VideoProperties: compute bit rate if constant and not specified

valnoel · valnoel · commit ce821634a075 · 2015-03-17T16:28:43.000+01:00
diff --git a/src/AvTranscoder/mediaProperty/VideoProperties.cpp b/src/AvTranscoder/mediaProperty/VideoProperties.cpp
@@ -392,7 +392,55 @@ size_t VideoProperties::getBitRate() const
 {
 	if( ! _codecContext )
 		throw std::runtime_error( "unknown codec context" );
-	return _codecContext->bit_rate;
+	// return bit rate of stream if present or VBR mode
+	if( _codecContext->bit_rate || _codecContext->rc_max_rate )
+		return _codecContext->bit_rate;
+	
+	// else compute bit rate from the first GOP
+	int gopFramesSize = 0;
+	if( !_formatContext || !_codecContext || !_codec )
+		return 0;
+	
+	if( _codecContext->width && _codecContext->height )
+	{
+		// discard no frame type when decode
+		_codecContext->skip_frame = AVDISCARD_NONE;
+
+#if LIBAVCODEC_VERSION_MAJOR > 54
+		AVFrame* frame = av_frame_alloc();
+#else
+		AVFrame* frame = avcodec_alloc_frame();
+#endif
+		AVPacket pkt;
+		av_init_packet( &pkt );
+		avcodec_open2( _codecContext, _codec, NULL );
+		int gotFrame = 0;
+		int count = 0;
+		
+		while( ! av_read_frame( const_cast<AVFormatContext*>( _formatContext ), &pkt ) )
+		{
+			if( pkt.stream_index == (int)_streamIndex )
+			{
+				avcodec_decode_video2( _codecContext, frame, &gotFrame, &pkt );
+				if( gotFrame )
+				{
+					gopFramesSize += frame->pkt_size;
+					++count;
+				}
+			}
+			av_free_packet( &pkt );
+			if( _codecContext->gop_size == count )
+				break;
+		}
+#if LIBAVCODEC_VERSION_MAJOR > 54
+		av_frame_free( &frame );
+#elif LIBAVCODEC_VERSION_MAJOR > 53
+		avcodec_free_frame( &frame );
+#else
+		av_free( frame );
+#endif
+	}
+	return (gopFramesSize / _codecContext->gop_size) * 8 * getFps();
 }
 
 size_t VideoProperties::getMaxBitRate() const
