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• What is the best way to fill AVFrame.data

  21 septembre 2015, par Tim Hsu

  I want to transfer opengl framebuffer data to AVCodec as fast as possible.

  I’ve already converted RGB to YUV with shader and read it with glReadPixels

  I still need to fill AVFrame data manually. Is there any better way ?

  AVFrame *frame;
  
  // Y
  
  frame->data[0][y*frame->linesize[0]+x] = data[i*3];
  
  // U
  
  frame->data[1][y*frame->linesize[1]+x] = data[i*3+1];
  
  // V
  
  frame->data[2][y*frame->linesize[2]+x] = data[i*3+2];

• FFMPEG bottleneck in relaying data from a dshow camera to stdout PIPE without any processing or conversion

  19 août 2020, par koonyook

  I have a USB camera (FSCAM_CU135) that can encode the video to MJPEG internally and it supports DirectShow. My goal is to retrieve the binary stream of the encoded video as it is (without decoding or preview) and send it to my program for further processing.

  


  I choose to use FFMPEG to read the MJPEG stream and pipe to stdout so that I can read it using Python's subprocess.Popen .

  


  ffmpeg -y -f dshow -vsync 2 -rtbufsize 1000M -video_size 1920x1440 -vcodec mjpeg -i video="FSCAM_CU135" -vcodec copy -f mjpeg pipe:1


  


  At this resolution, the camera is able to capture and transmit at 60 fps.
In this case, I expect FFMPEG to pass the data as fast as possible with no calculation.
With the output of FFMPEG I can tell how fast it moves the data from rtbuffer to the output pipe.

  


  With just one camera, FFMPEG works with no problem and move the data at 60 fps.
However, when I run 2 cameras simultaneously, the cameras still generate data at 60 fps but FFMPEG can only move the data around 55 fps. This means that I am unable to consume the video in realtime and the buffer consumption will be larger over time.

  


  I guess that FFMPEG didn't just simply move the data but did some processing such as searching for the beginning, the end, and the timestamp of each video frame so that it can count frames and report.
Is there a way to force FFMPEG to not doing those things and focus on passing the data only to make it faster ?

  


  If I purely use directshow API without FFMPEG, can it be faster ?

  


• How to extract the rttm format file from .wav audio file

  5 juillet 2023, par Lahfir

  I would like to extract the .rttm file for an input .wav audio file in python

  


  def extract_rttm_file(wav_path):
  """Extracts the .rttm file from the converted wav file.

  Args:
    wav_path: The path to the converted wav file.

  Returns:
    The path to the .rttm file.
  """

  output_path = os.path.splitext(wav_path)[0] + ".rttm"
  subprocess.call(["sox", wav_path, "-rttm", output_path])
  return output_path`


  


  I tried the above code but it doesn't ouput the rttm file