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• C# library for audio resampling that has the same abilities as FFmpeg

  21 avril 2013, par Designation

  I have to use a pure C# solution for resampling audio, which can produce me the exact same results as FFmpeg's audio sampling can.

  FFmpeg first builds some kind of polyphase filter bank, and then uses that for the sampling process (sorry for the vague phrasing, but I'm not too familiar with this topic). According to this brief documentation, the initialization can be customized this way :

  AVResampleContext* av_resample_init(
  
      int     out_rate,
  
      int     in_rate,
  
      int     filter_length,
  
      int     log2_phase_count,
  
      int     linear,
  
      double  cutoff   
  
      )

  The parameters are :

  • out_rate : output sample rate
  • in_rate : input sample rate
  • filter_length : length of each FIR filter in the filterbank relative to the cutoff freq
  • log2_phase_count : log2 of the number of entries in the polyphase filterbank
  • linear : if 1 then the used FIR filter will be linearly interpolated between the 2 closest, if 0 the closest will be used
  • cutoff : cutoff frequency, 1.0 corresponds to half the output sampling rate

  I'd need to use a C# library that is configurable in the same depth. I've been trying to use NAudio (more specifically, its WaveFormatConversionStream class), but there, I could only set the input and output sample rates, so I didn't get the expected results.

  So, is there a C# lib that could resample with the same settings as FFmpeg can ? Or one that has almost all of these settings or similar ones ? Note : I need a C# solution, not a wrapper !

• how to write image with yuv420 format data with PIL or something like that

  16 avril 2021, par nathan wu

  I have a video with yuv420p pixel format. 
At first I tried to read each frame's bytes of it using pipe and pixel format as rgb24. And I used PIL to make image of it.
However, the frames read with format of rgb24 seem to lose a little bit of quality.

  



  Here is the command of reading frame with rgb24 pixel format :

  



      ffmpeg -y -i input.mp4 -vcodec rawvideo -pix_fmt rgb24 -an -r 25 -f rawvideo pipe:1
    frame_data = self.process.stdout.read(1920*1080*3)


  



  Then I tried to read it with yuv420p pixel format.

  



      ffmpeg -y -i input.mp4 -vcodec rawvideo -pix_fmt yuv420p -an -r 25 -f rawvideo pipe:1
    frame_data = self.process.stdout.read(1920*1080*3/2)


  



  One single frame includes half of the bytes of rgb24 frame. It is 3110400 bytes within a 1920*1080 yuv420p frame. I tossed these data into PIL :

  



      Image.frombytes('YCbCr', (1920, 1080), frame_data)


  



  but PIL raise an error of not enough image data.
I looked up the modes that PIL support to write from bytes, none of it is 12_bit pixels.
I also tried to transform the yuv data into rgb data, but it took a lot more time than before when is a long video to process.

  



  Am I doing something wrong ? Is there any way to write an image with raw yuv data without any transform ??

  


• avcodec/mips : Improve hevc uni-w horiz mc msa functions

  9 octobre 2017, par Kaustubh Raste

  avcodec/mips : Improve hevc uni-w horiz mc msa functions
  Load the specific destination bytes instead of MSA load and pack.
  
  Pack the data to half word before clipping.
  
  Use immediate unsigned saturation for clip to max saving one vector register.
  Signed-off-by : Kaustubh Raste <kaustubh.raste@imgtec.com>
  
  Reviewed-by : Manojkumar Bhosale <Manojkumar.Bhosale@imgtec.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/mips/hevc_macros_msa.h
  • [DH] libavcodec/mips/hevc_mc_uniw_msa.c