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• avcodec/pnm : avoid mirroring PFM images vertically

  16 novembre 2022, par Leo Izen

  avcodec/pnm : avoid mirroring PFM images vertically
  PFM (aka Portable FloatMap) encodes its scanlines from bottom-to-top,
  
  not from top-to-bottom, unlike other NetPBM formats. Without this
  
  patch, FFmpeg ignores this exception and decodes/encodes PFM images
  
  mirrored vertically from their proper orientation.
  For reference, see the NetPBM tool pfmtopam, which encodes a .pam
  
  from a .pfm, using the correct orientation (and which FFmpeg reads
  
  correctly). Also compare ffplay to magick display, which shows the
  
  correct orientation as well.
  See : http://www.pauldebevec.com/Research/HDR/PFM/ and see :
  
  https://netpbm.sourceforge.net/doc/pfm.html for descriptions of this
  
  image format.
  Signed-off-by : Leo Izen <leo.izen@gmail.com>
  
  Reviewed-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/pnmdec.c
  • [DH] libavcodec/pnmenc.c
  • [DH] tests/ref/lavf/gbrpf32be.pfm
  • [DH] tests/ref/lavf/gbrpf32le.pfm
  • [DH] tests/ref/lavf/grayf32be.pfm
  • [DH] tests/ref/lavf/grayf32le.pfm

• Programmatically accessing PTS times in MP4 container

  9 novembre 2022, par mcandril

  Background

  


  For a research project, we are recording video data from two cameras and feed a synchronization pulse directly into the microphone ADC every second.

  


  Problem

  


  We want to derive a frame time stamp in the clock of the pulse source for each camera frame to relate the camera images temporally. With our current methods (see below), we get a frame offset of around 2 frames between the cameras. Unfortunately, inspection of the video shows that we are clearly 6 frames off (at least at one point) between the cameras.
I assume that this is because we are relating audio and video signal wrong (see below).

  


  Approach I think I need help with

  


  I read that in the MP4 container, there should be PTS times for video and audio. How do we access those programmatically. Python would be perfect, but if we have to call ffmpeg via system calls, we may do that too ...

  


  What we currently fail with

  


  The original idea was to find video and audio times as

  


  audio_sample_times = range(N_audiosamples)/audio_sampling_rate
video_frame_times = range(N_videoframes)/video_frame_rate


  


  then identify audio_pulse_times in audio_sample_times base, calculate the relative position of each video_time to the audio_pulse_times around it, and select the same relative value to the corresponding source_pulse_times.

  


  However, a first indication that this approach is problematic is already that for some videos, N_audiosamples/audio_sampling_rate differs from N_videoframes/video_frame_rate by multiple frames.

  


  What I have found by now

  


  OpenCV's cv2.CAP_PROP_POS_MSEC seems to do exactly what we do, and not access any PTS ...

  


  Edit : What I took from the winning answer

  


  container = av.open(video_path)
signal = []
audio_sample_times = []
video_sample_times = []

for frame in tqdm(container.decode(video=0, audio=0)):
    if isinstance(frame, av.audio.frame.AudioFrame):
        sample_times = (frame.pts + np.arange(frame.samples)) / frame.sample_rate
        audio_sample_times += list(sample_times)
        signal_f_ch0 = frame.to_ndarray().reshape((-1, len(frame.layout.channels))).T[0]
        signal += list(signal_f_ch0)
    elif isinstance(frame, av.video.frame.VideoFrame):
        video_sample_times.append(float(frame.pts*frame.time_base))

signal = np.abs(np.array(signal))
audio_sample_times = np.array(audio_sample_times)
video_sample_times = np.array(video_sample_times)


  


  Unfortunately, in my particular case, all pts are consecutive and gapless, so the result is the same as with the naive solution ...
By picture clues, we identified a section of 10s in the videos, somewhere in which they desync, but can't find any traces of that in the data.

  


• FFMPEG av_interleaved_write_frame() : Operation not permitted

  21 décembre 2020, par camslaz

  Ok I receiving a 'av_interleaved_write_frame() : Operation not permitted' error while trying to encode an MOV file. Firstly I need to outline the conditions behind it.

  



  I am encoding 12 different files of different resolution sizes and format types via a PHP script that runs on cron. Basically it grabs a 250mb HD MOV file and encodes it in 4 different frame sizes as MOV, MP4 and WMV file types.

  



  Now the script takes over 10mins to run and encode each of the files for the 250mb input file. I am outputting the processing times and as soon as the time on the script hits 10mins FFMPEG crashes and returns "av_interleaved_write_frame() : Operation not permitted" for the current file being encoded and all other remaining files yet to be encoded.

  



  If the input videos is 150MB the total time the script runs for is under 10mins so it encodes all of the videos fine. Additionally if I run the FFMPEG command on the individual file that it fails on for the 250mb file it encodes the file with no issues.

  



  From doing to research on the error "av_interleaved_write_frame()" it seems it is related to timestamps of what I understand to be of the input file. But in saying that it doesn't seem to be the case in my instance because I can encode the file with no problem if I do it individually.

  



  example ffmpeg command

  



  ffmpeg -i GVowbt3vsrXL.mov -s 1920x1080 -sameq -vf "unsharp" -y GVowbt3vsrXL_4.wmv


  



  Error output on the failed file at 10mins. Remember there is no issue with the command if I run it by itself it is only when the script hits 10mins.

  



  'output' =>
     array (
       0 => 'FFmpeg version SVN-r24545, Copyright (c) 2000-2010 the FFmpeg developers',
       1 => '  built on Aug 20 2010 23:32:02 with gcc 4.1.2 20080704 (Red Hat 4.1.2-48)',
       2 => '  configuration: --enable-shared --enable-gpl --enable-pthreads --enable-nonfree --cpu=opteron --extra-cflags=\'-O3 -march=opteron -mtune=opteron\' --enable-libmp3lame --enable-libx264 --enable-libxvid --enable-avfilter --enable-filter=movie --enable-avfilter-lavf --enable-swscale',
       3 => '  libavutil     50.23. 0 / 50.23. 0',
       4 => '  libavcore      0. 1. 0 /  0. 1. 0',
       5 => '  libavcodec    52.84. 1 / 52.84. 1',
       6 => '  libavformat   52.77. 0 / 52.77. 0',
       7 => '  libavdevice   52. 2. 0 / 52. 2. 0',
       8 => '  libavfilter    1.26. 1 /  1.26. 1',
       9 => '  libswscale     0.11. 0 /  0.11. 0',
       10 => 'Input #0, mov,mp4,m4a,3gp,3g2,mj2, from \'/home/hdfootage/public_html/process/VideoEncode/_tmpfiles/GVowbt3vsrXL/GVowbt3vsrXL.mov\':',
       11 => '  Metadata:',
       12 => '    major_brand     : qt',
       13 => '    minor_version   : 537199360',
       14 => '    compatible_brands: qt',
       15 => '  Duration: 00:00:20.00, start: 0.000000, bitrate: 110802 kb/s',
       16 => '    Stream #0.0(eng): Video: mjpeg, yuvj422p, 1920x1080 [PAR 72:72 DAR 16:9], 109386 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc',
       17 => '    Stream #0.1(eng): Audio: pcm_s16be, 44100 Hz, 2 channels, s16, 1411 kb/s',
       18 => '[buffer @ 0xdcd0e0] w:1920 h:1080 pixfmt:yuvj422p',
       19 => '[unsharp @ 0xe00280] auto-inserting filter \'auto-inserted scaler 0\' between the filter \'src\' and the filter \'Filter 0 unsharp\'',
       20 => '[scale @ 0xe005b0] w:1920 h:1080 fmt:yuvj422p -> w:1920 h:1080 fmt:yuv420p flags:0xa0000004',
       21 => '[unsharp @ 0xe00280] effect:sharpen type:luma msize_x:5 msize_y:5 amount:1.00',
       22 => '[unsharp @ 0xe00280] effect:none type:chroma msize_x:0 msize_y:0 amount:0.00',
       23 => 'Output #0, asf, to \'/home/hdfootage/public_html/process/VideoEncode/_tmpfiles/GVowbt3vsrXL/GVowbt3vsrXL_4.wmv\':',
       24 => '  Metadata:',
       25 => '    WM/EncodingSettings: Lavf52.77.0',
       26 => '    Stream #0.0(eng): Video: msmpeg4, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 1k tbn, 25 tbc',
       27 => '    Stream #0.1(eng): Audio: libmp3lame, 44100 Hz, 2 channels, s16, 64 kb/s',
       28 => 'Stream mapping:',
       29 => '  Stream #0.0 -> #0.0',
       30 => '  Stream #0.1 -> #0.1',
       31 => 'Press [q] to stop encoding',
       32 => '[msmpeg4 @ 0xdccb50] warning, clipping 1 dct coefficients to -127..127',


  



  Then it errors

  



  frame=   75 fps=  5 q=1.0 size=   12704kB time=2.90 bitrate=3588 6.0kbits av_interleaved_write_frame(): Operation not permitted',
     )


  



  Has any anybody encountered this sort of problem before ? It seems to be something to do with the timestamps but only because the script is running for a period longer then 10mins. It maybe related to PHP/Apache config but I don't know if it is FFMPEG or if it is server config I need to be looking at.