FFMPEG解码实时流，支持cpu、gpu解码

官网下载的ffmpeg目前只能下载到X64版本的库，具体编译请参考windows编译ffmpeg源码（32位库）_windows 32位ffmpeg动态库-CSDN博客

直接上代码

int VideoDecodeModule::Open(std::string strUrl)
{
	AVFormatContext *pFormatCtx = nullptr;
	AVCodec *pCodec = nullptr;
	AVCodecContext* pCodecCtx = nullptr;
	AVDictionary *opt = nullptr;
	std::string decodeName = "";
	AVBufferRef* pBufferRef = nullptr;
	int ret = 0;
	int videoStream = -1;
	char errorbuf[1024] = { 0 };
	av_dict_set(&opt, "buffer_size", "1024000", 0);        // 缓冲区大小 单位字节 解决高画质模糊的问题
	av_dict_set(&opt, "max_delay", "100", 0);              // 最大延时 单位微妙
	av_dict_set(&opt, "stimeout", "3000000", 0);           // 设置超时断开连接时间 3s 单位微妙
	av_dict_set(&opt, "rtsp_transport", "tcp", 0);         // 以tcp方式打开，如果以udp方式打开将tcp替换为udp
	av_dict_set(&opt, "fflags", "nobuffer", 0);
	av_dict_set(&opt, "rtbufsize", "6", 0);
	av_dict_set(&opt, "start_time_realtime", 0, 0);

	if ((ret = avformat_open_input(&pFormatCtx, strUrl.data(), nullptr, &opt)) != 0)
	{
		av_strerror(ret, errorbuf, sizeof(errorbuf));
		return -1;
	}
	
	m_spFormatContext = std::shared_ptr<AVFormatContext>(pFormatCtx, [](AVFormatContext* ctx){
		avformat_close_input(&ctx);
	});

	if ((ret = avformat_find_stream_info(pFormatCtx, nullptr)) < 0)
	{
		av_strerror(ret, errorbuf, sizeof(errorbuf));
		return -1;
	}

	if ((ret = av_find_best_stream(pFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, &pCodec, 0)) < 0)
	{
		av_strerror(ret, errorbuf, sizeof(errorbuf));
		return -1;
	}
	videoStream = ret;
	m_video = pFormatCtx->streams[videoStream];

	if (m_decodeType == DT_CPU)
	{
		if (!(pCodec = avcodec_find_decoder(m_video->codecpar->codec_id)))
		{
			int error = AVERROR(ENOMEM);
			return -1;
		}
	}
	else if (m_decodeType == DT_INTER_QSV)
	{
		decodeName = GetCodeName(m_video->codecpar->codec_id, DT_INTER_QSV);
		if (av_hwdevice_ctx_create(&pBufferRef, AV_HWDEVICE_TYPE_QSV, "auto", nullptr, 0) != 0)
		{
			return -1;
		}
		if (!(pCodec = avcodec_find_decoder_by_name(decodeName.data())))
		{
			int error = AVERROR(ENOMEM);
			return -1;
		}
	}
	else if (m_decodeType == DT_NVIDIA_CUDA)
	{
		decodeName = GetCodeName(m_video->codecpar->codec_id, DT_NVIDIA_CUDA);
		if (av_hwdevice_ctx_create(&pBufferRef, AV_HWDEVICE_TYPE_CUDA, "auto", nullptr, 0) != 0)
		{
			return -1;
		}
		if (!(pCodec = avcodec_find_decoder_by_name(decodeName.data())))
		{
			int error = AVERROR(ENOMEM);
			return -1;
		}
	}

	if (auto frame = av_frame_alloc())
	{
		m_spSwFrame = std::shared_ptr<AVFrame>(frame, [](AVFrame* p) {av_frame_free(&p); });
	}
	
	if (!(pCodecCtx = avcodec_alloc_context3(pCodec)))
	{
		return -1;
	}

	m_spCodecContext = std::shared_ptr<AVCodecContext>(pCodecCtx, [](AVCodecContext* ctx)
	{
		avcodec_free_context(&ctx);
	});

	m_spCodecContext->codec_id = m_video->codecpar->codec_id;
	if (m_video->codecpar->extradata_size)
	{
		m_spCodecContext->extradata = (uint8_t*)av_mallocz(m_video->codecpar->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
		if (!m_spCodecContext->extradata)
		{
			return -1;
		}
		memcpy(m_spCodecContext->extradata, m_video->codecpar->extradata, m_video->codecpar->extradata_size);
		m_spCodecContext->extradata_size = m_video->codecpar->extradata_size;
	}

	m_spCodecContext->flags2 |= AV_CODEC_FLAG2_FAST;    // 允许不符合规范的加速技巧。
	m_spCodecContext->thread_count = 8;                 // 使用8线程解码

	if ((ret = avcodec_parameters_to_context(m_spCodecContext.get(), m_video->codecpar)) < 0)
	{
		av_strerror(ret, errorbuf, sizeof(errorbuf));
		return -1;
	}
	
	if (m_decodeType == DT_INTER_QSV)
	{
		m_spCodecContext->opaque = pBufferRef;
		m_spCodecContext->get_format = GetHWQsvFormat;
	}
	else if (m_decodeType == DT_NVIDIA_CUDA)
	{
		m_spCodecContext->hw_device_ctx = av_buffer_ref(pBufferRef);
		m_spCodecContext->opaque = this;
		m_spCodecContext->get_format = GetHWCudaFormat;
	}

	if ((ret = avcodec_open2(m_spCodecContext.get(), pCodec, nullptr)) < 0)
	{
		av_strerror(ret, errorbuf, sizeof(errorbuf));
		return -1;
	}
	m_isConnect = true;
	return ret;
}

if (!spFrame)
		return;
	/// 解码的图片宽
	int width = spFrame->width;
	/// 解码的图片高
	int height = spFrame->height;
	// 计算转码后的图片裸数据需要的大小
	int nSrcbuffSize = av_image_get_buffer_size(m_pixelFormat, width, height, 1);
	if (nSrcbuffSize > m_dstBuffer.size())
	{
		m_dstBuffer.resize(nSrcbuffSize, '\0');
	}
	std::shared_ptr<SwsContext>	spSwsContext = nullptr;
	/// 判断是否需要格式转换
	if (m_pixelFormat != (AVPixelFormat)spFrame->format)
	{
		AVPixelFormat srcFmt = (AVPixelFormat)spFrame->format;
		SwsContext* image_sws_ctx = sws_getContext(width, height, srcFmt,
			width, height, m_pixelFormat, SWS_FAST_BILINEAR, nullptr, nullptr, nullptr);
		spSwsContext = std::shared_ptr<SwsContext>(image_sws_ctx, [](SwsContext* p) {sws_freeContext(p); });
		uint8_t* data[4] = { nullptr };
		int linesize[4] = { 0 };
		av_image_fill_arrays(data, linesize, m_dstBuffer.data(), m_pixelFormat, width, height, 1);

		int ret = sws_scale(spSwsContext.get(), (uint8_t const* const*)spFrame->data, spFrame->linesize, 0, height, data, linesize);
		if (ret < 0)
			return;
	}

	if (m_pFrameDataCallBack)
	{
		FrameInfo info;
		info.format = GetVideoFormatByAVPixelFormat(m_pixelFormat);
		info.width = width;
		info.height = height;
		info.pts = spFrame->pts / 1000;

		m_pFrameDataCallBack->cbFrameDataCallBack(m_dstBuffer.data(), m_dstBuffer.size(), info, m_pFrameDataCallBack->pUser);
	}

解码显示效果图