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• FFMPEG - How to save audio stream detached from video to file whithout transcoding

  15 septembre 2015, par Tony Than

  I try to use fwrite() to save audio stream. But, generated file can not be opened.
  At the same time, I also try to use av_frame_write() to write packet. But, it can not write.
  Please help me with this problem. How to write audio stream without transcoding....

  /* open the input file with generic avformat function */
  
  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) {
  
          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) {
  
              fwrite(reading_packet.data, 1, reading_packet.size, file);
  
              }
  
              av_free_packet(&reading_packet);   
  
          }
  
          fclose(file);
  
  
  
          return 0;
  
      }
  
  }

• Converting mp4 to ogg file format results in a large file

  26 avril 2014, par parags

  I have a MP4 file of 83MB (converted from MOV of about 772MB using FFMPEG).
  For the file to be playable from all browsers from HTML5 video tag, I am converting the MP4 to OGG, again using FFMPEG command

  ffmpeg -i object-creation.mp4 -acodec libvorbis -vcodec libtheora -q:v 5 -q:a 5 object-creation-3.ogg

  The result of the above command is a very large OGG file of around 500 MB. I would certainly not want to upload such huge files to Amazon S3 (which I am using for storage, and distribution).

  Is there something I am missing here ? Is the file not compressed enough ?

  Is it possible to have the resultant file of somewhat manageable size like 80-100 MB without any appreciable loss in quality over what is seen in MP4 format ? Why is it that even the source file is 83MB, the resultant file is too big in comparison ?

  Thanks
  Parag

• ffmpeg doesnt use all the pictures when creating a video

  9 septembre 2022, par Mikhael Karabas

  I have 75 pictures of the same size for an animation. named 0.png ... 74.png
when running ffmpeg to create a video out of them with 24 fps (commmand and log below) the resulting video instead of expected 75/24 = 3.125 sec. is 2.667 sec in lenght and consists only of first 64 frames(pictures), although ffmpeg tells it has processed 75 frames.
I have checked with

  


  ffmpeg -i output.webm out%%d.png - on the resulting video, it indeed exports 64 first frames and not the rest 11 of them.

  


  Cant undertand what am i doing wrong. please kindly advise.

  


  brief output below.

  


  complete log : https://drive.google.com/file/d/1_J7wLPU9PJZ7jztpiJ8g_bZKPZfiK02L/view?usp=sharing

  


  D:\ffmpeg\ffmpeg-64.exe -report -framerate 24 -f image2 -i %01d.png -c:v libvpx-vp9 -pix_fmt yuva420p -crf 10 -b:v 0 output.webm
ffmpeg started on 2022-09-09 at 19:03:15
Report written to "ffmpeg-20220909-190315.log"
Log level: 48
ffmpeg version 2021-12-17-git-b780b6db64-essentials_build-www.gyan.dev Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11.2.0 (Rev2, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-sdl2 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libgme --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libtheora --enable-libvo-amrwbenc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-librubberband
  libavutil      57. 11.100 / 57. 11.100
  libavcodec     59. 14.100 / 59. 14.100
  libavformat    59. 10.100 / 59. 10.100
  libavdevice    59.  0.101 / 59.  0.101
  libavfilter     8. 20.100 /  8. 20.100
  libswscale      6.  1.101 /  6.  1.101
  libswresample   4.  0.100 /  4.  0.100
  libpostproc    56.  0.100 / 56.  0.100
Input #0, image2, from '%01d.png':
  Duration: 00:00:03.13, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: png, rgba(pc), 300x400, 24 fps, 24 tbr, 24 tbn
File 'output.webm' already exists. Overwrite? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (png (native) -> vp9 (libvpx-vp9))
Press [q] to stop, [?] for help
[libvpx-vp9 @ 000002dad505c8c0] v1.11.0-62-g7f45e94d9
Output #0, webm, to 'output.webm':
  Metadata:
    encoder         : Lavf59.10.100
  Stream #0:0: Video: vp9, yuva420p(tv, progressive), 300x400, q=2-31, 24 fps, 1k tbn
    Metadata:
      encoder         : Lavc59.14.100 libvpx-vp9
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
frame=   75 fps=9.9 q=0.0 Lsize=    1056kB time=00:00:02.58 bitrate=3347.2kbits/s speed=0.342x
video:1036kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.942318%