ffmpeg yuv420保存jpg文件

int yuv420_to_jpg(void *data,int w,int h,char *file)
{
	av_register_all();
	AVFormatContext *pFormatCtx = avformat_alloc_context();
	AVOutputFormat *fmt = av_guess_format("mjpeg", NULL, NULL);
	pFormatCtx->oformat = fmt;
	if (avio_open(&pFormatCtx->pb,file, AVIO_FLAG_READ_WRITE) < 0){
		printf("Couldn‘t open output file.");
		return -1;
	}
	AVStream *video_st = avformat_new_stream(pFormatCtx, 0);
	if (video_st==NULL){
		return -1;
	}
	AVCodecContext *pCodecCtx = video_st->codec;
	pCodecCtx->codec_id = fmt->video_codec;
	pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
	pCodecCtx->pix_fmt = PIX_FMT_YUVJ420P;
	pCodecCtx->width = w;  
	pCodecCtx->height = h;
	pCodecCtx->time_base.num = 1;
	pCodecCtx->time_base.den = 25;
	AVCodec *pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
	if (!pCodec){
		return -1;
	}
	if (avcodec_open2(pCodecCtx, pCodec,NULL) < 0){
		return -1;
	}
	AVFrame *picture = av_frame_alloc();
	int size = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
	uint8_t *picture_buf = (uint8_t *)av_malloc(size);
	if (!picture_buf){
		return -1;
	}
	avpicture_fill((AVPicture *)picture, picture_buf, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
	avformat_write_header(pFormatCtx,NULL);
	int y_size = pCodecCtx->width * pCodecCtx->height;
	AVPacket pkt;
	av_new_packet(&pkt,y_size*3);
	memcpy(picture_buf,data,y_size*3/2);
	picture->data[0] = picture_buf;
	picture->data[1] = picture_buf+ y_size;
	picture->data[2] = picture_buf+ y_size*5/4;
	int got_picture = 0;
	int ret = avcodec_encode_video2(pCodecCtx, &pkt,picture, &got_picture);
	if(ret < 0){
		printf("Encode Error.\n");
		return -1;
	}
	if (got_picture==1){
		pkt.stream_index = video_st->index;
		ret = av_write_frame(pFormatCtx, &pkt);
	}
	av_free_packet(&pkt);
	av_write_trailer(pFormatCtx);
	if (video_st){
		avcodec_close(video_st->codec);
		av_free(picture);
		av_free(picture_buf);
	}
	avio_close(pFormatCtx->pb);
	avformat_free_context(pFormatCtx);
	return 1;
}