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• FFMPEG : audio out of sync

  15 novembre 2020, par Martin

  ffmpeg -rtsp_transport tcp -i "rtsp://.............." -re -stream_loop -1 -i audio.m4a -filter_complex "[0:a]highpass=f=200,lowpass=f=3000,volume=0.3[mic];[1:a]volume=0.1[mic2];[mic][mic2]amix=duration=shortest[a]" -map 0:v -map "[a]" -c:v copy -b:a 320k -c:a aac -f flv "rtmp://......."

  


  This is my working very well script thanks to @Ilogan

  


  But now i have a problem with an audio out of sync, i don't care about the second one, its just a file audio but the first one is from a microphone of camera IP so it should be synced with the video but now the sound from a microphone is almost 28 seconds later.

  


  Any tips how to do it ?

  


  adelay=28000 ? - nope, that didnt help since i need to delay the video to sync this with an audio.Also tried -use_wallclock_as_timestamps 1 but it didnt help neither.
Also i used -itsoffset 28 it helped but for a while, looks like that the delay time between video and audio is rising and now its 40sec+
Whats going on ?

  


  Now i'm trying with tpad=start_duration=28

  


  edit :

  


    Metadata:
    title           : NVT
    comment         : From NVT
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: h264 (High), yuvj420p(pc, progressive), 1920x1080, 5 fps, 30 tbr, 90k tbn, 10 tbc
    Stream #0:1: Audio: pcm_mulaw, 8000 Hz, mono, s16, 64 kb/s
    Stream #0:2: Data: none
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'audio.m4a':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    title           : Nature
    artist          : 
    date            : 2018
    encoder         : Lavf58.20.100
    comment         : 
  Duration: 08:20:49.15, start: 0.000000, bitrate: 129 kb/s
    Stream #1:0(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
    Metadata:
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/28/2020.
Stream mapping:
  Stream #0:1 (pcm_mulaw) -> highpass
  Stream #1:0 (aac) -> volume
  Stream #0:0 -> #0:0 (copy)
  amix -> Stream #0:1 (aac)
Press [q] to stop, [?] for help
[rtsp @ 0x82e490] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
Output #0, flv, to 'rtmp://....':
  Metadata:
    title           : NVT
    comment         : From NVT
    encoder         : Lavf58.20.100
    Stream #0:0: Video: h264 (High) ([7][0][0][0] / 0x0007), yuvj420p(pc, progressive), 1920x1080, q=2-31, 5 fps, 30 tbr, 1k tbn, 90k tbc
    Stream #0:1: Audio: aac (LC) ([10][0][0][0] / 0x000A), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      encoder         : Lavc58.35.100 aac
frame=    7 fps=0.0 q=-1.0 size=     572kB time=00:00:00.44 bitrate=10634.7kbitsframe=   13 fps= 13 q=-1.0 size=     697kB time=00:00:00.88 bitrate=6463.4kbits/frame=   25 fps= 16 q=-1.0 size=    1185kB time=00:00:01.48 bitrate=6533.1kbits/frame=   33 fps= 16 q=-1.0 size=    1390kB time=00:00:01.99 bitrate=5702.1kbits```


  


• c++ how to use lambdas to set ffmpeg's av_log_set_callback() to a member function ?

  13 février 2018, par Blake Senftner

  I’ve been researching how to use lambdas as callbacks, but I do not seem to be getting my syntax correct. I am working in C++ via Visual Studio 2013 Community, & I am pretty sure this type of lambda use is supported. I am working on a video library which is based on the FFMPEG libav libraries.

  The basic issue is the logging callback provided to library clients of FFMPEG’s libav. It has this calling structure :

  void logging_callback( void *ptr, int level, const char *fmt, va_list vargs  );

  This is fine for C or fine for C++ when the logging callback is a static member function, but I want to install a class member function, which needs the this parameter per the C++ nature of calling method functions.

  What I have so far looks like : (unrelated portions removed)

  class my_libav
  
  { 
  
     // logging messages callback for use by library client, any log messages generated 
  
     // by the library will be sent thru this to the lib client's logic:
  
     typedef void(*STREAM_LOGGING_CALLBACK_CB) (std::string msg, void* p_object);
  
  
  
     // my lib's logger has a void* param so clients can redirect to member functs easier
  
     void SetStreamLoggingCallback(STREAM_LOGGING_CALLBACK_CB p_stream_logger, void* p_object);
  
  
  
     // member function to be installed as FFMPEG's av_log_set_callback():
  
     void RedirectLoggingOutputs( void *ptr, int level, const char *fmt, va_list vargs );
  
  
  
     STREAM_LOGGING_CALLBACK_CB  mp_stream_logging_callback; // client's callback
  
     void*                       mp_stream_logging_object;   // client's data
  
  
  
  };
  
  
  
  void my_libav::SetStreamLoggingCallback(STREAM_LOGGING_CALLBACK_CB p_stream_logger, void* p_object)
  
  {
  
    mp_stream_logging_callback = p_stream_logger;
  
    mp_stream_logging_object = p_object;
  
  }
  
  
  
  void my_libav::RedirectLoggingOutputs(void *ptr, int level, const char *fmt, va_list vargs )
  
  {
  
    // logic that resolves the message and sends through client's callback
  
    // installed int mp_stream_logging_callback
  
  }
  
  
  
  my_libav::my_libav()
  
  {
  
    // this is the old static member function I deleted:
  
    // av_log_set_callback( &my_libav::logging_callback );
  
  
  
    // I tried using std::bind & placeholders, but this syntax is wrong too:
  
    // namespace ph = std::placeholders;
  
    // auto callback = std::bind( &my_libav::RedirectLoggingOutputs, this, ph::_1, ph::_2, ph::_3, ph::_4 );
  
    // 
  
    // av_log_set_callback( callback ); // <- 'callback' is not the correct type
  
  
  
    // this is my try at a lambda. I know that the *this* cannot be 
  
    // in the capture, but I don't know the right syntax to work around 
  
    // this issue:
  
    std::function 
  
          f2 = [this](void *ptr, int level, const char *fmt, va_list vargs ){
  
                          RedirectLoggingOutputs( ptr, level, fmt, vargs ); };
  
  
  
      av_log_set_callback( f2 ); // <- 'f2' is not the correct type, how to fix? 

  The syntax I am trying to fix is in the last 4 lines. What is the correct form ?

• Metal Gear Solid VP3 Easter Egg

  4 août 2011, par Multimedia Mike — Game Hacking

  Metal Gear Solid : The Twin Snakes for the Nintendo GameCube is very heavy on the cutscenes. Most of them are animated in real-time but there are a bunch of clips — normally of a more photo-realistic nature — that the developers needed to compress using a conventional video codec. What did they decide to use for this task ? On2 VP3 (forerunner of Theora) in a custom transport format. This is only the second game I have seen in the wild that uses pure On2 VP3 (first was a horse game). Reimar and I sorted out most of the details sometime ago. I sat down today and wrote a FFmpeg / Libav demuxer for the format, mostly to prove to myself that I still could.

  Things went pretty smoothly. We suspected that there was an integer field that indicated the frame rate, but 18 fps is a bit strange. I kept fixating on a header field that read 0x41F00000. Where have I seen that number before ? Oh, of course — it’s the number 30.0 expressed as an IEEE 32-bit float. The 4XM format pulled the same trick.

  Hexadecimal Easter Egg
  I know I finished the game years ago but I really can’t recall any of the clips present in the samples directory. The file mgs1-60.vp3 contains a computer screen granting the player access and illustrates this with a hexdump. It looks something like this :

  
  
  

  Funny, there are only 22 bytes on a line when there should be 32 according to the offsets. But, leave it to me to try to figure out what the file type is, regardless. I squinted and copied the first 22 bytes into a file :

   1F 8B 08 00   85 E2 17 38   00 03 EC 3A   0D 78 54 D5
   38 00 03 EC   3A 0D
  

  And the answer to the big question :

  $ file mgsfile
  mgsfile : gzip compressed data, from Unix, last modified : Wed Oct 27 22:43:33 1999
  

  A gzip’d file from 1999. I don’t know why I find this stuff so interesting, but I do. I guess it’s no more and less strange than writing playback systems like this.