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• FFmpeg iOS av_read_frame() hangs on cellular connections

  8 novembre 2014, par Moss

  I am able to play an RTMP audio + video stream on iOS. Works fantastic when everything is on a solid WiFi connection.

  When I switch to a cellular connection (great signal strength and LTE/4G), av_read_frame() will intermittently block for an unacceptable amount of time. In some cases, I’ve clocked 30+ seconds of hang time before it moves on and grabs the next frame.

  I attempted a work-around by using the AVIOInterruptCB interrupt callback to abort av_read_frame() if the function takes longer than 1 second to return.

  This definitely aborts av_read_frame() after 1 second, but unfortunately after I do this, future attempts to call av_read_frame() result in EIO errors (-5), which indicates (to me) that the connection has been severed. So I am forced to reconnect with avformat_open_input() ( 3-4 seconds), and then find the stream info again ( 2-3 seconds), and then start reading frames again. This is much better than 10+ seconds of waiting around for the next frame, but it’s much worse than what I wish I could do, which is to just retry immediately and grab the next frame.

  That means, from a cellular user’s perspective, their video locks up intermittently for 5-10 seconds while we reconnect the stream in the background from scratch. Not a great user experience.

  Is there a better way to manage av_read_frame() on a lossy cellular connection ? Or at least improve the reconnect time ? Suggestions ?

• ffmpeg connection reset by peer

  8 mars 2015, par Quentin Spottiswoode

  I have a problem when using ffmpeg :

  quite often my clients will have slightly dodgy internet connections but they subscribe to a service which is designed to record a stream that they are hosting, and record it for hosting on something like a wordpress site.

  ffmpeg is called by a python script. I would like, ideally, to know if ffmpeg will throw an exception or return a value that can be accessed by the python script and used as a variable to determine if there was a problem recording the audio.

  at the moment python calls ffmpeg using :

  os.system('ffmpeg -i [stream address] -t 1:00 -acodec copy ')

  when I simulate a connection loss (turning off the NIC on the virtual machine) ffmpeg prints to the terminal

  Connection reset by peer

• avcodec/webp : validate the distance prefix code

  2 mars 2015, par Andreas Cadhalpun

  avcodec/webp : validate the distance prefix code
  According to the WebP Lossless Bitstream Specification the highest
  
  allowed value for a prefix code is 39.
  If prefix_code is too large, the calculated extra_bits has an invalid
  
  value and triggers an assertion in get_bits.
  Signed-off-by : Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/webp.c