wrestling with libavcodec

1 files changed, 120 insertions, 0 deletions

diff --git a/avcodec_audio_example3-c++11.c b/avcodec_audio_example3-c++11.c
new file mode 100644
index 0000000..ddb88db
--- /dev/null
+++ b/avcodec_audio_example3-c++11.c
@@ -0,0 +1,120 @@
+	av_register_all();
+	
+	std::shared_ptr<AVFormatContext> avFormat(avformat_alloc_context(), &avformat_free_context);
+	
+	auto avFormatPtr = avFormat.get();
+	if (avformat_open_input(&avFormatPtr,filename.c_str(),nullptr, nullptr) != 0) {
+		cerr <<"Rotor: Error while calling avformat_open_input (probably invalid file format)" << endl;
+		return false;
+	}
+
+	if (avformat_find_stream_info(avFormat.get(), nullptr) < 0) {
+		cerr << "Rotor: Error while calling avformat_find_stream_info" << endl;
+		return false;
+	}
+	
+	av_dump_format(avFormat.get(), 0, 0, false); //avformat.h line 1256
+
+	AVStream* stream = nullptr;
+	for (unsigned int i = 0; i < avFormat->nb_streams; ++i) {
+		if (avFormat->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
+			// we've found a video stream!
+			stream = avFormat->streams[i];
+			break;
+		}
+	}
+	if (!stream) {
+		cerr <<"Rotor: Didn't find any audio stream in the file"<< endl;
+		return false;
+	}
+	
+	// getting the required codec structure
+	const auto codec = avcodec_find_decoder(stream->codec->codec_id); //returns AVCodec*
+	if (codec == nullptr) {
+		cerr <<"Rotor: Audio codec not available"<< endl;
+		return false;
+	}
+	
+	//AVCodecContext??  avFormat->streams[i]->codec 
+	
+	// allocating a structure
+	std::shared_ptr<AVCodecContext> audioCodec(avcodec_alloc_context3(codec), [](AVCodecContext* c) { avcodec_close(c); av_free(c); });
+
+	/* extradata???
+	// we need to make a copy of videoStream->codec->extradata and give it to the context
+	// make sure that this vector exists as long as the avVideoCodec exists
+	std::vector codecContextExtraData(stream->codec->extradata, stream->codec->extradata + stream->codec->extradata_size);
+	audioCodec->extradata = reinterpret_cast(codecContextExtraData.data());
+	audioCodec->extradata_size = codecContextExtraData.size();
+
+	// initializing the structure by opening the codec
+	if (avcodec_open2(avVideoCodec.get(), codec, nullptr) < 0) {
+		cerr <<"Rotor: Could not open codec"<< endl;
+		return false;
+	}
+	*/
+	
+	//avcodec.h line 1026
+	
+	
+	Packet packet(avFormat.get());
+	if (packet.packet.data == nullptr) {
+		//done
+		return true;
+	}
+	
+	cerr << "audio codec context -  sample rate: "<< audioCodec->sample_rate <<", channels: "<<audioCodec->channels<<", sample format: "<<audioCodec->sample_fmt<<endl;
+	
+	
+	do {
+		packet.reset(avFormat.get());
+		if (packet.packet.stream_index != stream->index)
+			continue;	// the packet is not about the video stream we want, let's jump again the start of the loop
+	} while(0);
+	
+	// allocating an AVFrame
+	std::shared_ptr<AVFrame> avFrame(avcodec_alloc_frame(), &av_free);
+
+	// the current packet of data
+	//Packet packet;
+	// data in the packet of data already processed
+	size_t offsetInData = 0;
+	
+	
+
+	/*
+	// the decoding loop, running until EOF
+	while (true) {
+		// reading a packet using libavformat
+		if (offsetInData >= packet.packet.size) {
+			do {
+				packet.reset(avFormat.get());
+				if (packet.stream_index != videoStream->index)
+					continue;
+			} while(0);
+		}
+
+		// preparing the packet that we will send to libavcodec
+		AVPacket packetToSend;
+		packetToSend.data = packet.packet.data + offsetInData;
+		packetToSend.size = packet.packet.size - offsetInData;
+		
+		// sending data to libavcodec
+		int isFrameAvailable = 0;
+		const auto processedLength = avcodec_decode_video2(avVideoCodec.get(), avFrame.get(), &isFrameAvailable, &packetToSend);
+		if (processedLength < 0) {
+			av_free_packet(&packet);
+			throw std::runtime_error("Error while processing the data");
+		}
+		offsetInData += processedLength;
+
+		// processing the image if available
+		if (isFrameAvailable) {
+			// display image on the screen
+
+			// sleeping until next frame
+			const auto msToWait = avVideoContext->ticks_per_frame * 1000 * avVideoContext->time_base.num / avVideoContext->time_base.den;
+			std::this_thread::sleep(std::chrono::milliseconds(msToWait));
+		}
+	}
+	*/
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