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• avcodec/libvpxenc : Apply codec options to alpha codec context

  3 septembre 2021, par Adam Chelminski

  avcodec/libvpxenc : Apply codec options to alpha codec context
  When encoding yuva420 (alpha) frames, the vpx encoder uses a second
  
  vpx_codec_ctx to encode the alpha stream. However, codec options were
  
  only being applied to the primary encoder. This patch updates
  
  codecctl_int and codecctl_intp to also apply codec options to the alpha
  
  codec context when encoding frames with alpha.
  This is necessary to take advantage of libvpx speed optimizations
  
  such as 'row-mt' and 'cpu-used' when encoding videos with alpha.
  
  Without this patch, the speed optimizations are only applied to the
  
  primary stream encoding, and the overall encoding is just as slow
  
  as it would be without the options specified.
  Signed-off-by : Adam Chelminski <chelminski.adam@gmail.com>
  
  Signed-off-by : James Zern <jzern@google.com>
  

  • [DH] libavcodec/libvpxenc.c
  • [DH] libavcodec/version.h

• Prevent FFmpeg from closing when a named pipe has been read completely

  21 octobre 2019, par Werther Berselli

  I’m doing a C++ application for a university project that takes a video file (e.g. matroska) and using FFmpeg (embedding commands inside std::system() instructions) apply these steps :

  • Extract chunks of frames (e.g. 10 seconds per chunk) and chunks of .aac audio

  • Apply some filters to frames

  • Encode video chunk and audio chunk with x264 and send it to a listening client using RTSP. This step is achieved using two named pipes, one for video and one for audio.

  • Receive the stream into another process and play it using ffplay (on localhost or lan).

  I need to divide my stream in chunks because I need eventually to satisfy real-time constraints, so I can’t apply filters before to my entire input video file and only then start streaming to client.
  My primary problem here is that once FFmpeg has emptied the two pipes, it close ; but other chunks of video and audio have still to be piped and streamed. I need FFmpeg to listen to the pipes waiting for new data.

  In bash I achieved this with the following commands.

  Start to listen in a prompt for a RTSP stream :

  ffplay -rtsp_flags listen rtsp://127.0.0.1@127.0.0.1:8090

  Create a video named pipe and an audio named pipe :

  mkfifo video_pipe
  
  mkfifo audio_pipe

  Use this command to prevent FFmpeg to close when video pipe is emptied :

  exec 7<>video_pipe

  (it is sufficient to apply it to the pipe video and neither will the audio pipe give problems)

  Activate FFmpeg command

  ffmpeg -probesize 2147483647 -re -s 1280x720 -pix_fmt rgb24 -i pipe:0 -vsync 0 -i audio_pipe -r 25 -vcodec libx264 -crf 23 -preset ultrafast -f rtsp -rtsp_transport tcp rtsp://127.0.0.1@127.0.0.1:8090 < video_pipe

  And then feed the pipes in another prompt :

  cat audiochunk.aac > audio_pipe & cat frame*.bmp > video_pipe

  These commands work well using 3 prompts, then I tried them in C++ embedding commands in std::system() instructions (using different threads) ; everything works, but once ffmpeg command empty the video pipe (finishing first chunk), it closes.
  exec command seems to be uneffective here.
  How could I prevent FFmpeg from closing ?

  Two days struggling on that problem, viewing all possible internet solution. I hope I was clear despite a great headache, thanks for your suggestions in advance.

  UPDATE :
  My C++ code is something like this ; I putted it in a single function on a single thread, but it doesn’t change it’s behaviour.
  I’m on Ubuntu 18.04.2

  void CameraThread::ffmpegJob()
  
  {
  
      std::string strvideo_length, command, timing;
  
      long video_length, begin_chunk, end_chunk;
  
      int begin_h, begin_m, begin_s, end_h, end_m, end_s;
  
  
  
      command = "ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 " + Configurations::file_name;
  
      strvideo_length = execCmd(command.c_str());
  
      strvideo_length.pop_back(); // remove \n character
  
      video_length = strToPositiveDigit(strvideo_length);
  
  
  
      if(video_length == -1)
  
      {
  
          std::cout << "Invalid input file";
  
          return;
  
      }
  
  
  
      std::system("bash -c \"rm mst-temp/mst_video_pipe\"");
  
      std::system("bash -c \"rm mst-temp/mst_audio_pipe\"");
  
      std::system("bash -c \"mkfifo mst-temp/mst_video_pipe\"");
  
      std::system("bash -c \"mkfifo mst-temp/mst_audio_pipe\"");
  
      // Keep video pipe opened
  
      std::system("bash -c \"exec 7<>mst-temp/mst_video_pipe\"");
  
  
  
      std::string rtsp_url = "rtsp://" + Configurations::my_own_used_ip + "@" + Configurations::client_ip +
  
              ":" + std::to_string(Configurations::port + 1);
  
  
  
      command = "ffmpeg -probesize 2147483647 -re -s 1280x720 -pix_fmt rgb24 -i pipe:0 "
  
                "-i mst-temp/mst_audio_pipe -r 25 -vcodec libx264 -crf 23 -preset ultrafast -f rtsp "
  
                "-rtsp_transport tcp " + rtsp_url + " < mst-temp/mst_video_pipe &"; // Using & to continue without block on command
  
      std::system(command.c_str());
  
  
  
      begin_chunk = -1 * VIDEO_CHUNK;
  
      end_chunk = 0;
  
  
  
      // Extract the complete audio track
  
      command = "bash -c \"ffmpeg -i " + Configurations::file_name + " -vn mst-temp/audio/complete.aac -y\"";
  
      std::system(command.c_str());
  
  
  
      while(true)
  
      {
  
          // Define the actual video chunk (in seconds) to use, if EOF is reached, exit
  
          begin_chunk += (end_chunk - begin_chunk);
  
          if(begin_chunk == video_length)
  
              break;
  
          if(end_chunk + VIDEO_CHUNK <= video_length)
  
              end_chunk += VIDEO_CHUNK;
  
          else
  
              end_chunk += (video_length - end_chunk);
  
  
  
          // Set begin and end H, M, S variables
  
          begin_h = static_cast<int>(begin_chunk / 3600);
  
          begin_chunk -= (begin_h * 3600);
  
          begin_m = static_cast<int>(begin_chunk / 60);
  
          begin_chunk -= (begin_m * 60);
  
          begin_s = static_cast<int>(begin_chunk);
  
          end_h = static_cast<int>(end_chunk / 3600);
  
          end_chunk -= (end_h * 3600);
  
          end_m = static_cast<int>(end_chunk / 60);
  
          end_chunk -= (end_m * 60);
  
          end_s = static_cast<int>(end_chunk);
  
  
  
          // Extract bmp frames and audio from video chunk
  
          // Extract frames
  
          timing = " -ss " + std::to_string(begin_h) + ":" + std::to_string(begin_m) +
  
                  ":" + std::to_string(begin_s) + " -to " + std::to_string(end_h) +
  
                  ":" + std::to_string(end_m) + ":" + std::to_string(end_s);
  
          command = "bash -c \"ffmpeg -i " + Configurations::file_name + timing +
  
                  " -compression_algo raw -pix_fmt rgb24 mst-temp/frames/output%03d.bmp\"";
  
          std::system(command.c_str());
  
          // Extract audio
  
          command = "bash -c \"ffmpeg -i mst-temp/audio/complete.aac" + timing +
  
                  " -vn mst-temp/audio/audiochunk.aac -y\"";
  
          std::system(command.c_str());
  
  
  
          // Apply elaborations on audio and frames.........................
  
  
  
          // Write modified audio and frames to streaming pipes
  
          command = "bash -c \"cat mst-temp/audio/audiochunk.aac > mst-temp/mst_audio_pipe &amp; "
  
                    "cat mst-temp/frames/output*.bmp > mst-temp/mst_video_pipe\"";
  
          std::system(command.c_str());
  
      }
  
  }
  
  </int></int></int></int></int></int>

• ffmpeg Sound going out of sync with -concat or -ss

  6 août 2012, par Jared Glass

  I have a tool that spits out video from a 3D application and then concats the individual videos to make a sequence. But the sound seems to go out of sync in the sequence (the inividual files are fine) and it stutters in VLC and Quicktime. Windows media player seems to handle it bes to my supprise, yet it still goes out of sync. I have two senarios, one works and one doesn't but i need both working :

  Working :
  get already created out movs...

  convert to avi :
  os.system( ffmpeg + " -i C:\clip.mov -sameq -r 24 -y C:\clip.avi")

  concat to avi sequence :
  os.system( ffmpeg + ''' -i concat: C:\clip.avi|C:\clip1.avi|C:\clip2.avi -sameq -r 24 -y C:\sequence.avi''' )

  convert sequence to mov :
  os.system( ffmpeg + " -i C:\sequence.avi -sameq -r 24 -y C:\sequence.mov")

  Not Working :
  create individual avi's from 3D program...

  cut down to correct length :
  os.system(ffmpeg + " -i C:\clip.avi -sameq -r 24 -ss " + startTime + " -vframes " + totalFrames + " -y C:\clip.avi" )

  concat to avi sequence :
  os.system( ffmpeg + ''' -i concat: C:\clip.avi|C:\clip1.avi|C:\clip2.avi -sameq -r 24 -y C:\sequence.avi''' )

  convert sequence to mov :
  os.system( ffmpeg + " -i C:\sequence.avi -sameq -r 24 -y C:\sequence.mov")

  convert individual avi's to mov :
  os.system( ffmpeg + " -i C:\clip.avi-sameq -r 24 -y C:\clip.mov")

  Please let me know where I've gone wrong ?