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• Ffmpeg cpp libav randomly uses high cpu and less gpu or uses high gpu and less cpu with hw accel

  29 avril 2024, par cngkyt

  I am using ffmpeg as library with cpp
the integration of library is perfectly done i am using AVFilterGraph as audio resampler and video pixfmt converter.

  


  I cannot share code because it is a complete library and contains too many files but i can assure there is no problem about code but maybe approach.

  


  My whole class is based on the transcode example of ffmpeg
text

  


  The problem is when i run my program that encodes approx 90 streams

  


  it starts with 25% cpu usage 80% gpu encode usage %85 gpu decode usage with 100% sm utilization

  


  or

  


  it starts with 80% cpu usage 45% gpu encode usage 50% gpu decode usage with 60% sm utilization

  


  when it start like second type of utilization videos are perfect
but when it starts like the first type of utilization videos are freezing

  


  my program uses pure gpu for encoding for all streams but using gpu decoding for every 3 cpu deoding
that means i use hwaccel for 1/3 of streams
because my cards are 4070 ti super and they have 2 NVENC 1 NVDEC chips

  


  my program takes udp streams and encode it and outputs udp mpegts

  


  bitrate and quality settings are persistent across streams depending on resolution

  


  i always test on same streams

  


  the problem happens randomly
but if it starts with high cpu and low gpu utilization it goes on like this
when i restart program problem occurs randomly again

  


  what can couse this

  


  just as an info i have experience on c++ more than 25 years

  


  if there is someone who can teach me something i will be happy

  


  thanks for your further helps

  


  i have tried to reproduce it with compiled ffmpeg instead of my libav library usage
same thing happens but not often

  


  i have tried using hevc_cuvid instead of hwacceleration with avcodec_find_decoder_by_name function

  


• About ffmepg. Some puzzles about using user defined filter

  12 novembre 2014, par Tian Gao

  All.

  I am just a starter in ffmpeg.

  I just downloaded it, and want to define the filter by myself. But, I met some problem, The filter I am to write is sure to be very complex, so I need use some class, which is define in cplusplus, to help me finish the task. So, I just created two files, .h file and .cpp file. And I want to define one specific class in these two files. And the class defined before, will be used in the filter file defined by my self. I know that the filter defined by users should be wrote as the strict formats. But, it always give out this wrong information,

  error: unknown type name 'class'

  And if i add some related lines, to command it compile the program by cplusplus, like this,

  #ifndef GY_FILTER_BLEND_H_
  
  #define GY_FILTER_BLEND_H_
  
  
  
  #include 
  
  #ifdef __cplusplus
  
  
  
  class testgy
  
  {
  
  public:
  
      int xx;
  
      testgy();
  
      ~testgy();
  
      void initial();
  
  
  
  };
  
  #endif
  
  
  
  #endif /* GY_FILTER_BLEND_H_ */

  This error info is to be shown,

  libavfilter/vf_gpu_scroll_left_right.c:64:5: error: unknown type name 'testgy'

  in vf_gpu_scroll_left_right.c , the related lines are as follows,

  #include "gy_filter_blend.h"
  
  
  
  AVFILTER_DEFINE_CLASS(tp_scroll_left_right);
  
  static av_cold int init(AVFilterContext *ctx)
  
  {
  
  
  
      TpScrollLeftDownContext *ctx_ptr = ctx->priv;
  
  
  
      testgy testGY;
  
      testGY.initial();
  
  
  
      __android_log_print(4 ,"gyy_1112" ,"testGY   = %d", testGY.xx);
  
      __android_log_print(4 ,"gyy_1112" ,"str   = %s", ctx_ptr->synthesisCmd0);
  
  
  
      tt  = gpu_filter_new(FILTER_TYPE_SCROLL_LEFT);
  
  
  
      gl_program_object_id_scroll_horizontal = -1;
  
      video_width = -1;
  
      video_height =-1;
  
  
  
      return 0;
  
  }

  So, The question is that I don’t know how to use the class defined by cplusplus, in c file. Anyone has some related experience before ?

  Thanks a lot !

• HEVC File bigger after converting from h264

  26 janvier 2019, par Aaroknight

  I’m currently working an an automated Python script for indexing and converting all my movies and episodes with ffmpeg. I use subprocess.call() for running the ffmpeg command and tested this command with some movies. As expected the big h264 files were converted to merely one third of what they used to have.

  But now that I was testing the method I found that a converted episode (about 400MB in h264) had over 1,6GB in hevc. I have absolutely no idea why the new file would be that much bigger in hevc.
  This is my code :

  def convert(path):
  
      outvid = path.strip(".mkv") + "h265.mkv"
  
  
  
      cmd = ["ffmpeg", "-i", path, "-map", "0", "-map_metadata", "0", "-map_chapters", "0", "-c:v", "libx265",
  
             "-c:a", "copy", "-c:s", "copy", "-preset", "ultrafast", "-x265-params", "lossless=1", outvid]
  
      subprocess.call(cmd)
  
  
  
  convert("/Volumes/2TB/Black Butler/Season 1/Black Butler S01E01.mkv")

  I don’t have that much experience with ffmpeg, nor with subprocess. This is one of my first bigger projects. I hope someone can tell me what the problem might be.

  UPDATE
  Problem applies only for small video files. I now just check for the file size and skip the small files. Wouldn’t have made much of a difference anyway.