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• reading video mpegts stream from stdin using libavformat libavcodec

  1er février 2012, par D Starkweather

  I'm trying to read video frames from stdin using ffmpeg's libav* lib collection. Simply passing "pipe:0" or "pipe :" as the filename to avformat_open_input_file() in my program does not do the trick. (e.g. cat /dev/video0 | ./myprogram OR ./myprogram < /dev/video0 ; it also fails using file.avi in place of /dev/video0).

  Peeking into ffmpeg.c, I find the following bit of code using tcsetattr() to set the termios :

  struct termios tty;
  
  
  
  if (tcgetattr (0, &tty) == 0) {
  
  oldtty = tty;
  
  restore_tty = 1;
  
  atexit(term_exit);
  
  
  
  tty.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP
  
                        |INLCR|IGNCR|ICRNL|IXON);
  
  tty.c_oflag |= OPOST;
  
  tty.c_lflag &= ~(ECHO|ECHONL|ICANON|IEXTEN);
  
  tty.c_cflag &= ~(CSIZE|PARENB);
  
  tty.c_cflag |= CS8;
  
  tty.c_cc[VMIN] = 1;
  
  tty.c_cc[VTIME] = 0;
  
  
  
  tcsetattr (0, TCSANOW, &tty);
  
  }
  
  signal(SIGQUIT, sigterm_handler); /* Quit (POSIX).  */
  
  }
  
  
  
  avformat_network_deinit();
  
  
  
  signal(SIGINT , sigterm_handler); /* Interrupt (ANSI).    */
  
  signal(SIGTERM, sigterm_handler); /* Termination (ANSI).  */
  
  signal(SIGXCPU, sigterm_handler);

  However, when I try this, it appears to have no effect. What settings do I need in the termios struct to continuously read video frames in ?

  Currently, all i am able to do is call av_read_frames a few times (return code 0) before it usually either segfaults or hangs waiting. The buffer usually contains just a blank screen (all black). With any luck, the video buffer will contain the first video frame it comes across, but does not update to the later frames.

  (I'm running this on Debian 6.0) Here's my version of ffmpeg :

  ffmpeg version N-36936-g4cf81d9 Copyright (c) 2000-2012 the FFmpeg
  developers built on Jan 19 2012 20:51:47 with gcc 4.4.5
  configuration : —enable-shared —enable-gray —enable-hardcoded-tables
  —enable-runtime-cpudetect —enable-libmp3lame —enable-libopenjpeg —enable-librtmp —enable-libtheora —enable-libvorbis —enable-libx264 —enable-libxvid —enable-zlib —enable-gpl libavutil 51. 34.101 / 51. 34.101 libavcodec 53. 57.100 /
  53. 57.100 libavformat 53. 30.100 / 53. 30.100 libavdevice 53. 4.100 / 53. 4.100 libavfilter 2. 59.101 / 2. 59.101 libswscale 2. 1.100 / 2. 1.100 libswresample 0. 6.100 /
  0. 6.100 libpostproc 52. 0.100 / 52. 0.100 Hyper fast Audio and Video encoder usage : ffmpeg [options] [[infile options] -i
  infile].

  Thank you very much for any help helpful tips. It is much appreciated.

  D. Grant Starkweather

• ffmpeg - find segments without audio

  21 juillet 2018, par OK200

  How to can find segments where the audio is not present using ffmpeg or sox or any other tool.

  when the video is played using player i’m getting decode error, so i need to analyse the source file. Please refer https://github.com/videojs/mux.js/issues/194

  ---

  Navigate to https://v2-4-0-dot-shaka-player-demo.appspot.com/demo/#asset=https://s3-ap-southeast-1.amazonaws.com/learnyst/testfolder/sample/expresshls/hls.m3u8 ;play and start playback.

  For the first 2 segments (https://s3-ap-southeast-1.amazonaws.com/learnyst/testfolder/sample/expresshls/zh3il5009f-yxhbaADHqLeCAo3k.ts and https://s3-ap-southeast-1.amazonaws.com/learnyst/testfolder/sample/expresshls/ZtV37gCCgR5cnwUrQliZEPG9zIU.ts) the callbacks get invoked, but not for the third one (https://s3-ap-southeast-1.amazonaws.com/learnyst/testfolder/sample/expresshls/X3cf3WEJqIG6EfX0Yjq8dvGthAc.ts) although they are present in the transmuxer’s internal listeners collection.

  The code that registers the callbacks :

    this.muxTransmuxer_ = new muxjs.mp4.Transmuxer({
  
      'keepOriginalTimestamps': true
  
    });
  
  
  
    this.muxTransmuxer_.on('data', this.onTransmuxed_.bind(this));
  
    this.muxTransmuxer_.on('done', this.onTransmuxDone_.bind(this));

  It looks like the 3rd segment does not contain any audio data, but the PMT says there is an audio track. Because of this code here https://github.com/videojs/mux.js/blob/master/lib/mp4/transmuxer.js#L1110 the transmuxer is waiting for audio data that is never coming.

  I need to find all the audio segments has data, is it possible to get the stats using ffmpeg or sox

• doc : add adpcm_ima_{ssi,apm}

  23 février 2020, par Zane van Iperen

  doc : add adpcm_ima_ssi,apm
  Signed-off-by : Zane van Iperen <zane@zanevaniperen.com>
  

  • [DH] doc/general.texi