pro

  


  • ... others

  


  


  and editing video using video_editor or video_editor_2 or video_editor_pits has become a problem

  


  and I believe downloading the binaries and doing the whole thing locally is not just tedious but illegal as well.

  


  so I broke down exactly what I need to edit videos in my flutter app

  


  and I found those package but not yet tested them

  


  Trimming : flutter_native_video_trimmer

  


  Compression : video_compress or video_compress_plus

  


  Muting : video_compress handles this

  


  Encoding : Not sure, I just need a simple MP4 video files

  


  Cropping : I can't find a solution for video cropping

  


  I don't need to rotate, reverse or do any fancy stuff to the videos, just those five functions.

  


  so now only remaining solution for this approach is to find a simple video cropping function and an encoder that work on flutter IOS & Android

  


  so my question is not looking for external library recommendation but
do you have any ideas how to crop a video in flutter natively ?

  


• ffmpeg throws error "Invalid file index 1 in filtergraph description" when used with concat and -/filter_complex [closed]

  20 février, par Ernst V

  I want to create mp4 videos from many small .jpg files (time-lapse). Each image is shown for 2 seconds and then fades to the next. This works fine when I issue the command with a few images (see below). But when the number of images reaches hundreds or thousands, I can no longer put them into a single command, but have to put the filenames and the complex filter into .txt files.

  


  Whatever I try, I always get the error "Invalid file index 1 in filtergraph description".

  


  This works fine :

  


  ffmpeg -loop 1 -i "image1.jpg" -loop 1 -i "image2.jpg" -loop 1 -i "image3.jpg" -loop 1 -i "image4.jpg" -loop 1 -i "image5.jpg" -filter_complex "[0:v]trim=0:2,setpts=PTS-STARTPTS[v0]; [1:v]trim=0:2,setpts=PTS-STARTPTS[v1]; [2:v]trim=0:2,setpts=PTS-STARTPTS[v2]; [3:v]trim=0:2,setpts=PTS-STARTPTS[v3]; [4:v]trim=0:2,setpts=PTS-STARTPTS[v4]; [v0][v1] xfade=transition=fade:duration=1:offset=1 [xf1]; [xf1][v2] xfade=transition=fade:duration=1:offset=2 [xf2]; [xf2][v3] xfade=transition=fade:duration=1:offset=3 [xf3]; [xf3][v4] xfade=transition=fade:duration=1:offset=4 [xf4]" -map "[xf4]" -c:v libx264 -crf 18 -pix_fmt yuv420p output.mp4


  


  But when I put the input files and the filter in txt files, it fails with the error above :

  


  ffmpeg -stream_loop 1 -f concat -safe 0 -i concat_list.txt -/filter_complex filter_script.txt -map "[xf4]" -c:v libx264 -crf 18 -pix_fmt yuv420p output.mp4


  


  This is the concat_list.txt :

  


  file 'image1.jpg'
file 'image2.jpg'
file 'image3.jpg'
file 'image4.jpg'
file 'image5.jpg'


  


  This is the filter_script.txt :

  


  [0:v]trim=0:2,setpts=PTS-STARTPTS[v0];[1:v]trim=0:2,setpts=PTS-STARTPTS[v1];[2:v]trim=0:2,setpts=PTS-STARTPTS[v2];[3:v]trim=0:2,setpts=PTS-STARTPTS[v3];[4:v]trim=0:2,setpts=PTS-STARTPTS[v4];[v0][v1] xfade=transition=fade:duration=1:offset=1 [xf1];[xf1][v2] xfade=transition=fade:duration=1:offset=2 [xf2];[xf2][v3] xfade=transition=fade:duration=1:offset=3 [xf3];[xf3][v4] xfade=transition=fade:duration=1:offset=4 [xf4]


  


  I tried adding/removing line breaks, semicolons, etc. Nothing helped.
Any idea what is going wrong here ? Thank you very much !

  


  My ffmpeg version is the most recent one :

  


  ffmpeg version 2025-02-17-git-b92577405b-full_build-www.gyan.dev