SDL2 播放视频文件(MP4)

1.简介

这里引入FFmpeg库，获取视频流数据，然后通过FFmpeg将视频流解码成YUV原始数据，再将YUV数据送入到SDL库中实现视频播放。

2.FFmpeg的操作流程

注册API：av_register_all()
构建输入AVFormatContext上下文：avformat_open_input()
查找音视频流信息：avformat_find_stream_info()
查找解码器：avcodec_find_decoder()
打开解码器：avcodec_open2()
然后通过while循环，不停的读取数据：av_read_frame()
帧解码：avcodec_send_packet()和avcodec_receive_frame()

3.SDL显示视频流程

初始化SDL：SDL_Init();
创建窗口：SDL_CreateWindow();
创建渲染器：SDL_CreateRenderer();
创建纹理：SDL_CreateTexture();
设置纹理数据：SDL_UpdateTexture();
纹理复制给渲染目标：使用SDL_RenderCopy()将纹理数据复制给渲染目标。在使用SDL_RenderCopy()之前，可以使用SDL_RenderClear()先使用清空渲染目标。
显示界面：SDL_RenderPresent()；

4.示例

#include <stdio.h>
#include <SDL.h>

extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
};

#define __STDC_CONSTANT_MACROS
//Refresh Event
#define SFM_REFRESH_EVENT  (SDL_USEREVENT + 1)
#define SFM_BREAK_EVENT  (SDL_USEREVENT + 2)

int thread_exit = 0;
int thread_pause = 0;

int sfp_refresh_thread(void *opaque) 
{
	while (!thread_exit) 
	{
		if (!thread_pause) 
		{
			SDL_Event event;
			event.type = SFM_REFRESH_EVENT;
			SDL_PushEvent(&event);
		}
		SDL_Delay(40);
	}

	//Break
	SDL_Event event;
	event.type = SFM_BREAK_EVENT;
	SDL_PushEvent(&event);

	return 0;
}

AVFrame *recv(AVCodecContext *codecCtx)
{
	if (!codecCtx)
	{
		return NULL;
	}

	AVFrame *frame = av_frame_alloc();
	int ret = avcodec_receive_frame(codecCtx, frame);

	if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
	{
		av_frame_free(&frame);
		return NULL;
	}
	else if (ret < 0)
	{
		av_frame_free(&frame);
		return NULL;
	}

	return frame;
}


#undef main
int main(int argc, char* argv[])
{
	///ffmpeg
	avformat_network_init();

	AVFormatContext* pFormatCtx = NULL;
	const char* inputUrl = "./3.mp4";

	///打开输入的流
	int ret = avformat_open_input(&pFormatCtx, inputUrl, NULL, NULL);
	if (ret != 0)
	{
		printf("Couldn't open input stream.\n");
		return -1;
	}

	//查找流信息
	if (avformat_find_stream_info(pFormatCtx, NULL) < 0)
	{
		printf("Couldn't find stream information.\n");
		return -1;
	}

	//找到视频流索引
	int video_index = av_find_best_stream(pFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
	AVStream* st = pFormatCtx->streams[video_index];
	AVCodec* codec = nullptr;
	//找到解码器
	codec = avcodec_find_decoder(st->codecpar->codec_id);
	if (!codec)
	{
		fprintf(stderr, "Codec not found\n");
		return -1;
	}

	//申请AVCodecContext
	AVCodecContext* pCodecCtx = avcodec_alloc_context3(codec);
	if (!pCodecCtx)
	{
		return -1;
	}

	avcodec_parameters_to_context(pCodecCtx, pFormatCtx->streams[video_index]->codecpar);

	//打开解码器
	if ((ret = avcodec_open2(pCodecCtx, codec, NULL) < 0))
	{
		return -1;
	}

	AVFrame *pFrameYUV = av_frame_alloc();
	AVPacket* pkt = av_packet_alloc();

	unsigned char *out_buffer = (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, 
		out_buffer,
		AV_PIX_FMT_YUV420P,
		pCodecCtx->width, 
		pCodecCtx->height,
		1
	);

	//------------SDL----------------
	int screen_w, screen_h;
	SDL_Rect sdlRect;
	
	struct SwsContext *img_convert_ctx;
	char filepath[] = "Titanic.ts";


	//Output Info-----------------------------
	printf("---------------- File Information ---------------\n");
	av_dump_format(pFormatCtx, 0, filepath, 0);
	printf("-------------------------------------------------\n");

	img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
		pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);


	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
		printf("Could not initialize SDL - %s\n", SDL_GetError());
		return -1;
	}

	//SDL 2.0 Support for multiple windows
	screen_w = pCodecCtx->width;
	screen_h = pCodecCtx->height;
	SDL_Window *screen = SDL_CreateWindow("SDL Play Video", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
		screen_w, screen_h, SDL_WINDOW_OPENGL);

	if (!screen) 
	{
		printf("SDL: could not create window - exiting:%s\n", SDL_GetError());
		return -1;
	}

	SDL_Renderer *sdlRenderer = SDL_CreateRenderer(screen, -1, 0);
	//IYUV: Y + U + V  (3 planes)
	//YV12: Y + V + U  (3 planes)
	SDL_Texture *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;
	SDL_Thread *video_tid = SDL_CreateThread(sfp_refresh_thread, NULL, NULL);
	//------------SDL End------------
	//Event Loop
	SDL_Event event;
	for (;;) 
	{
		//Wait
		SDL_WaitEvent(&event);
		if (event.type == SFM_REFRESH_EVENT) 
		{
			//不断的读取一帧数据
			while (1) 
			{
				if (av_read_frame(pFormatCtx, pkt) < 0)
					thread_exit = 1;

				if (pkt->stream_index == video_index)
					break;
			}

			//一次send 多次recv
			int ret = avcodec_send_packet(pCodecCtx, pkt);
			if (ret < 0)
				continue;

			//释放资源
			av_packet_unref(pkt);

			while (1)
			{
				AVFrame *pFrame = recv(pCodecCtx);
				if (!pFrame)
					break;

				sws_scale(img_convert_ctx, (const unsigned char* const*)pFrame->data, pFrame->linesize, 0,
								pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);
				//SDL---------------------------
				SDL_UpdateTexture(sdlTexture, NULL, pFrameYUV->data[0], pFrameYUV->linesize[0]);
				SDL_RenderClear(sdlRenderer);
				//SDL_RenderCopy( sdlRenderer, sdlTexture, &sdlRect, &sdlRect );  
				SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
				SDL_RenderPresent(sdlRenderer);
				//SDL End-----------------------

				av_frame_free(&pFrame);
			}
		}
		else if (event.type == SDL_KEYDOWN) 
		{
			//空格键暂停播放
			if (event.key.keysym.sym == SDLK_SPACE)
				thread_pause = !thread_pause;
		}
		else if (event.type == SDL_QUIT) 
		{
			thread_exit = 1;
		}
		else if (event.type == SFM_BREAK_EVENT) 
		{
			break;
		}
	}

	SDL_Quit();
	//--------------
	sws_freeContext(img_convert_ctx);
	avcodec_close(pCodecCtx);
	avcodec_free_context(&pCodecCtx);
	avformat_close_input(&pFormatCtx);
	av_frame_free(&pFrameYUV);
	av_packet_free(&pkt);

	return 0;
}