FFmpeg —— 8.示例程序（二）：屏幕录制并保存为YUV、H264格式文件

男娘i 2021-09-24 03:58 600阅读 0赞

屏幕录制的命令行形式可以参考以下链接

[https://blog.csdn.net/leixiaohua1020/article/details/38284961][https_blog.csdn.net_leixiaohua1020_article_details_38284961]

我们所做的示例程序，说白了，就是通过API程序代码来实现命令行的操作指令。

# 命令行形式 #

## 设备列表  ##

ffmpeg -list_devices true -f dshow -i dummy

## 查看设备选项 ##

ffmpeg -list_options true -f dshow -i video="Integrated Camera"

##  播放摄像头数据 ##

ffplay -s 1280x720 -f dshow -i video="Integrated Camera"

设置分辨率为 1280x720

## 屏幕录制 ##

### Linux版本 ###

Linux下可以使用x11grab

ffmpeg -f x11grab -s 1600x900 -r 50 -vcodec libx264 –preset:v ultrafast –tune:v zerolatency -crf 18 -f mpegts udp://localhost:1234

###  Windows版本 ###

Windows下屏幕录制的设备：gdigrab

gdigrab是基于GDI的抓屏设备，可以用于抓取屏幕的特定区域。在这里记录一下gdigrab的用法。  
gdigrab通过设定不同的输入URL，支持两种方式的屏幕抓取：  
（1）“desktop”：抓取整张桌面。或者抓取桌面中的一个特定的区域。  
（2）“title=\{窗口名称\}”：抓取屏幕中特定的一个窗口。

最简单的抓屏：

ffmpeg -f gdigrab -i desktop out.mpg

从屏幕的（10,20）点处开始，抓取640x480的屏幕，设定帧率为5

ffmpeg -f gdigrab -framerate 5 -offset_x 10 -offset_y 20 -video_size 640x480 -i desktop out.mpg

# 程序源码 #

/**
     * 最简单的基于FFmpeg的AVDevice例子（屏幕录制）
     * Simplest FFmpeg Device (Screen Capture)
     *
     * 归根结底，我们就是为了实现以下屏幕录制的命令：
     * ffmpeg -f gdigrab -i desktop out.mpg
     *
     * 本程序实现了屏幕录制功能。可以录制并播放桌面数据。是基于FFmpeg
     * 的libavdevice类库最简单的例子。通过该例子，可以学习FFmpeg中
     * libavdevice类库的使用方法。
     * 本程序在Windows下可以使用2种方式录制屏幕：
     *  1.gdigrab: Win32下的基于GDI的屏幕录制设备。
     *             抓取桌面的时候，输入URL为“desktop”。
     *  2.dshow: 使用Directshow。注意需要安装额外的软件screen-capture-recorder
     * 在Linux下可以使用x11grab录制屏幕。
     * 在MacOS下可以使用avfoundation录制屏幕。
     */
    
    #include <stdio.h>
    
    extern "C"
    {
    #include "libavcodec/avcodec.h"
    #include "libavformat/avformat.h"
    #include "libswscale/swscale.h"
    #include "libavdevice/avdevice.h"
    #include "libavutil/imgutils.h"
    #include "libavutil/dict.h"
    #include "SDL2/SDL.h"
    }
    
    #define OUTPUT_YUV420P 1
    #define OUTPUT_H264 1
    
    int main(int argc, char *argv[])
    {
    	AVFormatContext *pFormatCtx;
    	AVStream *videoStream;
    	AVCodecContext *pCodecCtx;
    	AVCodec *pCodec;
    	AVFrame *pFrame, *pFrameYUV;
    	AVPacket *pPacket;
    	SwsContext *pImgConvertCtx;
    
    	int videoIndex = -1;
    	unsigned int i = 0;
    
    	SDL_Window *screen;
    	SDL_Renderer *sdlRenderer;
    	SDL_Texture *sdlTexture;
    	SDL_Rect sdlRect;
    
    	int screen_w = 0;
    	int screen_h = 0;
    
    	printf("Starting...\n");
    
    	//register device
    	avdevice_register_all();
    
    	pFormatCtx = avformat_alloc_context();
    
    	//use gdigrab
    	AVInputFormat *ifmt = av_find_input_format("gdigrab");
    	if (!ifmt)
    	{
    		printf("can't find input device.\n");
    		return -1;
    	}
    
    	AVDictionary *options = NULL;
    	if (avformat_open_input(&pFormatCtx, "desktop", ifmt, &options) != 0)
    	{
    		printf("can't open input stream.\n");
    		return -1;
    	}
    
    	if (avformat_find_stream_info(pFormatCtx, NULL) < 0)
    	{
    		printf("can't find stream information.\n");
    		return -1;
    	}
    
    	for (i = 0; i < pFormatCtx->nb_streams; i++)
    	{
    		if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
    		{
    			videoIndex = i;
    			break;
    		}
    	}
    
    	if (videoIndex == -1)
    	{
    		printf("can't find a video stream.\n");
    		return -1;
    	}
    
    	videoStream = pFormatCtx->streams[videoIndex];
    	pCodec = avcodec_find_decoder(videoStream->codecpar->codec_id);
    	if (pCodec == NULL)
    	{
    		printf("codec not found.\n");
    		return -1;
    	}
    
    	pCodecCtx = avcodec_alloc_context3(pCodec);
    	if (!pCodecCtx)
    	{
    		printf("can't alloc codec context.\n");
    		return -1;
    	}
    
    	avcodec_parameters_to_context(pCodecCtx, videoStream->codecpar);
    
    	if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
    	{
    		printf("can't open codec.\n");
    		return -1;
    	}
    
    	pFrame = av_frame_alloc();
    	pFrameYUV = av_frame_alloc();
    	pPacket = (AVPacket*) av_malloc(sizeof(AVPacket));
    
    	unsigned char *outBuffer = (unsigned char*) av_malloc(
    			av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width,
    					pCodecCtx->height, 1));
    	av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize, outBuffer,
    			AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1);
    
    	pImgConvertCtx = sws_getContext(pCodecCtx->width, pCodecCtx->height,
    			pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height,
    			AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
    
    #if OUTPUT_YUV420P
    	FILE *fpYUV = fopen("output.yuv", "wb+");
    #endif
    
    #if OUTPUT_H264
    	AVCodecContext *pH264CodecCtx;
    	AVCodec *pH264Codec;
    
    	FILE *fpH264 = fopen("output.h264", "wb+");
    
    	//查找H264编码器
    	pH264Codec = avcodec_find_encoder(AV_CODEC_ID_H264);
    	if (!pH264Codec)
    	{
    		printf("can't find h264 codec.\n");
    		return -1;
    	}
    
    	pH264CodecCtx = avcodec_alloc_context3(pH264Codec);
    	pH264CodecCtx->codec_id = AV_CODEC_ID_H264;
    	pH264CodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
    	pH264CodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
    	pH264CodecCtx->width = pCodecCtx->width;
    	pH264CodecCtx->height = pCodecCtx->height;
    	pH264CodecCtx->time_base.num = 1;
    	pH264CodecCtx->time_base.den = 15;	//帧率（即一秒钟多少张图片）
    	pH264CodecCtx->bit_rate = 800000;	//比特率（调节这个大小可以改变编码后视频的质量）
    	pH264CodecCtx->gop_size = 12;
    	pH264CodecCtx->qmin = 10;
    	pH264CodecCtx->qmax = 51;
    	//some formats want stream headers to be separate
    	if (pH264CodecCtx->flags & AVFMT_GLOBALHEADER)
    	{
    		pH264CodecCtx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
    	}
    
    	// set option
    	AVDictionary *params = NULL;
    	//H.264
    	av_dict_set(&params, "preset", "superfast", 0);
    	av_dict_set(&params, "tune", "zerolatency", 0);	//实现实时编码
    	if (avcodec_open2(pH264CodecCtx, pH264Codec, &params) < 0)
    	{
    		printf("can't open video encoder.\n");
    		return -1;
    	}
    
    #endif
    
    	//SDL handle
    	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))
    	{
    		printf("can't initialize SDL - %s\n", SDL_GetError());
    		return -1;
    	}
    
    	screen_w = pCodecCtx->width;
    	screen_h = pCodecCtx->height;
    
    	screen = SDL_CreateWindow("Simplest ffmpeg device(screen capture)",
    	SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, screen_w, screen_h,
    			SDL_WINDOW_OPENGL);
    	if (!screen)
    	{
    		printf("SDL: can't create window - exiting: %s\n", SDL_GetError());
    		return -1;
    	}
    
    	sdlRenderer = SDL_CreateRenderer(screen, -1, 0);
    	sdlTexture = SDL_CreateTexture(sdlRenderer, SDL_PIXELFORMAT_IYUV,
    			SDL_TEXTUREACCESS_STREAMING, pCodecCtx->width, pCodecCtx->height);
    
    	sdlRect.x = 0;
    	sdlRect.y = 0;
    	sdlRect.w = screen_w;
    	sdlRect.h = screen_h;
    
    	while (av_read_frame(pFormatCtx, pPacket) >= 0)
    	{
    		if (pPacket->stream_index == videoIndex)
    		{
    			int ret = avcodec_send_packet(pCodecCtx, pPacket);
    			if (ret < 0)
    			{
    				printf("Decode error.\n");
    				return -1;
    			}
    
    			if (avcodec_receive_frame(pCodecCtx, pFrame) >= 0)
    			{
    				sws_scale(pImgConvertCtx,
    						(const unsigned char* const*) pFrame->data,
    						pFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data,
    						pFrameYUV->linesize);
    
    #if OUTPUT_YUV420P
    				int y_size = pCodecCtx->width * pCodecCtx->height;
    				fwrite(pFrameYUV->data[0], 1, y_size, fpYUV);		//Y
    				fwrite(pFrameYUV->data[1], 1, y_size / 4, fpYUV);	//U
    				fwrite(pFrameYUV->data[2], 1, y_size / 4, fpYUV);	//V
    #endif
    
    #if OUTPUT_H264
    				pFrameYUV->format = pCodecCtx->pix_fmt;
    				pFrameYUV->width = pCodecCtx->width;
    				pFrameYUV->height = pCodecCtx->height;
    				int ret = avcodec_send_frame(pH264CodecCtx, pFrameYUV);
    				if (ret < 0)
    				{
    					printf("failed to encode.\n");
    					return -1;
    				}
    
    				if (avcodec_receive_packet(pH264CodecCtx, pPacket) >= 0)
    				{
    					ret = fwrite(pPacket->data, 1, pPacket->size, fpH264);
    					if (ret < 0)
    					{
    						printf("write into output.h264 failed.\n");
    					}
    				}
    #endif
    				SDL_UpdateTexture(sdlTexture, &sdlRect, pFrameYUV->data[0],
    						pFrameYUV->linesize[0]);
    				SDL_RenderClear(sdlRenderer);
    				SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, &sdlRect);
    				SDL_RenderPresent(sdlRenderer);
    				SDL_Delay(40);
    			}
    		}
    
    		av_packet_unref(pPacket);
    	}
    
    	sws_freeContext(pImgConvertCtx);
    
    #if OUTPUT_YUV420P
    	fclose(fpYUV);
    #endif
    
    #if OUTPUT_H264
    	fclose(fpH264);
    #endif
    
    	SDL_Quit();
    
    	av_free(outBuffer);
    	av_frame_free(&pFrameYUV);
    	av_frame_free(&pFrame);
    	avcodec_close(pCodecCtx);
    	avcodec_close(pH264CodecCtx);
    	avformat_close_input(&pFormatCtx);
    
    
    	return 0;
    }

[https_blog.csdn.net_leixiaohua1020_article_details_38284961]: https://blog.csdn.net/leixiaohua1020/article/details/38284961