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• vc1dec : redesign the intensity compensation

  24 avril 2013, par Michael Niedermayer

  vc1dec : redesign the intensity compensation
  The existing implementation had little to do with VC1.
  
  This could be implemented by adjusting the reference frames
  
  ithemselfs but that would make frame multi-threading difficult.
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/vc1.c
  • [DH] libavcodec/vc1.h
  • [DH] libavcodec/vc1dec.c

• FFMPEG DASH - Live Streaming a Sequence of MP3 Clips

  4 décembre 2018, par Daniel

  I am attempting to create a online radio application using FFMPEG - an audio only DASH stream.

  I have a directory of mp3 clips (all of the same bitrate and sample size) which I am encoding to the AAC format and outputting to a mpd.

  This is the current command I am working with to stream a single mp3 file :

  ffmpeg -re -i <input />.mp3 -c:a aac -use_timeline 1 -use_template 1 -window_size 5 -f dash <out>.mpd
  
  </out>

  (Input and output paths have been substituted for < input >.mp3 and < output >.mpd in this snippet)

  I am running a web server and have made the mpd accessible on it. I am testing the stream using VLC player at the moment.

  The problem :
  Well, the command works, but it will only work for one clip at a time. Once the next command is run immediately proceeding the completion of the first, VLC player will halt and I need to refresh the player to continue.

  I’m aiming for an uninterrupted stream wherein the clips play in sequence.
  I imagine the problem is that a new mpd is being created with no reference to the previous one, and what I ought to be doing is appending segments to the existing mpd - but I don’t know how to do that using FFMPEG.

  The question : Is there such a command to append segments to a previously existing mpd file in FFMPEG ? or am I coming at this problem all wrong ? Perhaps I should be using FFMPEG to format the clips into these segments, but then adjusting the mpd file manually.

  Any help or suggestions would be very much appreciated !

• Parallel transcoding with FFmpeg on M1 Mac

  27 août 2021, par Pushkar

  I'm trying to determine how effective an M1 Mac would be for transcoding video using FFmpeg (specifically resizing and adjusting bitrate). I can do single transcodes using a command like this :

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  ffmpeg -I in.mp4 -nostdin -c:v h264_videotoolbox -c:a copy -vf scale=1280:720 -b:v 8000k out.mp4


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  Now, when I run this, I can see the process in Activity Monitor, but it shows significant CPU use but 0% GPU use, although it's certainly using some form of hardware acceleration (using libx264 instead of h264_videotoolbox is much slower).

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  When I try running multiple processes concurrently, the timings suggest little evidence of parallel execution :

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  Test	Timing
  convert single test file	6.8s
  convert file 5 times sequentially	33.6s
  convert file 5 times in parallel	31.5s

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  Since the M1 chip is supposed to have 7 or 8 GPUs inside it, I expected to see quite good parallelism, so are there options which I'm missing which would :
  

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  1. ensure that the transcoding is actually running on the GPU ?

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  2. allow parallel execution across the multiple GPUs ?

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