ffmpeg 解码视频（h264、mpeg2）输出yuv420p文件
播放yuv可以参考：ffplay -pixel_format yuv420p -video_size 768x320 -framerate 25 out.yuv

main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>#include <libavutil/frame.h>
#include <libavutil/mem.h>#include <libavcodec/avcodec.h>#define VIDEO_INBUF_SIZE        10240
#define VIDEO_REFILL_THRESH     4096static void decode(AVCodecContext* dec_ctx, AVPacket* pkt, AVFrame* frame, FILE* outfile)
{int ret;//发一帧数据进行解码int send_ret = 1;do{ret = avcodec_send_packet(dec_ctx, pkt);if(ret == AVERROR(EAGAIN))//AVERROR(EAGAIN) 传入失败，表示先要receive frame再重新send packet{send_ret = 0;printf("avcodec_send_packet  ret == AVERROR(EAGAIN)\n");}else if(ret < 0){printf("avcodec_send_packet  ret < 0\n");return;}while(ret >= 0){//调用avcodec_receive_frame会在内部首先调用av_frame_unref来释放frame本来的数据//就是这次调用会将上次调用返回的frame数据释放ret = avcodec_receive_frame(dec_ctx, frame);if(ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)return;else if(ret < 0){printf("avcodec_receive_frame = ret < 0\n");return;}//在第一帧的时候输出一下音频信息static int print_info = 1;if(print_info){print_info = 0;printf("width : %uHz\n", frame->width);printf("height : %u\n", frame->height);printf("fformat : %u\n", frame->format);}//写入h264文件，yuv420p//yuv420格式 ：yyyyyyy......uuuu.....vvvvv.......fwrite(frame->data[0], 1, frame->width * frame->height, outfile);//y分量fwrite(frame->data[1], 1, (frame->width) * (frame->height) / 4, outfile);//u分量fwrite(frame->data[2], 1, (frame->width) * (frame->height) / 4, outfile);//v分量}}while(!send_ret);
}#define H264 0
int main()
{printf("Hello video decoder!\n");const char* outfilename = "out.yuv";#if H264const char* filename = "test.h264";
#elseconst char* filename = "test.mpeg2";
#endifconst AVCodec* codec = NULL;AVCodecContext* codec_ctx = NULL;AVCodecParserContext* parser = NULL;int len = 0;int ret = 0;FILE* infile = NULL;FILE* outfile = NULL;// AV_INPUT_BUFFER_PADDING_SIZE 在输入比特流结尾的要求附加分配字节的数量上进行解码//具体什么影响不知道uint8_t inbuf[VIDEO_INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];uint8_t* data = NULL;size_t data_size = 0;AVPacket* pkt = NULL;AVFrame* de_frame = NULL;//申请AVPacket本身的内存pkt = av_packet_alloc();enum AVCodecID video_codec_id = AV_CODEC_ID_NONE;if(strstr(filename, ".h264") != NULL){video_codec_id = AV_CODEC_ID_H264;}else if(strstr(filename, ".mpeg2") != NULL){video_codec_id = AV_CODEC_ID_MPEG2VIDEO;}else{printf("video_codec_id = AV_CODEC_ID_NONE\n");return 0;}//查找解码器codec = avcodec_find_decoder(video_codec_id);if(!codec){printf("Codec not find!\n");return 0;}//根据解码器ID获取裸流的解析器printf("video decoder end!\n");parser = av_parser_init(codec->id);if(!parser){printf("Parser not find!\n");return 0;}//分配codec使用的上下文codec_ctx = avcodec_alloc_context3(codec);if(!codec_ctx){printf("avcodec_alloc_context3 failed!\n");return 0;}//将解码器和解码使用的上下文关联if(avcodec_open2(codec_ctx, codec, NULL) < 0){printf("avcodec_open2 failed!\n");return 0;}//打开文件infile = fopen(filename, "rb");if(!infile){printf("infile fopen failed!\n");return 0;}//输出文件outfile = fopen(outfilename, "wb");if(!outfile){printf("outfilie fopen failed!\n");return 0;}int file_end = 0;//读取文件 开始解码data = inbuf;data_size = fread(inbuf, 1, VIDEO_INBUF_SIZE, infile);de_frame = av_frame_alloc();while (data_size > 0){//获取传入到avcodec_send_packet一个packet的数据量//(一帧)ret = av_parser_parse2(parser, codec_ctx, &pkt->data, &pkt->size,data, data_size,AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);if(ret < 0){printf("av_parser_parser2 Error!\n");return 0;}//使用了多少数据做一个偏移data += ret;data_size -= ret;if(pkt->size)decode(codec_ctx, pkt, de_frame, outfile);//如果当前缓冲区中数据少于VIDEO_REFILL_THRESH就再读//避免多次读文件if((data_size < VIDEO_REFILL_THRESH) && !file_end){//剩余数据移动缓冲区前memmove(inbuf, data, data_size);data = inbuf;//跨过已有数据存储len = fread(data + data_size, 1, VIDEO_INBUF_SIZE - data_size, infile);if(len > 0)data_size += len;else if(len == 0){file_end = 1;printf("file end!\n");}}}//冲刷解码器pkt->data = NULL;pkt->size = 0;decode(codec_ctx, pkt, de_frame, outfile);fclose(infile);fclose(outfile);avcodec_free_context(&codec_ctx);av_parser_close(parser);av_frame_free(&de_frame);av_packet_free(&pkt);printf("video decoder end!\n");return 0;
}