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• FFMPEG- Duration of audio file is inaccurate

  17 septembre 2015, par Tony Than

  I have video file (mp4). I want to detach audio stream (AAC format) from that file and save in PC.
  With below code, Generated aac file canplay now on KM player, but can not play on VLC player. Information of duration displays on player is wrong.
  Please help me with this problem.

   err = avformat_open_input(input_format_context, filename, NULL, NULL);
  
  if (err < 0) {
  
      return err;
  
  }
  
  
  
  /* If not enough info to get the stream parameters, we decode the
  
     first frames to get it. (used in mpeg case for example) */
  
  ret = avformat_find_stream_info(*input_format_context, 0);
  
  if (ret < 0) {
  
      av_log(NULL, AV_LOG_FATAL, "%s: could not find codec parameters\n", filename);
  
      return ret;
  
  }
  
  
  
  /* dump the file content */
  
  av_dump_format(*input_format_context, 0, filename, 0);
  
  
  
  for (size_t i = 0; i < (*input_format_context)->nb_streams; i++) {
  
      AVStream *st = (*input_format_context)->streams[i];
  
      if (st->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
  
          *input_codec_context = st->codec;
  
          *input_audio_stream = st;
  
  
  
          FILE *file = NULL;
  
          file = fopen("C:\\Users\\MyPC\\Downloads\\Test.aac", "wb");
  
          AVPacket reading_packet;
  
          av_init_packet(&reading_packet);
  
          while (av_read_frame(*input_format_context, &reading_packet) == 0) {
  
              if (reading_packet.stream_index == (int) i) {
  
  
  
                  uint8_t adts_header[7];
  
                  unsigned int obj_type = 0;
  
                  unsigned int num_data_block = (reading_packet.size)/1024;
  
                  int rate_idx = st->codec->sample_rate, channels = st->codec->channels;
  
  
  
                   uint16_t frame_length;
  
  
  
                  // include the header length also
  
                   frame_length = reading_packet.size + 7;
  
  
  
                  /* We want the same metadata */
  
                  /* Generate ADTS header */
  
                  if(adts_header == NULL) return -1;
  
                  /* Sync point over a full byte */
  
                  adts_header[0] = 0xFF;
  
                  /* Sync point continued over first 4 bits + static 4 bits
  
                  * (ID, layer, protection)*/
  
                  adts_header[1] = 0xF1;
  
                  /* Object type over first 2 bits */
  
                  adts_header[2] = obj_type << 6;
  
                  /* rate index over next 4 bits */
  
                  adts_header[2] |= (rate_idx << 2);
  
                  /* channels over last 2 bits */
  
                  adts_header[2] |= (channels & 0x4) >> 2;
  
                  /* channels continued over next 2 bits + 4 bits at zero */
  
                  adts_header[3] = (channels & 0x3) << 6;
  
                  /* frame size over last 2 bits */
  
                  adts_header[3] |= (frame_length & 0x1800) >> 11;
  
                  /* frame size continued over full byte */
  
                  adts_header[4] = (frame_length & 0x1FF8) >> 3;
  
                  /* frame size continued first 3 bits */
  
                  adts_header[5] = (frame_length & 0x7) << 5;
  
                  /* buffer fullness (0x7FF for VBR) over 5 last bits*/
  
                  adts_header[5] |= 0x1F;
  
                  /* buffer fullness (0x7FF for VBR) continued over 6 first bits + 2 zeros
  
                  * number of raw data blocks */
  
                  adts_header[6] = 0xFA;
  
                  adts_header[6] |= num_data_block & 0x03; // Set raw Data blocks.
  
  
  
                  fwrite(adts_header, 1, 7, file);
  
                  fwrite(reading_packet.data, 1, reading_packet.size, file);
  
              }
  
              av_free_packet(&reading_packet);   
  
          }
  
          fclose(file);
  
  
  
          return 0;
  
      }
  
  }

• FFMPEG merge mp4 file and mp3 file into mp4

  10 avril 2017, par Cường Trần

  I have video file in mp4 format (video.mp4), its length is 20 seconds. From 0 seconds to 10 seconds, the video has sound, and from 10 seconds to 20 seconds, there is no sound.

  I also have mp3 file (audio.mp3) and has length 10 seconds.

  I want to merge video.mp4 and audio.mp3 into result.mp4. The result.mp4 file should have video stream and its audio stream from 01 second to 10 seconds as original and audio stream from 10 seconds to 20 seconds of audio.mp3 as merged.

  I use the command to merge :

  ffmpeg -i video.mp4 -i audio.mp3 -filter_complex "aevalsrc=0:d=10[s1];[s1][1:a]concat=n=2:v=1:a=1[aout]" -c:v copy -map 0:v -map [aout] result.mp4

  But i get the result.mp4 with video : there is no sound from 01-10 seconds, only new sound from 10-20 seconds.

  It is the seem that my command don’t keep the sound from original mp4 file, it has removed it and just keep the new sound.

  Could you please help ?

• Update jpg during live broadcast with ffmpeg

  13 mars 2021, par FoxFr

  I encounter a problem with a stream ffmpeg, i search from several hours how my jpg wasn't update during my live, indeed i wish to cast a jpg updated each 5 seconds beteween other video inputs

  


  

  • i create a new jpg each 5 seconds

  


  • i wish to cast this new image each 5 seconds

  


  


  I can't find an option to refresh each 1 sec or more, u know ?

  


  -loop 1  -i /home/pi/videopi/map/map.jpg


  


  i try to add -update 1 , without success