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• Running FFMPEG commands inside Docker container with Python corrupts video

  15 novembre 2023, par AFortunato

  I have a Docker container running a Python web server. Somewhere in the server, I'm using
asyncio.create_subprocess_shell to run an FFMPEG command that trims and crops a video like :

  


  ffmpeg -ss {start} -to {end} -i {video_path} -vf "crop={width}:{height}:{x_offset}:{y_offset}" -c:a copy -crf 0 -preset ultrafast {output_file}


  


  Whenever I do this with a video with less than 1080p of resolution, everything works great. But if I use HD, 4k etc videos, whatever timestamps I put in start and end, I always get a 1 second video of the last second of the original video.

  


  I'm calling FFMPEG like this

  


  process = await asyncio.create_subprocess_shell(
            command, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE
        )


  


  I don't see any errors when running this AND the weird part is that, if I enter the container with
docker exec -it <container> sh</container>

  


  And I run the exact same command in ffmpeg, it works perfectly.

  


  I have no idea what the problem can be, can anyone help me ?

  


• Why ffmpeg takes so long time to decode 1 frame from high resolution gif

  29 août 2018, par Yueh-Ming Chien

  I am working on gif to png decode. My command is like :

  ffmpeg -probesize 20M -y -i "GIF_High resolution_4952x7000.gif" -y
  -frames:v 1 %03d.png

  Input : gif (4952x7000)

  Output : png

  And here’s output result :
  

  It takes about 13 seconds.
  If I use python to call subprocess.Popen() to execute it, it causes UI to hang.
  And I found something weird in Process Monitor :
  

  It stuck in process profiling for a long time. I don’t know why. Can anyone help ? I’ll appreciate that.

• Get MP3 content in C ? ffmpeg or mpg123lib ?

  20 novembre 2014, par Nicolás Múnera

  I’m trying for a personal project of mine to mix two mp3 files into one. I’ve been investigating for a couple of days how to read an mp3 with C and i’ve come up with two libraries, ffmpeg and mpg3lib, unfortunately the documentation is a little bit confusing.

  For now I’m trying to get the content of one MP3 file, I just want to understand which parts are valuable and which parts of the data I get are the ones i’m supposed to mix together. This is what i’ve got so far :

  int cont = 0;
  
  fprintf(stderr, "Starting decode...\n");
  
  while(1)
  
  {
  
           len = fread(buf, sizeof(unsigned char), INBUFF, in);
  
           if(len <= 0)
  
                   break;
  
           inc += len;
  
           ret = mpg123_feed(m, buf, len);
  
  
  
           while(ret != MPG123_ERR && ret != MPG123_NEED_MORE)
  
           {
  
                   ret = mpg123_decode_frame(m, &num, &audio, &bytes);
  
                   if(ret == MPG123_NEW_FORMAT)
  
                   {
  
                       mpg123_getformat(m, &rate, &channels, &enc);
  
                       initwavformat();
  
                       initwav();
  
                       fprintf(stderr, "New format: %li Hz, %i channels, encoding value %i\n", rate, channels, enc);
  
                   }
  
  
  
                   printf("Frame # %d: %s\n",cont,audio);          
  
                   fwrite(audio, sizeof(unsigned char), bytes, out);
  
                   outc += bytes;
  
           }
  
       if(ret == MPG123_ERR){
  
               fprintf(stderr, "Error: %s", mpg123_strerror(m));
  
               break; 
  
       }
  
   cont++;
  
   }

  With this code, I think i’m getting the content of the MP3, but when I print it I just get some weird characters, so I don’t know which strategy i should take.

  Could you guys give me a little bit of advice with this ?

  Thank you !