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• Download from YouTube as ".wav" instead of ".webm"

  11 août 2022, par Bastian Gerjol

  I am trying to extract an audio from a YouTube Video as an .wav file.
However, the script that I am running keeps giving me .webm files.
The code I am using is the following :

  


  from __future__ import unicode_literals
import youtube_dl

ydl_opts = {
    'format': 'bestaudio/best',
    'postprocessors': [{
        'key': 'FFmpegExtractAudio',
        'preferredcodec': 'wav',
        'preferredquality': '192'
    }],
    'postprocessor_args': [
        '-ar', '16000'
    ],
    'prefer_ffmpeg': True,
    'keepvideo': True
}

with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    ydl.download(['https://www.youtube.com/watch?v=2Xq7iJKzhR4'])


  


  Is there a way to change the output and keep the highest possible audio quality ?

  


  I tried setting prefer_ffmpeg': True to False & keepvideo': True to False but that did not change anything.

  


  I would appreciate suggestions and please keep in mind that I never used Python before.

  


• Should I use aevalsrc or anullsrc ? I got flooded with "cur_dts is invalid st:0" or "Delay between the first packet", encoding stalls at frame 127

  28 avril 2022, par jokoon

  Context : this command is generated with a python script, it aims at concatenating different small videos of different format, with a 0.5s pause, considering some video don't have an audio track.

  


  ffmpeg.exe
-report
-i
input0.mp4
-i
input1.mp4
-i
input2.mp4
-i
input3.mp4
-i
input4.mp4
-i
input5.mp4
-i
input6.mp4
-i
input7.mp4
-i
input8.mp4
-f
lavfi
-i
color=c=black:s=480x270:d=0.5:r=24,format=yuv420p
-f
lavfi
-i
anullsrc
-filter_complex_script
filter_complex_script.txt
-map
[final_video]
-map
[final_audio]
-c:a
aac
concatenated-2022-04-27--23-53.mp4


  


  —

  


  [0]fps=24[fps0];
[fps0]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled0];
[1]fps=24[fps1];
[fps1]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled1];
[2]fps=24[fps2];
[fps2]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled2];
[3]fps=24[fps3];
[fps3]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled3];
[4]fps=24[fps4];
[fps4]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled4];
[5]fps=24[fps5];
[fps5]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled5];
[6]fps=24[fps6];
[fps6]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled6];
[7]fps=24[fps7];
[fps7]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled7];
[8]fps=24[fps8];
[fps8]scale=480:270:force_original_aspect_ratio=decrease,pad=480:270:-1:-1,setsar=1[rescaled8];
[rescaled0][10:a][9:v][10:a][rescaled1][10:a][9:v][10:a][rescaled2][10:a][9:v][10:a][rescaled3][10:a][9:v][10:a][rescaled4][10:a][9:v][10:a][rescaled5][5:a][9:v][10:a][rescaled6][6:a][9:v][10:a][rescaled7][7:a][9:v][10:a][rescaled8][8:a]concat=n=17:v=1:a=1[final_video][final_audio]


  


  I either have thousands of
[mp4 @ 000002132cefe100] Delay between the first packet and last packet in the muxing queue is 10007800 > 10000000: forcing output

  


  when I use

  


  -f lavfi -i anullsrc
so I tried using -f lavfi -i aevalsrc=0:n=1

  


  instead, I have have thousands of

  


  cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)

  


  The encoding "stalls" at frame 127, it keeps doing things, but the frame counter doesn't increment.

  


  Here are the inputs :

  


  I skipped the yuvj420p input as it generated warnings (looks like it's not a big problem)

  


  

  


  Here is a log (I trimmed it a bit) : (I think it's a bit large for stackoverflow)

  


  https://bpa.st/HB7A

  


• libav : How to clear real-time buffer ?

  29 novembre 2018, par user67

  Here’s the c++ code that I’m using to access my webcam.

  int Camera::Init(char* file_name,
  
                  char* device_name,
  
                  char* format,
  
                  char* resolution,
  
                  char* frame_rate,
  
                  char* pixel_format)
  
  {
  
      av_log(NULL, AV_LOG_INFO, "---INIT STARTED\n");
  
      avdevice_register_all();
  
      av_register_all();
  
  
  
      AVDictionary* properties_collection = NULL;
  
      av_dict_set(&properties_collection, "f", format, NULL);
  
      av_dict_set(&properties_collection, "video_size", resolution, NULL);
  
      av_dict_set(&properties_collection, "framerate", frame_rate, NULL);
  
      av_dict_set(&properties_collection, "pix_fmt", pixel_format, NULL);
  
      AVInputFormat *input_format = av_find_input_format("dshow");
  
      char command_line[256];
  
      sprintf(command_line, "video=%s", device_name);
  
      AVFormatContext *input_context = avformat_alloc_context();
  
      //input_context->flags |= AVFMT_FLAG_NOBUFFER;      //DOESN'T HELP
  
      //input_context->max_picture_buffer = 0;            //ERR
  
  
  
      int err_code = 0;
  
      err_code = avformat_open_input(&input_context,
  
                                      command_line,
  
                                      input_format,
  
                                      &properties_collection);
  
      int i = 0;
  
      while (i++ < 30)
  
      {
  
          Sleep(1000);
  
          //avformat_flush(input_context); //DOESN'T HELP
  
          //av_free(input_context); //ERR
  
      }
  
      system("pause");
  
      return 0;
  
  }

  Right after "avformat_open_input()" it starts reading frames to some internal buffer without me even calling "av_read_frame()".
  After about 10 seconds it start’s giving me error messages :

  [dshow @ 0014ed40] real-time buffer [VirtualBox Webcam - FULL HD 1080P Webcam] [video input] 
  
  too full or near too full (62% of size: 3041280 [rtbufsize parameter])! 
  
  frame dropped!
  
  ...
  
  ...
  
  ...
  
  [dshow @ 0014ed40] real-time buffer [VirtualBox Webcam - FULL HD 1080P Webcam] [video input] 
  
  too full or near too full (100% of size: 3041280 [rtbufsize parameter])! 
  
  frame dropped!

  How to clear this buffer or avoid using it ?

  Thanks in advance.

  P.S.Please pardon my english.

  P.P.S.Have a good day.