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• How to decode h264 video encoded from yuv444p frames ?

  22 octobre 2015, par Bing Liu

  I had an h264 video stream encoded from yuv444p frames, it was played well using vlc or mpv player.

  But when I tried to decode it using libavcodec, it just looked like this.

  wrong result ;

  The source frame is an upsize down vlc-player logo.

  Here is the intialization of the decoder :

  AVCodec *codec = avcodec_find_decoder(AV_CODEC_ID_H264);
  
  AVCodecContext *codecCtx = avcodec_alloc_context3(codec);
  
  avcodec_open2(codecCtx, codec, NULL);

  The decoder worked well when decoding packets encoded from yuv420p.
  Did I miss anything when decoding those packets encoded from yuv444p frames ?

  Update：I converted the yuv444p output into BGRA with sws_scale(), then I make a transforment with the follow codes ;

  int offset_out = 0, offset_tmp = 0;
  
  uint32_t *tmp = (uint32_t *)malloc(width * height * 4);
  
  for (int i = 0; i < width * height; i++) { 
  
      if ((i + width + 9) % (width + 9) > width) {
  
          out[offset_out++] = in[i];
  
      } else {
  
          tmp[offset_tmp++] = in[i];
  
      }
  
  }
  
  memcpy(out + offset_out, tmp, offset_tmp);
  
  free(tmp);

  Then the picture looked all right.

  There is a number 9 in i + width + 9. I guessed that cause I knew the width and height of the source picture. But what if the width or height was changed to some value else, 9 didn’t work.

  I want to know what’s wrong with the decoder.

• How does Rust work with process arguments ?

  1er octobre 2022, par SoptikHa

  I'm really confused about Rust processes. I'm trying to call something like this :

  



  ffmpeg -i path/to/test-video.webm -ab 160k -ac 2 -vn -f mp3 -


  



  This should extract sound out of video and send it to stdout. So I've done this :

  



  let sound: std::process::Output = Command::new("ffmpeg")
    .arg(format!("-i {}", args.input.to_str().unwrap()))
    .arg("-ab 160k")
    .arg("-ac 2")
    .arg("-vn")
    .arg("-f mp3")
    .arg("-")
    .stdout(Stdio::piped())
    .stdin(Stdio::inherit())
    .stderr(Stdio::inherit())
    .output()
    .unwrap();


  



  But for some reason, this doesn't work. It prints this to stderr :

  



  Unrecognized option 'i path/to/test-video.webm'.
Error splitting the argument list: Option not found


  



  When I remove the slashes from args (so it looks like .arg(format!("i {}", ...)).arg("ab 160k")..., I get this :

  



  Output file #0 does not contain any stream


  



  I think I misunderstood how this works, but I tested it on other applications and it seemed to work the way I'm doing it now. What did I miss, how does Rust work with these arguments ?

  



  And just to be clear, I know about the ffmpeg crates, but they don't work for me for some reason, I can't even compile them.

  


• libavdevice.so.57 : failed to map segment from shared object : Permission denied"

  10 septembre 2016, par user3579130

  I have successfully installed ffmpeg ver. 4.4.7 on centos, with shared enabled as such :

  [root@localhost ~]# ffmpeg
  
  ffmpeg version N-81555-g496d97f Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-17)
  
    configuration: --prefix=/usr/local/ffmpeg_build --extra-cflags=-I/usr/local/ffmpeg_build/include --extra-ldflags=-L/usr/local/ffmpeg_build/lib --bindir=/usr/local/bin --pkg-config-flags=--static --enable-gpl --enable-nonfree --enable-libfdk-aac --enable-libx264 --enable-libx265 --enable-shared
  
    libavutil      55. 29.100 / 55. 29.100
  
    libavcodec     57. 54.102 / 57. 54.102
  
    libavformat    57. 48.102 / 57. 48.102
  
    libavdevice    57.  0.102 / 57.  0.102
  
    libavfilter     6. 60.100 /  6. 60.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  1.100 /  2.  1.100
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Hyper fast Audio and Video encoder
  
  usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

  However, when I run in php, through exec I get

  "/usr/local/bin/ffmpeg : error while loading shared libraries :
  libavdevice.so.57 : failed to map segment from shared object :
  Permission denied"

  I know the web server executes the command as user ’apache’ and not root, but I installed ffmpeg in /usr/local/ffmpeg_build for that specific reason, so that the regular users can use ffmpeg.

  What did I miss ? What does this error mean ?