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• why type casting on non-pointer struct give syntax error

  31 mars 2016, par Sany Liew

  I am using Visual C++ express 2008 try to compile code similar to below :

  no problem

  {
  
    ...
  
    AVRational test = {1, 1000};
  
    ...
  
  }

  but has problem when it is as below :

  {
  
    ...
  
    AVRational test = (AVRational){1, 1000};
  
    ...
  
  }

  gave errors :

  1>..\..\..\projects\test\xyz.cpp(1139) : error C2059: syntax error : '{'
  
  1>..\..\..\projects\test\xyz.cpp(1139) : error C2143: syntax error : missing   ';' before '{'
  
  1>..\..\..\projects\test\xyz.cpp(1139) : error C2143: syntax error : missing ';' before '}'

  where AVRational (ffmpeg.org library) is defined as :

  typedef struct AVRational{
  
      int num; ///< numerator
  
      int den; ///< denominator
  
  } AVRational;

  FFmpeg come with some pre-define value such as

  #define AV_TIME_BASE_Q (AVRational){1, AV_TIME_BASE}

  which is used as below

  av_rescale_q(seek_target, AV_TIME_BASE_Q, pFormatCtx->streams[stream_index]->time_base);

  will failed to compile on Visual C++ express 2008

  It seem like the same code will be compiled with no error/warning on gcc compiler. Why I get this error on VC++ ? Is it a C/C++ standard way to do casting on struct value ? Anyway I can avoid this error while still able to use the defined AV_TIME_BASE_Q ?

• FFMPEG and Mencoder building screenshot returns 0 size images

  12 avril 2014, par Genus

  I have a script and it used to work fine but suddenly it stopped working and giving me zero size images as screenshot after video convert.

  here is the command for video screenshot.

  $cmd = $GLOBALS["paths"]["ffmpeg"]." -y -i ".$file." -f mjpeg -r 1 -ss ".$time." -vframes 1 -an ".$tmpdir."/00000001.jpg 2>&1";
  
      exec($cmd,$results);

  Debug :

  -----------------------------------------------------
  
  
  
  ------------mencoder_and_fmpeg.php SCREENSHOT -------
  
  
  
  -----------------------------------------------------
  
  
  
    COMMAND: ffmpeg -y -i /home/TESTING/public_html/vid/6d/ad/29/6dad2946a2ba102.flv -f mjpeg -r 1 -ss 14.48 -vframes 1 -an /home/TESTING/public_html/scr/42/3a/92/00000001.jpg 2>&1
  
  
  
    FFmpeg version SVN-r16244, Copyright (c) 2000-2008 Fabrice Bellard, et al.
  
  
  
    configuration: --disable-mmx --enable-shared --enable-libvorbis --enable-gpl --enable-swscale --enable-pthreads --disable-static --disable-demuxer=v4l --disable-demuxer=v4l2 --enable-libtheora --enable-gpl --enable-libspeex --enable-libmp3lame --enable-libfaac --enable-libfaad --enable-libfaadbin --enable-libamr-nb --enable-libamr-wb --enable-nonfree --enable-libxvid
  
    libavutil     49.12. 0 / 49.12. 0
  
    libavcodec    52. 7. 0 / 52.108. 0
  
    libavformat   52.23. 1 / 52.92. 0
  
    libavdevice   52. 1. 0 / 52. 2. 3
  
    libswscale     0. 6. 1 /  0.12. 0
  
  
  
    built on Apr  9 2011 22:48:41, gcc: 4.1.2 20080704 (Red Hat 4.1.2-50)
  
    built by Admin-Ahead Server Technologies FFmpeg installer v5.0.6b
  
    Seems stream 0 codec frame rate differs from container frame rate: 1000.00 (1000/1) -> 10.92 (131/12)
  
    Stream mapping:
  
    Stream #0.0 -> #0.0
  
  
  
    Press [q] to stop encoding
  
    ffmpeg: symbol lookup error: ffmpeg: undefined symbol: frame_hook_process

• Android camera stream with rtmp has stable 5 second latency

  8 avril 2014, par native1989

  I use ffmpeg with h264 build and javacv on android to stream video from camera to rtmp server.
  I was trying to set all possible video framerates and bitrates, set preset ultrafast, but I still have stable 5 seconds delay.
  If i use android mediarecorder sending mpegts stream with rtmp to server,i have only 2 seconds delay, and if I use -fflags nobuffer options on the client(ffmpeg), the video is appearing immediately.

  I don`t know how in android ffmpeg reduces this latency.
  Here the code :

      recorder = new FFmpegFrameRecorder(ffmpeg_link, imageWidth, imageHeight, 1);
  
      recorder.setFormat("flv");
  
      recorder.setFrameRate(frameRate);
  
      recorder.setVideoBitrate(900*1000);
  
      recorder.setVideoCodec(avcodec.AV_CODEC_ID_H264);
  
      recorder.setVideoOption("preset", "ultrafast");
  
      recorder.setVideoOption("tune", "zerolatency");
  
      recorder.setVideoOption("fflags", "nobuffer");
  
      recorder.setVideoOption("analyzeduration", "0");