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• FFMPEG - frame PTS and DTS increasing faster than it should

  20 juillet 2022, par hi im Bacon

  I am pulling footage from an RTSP camera, standardising it, and then segmenting the footage for processing. I am standardising by reducing the resolution and setting the frame rate to 12 fps.

  


  I am encoding in the PTS times the wall time of each frame as the camera is a live source and I'd like to be able to know exactly when a frame is occurring (I'm not fussed that it's not going to be perfectly on, if it's all out by a second or two because of latency that is fine by me)

  


  FFMPEG is run from python subprocessing using the following command :

  


  command = [
    "ffmpeg", "-y",
    "-rtsp_transport", "tcp", URL,
    "-pix_fmt", "yuvj422p",
    "-c:v", "libx264", # Change the video codec to the kinesis required codec
    "-an", # Remove any audio channels
    "-vf", "scale='min(1280,iw)':'min(720,ih)':force_original_aspect_ratio=decrease",
    "-r", "12",
    "-vsync", "cfr",
    "-x264opts", "keyint=12:min-keyint=12",,
    "-f", "segment",  # Set the output format as chuncked segments
    "-segment_format", segment_format,  # Set each segments format E.G. matroska, mp4
    "-segment_time", str(segment_length),  # Set the length of the segment in seconds
    "-initial_offset", str(initial_pts_offset),
    "-strftime", "1",  # Use the strformat notication in naming of the video segements
    "{}/%Y-%m-%dT%H%M%S.{}".format(directory, extension)  # Define the name and location of the segments,
    '-loglevel', 'error'
]


  


  The problem I am having is that the timestamps of the frames increase at a faster than real time rate. The initial offset is set to the time that FFMPEG is kicked off, the frames received should always be less than right now. I am using a segment length of 30 seconds and after only 5 minutes, finished segments will have a start timestamp greater than the present wall time.

  


  The rate of increase looks around 3-4 times faster than it should.

  


  Why is this the case ? how can I avoid this ? is my understand of -r right ?

  


  I believed that -r drops extra frames, evens out the frame times creating new frames where needed, but not actually changing the perceived speed of the footage. The final frame time should not be greater than the segment length away from the first frame time.

  


  I have tried using a system (filter) that sets the PTS time according to the consumer wall time setpts='time(0)/TB' but this has led to quite choppy footage as the frames can be received/processed at different rates based on the connection.

  


  The quality of the segments is great, all the data is there... just getting the times right is seeming impossible.

  


• ClassX installation "codec not found" due to dependencies [migrated]

  25 mars 2014, par khateeb

  ClassX is an interactive lecture streaming system developed in the Electrical Engineering Department at Stanford University.
  Unlike conventional lecture capturing systems, ClassX requires very simple consumer-grade equipment and minimal human operation.

  I faced problems during installing it, I hope you have a solution.

  BTW : I successfully installed it 2 years ago, but now I think the problem as the dependencies and Ubuntu versions are different than the versions we used two years ago.

  Detailed description of the problem :

  • I'm using Ubuntu 12.04
  • I followed the instructions @ ClassX installation guide, and all steps till step 4 are successfully done (the encoder bin file generated).
  • When trying to encode the video using the classX web system, it shows the encoding completed after few seconds.However, there are no tiles generated.

  • I tried to execute the command at CX_log.txt, and the following error appears.

    mahmoud@Mahmoud-HP-Pavilion-dv5-Notebook-PC : $ sudo perl /var/www/ClassXWebSystem/system/publishers/web/actions/encode.pl "/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/lecSEven" "/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251" "/var/www/ClassXWebSystem/content/streaming/FALL_2013_2014/CS106A_FALL_2013_2014/lecSEven" "/var/www/ClassXWebSystem/system/publishers/bin" classx y n n
    [sudo] password for mahmoud :
    00068.jpg
    ..
    .
    00068.mp4
    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251/00068.mp4' :
    Metadata :
    major_brand : isom
    minor_version : 512
    compatible_brands : isomiso2avc1mp41
    encoder : Lavf52.39.0
    Duration : 00:02:30.05, start : 0.000000, bitrate : 8141 kb/s
    Stream #0.0(und) : Video : h264, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 8007 kb/s, 29.95 fps, 29.97 tbr, 2997 tbn, 59.94 tbc
    Stream #0.1(und) : Audio : aac, 44100 Hz, stereo, s16, 128 kb/s
    Output #0, mp4, to '/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251/stream0.mp4' :
    Stream #0.0 : Video : [0][0][0][0] / 0x0000, yuv420p, 640x360, q=32-36, 64 kb/s, 90k tbn, 14.99 tbc
    codec not found

• ClassX installation "codec not found" due to dependencies [migrated]

  25 mars 2014, par khateeb

  ClassX is an interactive lecture streaming system developed in the Electrical Engineering Department at Stanford University.
  Unlike conventional lecture capturing systems, ClassX requires very simple consumer-grade equipment and minimal human operation.

  I faced problems during installing it, I hope you have a solution.

  BTW : I successfully installed it 2 years ago, but now I think the problem as the dependencies and Ubuntu versions are different than the versions we used two years ago.

  Detailed description of the problem :

  • I’m using Ubuntu 12.04
  • I followed the instructions @ ClassX installation guide, and all steps till step 4 are successfully done (the encoder bin file generated).
  • When trying to encode the video using the classX web system, it shows the encoding completed after few seconds.However, there are no tiles generated.

  • I tried to execute the command at CX_log.txt, and the following error appears.

    mahmoud@Mahmoud-HP-Pavilion-dv5-Notebook-PC : $ sudo perl /var/www/ClassXWebSystem/system/publishers/web/actions/encode.pl "/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/lecSEven" "/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251" "/var/www/ClassXWebSystem/content/streaming/FALL_2013_2014/CS106A_FALL_2013_2014/lecSEven" "/var/www/ClassXWebSystem/system/publishers/bin" classx y n n
    [sudo] password for mahmoud :
    00068.jpg
    ..
    .
    00068.mp4
    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from ’/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251/00068.mp4’ :
    Metadata :
    major_brand : isom
    minor_version : 512
    compatible_brands : isomiso2avc1mp41
    encoder : Lavf52.39.0
    Duration : 00:02:30.05, start : 0.000000, bitrate : 8141 kb/s
    Stream #0.0(und) : Video : h264, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 8007 kb/s, 29.95 fps, 29.97 tbr, 2997 tbn, 59.94 tbc
    Stream #0.1(und) : Audio : aac, 44100 Hz, stereo, s16, 128 kb/s
    Output #0, mp4, to ’/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251/stream0.mp4’ :
    Stream #0.0 : Video : [0][0][0][0] / 0x0000, yuv420p, 640x360, q=32-36, 64 kb/s, 90k tbn, 14.99 tbc
    codec not found