FFmpeg_11_视频流自定义分辨率播放

      /******************
程序功能：
    内存方式读取视频流，对视频流自定义分辨率进行播放
******************/
#include "sdl2\SDL.h"
extern "C"
{
#include "libavformat\avformat.h"
#include "libswscale\swscale.h"
};
FILE *fp = NULL;
int read_buffer(void *opaque,uint8_t *buf,int buf_size)
{
	if(!feof(fp))
	{
		int true_size = fread(buf,1,buf_size,fp);
		return true_size;
	}
	else
		return -1;
}
/*
	缩放一帧视频画面的分辨率（适用于YUV420P类型的视频帧）：
	pCodecCtx -- 保存了相应流的详细编码信息的结构体（如视频的宽、高、编码类型等）
	pFrame -- 用于保存数据帧的数据结构（分辨率改变前）
	pNewFrame -- 用于保存数据帧的数据结构（分辨率改变后）
	NewWidth -- 新分辨率的宽度
	NewHeight -- 新分辨率的高度
*/
void ResolutionChange(AVCodecContext *pCodecCtx,AVFrame *pFrame,AVFrame *pNewFrame,int pNewWidth,int pNewHeight)
{
	pNewFrame->linesize[0] = pNewWidth;
	pNewFrame->linesize[1] = pNewWidth/2;
	pNewFrame->linesize[2] = pNewWidth/2;
	//用 sws_getContext函数 得到 sws_scale函数 运行的上下文，之后用 sws_scale函数 将图形缩放
	struct SwsContext *pSwsCtx = NULL;
	pSwsCtx = sws_getContext(pCodecCtx->width,pCodecCtx->height,PIX_FMT_YUV420P,pNewWidth,pNewHeight,PIX_FMT_YUV420P,SWS_SINC,NULL,NULL,NULL);
	if(pSwsCtx == NULL)
		return ;
	sws_scale(pSwsCtx,pFrame->data,pFrame->linesize,0,pCodecCtx->height,pNewFrame->data,pNewFrame->linesize);
	sws_freeContext(pSwsCtx);
}
int main(int argc,char** argv)
{
	av_register_all();

	AVFormatContext *pFormatCtx = NULL;
	pFormatCtx = avformat_alloc_context();
	char filepath[]="test.flv";
	fp = fopen(filepath,"rb");
	if(fp == NULL)
		exit(1);
	unsigned char *aviobuffer = (unsigned char *)av_malloc(32768);//32K
	AVIOContext *avio = avio_alloc_context(aviobuffer,32768,0,NULL,read_buffer,NULL,NULL);
	pFormatCtx->pb = avio;
	if(avformat_open_input(&pFormatCtx,NULL,NULL,NULL) != 0)
		exit(1);
	if(avformat_find_stream_info(pFormatCtx,NULL) < 0)
		exit(1);

	int videoIndex = -1;
	for(int i=0;i<pFormatCtx->nb_streams;i++)
	{
		if(pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
		{
			videoIndex = i;
            break;
		}
	}
	if(videoIndex == -1)
        exit(1);

	AVCodecContext *pCodecCtx;
	pCodecCtx = pFormatCtx->streams[videoIndex]->codec;
	AVCodec *pCodec;
	pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
	if(pCodec == NULL)
		exit(1);
	if(avcodec_open2(pCodecCtx,pCodec,NULL) < 0)
		exit(1);

	AVFrame *pFrame,*pNewFrame;
    pFrame = av_frame_alloc();
    pNewFrame = av_frame_alloc();
	if((pFrame == NULL) || (pNewFrame == NULL))
		exit(1);
	//自定义分辨率
	int NewWidth = 640,NewHeight = 480;
	int PictureSize = avpicture_get_size(PIX_FMT_YUV420P,NewWidth,NewHeight);
	uint8_t* buffer = (uint8_t *)av_malloc(PictureSize*sizeof(uint8_t));
	avpicture_fill((AVPicture *)pNewFrame,buffer,PIX_FMT_YUV420P,NewWidth,NewHeight);

	if(SDL_Init(SDL_INIT_VIDEO|SDL_INIT_AUDIO|SDL_INIT_TIMER))
		exit(1);
	SDL_Window *window = nullptr;
	window = SDL_CreateWindow("MyPlayer",SDL_WINDOWPOS_UNDEFINED,SDL_WINDOWPOS_UNDEFINED,NewWidth,NewHeight,SDL_WINDOW_OPENGL);
	if(!window)
		exit(1);
	SDL_Renderer *renderer = nullptr;
	renderer = SDL_CreateRenderer(window,-1,0);
	if(renderer == nullptr)
		exit(1);
	SDL_Texture *texture = nullptr;
	texture = SDL_CreateTexture(renderer,SDL_PIXELFORMAT_YV12,SDL_TEXTUREACCESS_STREAMING,NewWidth,NewHeight);
    SDL_Rect rect;
	SDL_Event event;

	AVPacket *packet=(AVPacket *)malloc(sizeof(AVPacket));
	av_new_packet(packet,PictureSize);
	int frameFinished;
	while(av_read_frame(pFormatCtx,packet) >= 0)
	{
		if(packet->stream_index == videoIndex)
		{
			if(avcodec_decode_video2(pCodecCtx,pFrame,&frameFinished,packet) >= 0)
			{
				if(frameFinished)
				{
					ResolutionChange(pCodecCtx,pFrame,pNewFrame,NewWidth,NewHeight);
					rect.x = 0;
					rect.y = 0;
					rect.w = NewWidth;
					rect.h = NewHeight;
					SDL_UpdateYUVTexture(texture,&rect,pNewFrame->data[0],pNewFrame->linesize[0],pNewFrame->data[1],pNewFrame->linesize[1],pNewFrame->data[2],pNewFrame->linesize[2]);
					SDL_RenderClear(renderer);
					SDL_RenderCopy(renderer,texture,&rect,&rect);
                    SDL_RenderPresent(renderer);
					SDL_Delay(20);
				}
			}
			else
				exit(1);
		}
		av_free_packet(packet);
		SDL_PollEvent(&event);
		switch(event.type)
		{
		case SDL_QUIT:
			SDL_Quit();
			exit(1);
			break;
		default:
			break;
		}
	}
	SDL_DestroyTexture(texture);
	SDL_Quit();
	av_free(buffer);
	av_frame_free(&pNewFrame);
    av_frame_free(&pFrame);
    avcodec_close(pCodecCtx);
    avformat_close_input(&pFormatCtx);
	return 0;
}