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• QtAV/ffmpeg youtube : bufferProgressChanged and positionChanged together

  11 décembre 2017, par Maignan Arnaud

  I’m trying to make a streaming tester with QtAV, under linux, mac and windows.
  Under these 3 systems, when I play a youtube video
  like :

  https://r3---sn-gx1v2vax-atne.googlevideo.com/videoplayback?initcwndbps=3892500&dur=12.208&signature=...

  The problem is :
  The player continues to change it’s position (timer) while it’s still buffering.
  I noticed this only with youTube videos (other video providers are working well) but it’s the one I need to implement.

  Reproduction steps :
  Compile ffmpeg with SSL, take Youtube URL (1080p) from raw page, bandwidth clamping to stalled your video, read this url with QtAV and output this player events :
  mediaStatusChanged, loaded, stateChanged, started, notifyIntervalChanged,
  bufferProgressChanged, positionChanged

  First bad solutions :
  Changing player config like setBufferValue, dont seems to solve my problem (but I may not have tried all possible combinations)

  m_player->setBufferMode(BufferMode::BufferTime);//BufferTime, BufferBytes, BufferPackets
  
  //m_player->setSeekType(SeekType::KeyFrameSeek);//AccurateSeek, KeyFrameSeek, AnyFrameSeek
  
  m_player->setBufferValue(1000);

  Searching to modify QtAV code source, seems complicated to me, but I noticed that void AVPlayer::timerEvent(QTimerEvent *te) have a lot of commented code and particularly, this comment below makes me think that maybe QtAV developper didn’t implement everything yet :

  qint64 AVPlayer::position() const
  
  {
  
      // TODO: videoTime()?
  
      const qint64 pts = d->clock->value()*1000.0;
  
      […]
  
  }

  Expected behavior :

  When bufferProgressChanged, the video must be paused, and replay only when buffer is 100%.
  For example, when mediaStatusChanged=BufferedMedia.
  So the event positionChanged should never change, unless the event bufferProgressChanged == 1 or 0

  Actual behavior :
  See complet logs file :
  https://github.com/wang-bin/QtAV/issues/1004

• FFMPEG : Encoding settings to meet YouTube recommendation.

  1er novembre 2016, par Dinindu Perera

  So I need to encode to meet these guidelines from YouTube for 480p and 1080p videos. I need help in the settings of FFMPEG. The video should encode reasonably fast.

  These are the guidelines :
  480p 30fps x264
  

  • Video Bitrate : 2560 kbps
  • Audio Bitrate : 384 kbps

  1080p 30fps x264
  

  • Video Bitrate : 8192 kbps
  • Audio Bitrate : 384 kbps

  I’m still learning the ropes with video encoding. Thanks in advance :)

• FFMPEG (Input 8K AAC -> (AAC FLV) youtube streaming noise

  17 septembre 2017, par Biswa Das

  Hello I run a streaming encoder for a non profit cause. Chosen FFMPEG as it’s very simple and doing the job near perfectly however the audio is noisy popping and cracking. Video is crystal clear.

  ffmpeg version N-86950-g1bef008 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 7.1.0 (GCC)

  Here is my command.

  ffmpeg -rtsp_transport tcp -i $RTSP_SRC -vcodec copy -af "volume=12dB" -ar 8000 -acodec aac -f flv rtmp://a.rtmp.youtube.com/live2/$DEST_KEY

  However when I just play the stream the noise levels are quite acceptable.

  ffplay -rtsp_transport tcp -i $RTSP_SRC

  What I have tried so far.

  • Change input audio sampling from 8K to 16K (that’s all is supported currently). It made the noise problem much worse. I can’t change it to a native FLV sampling(44100 or 22050 or 11025) at least not yet, the integrated rtsp stream does not support it.)
  • My working theory is during resampling stream noise is getting boosted. So to eliminate that I tried audio copy codec even then there is no significant improvement.