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• apedec : do not buffer decoded samples over AVPackets

  27 août 2013, par Rafaël Carré

  apedec : do not buffer decoded samples over AVPackets
  Only consume an AVPacket when all the samples have been read.
  When the rate of samples output is limited (by the default value
  
  of max_samples), consuming the first packet immediately will cause
  
  timing problems :
   The first packet with PTS 0 will output 4608 samples and be
  
  consumed entirely
  
   The second packet with PTS 64 will output the remaining samples
  
  (typically, a lot, that’s why max_samples exist) until the decoded
  
  samples of the first packet have been exhausted, at which point the
  
  samples of the second packet will be decoded and output when
  
  av_decode_frame is called with the next packet).
  That means there’s a PTS jump since the first packet is ’decoded’
  
  immediately, which can be seen with avplay or mplayer : the timing
  
  jumps immediately to 6.2s (which is the size of a packet).
  Sample : http://streams.videolan.org/issues/6348/Goldwave-MAClib.ape
  
  Signed-off-by : Justin Ruggles <justin.ruggles@gmail.com>
  

  • [DBH] libavcodec/apedec.c

• Running PowerShell command in Universal Windows Platform C#

  6 juin 2017, par stephen

  So I am trying to write a basic application to cut and export a subsection of a video. I have come across (and decided to use) the FFMPEG command line tools to do the cropping. This seemed straight forward (https://stackoverflow.com/a/5047426/6728859), but Universal Windows apps do not support System.Diagnostics.Process. Instead, it was suggested that they do support Powershell, which means I could do it by following (https://blogs.msdn.microsoft.com/kebab/2014/04/28/executing-powershell-scripts-from-c/). However, I get the following errors

  Cannot find type System.SystemException in module CommonLanguageRuntimeLibrary

  Cannot resolve Assembly or Windows Metadata file 'System.Configuration.Install.dll'

  From my limited understanding System.SystemException was removed in UWP, and I’m not sure where to find System.Configuration.Install.dll.

  Now to get PowerShell I had to include System.Management.Automation which I got from C:\Program Files (x86)\Reference Assemblies\Microsoft\WindowsPowerShell\3.0 which doesn’t seem correct to me, but I could be wrong.

  Is it possible to run commands in a UWP, or does anyone have any suggestions ?

• How to process video stream ?

  27 avril 2016, par sharpener

  I would like to ask some experienced multimedia professional how to proceed with following task :

  Given URL provides video stream and we would like to get access to decoded frames (byte stream in memory) in managed Win7+ application (C#). We don’t want to render/present the frames the standard way. The video format is known but not fixed (might get changed between two successive sessions, but we will know the parameters).

  So far, I have found there are several methods and I have build following picture in my mind :

  1. ffmpeg wrapper
     • Pros
       1. Self contained (no dependency to windows technologies)
       2. Powerful
     • Cons
       1. Little more complex to understand
       2. Lot of different wrapping variants (FFmpeg.NET, ffmpeg-sharp, ffmpeg-shard, FFmpeg.AutoGen, ...)
  2. DirectShow wrapper
     • Pros
       1. Widely used/supported technology (variaous filters freely available)
       2. Nice/detailed documentation on MSDN
     • Cons
       1. Quite old
       2. Considered obsolete from the point of author’s view (available only for desktop model on runtime >= Win8)
  3. MediaFoundation wrapper
     • Pros
       1. Theoretical successor of DirectShow, so should be available in the future
     • Cons
       1. Seems to be not as good as DirectShow
       2. Not very popular, limited "community" support
  4. FFmpegInterop wrapper
     • Pros
       1. Microsoft’s open source wrapper alternative
     • Cons
       1. Not available for runtime < Win8