最近因为项目需要，需要解码mp4文件或h264裸流。在总结网友资料以及ffmpeg新旧版本的不同而写的测试代码。成功将mp4文件解码（h264裸流也同样可解，需要改变源输入而已）
static void SaveFramePPM(uint8_t* pData_rgb, int width, int height, int iFrame)
{if (iFrame > 5)return;FILE *pFile=NULL;char szFilename[32] = {0};sprintf(szFilename, "d:\\test\\video\\%d.ppm", iFrame);if(NULL==( pFile = fopen(szFilename, "wb")))return;fprintf(pFile, "P6\n%d %d\n255\n", width, height);fwrite(pData_rgb, 1, height * width * 3, pFile);fclose(pFile);
}int Mp4ToPPm(const char* filepath) {// char filepath[] = "d:\\test\\video\\gop121.h264";int nCount = 0;int i = 0, videoIndex = -1, numBytes = 0, numBytes_rgb=0;int outLinesize_rgb[4] = {0}, ret = 0, ret1 = 0;uint8_t *out_buffer = NULL, *out_buffer_rgb = NULL；uint8_t *outData_rgb[4] = {NULL,NULL,NULL,NULL};AVFormatContext *pFormatCtx = NULL;AVCodecContext *pCodecCtx = NULL;AVCodec *pCodec = NULL;AVFrame *pFrame = NULL, * pFrameYUV = NULL;AVPacket packet;static struct SwsContext *img_convert_ctx=NULL;if (NULL == (pFormatCtx = avformat_alloc_context()))return -1;if (avformat_open_input(&pFormatCtx, filepath, NULL, NULL) != 0) {printf("Can't open the file\n");return -1;}if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {printf("Couldn't find stream information.\n");return -1;}av_dump_format(pFormatCtx, 0, filepath, 0);for (i = 0; i < pFormatCtx->nb_streams; i++) {if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {videoIndex = i;break;}}if (videoIndex == -1)return -1;if (NULL == (pCodec = avcodec_find_decoder(pFormatCtx->streams[videoIndex]->codecpar->codec_id))){printf("Unsupported codec!\n");return -1;}if (NULL == (pCodecCtx = avcodec_alloc_context3(pCodec)))return -1;if (avcodec_parameters_to_context(pCodecCtx, pFormatCtx->streams[videoIndex]->codecpar) < 0){printf("Could not copy parameters to codec.\n");return -1;}if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {printf("Could not open codec.\n");return -1;}if (NULL == (pFrame = av_frame_alloc()))return -1;if (NULL == (pFrameYUV = av_frame_alloc()))return -1;img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,\pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_RGB24, SWS_POINT, NULL, NULL, NULL);numBytes_rgb = av_image_get_buffer_size(AV_PIX_FMT_RGB24, pCodecCtx->width,pCodecCtx->height, 1);out_buffer_rgb = (uint8_t*)av_malloc(numBytes_rgb * sizeof(uint8_t));outData_rgb[0] = out_buffer_rgb;outLinesize_rgb[0] = pCodecCtx->width * 3;outLinesize_rgb[1] = outLinesize_rgb[2] = outLinesize_rgb[3] = 0;av_new_packet(&packet, numBytes);while (av_read_frame(pFormatCtx, &packet) >= 0) {if (packet.stream_index == videoIndex) {// ret = avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);// if (ret >= 0) if ((ret = avcodec_send_packet(pCodecCtx, &packet)) >= 0&& (ret1 = avcodec_receive_frame(pCodecCtx, pFrame)) >= 0){sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data,pFrame->linesize, 0,pCodecCtx->height, outData_rgb, outLinesize_rgb);SaveFramePPM(out_buffer_rgb, pCodecCtx->width, pCodecCtx->height, nCount);++ nCount;}}av_packet_unref(&packet);}av_free(out_buffer_rgb);av_frame_free(&pFrame);av_frame_free(&pFrameYUV);avcodec_close(pCodecCtx);avformat_close_input(&pFormatCtx);return 0;
}