FFmpeg开发实战（六）：jpeg转换为yuv格式图像

Myth丶恋晨 2022-10-17 13:43 798阅读 0赞

### 文章目录 ###

*  0. 参考文献
 *  1. jpeg转yuv
 *  2. 源码下载

--------------------

JPG和PNG等图片的解码方式和视频解码是一样的，因为视频是由一幅一幅的图片组成的，只不过视频的帧是会前后参考的，而JPG等图片是单独的一帧而已。

# 0. 参考文献 #

[ffmpeg解码JPG和PNG等图片][ffmpeg_JPG_PNG]

# 1. jpeg转yuv #

int main(int argc, char* argv[]) 
    {
        
    	int i;
    	char szFileName[128] = {
         0 };
    	int decLen = 0;
    	int frame = 0;
    
    	AVCodecContext *pCodecCtx = NULL;
    	AVFrame *pFrame = NULL;
    	AVCodec *pCodec = NULL;
    	AVFormatContext *pFormatCtx = NULL;
    
    	/*if (argc != 3)
    	{
    		fprintf(stderr, "ERROR:need 3 argument!n");
    		exit(-1);
    	}*/
    
    	sprintf(szFileName, "%s", "H:/bmp2jpg/1.jpeg");
    
    #ifdef ENABLE_DEMUX_SAVE
    	FILE* frvdemux = fopen("rvdemuxout.rm", "wb+");
    	if (NULL == frvdemux)
    	{
        
    		fprintf(stderr, "create rvdemuxout file failedn");
    		exit(1);
    	}
    #endif
    
    	/* output yuv file name */
    	sprintf(ffrvout, "%s", "H:/bmp2jpg/1.yuv");
    
    	pfout = fopen(ffrvout, "wb+");
    	if (NULL == pfout)
    	{
        
    		printf("create output file failedn");
    		exit(1);
    	}
    	printf("==========> Begin test ffmpeg call ffmpeg rv decodern");
    	av_register_all();
    
    	/* Open input video file */
    	//printf("before avformat_open_input [%s]n", szFileName);
    	if (avformat_open_input(&pFormatCtx, szFileName, NULL, NULL) != 0)
    	{
        
    		fprintf(stderr, "Couldn't open input filen");
    		return -1;
    	}
    	//printf("after avformat_open_inputn");
    
    	/* Retrieve stream information */
    	if (avformat_find_stream_info(pFormatCtx, 0) < 0)
    	{
        
    		printf("av_find_stream_info ERRORn");
    		return -1;
    	}
    	//printf("after av_find_stream_info, n");
    
    
    	/* Find the first video stream */
    	int videoStream = -1;
    	printf("==========> pFormatCtx->nb_streams = %dn", pFormatCtx->nb_streams);
    
    	for (i = 0; i < pFormatCtx->nb_streams; i++) {
        
    		if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
        
    			videoStream = i;
    			printf("the first video stream index: videoStream = %dn", videoStream);
    			break;
    		}
    	}
    
    	if (videoStream == -1)
    		return -1;        // Didn't find a video stream
    
    	/* Get a pointer to the codec context for the video stream */
    	pCodecCtx = pFormatCtx->streams[videoStream]->codec;
    	printf("pCodecCtx->codec_id = %dn", pCodecCtx->codec_id);
    
    	pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    	if (pCodec == NULL) {
        
    		fprintf(stderr, "can not find decoder!n");
    		return -1;
    	}
    
    	/* Open codec */
    	if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
    	{
        
    		printf("cannot open software codecn");
    		return -1; // Could not open codec
    	}
    	printf("==========> Open software codec successn");
    
    	pFrame = av_frame_alloc();
    	if (pFrame == NULL)
    	{
        
    		fprintf(stderr, "avcodec_alloc_frame() ERRORn");
    		return -1;
    	}
    
    	/* flag whether we get a decoded yuv frame */
    	int frameFinished;
    	int packetno = 0;
    
    	AVPacket packet;
    	av_init_packet(&packet);
    
    	while (av_read_frame(pFormatCtx, &packet) >= 0) {
        
    		//printf("[main]avpkt->slice_count=%dn", packet.sliceNum);
    
    		/* Is this a packet from the video stream? */
    		if (packet.stream_index == videoStream) {
        
    			packetno++;
    #ifdef ENABLE_PRINT_FRAME_BYTES
    			if (1) {
        
    				int i;
    				int size = packet.size < PRINT_BYTES ? packet.size : PRINT_BYTES;
    				unsigned char *data = packet.data;
    				printf("===>[%5d] [", packet.size);
    				for (i = 0; i < size; i++)
    					printf("%02x ", data[i]);
    				printf("]n");
    			}
    #endif
    #ifdef ENABLE_DEMUX_SAVE
    			fwrite(packet.data, 1, packet.size, frvdemux);
    #endif
    			//printf("[the %d packet]packet.size = %dn", packetno++, packet.size);
    
    			while (packet.size > 0) {
        
    				decLen = avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
    				//printf("[video_decode_example]after avcodec_decode_video2,decoded=%dn",decLen);
    
    				if (decLen < 0) {
        
    					fprintf(stderr, "[video_decode_example]Error while decoding frame %dn", frame);
    					//exit(1);
    					/* FIXME if decode one frame err, ignore this frame */
    					decLen = packet.size;
    				}
    
    				if (frameFinished) {
        
    					printf("got a yuv framen");
    					//printf(stderr, "[video_decode_example]saving frame %3dn", frame);
    
    					/* the picture is allocated by the decoder. no need to free it */
    					if (frame == 0) {
        
    						printf("[video_decode_example]picture->linesize[0]=%d, c->width=%d,c->height=%dn",
    							pFrame->linesize[0], pCodecCtx->width, pCodecCtx->height);
    						printf("===>YUV format = %dn", pFrame->format);
    					}
    #ifdef ENABLE_YUV_SAVE
    					/* save yuv pic */
    					if (frame < FRAME_NUM) {
        
    						switch (pFrame->format) {
        
    						case 0:    /* YUV420P */
    						case 12:
    							yuv420p_save(pFrame, pCodecCtx);
    							break;
    						case 2:    /* RGB24 */
    							rgb24_save(pFrame, pCodecCtx);
    							break;
    						case 13:    /* YUVJ422P */
    							yuv422p_save(pFrame, pCodecCtx);
    							break;
    						case 14:    /* YUVJ444P */
    							yuv444p_save(pFrame, pCodecCtx);
    							break;
    						default:
    							fprintf(stderr, "unsupport YUV format for savingn");
    							break;
    						}
    						fprintf(stderr, "===>save pic successn");
    					}
    #endif
    					/* frame index grow */
    					frame++;
    				}
    				//printf("===========> %dn", decLen);
    				/* left data in pkt , go on decoding */
    				packet.data += decLen;
    				packet.size -= decLen;
    			}
    			if (frame == FRAME_NUM) {
        
    				printf("==========> decoded [%d pkt frames] ---> save [%d YUV frames], enough to stop!n", packetno, FRAME_NUM);
    				break;
    			}
    		}
    
    		/* FIXME no need free in this file */
    		//printf("free packet that was allocated by av_read_framen");
    		// Free the packet that was allocated by av_read_frame
    		//av_free_packet(&packet);
    	}
    
    	printf("decoding job down! begin to freen");
    	/* Free the YUV frame */
    	av_free(pFrame);
    
    	/* Close the codec */
    	avcodec_close(pCodecCtx);
    
    	/* Close the video file */
    	avformat_free_context(pFormatCtx);
    	fclose(pfout);
    
    	printf("==========> END-OKn");
        return 0;
    }

# 2. 源码下载 #

[jpeg转换为yuv格式图像源码][jpeg_yuv]

[ffmpeg_JPG_PNG]: https://blog.csdn.net/nimeghbia/article/details/76850304
[jpeg_yuv]: https://download.csdn.net/download/WHEgqing/19360870