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• running multiple tasks (ffmpeg) at the same time in a django app

  23 novembre 2020, par Soufiane

  at the title says it, I made a django app that cuts and merge files with ffmpeg
while testing (me being the only user), it looks fine, but later when using the app from different browsers running tasks at the same time, looks like it's a queue of tasks and other users will wait for their turn,
what I'm thinking about is, is there a possibility to run multiple tasks simultaneously at the same time, like (screens on linux) under django framework ?
thanks a lot

  


• 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 !

• nv12 to rgb24 color misalignment issue

  5 octobre 2023, par Kostas Kourkounis

  NV12 pixel format conversion to RGB24 issue

  


  I use gpu decoding from ffmpeg. The AVFrames I get I have to converted to rgb24 (Bitmap). When I use sw_scale (nv12->bgr24) all colors are ok, but the left border show the following disterbunce.

  


  sw_scale conversion

  


  Is this issue familiar to anyone ? Anything for suggestion ?

  


  When I use custom conversion taken from project "PixelFormatConverter"

  


  I get the following result (border distortion, and color misalignment) :

  


  border distortion

  


  color misalignment

  


  Is these issues familiar to anyone ? Anything for suggestion ?

  


  After the conversion I create the bitmap and display it. For Bitmap creation I use the following :

  


  frame is AVFrame (NV12) taken from FFMPEG
int image_size = av_image_get_buffer_size(AV_PIX_FMT_BGR24, frame->width, frame->height, 32);

size_t sizeof_file_header = sizeof(BITMAPFILEHEADER);
size_t sizeof_info_header = sizeof(BITMAPINFOHEADER);

bmpheader.bfType = 0x4d42;
bmpheader.bfReserved1 = 0;
bmpheader.bfReserved2 = 0;
bmpheader.bfOffBits = sizeof_file_header + sizeof_info_header;
bmpheader.bfSize = bmpheader.bfOffBits + image_size;

bmpinfo.biSize = sizeof_info_header;
bmpinfo.biWidth = frame->width;
bmpinfo.biHeight = frame->height;
bmpinfo.biPlanes = 1;
bmpinfo.biBitCount = 24;
bmpinfo.biCompression = BI_RGB;
bmpinfo.biSizeImage = 0;
bmpinfo.biXPelsPerMeter = 0;
bmpinfo.biYPelsPerMeter = 0;
bmpinfo.biClrUsed = 0;
bmpinfo.biClrImportant = 0;

uint8_t* buffer = new uint8_t[bmpheader.bfSize];

memcpy(buffer, &bmpheader, sizeof_file_header);
memcpy(buffer + sizeof_file_header, &bmpinfo, sizeof_info_header);

NV12_TO_BGR24(frame->data[0], (buffer + (bmpheader.bfOffBits)), frame->width, frame->height);


  


  Can anyone spot the issue ?