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• avcodec/nvenc : De-compensate aspect ratio compensation of DVD-like content.

  28 janvier 2015, par Philip Langdale

  avcodec/nvenc : De-compensate aspect ratio compensation of DVD-like content.
  For reasons we are not privy to, nvidia decided that the nvenc encoder
  
  should apply aspect ratio compensation to ’DVD like’ content, assuming that
  
  the content is not bt.601 compliant, but needs to be bt.601 compliant. In
  
  this context, that means that they make the following, questionable,
  
  assumptions :
  1) If the input dimensions are 720x480 or 720x576, assume the content has
  
  an active area of 704x480 or 704x576.
  2) Assume that whatever the input sample aspect ratio is, it does not account
  
  for the difference between ’physical’ and ’active’ dimensions.
  From, these assumptions, they then conclude that they can ’help’, by adjusting
  
  the sample aspect ratio by a factor of 45/44. And indeed, if you wanted to
  
  display only the 704 wide active area with the same aspect ratio as the full
  
  720 wide image - this would be the correct adjustment factor, but what if you
  
  don’t ? And more importantly, what if you’re used to ffmpeg not making this kind
  
  of adjustment at encode time - because none of the other encoders do this !
  And, what if you had already accounted for bt.601 and your input had the
  
  correct attributes ? Well, it’s going to apply the compensation anyway !
  
  So, if you take some content, and feed it through nvenc repeatedly, it
  
  will keep scaling the aspect ratio every time, stretching your video out
  
  more and more and more.
  So, clearly, regardless of whether you want to apply bt.601 aspect ratio
  
  adjustments or not, this is not the way to do it. With any other ffmpeg
  
  encoder, you would do it as part of defining your input paramters or
  
  do the adjustment at playback time, and there’s no reason by nvenc
  
  should be any different.
  This change adds some logic to undo the compensation that nvenc would
  
  otherwise do.
  nvidia engineers have told us that they will work to make this
  
  compensation mechanism optional in a future release of the nvenc
  
  SDK. At that point, we can adapt accordingly.
  Signed-off-by : Philip Langdale <philipl@overt.org>
  
  Reviewed-by : Timo Rothenpieler <timo@rothenpieler.org>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/nvenc.c

• Nginx with rtmp-module stalls between streams

  14 janvier 2015, par churchmf

  I’m experiencing some troubles using NGINX with rtmp-module as a media server. I wish to present a continuous video as a live stream (with up to 60 second latency). However, due to some hardware constraints, I am unable to stream directly from the device. Instead, I can save out X amount of seconds from the device’s buffer as an MP4. My solution has been to save X seconds of video from the device then stream that X seconds, rise and repeat. This has been working mostly well, except for stalls ( 20 seconds) in the stream between calls.

  I have searched far and wide for a solution to this however most of the people experiencing this problem have the collection of videos before starting the stream and can simply concatenate them.

  My running theory is that when a stream finishes, it does an unpublish event in NGINX followed by a timeout period. This prevents the NGINX server from receiving the next publish until the timeout period has expired. I have tried adjusting nginx.config values related to timeouts, respawns, restarts, and publish, but to no avail.

  Pseudocode :
  while true
   > capture X seconds of video to "output.mp4" (this takes less than 300ms)
   > stream the MP4 with FFMPEG (takes X seconds using -re)

  FFMPEG call :
  ffmpeg -re -i "output.mp4" -vcodec libx264 -preset veryfast -maxrate 2000k -bufsize 4000k -g 60 -acodec libmp3lame -b:a 128k -ac 2 -ar 44100 -f flv rtmp :/MYSERVER/live/output

  I am using JWPlayer client side to watch the video stream, however I experience similar issues using VLC.

  I have been trying to figure this out for a few days and I would appreciate any insight an expert to video streaming and NGINX can give. Thank you !

• ffserver configuration vs ffmpeg parameters

  7 janvier 2015, par bogdanioan.gabor

  I’m not understanding which is the priority when you’re setting movflags (and other parameters) in the ffmpeg, but also into the ffserver.
  Example :

  I have the ffserver configuration like that :

  Port 8080
  
  BindAddress 0.0.0.0
  
  MaxHTTPConnections 10
  
  MaxClients 10
  
  MaxBandwidth 40000
  
  
  
  <feed>
  
      File /tmp/feed.ffm
  
      Feed feed.ffm
  
  
  
      VideoCodec libx264
  
      AVOptionVideo flags +global_header
  
      AVOptionVideo movflags faststart+frag_key_frame+empty_moov
  
  
  
      NoAudio
  
  </feed>

  And the ffmpeg command :

  ffmpeg -rtsp_transport tcp -i "rtsp://x.x.x.x" -an -vcodec copy -movflags faststart+frag_keyframe+empty_moov "http://127.0.0.1:8080/feed.ffm"

  Questions :
  1. Which one has precedence : the parameters from the ffmpeg, or the one from ffserver.
  2. I’m using ffprobe for testing the stream which comes from ffserver. I’ve used faststart, but I’m still getting the "moov atom not found" error ; shouldn’t faststart flag move the moov atom to beginning ?

  More info :

  ffserver version :

  ffserver version 2.3.4 Copyright (c) 2000-2014 the FFmpeg developers
  
  built on Dec  4 2014 09:23:21 with gcc 4.8.2 (GCC) 20140120 (Red Hat 4.8.2-16)
  
  configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' --enable-bzlib --disable-crystalhd --enable-gnutls --enable-libass --enable-libcdio --enable-libdc1394 --disable-indev=jack --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-openal --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libx264 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-runtime-cpudetect
  
  libavutil      52. 92.100 / 52. 92.100
  
  libavcodec     55. 69.100 / 55. 69.100
  
  libavformat    55. 48.100 / 55. 48.100
  
  libavdevice    55. 13.102 / 55. 13.102
  
  libavfilter     4. 11.100 /  4. 11.100
  
  libavresample   1.  3.  0 /  1.  3.  0
  
  libswscale      2.  6.100 /  2.  6.100
  
  libswresample   0. 19.100 /  0. 19.100
  
  libpostproc    52.  3.100 / 52.  3.100

  ffmpeg version :

  ffmpeg version 2.3.4 Copyright (c) 2000-2014 the FFmpeg developers
  
  built on Dec  4 2014 09:23:21 with gcc 4.8.2 (GCC) 20140120 (Red Hat 4.8.2-16)
  
  configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' --enable-bzlib --disable-crystalhd --enable-gnutls --enable-libass --enable-libcdio --enable-libdc1394 --disable-indev=jack --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-openal --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libx264 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-runtime-cpudetect
  
  libavutil      52. 92.100 / 52. 92.100
  
  libavcodec     55. 69.100 / 55. 69.100
  
  libavformat    55. 48.100 / 55. 48.100
  
  libavdevice    55. 13.102 / 55. 13.102
  
  libavfilter     4. 11.100 /  4. 11.100
  
  libavresample   1.  3.  0 /  1.  3.  0
  
  libswscale      2.  6.100 /  2.  6.100
  
  libswresample   0. 19.100 /  0. 19.100
  
  libpostproc    52.  3.100 / 52.  3.100

  Thank you.