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• how to stream h.264 video with mp3 audio using libavcodec ?

  18 septembre 2012, par dasg

  I read h.264 frames from webcamera and capture audio from microphone. I need to stream live video to ffserver. During debug I read video from ffserver using ffmpeg with following command :

  ffmpeg -i http://127.0.0.1:12345/robot.avi -vcodec copy -acodec copy out.avi

  My video in output file is slightly accelerated. If I add a audio stream it is accelerated several times. Sometimes there is no audio in the output file.

  Here is my code for encoding audio :

  #include "v_audio_encoder.h"
  
  
  
  extern "C" {
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  }
  
  #include <cassert>
  
  
  
  struct VAudioEncoder::Private
  
  {
  
      AVCodec *m_codec;
  
      AVCodecContext *m_context;
  
  
  
      std::vector m_outBuffer;
  
  };
  
  
  
  VAudioEncoder::VAudioEncoder( int sampleRate, int bitRate )
  
  {
  
      d = new Private( );
  
      d->m_codec = avcodec_find_encoder( CODEC_ID_MP3 );
  
      assert( d->m_codec );
  
      d->m_context = avcodec_alloc_context3( d->m_codec );
  
  
  
      // put sample parameters
  
      d->m_context->channels = 2;
  
      d->m_context->bit_rate = bitRate;
  
      d->m_context->sample_rate = sampleRate;
  
      d->m_context->sample_fmt = AV_SAMPLE_FMT_S16;
  
      strcpy( d->m_context->codec_name, "libmp3lame" );
  
  
  
      // open it
  
      int res = avcodec_open2( d->m_context, d->m_codec, 0 );
  
      assert( res >= 0 );
  
  
  
      d->m_outBuffer.resize( d->m_context->frame_size );
  
  }
  
  
  
  VAudioEncoder::~VAudioEncoder( )
  
  {
  
      avcodec_close( d->m_context );
  
      av_free( d->m_context );
  
      delete d;
  
  }
  
  
  
  void VAudioEncoder::encode( const std::vector&amp; samples, std::vector&amp; outbuf )
  
  {
  
      assert( (int)samples.size( ) == d->m_context->frame_size );
  
  
  
      int outSize = avcodec_encode_audio( d->m_context, d->m_outBuffer.data( ),
  
                                          d->m_outBuffer.size( ), reinterpret_cast<const>( samples.data( ) ) );
  
      if( outSize ) {
  
          outbuf.resize( outSize );
  
          memcpy( outbuf.data( ), d->m_outBuffer.data( ), outSize );
  
      }
  
      else
  
          outbuf.clear( );
  
  }
  
  
  
  int VAudioEncoder::getFrameSize( ) const
  
  {
  
      return d->m_context->frame_size;
  
  }
  
  </const></cassert>

  Here is my code for streaming video :

  #include "v_out_video_stream.h"
  
  
  
  extern "C" {
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libavutil></libavutil>avstring.h>
  
  #include <libavformat></libavformat>avio.h>
  
  }
  
  
  
  #include <stdexcept>
  
  #include <cassert>
  
  
  
  struct VStatticRegistrar
  
  {
  
      VStatticRegistrar( )
  
      {
  
          av_register_all( );
  
          avformat_network_init( );
  
      }
  
  };
  
  
  
  VStatticRegistrar __registrar;
  
  
  
  struct VOutVideoStream::Private
  
  {
  
      AVFormatContext * m_context;
  
      int m_videoStreamIndex;
  
      int m_audioStreamIndex;
  
  
  
      int m_videoBitrate;
  
      int m_width;
  
      int m_height;
  
      int m_fps;
  
      int m_bitrate;
  
  
  
      bool m_waitKeyFrame;
  
  };
  
  
  
  VOutVideoStream::VOutVideoStream( int width, int height, int fps, int bitrate )
  
  {
  
      d = new Private( );
  
      d->m_width = width;
  
      d->m_height = height;
  
      d->m_fps = fps;
  
      d->m_context = 0;
  
      d->m_videoStreamIndex = -1;
  
      d->m_audioStreamIndex = -1;
  
      d->m_bitrate = bitrate;
  
      d->m_waitKeyFrame = true;
  
  }
  
  
  
  bool VOutVideoStream::connectToServer( const std::string&amp; uri )
  
  {
  
      assert( ! d->m_context );
  
  
  
      // initalize the AV context
  
      d->m_context = avformat_alloc_context();
  
      if( !d->m_context )
  
          return false;
  
      // get the output format
  
      d->m_context->oformat = av_guess_format( "ffm", NULL, NULL );
  
      if( ! d->m_context->oformat )
  
          return false;
  
  
  
      strcpy( d->m_context->filename, uri.c_str( ) );
  
  
  
      // add an H.264 stream
  
      AVStream *stream = avformat_new_stream( d->m_context, NULL );
  
      if ( ! stream )
  
          return false;
  
      // initalize codec
  
      AVCodecContext* codec = stream->codec;
  
      if( d->m_context->oformat->flags &amp; AVFMT_GLOBALHEADER )
  
          codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
      codec->codec_id = CODEC_ID_H264;
  
      codec->codec_type = AVMEDIA_TYPE_VIDEO;
  
      strcpy( codec->codec_name, "libx264" );
  
  //    codec->codec_tag = ( unsigned(&#39;4&#39;) &lt;&lt; 24 ) + (unsigned(&#39;6&#39;) &lt;&lt; 16 ) + ( unsigned(&#39;2&#39;) &lt;&lt; 8 ) + &#39;H&#39;;
  
      codec->width = d->m_width;
  
      codec->height = d->m_height;
  
      codec->time_base.den = d->m_fps;
  
      codec->time_base.num = 1;
  
      codec->bit_rate = d->m_bitrate;
  
      d->m_videoStreamIndex = stream->index;
  
  
  
      // add an MP3 stream
  
      stream = avformat_new_stream( d->m_context, NULL );
  
      if ( ! stream )
  
          return false;
  
      // initalize codec
  
      codec = stream->codec;
  
      if( d->m_context->oformat->flags &amp; AVFMT_GLOBALHEADER )
  
          codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
      codec->codec_id = CODEC_ID_MP3;
  
      codec->codec_type = AVMEDIA_TYPE_AUDIO;
  
      strcpy( codec->codec_name, "libmp3lame" );
  
      codec->sample_fmt = AV_SAMPLE_FMT_S16;
  
      codec->channels = 2;
  
      codec->bit_rate = 64000;
  
      codec->sample_rate = 44100;
  
      d->m_audioStreamIndex = stream->index;
  
  
  
      // try to open the stream
  
      if( avio_open( &amp;d->m_context->pb, d->m_context->filename, AVIO_FLAG_WRITE ) &lt; 0 )
  
           return false;
  
  
  
      // write the header
  
      return avformat_write_header( d->m_context, NULL ) == 0;
  
  }
  
  
  
  void VOutVideoStream::disconnect( )
  
  {
  
      assert( d->m_context );
  
  
  
      avio_close( d->m_context->pb );
  
      avformat_free_context( d->m_context );
  
      d->m_context = 0;
  
  }
  
  
  
  VOutVideoStream::~VOutVideoStream( )
  
  {
  
      if( d->m_context )
  
          disconnect( );
  
      delete d;
  
  }
  
  
  
  int VOutVideoStream::getVopType( const std::vector&amp; image )
  
  {
  
      if( image.size( ) &lt; 6 )
  
          return -1;
  
      unsigned char *b = (unsigned char*)image.data( );
  
  
  
      // Verify NAL marker
  
      if( b[ 0 ] || b[ 1 ] || 0x01 != b[ 2 ] ) {
  
          ++b;
  
          if ( b[ 0 ] || b[ 1 ] || 0x01 != b[ 2 ] )
  
              return -1;
  
      }
  
  
  
      b += 3;
  
  
  
      // Verify VOP id
  
      if( 0xb6 == *b ) {
  
          ++b;
  
          return ( *b &amp; 0xc0 ) >> 6;
  
      }
  
  
  
      switch( *b ) {
  
      case 0x65: return 0;
  
      case 0x61: return 1;
  
      case 0x01: return 2;
  
      }
  
  
  
      return -1;
  
  }
  
  
  
  bool VOutVideoStream::sendVideoFrame( std::vector&amp; image )
  
  {
  
      // Init packet
  
      AVPacket pkt;
  
      av_init_packet( &amp;pkt );
  
      pkt.flags |= ( 0 >= getVopType( image ) ) ? AV_PKT_FLAG_KEY : 0;
  
  
  
      // Wait for key frame
  
      if ( d->m_waitKeyFrame ) {
  
          if( pkt.flags &amp; AV_PKT_FLAG_KEY )
  
              d->m_waitKeyFrame = false;
  
          else
  
              return true;
  
      }
  
  
  
      pkt.stream_index = d->m_videoStreamIndex;
  
      pkt.data = image.data( );
  
      pkt.size = image.size( );
  
      pkt.pts = pkt.dts = AV_NOPTS_VALUE;
  
  
  
      return av_write_frame( d->m_context, &amp;pkt ) >= 0;
  
  }
  
  
  
  bool VOutVideoStream::sendAudioFrame( std::vector&amp; audio )
  
  {
  
      // Init packet
  
      AVPacket pkt;
  
      av_init_packet( &amp;pkt );
  
      pkt.stream_index = d->m_audioStreamIndex;
  
      pkt.data = audio.data( );
  
      pkt.size = audio.size( );
  
      pkt.pts = pkt.dts = AV_NOPTS_VALUE;
  
  
  
      return av_write_frame( d->m_context, &amp;pkt ) >= 0;
  
  }
  
  </cassert></stdexcept>

  Here is how I use it :

  BOOST_AUTO_TEST_CASE(testSendingVideo)
  
  {
  
      const int framesToGrab = 90000;
  
  
  
      VOutVideoStream stream( VIDEO_WIDTH, VIDEO_HEIGHT, FPS, VIDEO_BITRATE );
  
      if( stream.connectToServer( URI ) ) {
  
          VAudioEncoder audioEncoder( AUDIO_SAMPLE_RATE, AUDIO_BIT_RATE );
  
          VAudioCapture microphone( MICROPHONE_NAME, AUDIO_SAMPLE_RATE, audioEncoder.getFrameSize( ) );
  
  
  
          VLogitecCamera camera( VIDEO_WIDTH, VIDEO_HEIGHT );
  
          BOOST_REQUIRE( camera.open( CAMERA_PORT ) );
  
          BOOST_REQUIRE( camera.startCapturing( ) );
  
  
  
          std::vector image, encodedAudio;
  
          std::vector voice;
  
          boost::system_time startTime;
  
          int delta;
  
          for( int i = 0; i < framesToGrab; ++i ) {
  
              startTime = boost::posix_time::microsec_clock::universal_time( );
  
  
  
              BOOST_REQUIRE( camera.read( image ) );
  
              BOOST_REQUIRE( microphone.read( voice ) );
  
              audioEncoder.encode( voice, encodedAudio );
  
  
  
              BOOST_REQUIRE( stream.sendVideoFrame( image ) );
  
              BOOST_REQUIRE( stream.sendAudioFrame( encodedAudio ) );
  
  
  
              delta = ( boost::posix_time::microsec_clock::universal_time( ) - startTime ).total_milliseconds( );
  
              if( delta < 1000 / FPS )
  
                  boost::thread::sleep( startTime + boost::posix_time::milliseconds( 1000 / FPS - delta ) );
  
          }
  
  
  
          BOOST_REQUIRE( camera.stopCapturing( ) );
  
          BOOST_REQUIRE( camera.close( ) );
  
      }
  
      else
  
          std::cout << "failed to connect to server" << std::endl;
  
  }

  I think my problem is in PTS and DTS. Can anyone help me ?

• cvCaptureFromFile always returns NULL, Visual Studio 2005

  14 septembre 2012, par user1671173

  I've got a problem with the cvCaptureFromFile function. It always returns NULL. I've done some research on the internet and I've added PATH to ffmpeg's "bin" directory.
  But it's still the same. So I've tried to open the desired file with ffplay.exe. It returns an error which says "Invalid data found when processing an input". It is a "mjpg" file, which should be played with ffmpeg. Then I tried the same with some "mpg" file.
  Now the message is "no such file or directory" which is not true, because the file is in the place. What else should I do ?
  The files all right with Media-Player and VLC player.
  Please help !

• Selecting a library / framework for video capture & recording

  21 décembre 2011, par Saurabh Gandhi

  In one of the project that we have undertaken we are looking for a video capture & recording library. Our groundwork (based on google search) shows that vlc (libvlc), ffmpeg (libavcodec) and gstreamer are the three popular free and open source libraries / multimedia frameworks available for the same. How do these libraries compare on the following parameters :

  1. Licensing policy to allow use within a commercial product without the need to open source any of the components of the product that is using the library
  2. Ability to be used effectively in a multi-threaded environment (library should be inherently thread-safe)
  3. Easy to use and maintain
  4. Documentation : API should be well documented...this is relative... :)

  Our primary intention is to be able to capture RTSP video streams (H.264/MPEG-2/MJPEG encoded), convert these streams to raw video / frames so that it can be used for analysis / processing and later on compress these frames and store it on the disk in the form of an MP4 file (using MPEG2 / H.264 encoding).

  P.S. We understand that FFmpeg is also one of the components of vlc since vlc uses libavcodec library. Is the same true for gstreamer as well ? Does it have any ffmpeg dependency ?

  Awaiting your responses.

  Regards,

  Saurabh Gandhi