FFMPEG学习----分离视频里的H.264与YUV数据

#include <stdio.h>

extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
};

#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "swscale.lib")
#pragma comment(lib, "avutil.lib")

int main(int argc, char* argv[])
{
	AVFormatContext		*pFormatCtx = NULL;
	AVCodecContext		*pCodecCtx = NULL;
	AVCodec				*pCodec = NULL;
	AVFrame				*pFrame = NULL, *pFrameYUV = NULL;
	unsigned char		*out_buffer = NULL;
	AVPacket			packet;
	struct SwsContext	*img_convert_ctx = NULL;
	int					y_size;
	int					got_picture;
	int					i, videoIndex;
	int					frame_cnt = 1;

	char filepath[] = "Titanic.ts";

	FILE *fp_yuv = fopen("film.yuv", "wb+");
	FILE *fp_h264 = fopen("film.h264", "wb+");
	if (fp_yuv == NULL || fp_h264 == NULL)
	{
		printf("FILE open error");
		return -1;
	}

	av_register_all();

	if (avformat_open_input(&pFormatCtx, filepath, NULL, NULL) != 0){
		printf("Couldn't open an input stream.\n");
		return -1;
	}
	if (avformat_find_stream_info(pFormatCtx, NULL) < 0){
		printf("Couldn't find stream information.\n");
		return -1;
	}
	videoIndex = -1;
	for (i = 0; i < pFormatCtx->nb_streams; i++)
		if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO){
			videoIndex = i;
			break;
		}

	if (videoIndex == -1){
		printf("Couldn't find a video stream.\n");
		return -1;
	}

	pCodecCtx = pFormatCtx->streams[videoIndex]->codec;
	pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
	if (pCodec == NULL){
		printf("Codec not found.\n");
		return -1;
	}
	if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0){
		printf("Could not open codec.\n");
		return -1;
	}

	pFrame = av_frame_alloc();
	pFrameYUV = av_frame_alloc();
	if (pFrame == NULL || pFrameYUV == NULL)
	{
		printf("memory allocation error\n");
		return -1;
	}
	out_buffer = (unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1));
	av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize, out_buffer,
		AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1);
	img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
		pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);

	while (av_read_frame(pFormatCtx, &packet) >= 0)
	{
		if (packet.stream_index == videoIndex)
		{
			//分离出h.264数据
			fwrite(packet.data, 1, packet.size, fp_h264);

			if (avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, &packet) < 0)
			{
				printf("Decode Error.\n");
				return -1;
			}
			if (got_picture)
			{
				sws_scale(img_convert_ctx, (const unsigned char* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
					pFrameYUV->data, pFrameYUV->linesize);

				//分离出YUV数据
				y_size = pCodecCtx->width * pCodecCtx->height;
				fwrite(pFrameYUV->data[0], 1, y_size, fp_yuv);		//Y
				fwrite(pFrameYUV->data[1], 1, y_size / 4, fp_yuv);	//U
				fwrite(pFrameYUV->data[2], 1, y_size / 4, fp_yuv);	//V

				printf("Succeed to decode %d frame!\n", frame_cnt);
				frame_cnt++;
			}
		}
		av_free_packet(&packet);
	}

	fclose(fp_yuv);
	fclose(fp_h264);
	sws_freeContext(img_convert_ctx);
	av_frame_free(&pFrameYUV);
	av_frame_free(&pFrame);
	avcodec_close(pCodecCtx);
	avformat_close_input(&pFormatCtx);

	return 0;
}

压缩率大于100倍了。

当av_read_frame()循环退出的时候，实际上解码器中可能还包含剩余的几帧数据。因此需要通过“flush_decoder”将这几帧数据输出。“flush_decoder”功能简而言之即直接调用avcodec_decode_video2()获得AVFrame，而不再向解码器传递AVPacket。参考代码如下：

	//FIX: Flush Frames remained in Codec
	while (1) {
		ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
		if (ret < 0)
			break;
		if (!got_picture)
			break;
		sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);
		//处理...
	}