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• adaptive compression with ffmpeg

  3 février 2016, par paunescuionica

  I’m currently developing an application which will enable visualizing images from different sources (mostly IP cameras) in browser (in a HTML5 video element). The UI will allow for matrix view so, normally 16 or more cameras will be displayed at the same time.
  From cameras I get MJPEG streams or JPEG images (which I "convert" to MJPEG streams). So, for a camera, I have an MJPEG stream which I set as input for ffmpeg. I instruct ffmpeg to convert this to MP4 & H.264, and expose the output as a tcp stream, like this :

  ffmpeg -f mjpeg -i "http://localhost/video.mjpg" -f mp4 -vcodec libx264 "tcp ://127.0.0.1:5001 ?listen"

  This works just fine on localhost, I get the stream displayed in the web page, at best quality.

  But this has to work in various network conditions. I played a bit with chrome throttling settings, and noticed that if the network speed is just a bit below the required speed (given by the current compression settings I use in ffmpeg), the things start to go wrong : from stream start being delayed (so, no longer a live stream), up to complete freeze of ’live’ image in browser.

  What I need is an "adaptive" way to do the compression, in relation with current network speed.

  My questions are :

  • is ffmpeg able to handle this, to adapt to network conditions - automatically reduce compression quality when speed is low ; so the image in browser will be lower quality, but live (which is most important in my case)

  • if not, is there a way to workaround this ?

  • is there a way to detect the network bottleneck ? (and then restart ffmpeg with lower compression parameters ; this is not a dynamic adaptive streaming, but better than nothing)

  Thank you in advance !

• alac : Reject rice_limit 0 if compression is used

  24 avril 2015, par Andreas Cadhalpun

  alac : Reject rice_limit 0 if compression is used
  If in compression mode rice_limit = 0 leads to call
  
  `show_bits(gb, k)` in `decode_scalar` with k = 0.
  Request a sample in case it is valid and it should be accepted.
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  CC : libav-stable@libav.org
  

  • [DBH] libavcodec/alac.c

• ffmpeg video compression / specifc file size

  16 mars 2015, par jesders88

  Currently I have 80mb movies that I want to use ffmpeg to convert down to say about 10mb or 15mb. I know there will be a quality loss but they will need to have sound. Is there a way to either specify a file size or higher compression than what I have done previously

  ffmpeg -i movie.mp4 -b 2255k -s 1280x720 movie.hd.ogv

  They are currently about 25mb a piece