ffmpeg_videoDecoder.cpp

/*
最简单的基于FFmpeg的视频解码器
simplest FFmpeg Video Decoder 

杨栋 yang dong

本程序实现了H264解码为YUV像素数据
本程序更新了新版本的接口，修改了被弃用的接口（ffmpeg 4.2）
*/


#include <stdio.h>

#define __STDC_CONSTANT_MACROS

#ifdef _WIN32
//Windows
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#ifdef __cplusplus
};
#endif
#endif


int main(int argc, char* argv[])
{
	AVFormatContext	*pFormatCtx;
	int				i, videoindex;
	AVCodecContext	*pCodecCtx;
	AVCodec			*pCodec;
	AVFrame	*pFrame, *pFrameYUV;
	uint8_t *out_buffer;
	AVPacket *packet;
	int y_size;
	int ret, got_picture;
	struct SwsContext *img_convert_ctx;

	char filepath[] = "F:\\VS2017\\workspace\\opencv_ffmpeg_encode\\test.h264";  //bigbuckbunny_480x272.h264
	errno_t err;
	FILE *fp_yuv;
	err = fopen_s(&fp_yuv, "output.yuv", "wb+");
	if (err)
	{
		printf("could not open output.yuv \n");
	}

	//av_register_all();
	avformat_network_init();
	pFormatCtx = avformat_alloc_context();

	if (avformat_open_input(&pFormatCtx, filepath, NULL, NULL) != 0) {
		printf("Couldn't open 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]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
			videoindex = i;
			break;
		}

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

	//pCodecCtx = pFormatCtx->streams[videoindex]->codec;
	pCodecCtx = avcodec_alloc_context3(NULL);
	if (pCodecCtx == NULL)
	{
		printf("Could not allocate AVCodecContext\n");
		return -1;
	}
	avcodec_parameters_to_context(pCodecCtx, pFormatCtx->streams[videoindex]->codecpar);
	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();

	//pCodecCtx->width = 640;
	//pCodecCtx->height = 480;

	out_buffer = (uint8_t *)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);
	packet = (AVPacket *)av_malloc(sizeof(AVPacket));
	//Output Info-----------------------------
	printf("--------------- File Information ----------------\n");
	av_dump_format(pFormatCtx, 0, filepath, 0);
	printf("-------------------------------------------------\n");
	img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
		pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, 4, NULL, NULL, NULL);
	//SWS_BICUBIC
	while (av_read_frame(pFormatCtx, packet) >= 0) {
		if (packet->stream_index == videoindex) {
			//ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
			ret = avcodec_send_packet(pCodecCtx, packet);
			got_picture = avcodec_receive_frame(pCodecCtx, pFrame);
			if (ret < 0) {
				printf("Decode Error.\n");
				return -1;
			}
			if (!got_picture) {
				sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
					pFrameYUV->data, pFrameYUV->linesize);

				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 1 frame!\n");

			}
		}
		av_packet_unref(packet);
	}
	//flush decoder
	//FIX: Flush Frames remained in Codec
	while (1) {
		//ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
		ret = avcodec_send_packet(pCodecCtx, packet);
		got_picture = avcodec_receive_frame(pCodecCtx, pFrame);
		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);

		int 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("Flush Decoder: Succeed to decode 1 frame!\n");
	}

	sws_freeContext(img_convert_ctx);

	fclose(fp_yuv);

	av_frame_free(&pFrameYUV);
	av_frame_free(&pFrame);
	avcodec_close(pCodecCtx);
	avformat_close_input(&pFormatCtx);

	return 0;
}