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• Faster frame extraction than ffmpeg

  23 janvier 2013, par Ben Ford

  I have a video analytics program that processes assorted frames from a video. (Several hours long)
  The video is likely going to be an MP4 but may be other formats going forwards.

  At the moment, I have a C# wrapper around an ffmpeg call to extract an individual frame at the requested time. (I'm using the ffmpeg.exe binary. Not the libraries directly)
  At the moment, this all works. But it's slow. Very slow.

  I've found ways to improve the speed by storing the extracted frames in a ramdisk while they're being processed. Changing the stored image format etc...

  I just wanted to check if anyone could think of any way to pull individual frames out. At split-second accuracy.
  I know this is probably possible with DShow etc... I went straight to FFMPEG as I've used it before. But if DShow is likely to be faster I'll gladly change !

• How to process single segment from fragmented mp4 container ?

  14 septembre 2020, par user14258924

  I have fragmented mp4 that I stream. First the mp4 header and then individual segments that are each one GOP. It is h264 and aac encoded video that I am getting from RTMP server.

  


  I would like to process these individual segments with ffmpeg(I doubt there are other tools available). Either adjust resolution or bitrate or even transcode to vp8/9 or avi1 if needed.

  


  But it seems that ffmpeg cannot handle this because the segment has no header. So I wodner if there is a flag or set of flags for ffmpeg to be able to process these segments without the header ? I could possibly just take the raw h264 and aac packets from the RTMP and not pack it into MP4 container beforehand, if that helps - would ffmpeg be able to process these ?

  


• android chromecast mp4 by ffmpeg - shorter files play, some longer ones buffer but dont play

  20 octobre 2014, par Robert Rowntree

  Using Android SDK for CC, CCL, and ’styled receiver’ CC app.

  Video Files created by a heroku/ffmpeg bin that will play on any other client i tried (VLC ubuntu... ) and that will even play in chrome on a tab that’s being cast to chromecast will NOT PLAY natively on chromecast apps. They will appear as normal load in the UI of the app. CCL logs will show them buffering OK , but they never enter a play state from the buffering state. Debugging the receiver shows nothing unusual ( network tab, or Console ). They just buffer and dont play.

  If a slightly shorter version of the same , 2 ffmpeg input files is prepared and hosted, it seems to play fine in shorter versions under about 14 seconds long but will not play if a 16 second version is created.

  I used a number of chromecast apps including Allcast to test this. always got same result.

  2 dropbox mp4 links created with the ffmpeg cli here are below. A 14 second version of the output mp4 file plays fine on several Chromecast/android apps and a 16 second version fails.

  file len 14s

  file len 16s Wont play in CC apps

  ffprobe output on the files at :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'tst-nonplay-shorter_14s.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf54.29.105
  
    Duration: 00:00:14.07, start: 0.046440, bitrate: 311 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p, 1080x614 [SAR 1535:1539 DAR 100:57], 199 kb/s, 1 fps, 1 tbr, 16384 tbn, 2 tbc
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 22050 Hz, mono, s16, 110 kb/s
  
      Metadata:
  
        handler_name    : SoundHandler

  and the file 2 seconds longer that wont play

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'tst-nonplay-shorter_16s.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf54.29.105
  
    Duration: 00:00:16.06, start: 0.046440, bitrate: 286 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p, 1080x614 [SAR 1535:1539 DAR 100:57], 174 kb/s, 1 fps, 1 tbr, 16384 tbn, 2 tbc
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 22050 Hz, mono, s16, 110 kb/s
  
      Metadata:
  
        handler_name    : SoundHandler

  Used ’qtfaststart’ and checked for MOOV ATOM issues and dont think that’s relevant.

  I think i can limit recordings in my app to 14 seconds and avoid problems that way, but I would like to understand what is up with the chromecast GETS on MP4’s generated by ffmpeg.