ffmpeg解码mp4视频数据保存成图片

/********
*本代码参考自雷神博客
*
**********/
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavdevice/avdevice.h>
#include<libswresample/swresample.h>
#include <libavutil/pixfmt.h>
#include <libswscale/swscale.h>
#ifdef __cplusplus
};
#endif

#define MAX_AUDIO_FRAME_SIZE  192000
#define SAMPLE_PRT(fmt...)   \
do {\
printf("[%s]-%d: ", __FUNCTION__, __LINE__);\
printf(fmt);\
}while(0)

//'1': Use H.264 Bitstream Filter
#define USE_H264BSF 1

void save_pnm(AVFrame *pFrame, int w, int h,int index)
{

FILE *fl;
char szFilename[32];
int  y;

// Open file
sprintf(szFilename, "%d.pnm", index);
fl=fopen(szFilename, "wb");

if(fl==NULL)
return;

fprintf(fl, "P6\n%d %d\n255\n", w, h); // 加入pnm文件头
// Write pixel data
for(y=0; y<h; y++)
{
fwrite(pFrame->data[0]+y*pFrame->linesize[0], 1, w*3, fl);
}

// Close file
fclose(fl);

}

int main(int argc, char *argv[])
{
char *file_path = "/home/grid/hefang";

AVFormatContext *pFormatCtx;
AVCodecContext *pCodecCtx;
AVCodec *pCodec;
AVFrame *pFrame, *pFrameRGB;
AVPacket *packet;
uint8_t *out_buffer;

static struct SwsContext *img_convert_ctx;

int videoStream, i, numBytes;
int ret, got_picture;

av_register_all(); //初始化FFMPEG  调用了这个才能正常适用编码器和解码器

//Allocate an AVFormatContext.
pFormatCtx = avformat_alloc_context();

if (avformat_open_input(&pFormatCtx, file_path, NULL, NULL) != 0) {
SAMPLE_PRT("open file error\n");
return -1;
}

if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
SAMPLE_PRT("Could't find stream infomation\n");
return -1;
}

videoStream = -1;

for (i = 0; i < pFormatCtx->nb_streams; i++) {
if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
videoStream = i;
}
}

if (videoStream == -1) {
SAMPLE_PRT("no find vedio_stream");
return -1;
}

///查找解码器
pCodecCtx = pFormatCtx->streams[videoStream]->codec;
pCodec = avcodec_find_decoder(pCodecCtx->codec_id);

if (pCodec == NULL) {
SAMPLE_PRT(" not found decodec.\n");
return -1;
}

///打开解码器
if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
SAMPLE_PRT("Could not open decodec.");
return -1;
}

pFrame = av_frame_alloc();
pFrameRGB = av_frame_alloc();

img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,
pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height,
AV_PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);

numBytes = avpicture_get_size(AV_PIX_FMT_RGB24, pCodecCtx->width,pCodecCtx->height);

out_buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
avpicture_fill((AVPicture *) pFrameRGB, out_buffer, AV_PIX_FMT_RGB24,
pCodecCtx->width, pCodecCtx->height);

int y_size = pCodecCtx->width * pCodecCtx->height;

packet = (AVPacket *) malloc(sizeof(AVPacket)); //分配一个packet
av_new_packet(packet, y_size); //分配packet的数据

av_dump_format(pFormatCtx, 0, file_path, 0); //输出视频信息

int index = 0;

while (av_read_frame(pFormatCtx, packet) >=0){
if (packet->stream_index == videoStream) {
ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture,packet);

if (ret < 0) {
SAMPLE_PRT("decode error.");
return -1;
}

if (got_picture) {
sws_scale(img_convert_ctx,
(uint8_t const * const *) pFrame->data,
pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data,
pFrameRGB->linesize);

save_pnm(pFrameRGB, pCodecCtx->width,pCodecCtx->height,index++); //保存图片
if (index > 100) return 0; //100张
}
}
av_free_packet(packet);
}
av_free(out_buffer);
av_free(pFrameRGB);
avcodec_close(pCodecCtx);
avformat_close_input(&pFormatCtx);

return 0;
}