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• How to accurately detect the start of the main beat and soundtracks in diverse audio tracks ?

  18 juin 2024, par SnoofFloof

  I'm working on a project where I need to edit soundtracks. The challenge is to detect when the main beat and melody of any given soundtrack is properly developed. I am certain there is better terminology to describe what I am aiming for, but ideally, I want to skip the "build-up" and immediately have the song starting at the "main part". This needs to work for various songs across different genres, which often have different structures and onset patterns, making it difficult to streamline the process.

  


  For example :

  


  https://www.youtube.com/watch?v=P77CNtHrnmI -> I would want to my code to identify the onset at 0:24

  


  https://www.youtube.com/watch?v=OOsPCR8SyRo -> Onset detection at 0:12

  


  https://www.youtube.com/watch?v=XKiZBlelIzc -> Onset detection at 0:19

  


  I've tried using librosa to analyze the onset strength and detect beats, but the current implementation either detects the very beginning of the song or fails to consistently identify when the beat is fully developed.

  


  This was my approach ;

  


  def analyze_and_edit_audio(input_file, output_file):
    y, sr = librosa.load(input_file)
    tempo, beat_frames = librosa.beat.beat_track(y=y, sr=sr)
    beat_times = librosa.frames_to_time(beat_frames, sr=sr)
    main_beat_start = beat_times[0]


  


  I have very little experience with librosa/audio editing, so I would appreciate any suggestions you might have !

  


• 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.

  

• 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 !