直接将视频文件原码流转换成YUV，输出到屏幕显示

#include "stdafx.h"

#define inline _inline
#ifndef INT64_C
#define INT64_C(c) (c ## LL)
#define UINT64_C(c) (c ## ULL)
#endif

#ifdef __cplusplus
extern "C" {
#endif

#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
#ifdef __cplusplus
}
#endif
#include <stdio.h>
#include "SDL.h"
#include "SDL_thread.h"
#include <windows.h>
static void SaveFrame(AVFrame *pFrame, int width, int height, int iFrame);
#define SDL_AUDIO_BUFFER_SIZE 1024
static int sws_flags = SWS_BICUBIC;

int main(int argc, char *argv[])
{
AVFormatContext *pFormatCtx;
int i, videoStream(-1);
AVCodecContext *pCodecCtx;
AVCodec *pCodec;
AVFrame *pFrame;
AVPacket packet;
int frameFinished;
float aspect_ratio;
AVCodecContext *aCodecCtx;
SDL_Overlay *bmp;
SDL_Surface *screen;
SDL_Rect rect;
SDL_Event event;

av_register_all();
const char* filename = "D:\\Wildlife.wmv";
pFormatCtx = avformat_alloc_context();
if (!pFormatCtx)
{
fprintf(stderr, "Memory error/n");
exit(1);
}
//打开视频文件
if(avformat_open_input(&pFormatCtx, filename, NULL, NULL)!=0)
return -1;
//查找视频流信息
if(av_find_stream_info(pFormatCtx)<0)
return -1; // Couldn't find stream information
// Dump information about file onto standard error
av_dump_format(pFormatCtx, 0, argv[1], 0);

// 查找视频帧
for(i=0; i<pFormatCtx->nb_streams; i++)
{
if(pFormatCtx->streams[i]->codec->codec_type== AVMEDIA_TYPE_VIDEO&& videoStream<0)
{
videoStream=i;
}
}
if(videoStream==-1)
return -1; // Didn't find a video stream

// 查找解码器

pCodecCtx=pFormatCtx->streams[videoStream]->codec;
pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
if(pCodec==NULL)
{
fprintf(stderr, "Unsupported codec!/n");
return -1; // Codec not found
}
// 打开解码器
if(avcodec_open(pCodecCtx, pCodec)<0)
return -1; // Could not open codec

// 申请帧内存
pFrame=avcodec_alloc_frame();

uint8_t *buffer;
int numBytes;
// Determine required buffer size and allocate buffer
numBytes=avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width,
pCodecCtx->height);
buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));

if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))
{
fprintf(stderr, "Could not initialize SDL - %s/n", SDL_GetError());
exit(1);
}

#ifndef __DARWIN__
screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, 0);
#else
screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 24, 0);
#endif
if(!screen)
{
fprintf(stderr, "SDL: could not set video mode - exiting/n");
exit(1);
}

bmp = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height,
SDL_YV12_OVERLAY, screen);

static struct SwsContext *img_convert_ctx;
if (img_convert_ctx == NULL)
{
img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,
pCodecCtx->pix_fmt,
pCodecCtx->width, pCodecCtx->height,
PIX_FMT_YUV420P,
sws_flags, NULL, NULL, NULL);
if (img_convert_ctx == NULL)
{
fprintf(stderr, "Cannot initialize the conversion context/n");
exit(1);
}
}
i=0;
//不停的从码流中提取帧数据
while(av_read_frame(pFormatCtx, &packet)>=0)
{
// 判定数据包是否来自视频流
if(packet.stream_index==videoStream)
{
// 解码
avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished,
&packet);
// Did we get a video frame?
if(frameFinished)
{
// Convert the image from its native format to RGB
/*sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize,
0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);*/
// Save the frame to disk
/*if(++i<=5)
SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, i);*/
//创建一个覆盖，用于显示
SDL_LockYUVOverlay(bmp);
AVPicture pict;
pict.data[0] = bmp->pixels[0];
pict.data[1] = bmp->pixels[2];
pict.data[2] = bmp->pixels[1];

pict.linesize[0] = bmp->pitches[0];
pict.linesize[1] = bmp->pitches[2];
pict.linesize[2] = bmp->pitches[1];

// Convert the image into YUV format that SDL uses
/*img_convert(&pict, PIX_FMT_YUV420P,
(AVPicture *)pFrame, pCodecCtx->pix_fmt,
pCodecCtx->width, pCodecCtx->height);*/
sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize,
0, pCodecCtx->height, pict.data, pict.linesize);
//解锁覆盖
SDL_UnlockYUVOverlay(bmp);
rect.x = 0;
rect.y = 0;
rect.w = pCodecCtx->width;
rect.h = pCodecCtx->height;
//显示
SDL_DisplayYUVOverlay(bmp, &rect);
Sleep(20);
}
}

// Free the packet that was allocated by av_read_frame
av_free_packet(&packet);

SDL_PollEvent(&event);
switch(event.type)
{
case SDL_QUIT:
SDL_Quit();
exit(0);
break;
default: break;
}
};
// Free the YUV image
av_free(buffer);

// Free the YUV frame
av_free(pFrame);
// Close the codec
avcodec_close(pCodecCtx);
// Close the video file
av_close_input_file(pFormatCtx);
return 0;
}