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• Video transcoding during stream

  31 juillet 2017, par Wajahat

  I am trying to setup a testbed that will be used for experimentation, and I have deployed some VMs over Openstack and the setup looks like this currently :
  
  The far right machine is running Apache2 server and video is hosted in /var/www/html/videos folder. VNF1 and VNF2 machines are acting as intermediate routers with static routes configured to route traffic to Apache server machine.

  The client machine runs VLC player to stream video on-demand from the server over HTTP like this :

  vlc http://10.10.2.7/videos/bunny.mp4

  Now, I want to be able to do dynamic transcoding of video while it is being streamed, but I don’t want to do transcoding at server side (for experiment’s purpose the server is not in our control) neither at client side but somewhere in the middle machines (VNF1 for example) so that it is transparent to client.
  Basically, I want to implement video transcoder as a network function.

  I have found FFmpeg which I think should be able to get this done, ffmpeg-server for example allows streaming over HTTP, but I am not exactly sure how to use it for transcoding video traffic ?

• avfilter/af_headphone : Only attempt once to init coeffs

  25 août 2020, par Andreas Rheinhardt

  avfilter/af_headphone : Only attempt once to init coeffs
  The headphone filter does most of its initialization after its init
  
  function, because it can perform certain tasks only after all but its
  
  first input streams have reached eof. When this happens, it allocates
  
  certain buffers and errors out if an allocation fails.
  Yet the filter didn't check whether some of these buffers already exist
  
  (which may happen if an earlier attempt has been interrupted in the
  
  middle (due to an allocation error)) in which case the old buffers leak.
  This commit makes sure that initializing the buffers is only attempted
  
  once ; if not successfull at the first attempt, future calls to the
  
  filter will error out. Trying to support resuming initialization doesn't
  
  seem worthwhile.
  Notice that some allocations were freed before a new allocation was
  
  performed ; yet this effort was incomplete. Said code has been removed.
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavfilter/af_headphone.c

• ffmpeg_opt : restore documented stream selection behaviour

  28 juillet 2021, par Gyan Doshi

  ffmpeg_opt : restore documented stream selection behaviour
  11d3b03fcb added consideration of default stream disposition for audio
  
  and video when choosing the 'best' stream among all the inputs. This can
  
  lead to video streams with lower resolution or audio streams with fewer
  
  channels being selected.
  Stream disposition, however, only sets a priority for a stream
  
  among all other streams in the *same input*. It cannot set a priority
  
  for a stream across all inputs.
  This patch sets a middle-way and selects the best stream from each file
  
  with default disposition considered. Then it discards disposition weight
  
  and selects best stream as per the original criteria of highest
  
  resolution for video and most channels for audio.
  

  • [DH] fftools/ffmpeg_opt.c