FFmpeg中编码类型为rawvideo无须解码直接显示测试代码

Myth丶恋晨 2021-12-16 04:08 637阅读 0赞

在 [https://blog.csdn.net/fengbingchun/article/details/93975325][https_blog.csdn.net_fengbingchun_article_details_93975325] 中介绍过通过FFmpeg可以直接获取usb视频流并解码显示的测试代码，当时通过usb获取到的视频流编码类型为AV\_CODEC\_ID\_RAWVIDEO，像素格式为AV\_PIX\_FMT\_YUYV422，其实编码类型为rawvideo的视频流可以不经过解码操作直接就可进行显示，测试代码如下：

#include "funset.hpp"
    #include <stdio.h>
    #include <iostream>
    #include <memory>
    #include <fstream>
    
    #ifdef __cplusplus
    extern "C" {
    #endif
    
    #include <libavdevice/avdevice.h>
    #include <libavformat/avformat.h>
    #include <libavcodec/avcodec.h>
    #include <libswscale/swscale.h>
    #include <libavutil/mem.h>
    #include <libavutil/imgutils.h>
    
    #ifdef __cplusplus
    }
    #endif
    
    #include <opencv2/opencv.hpp>
    
    int test_ffmpeg_stream_show()
    {
    	avdevice_register_all();
    
    #ifndef _MSC_VER
    	const char* input_format_name = "video4linux2";
    	const char* url = "/dev/video0";
    
    	AVInputFormat* input_fmt = av_find_input_format(input_format_name);
    	AVFormatContext* format_ctx = avformat_alloc_context();
    
    	int ret = avformat_open_input(&format_ctx, url, input_fmt, nullptr);
    	if (ret != 0) {
    		fprintf(stderr, "fail to open url: %s, return value: %d\n", url, ret);
    		return -1;
    	}
    
    	ret = avformat_find_stream_info(format_ctx, nullptr);
    	if (ret < 0) {
    		fprintf(stderr, "fail to get stream information: %d\n", ret);
    		return -1;
    	}
    
    	int video_stream_index = -1;
    	for (unsigned int i = 0; i < format_ctx->nb_streams; ++i) {
    		const AVStream* stream = format_ctx->streams[i];
    		if (stream->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
    			video_stream_index = i;
    			fprintf(stdout, "type of the encoded data: %d, dimensions of the video frame in pixels: width: %d, height: %d, pixel format: %d\n",
    				stream->codecpar->codec_id, stream->codecpar->width, stream->codecpar->height, stream->codecpar->format);
    		}
    	}
    
    	if (video_stream_index == -1) {
    		fprintf(stderr, "no video stream\n");
    		return -1;
    	}
    
    	AVCodecParameters* codecpar = format_ctx->streams[video_stream_index]->codecpar;
    	const AVCodec* codec = avcodec_find_decoder(codecpar->codec_id);
    	if (!codec) {
    		fprintf(stderr, "fail to avcodec_find_decoder\n");
    		return -1;
    	}
    
    	AVCodecContext* codec_ctx = avcodec_alloc_context3(codec);
    	if (!codec_ctx) {
    		fprintf(stderr, "fail to avcodec_alloc_context3\n");
    		return -1;
    	}
    
    	codec_ctx->pix_fmt = AVPixelFormat(codecpar->format);
    	codec_ctx->height = codecpar->height;
    	codec_ctx->width = codecpar->width;
    	codec_ctx->thread_count = 16;
    	ret = avcodec_open2(codec_ctx, codec, nullptr);
    	if (ret != 0) {
    		fprintf(stderr, "fail to avcodec_open2: %d\n", ret);
    		return -1;
    	}
    
    	AVPacket* packet = (AVPacket*)av_malloc(sizeof(AVPacket));
    	SwsContext* sws_ctx = sws_getContext(codec_ctx->width, codec_ctx->height, codec_ctx->pix_fmt, codec_ctx->width, codec_ctx->height, AV_PIX_FMT_BGR24, 0, nullptr, nullptr, nullptr);
    	if (!packet || !sws_ctx) {
    		fprintf(stderr, "fail to alloc\n");
    		return -1;
    	}
    
    	uint8_t *bgr_data[4], *yuyv422_data[4];
    	int bgr_linesize[4], yuyv422_linesize[4];
    	av_image_alloc(bgr_data, bgr_linesize, codec_ctx->width, codec_ctx->height, AV_PIX_FMT_BGR24, 1);
    	av_image_alloc(yuyv422_data, yuyv422_linesize, codec_ctx->width, codec_ctx->height, AV_PIX_FMT_YUYV422, 1);
    	cv::Mat mat(codec_ctx->height, codec_ctx->width, CV_8UC3);
    	const char* winname = "usb video";
    	cv::namedWindow(winname);
    	const uint8_t *srcSlice[1];
    
    	while (1) {
    		ret = av_read_frame(format_ctx, packet);
    		if (ret >= 0 && packet->stream_index == video_stream_index) {
    			srcSlice[0] = packet->data;
    			sws_scale(sws_ctx, srcSlice, yuyv422_linesize, 0, codec_ctx->height, bgr_data, bgr_linesize);
    			mat.data = bgr_data[0];
    			cv::imshow(winname, mat);
    		}
    
    		av_packet_unref(packet);
    
    		int key = cv::waitKey(25);
    		if (key == 27) break;
    	}
    
    	cv::destroyWindow(winname);
    	sws_freeContext(sws_ctx);
    	avformat_close_input(&format_ctx);
    	av_freep(packet);
    	av_freep(&bgr_data[0]);
    	av_freep(&yuyv422_data[0]);
    
    	fprintf(stdout, "test finish\n");
    
    	return 0;
    #else
    	fprintf(stderr, "Error: this interface only support usb camera: encode type: rawvideo\n");
    	return -1;
    #endif
    }

执行结果如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlbmdiaW5nY2h1bg_size_16_color_FFFFFF_t_70][]

**GitHub**：[https://github.com//fengbingchun/OpenCV\_Test][https_github.com_fengbingchun_OpenCV_Test]

[https_blog.csdn.net_fengbingchun_article_details_93975325]: https://blog.csdn.net/fengbingchun/article/details/93975325
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlbmdiaW5nY2h1bg_size_16_color_FFFFFF_t_70]: /images/20211214/9aa1d2bba1e74328adf931ada0f3141e.png
[https_github.com_fengbingchun_OpenCV_Test]: https://github.com//fengbingchun/OpenCV_Test