FFmpeg+SDL（雷神）-（3）

(3) FFmpeg视频解码器
代码记录

---

#include <stdio.h>

#define __STDC_CONSTANT_MACROS

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

char* pict_type(AVFrame *pFrame)
{
    if(pFrame->pict_type==AV_PICTURE_TYPE_NONE) {
        return "AV_PICTURE_TYPE_NONE";
    }
    else if(pFrame->pict_type==AV_PICTURE_TYPE_I) {
        return "AV_PICTURE_TYPE_I";
    }
    else if(pFrame->pict_type==AV_PICTURE_TYPE_P) {
        return "AV_PICTURE_TYPE_P";
    }
    else if(pFrame->pict_type==AV_PICTURE_TYPE_B) {
        return "AV_PICTURE_TYPE_B";
    }
    else if(pFrame->pict_type==AV_PICTURE_TYPE_S) {
        return "AV_PICTURE_TYPE_S";
    }
    else if(pFrame->pict_type==AV_PICTURE_TYPE_SI) {
        return "AV_PICTURE_TYPE_SI";
    }
    else if(pFrame->pict_type==AV_PICTURE_TYPE_SP) {
        return "AV_PICTURE_TYPE_SP";
    }
}

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;
    //输入文件路径
    char filepath[]="Titanic.ts";

    int frame_cnt;

    av_register_all();//注册所有组件
    avformat_network_init();
    pFormatCtx = avformat_alloc_context();

    if(avformat_open_input(&pFormatCtx,filepath,NULL,NULL)!=0){//打开输入视频文件
        printf("Couldn't open input stream.\n");
        return -1;
    }
    if(avformat_find_stream_info(pFormatCtx,NULL)<0){//获取视频文件信息
        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("Didn't find a video stream.\n");
        return -1;
    }

    pCodecCtx=pFormatCtx->streams[videoindex]->codec;
    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);//查找解码器
    if(pCodec==NULL){
        printf("Codec not found.\n");
        return -1;
    }
    if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){//打开解码器
        printf("Could not open codec.\n");
        return -1;
    }

    /*
     * 在此处添加输出视频信息的代码
     * 取自于pFormatCtx，使用fprintf()
     */
    FILE *fp=fopen("info.txt","wb+");
    fprintf(fp,"封装格式参数: 封装格式=%s、比特率=%d、时长=%d\n",pFormatCtx->iformat->long_name,pFormatCtx->bit_rate,pFormatCtx->duration);
    fprintf(fp,"视频编码参数: 编码方式=%s、宽高=%d*%d\n",pFormatCtx->streams[videoindex]->codec->codec->long_name,pFormatCtx->streams[videoindex]->codec->width,pFormatCtx->streams[videoindex]->codec->height);
    //fclose(fp);

    pFrame=av_frame_alloc();
    pFrameYUV=av_frame_alloc();
    out_buffer=(uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height));
    avpicture_fill((AVPicture *)pFrameYUV, out_buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
    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, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL); 

    FILE *fp_264=fopen("test264.h264","wb+");
    FILE *fp_yuv=fopen("testyuv.yuv","wb+");

    frame_cnt=0;
    while(av_read_frame(pFormatCtx, packet)>=0){//从输入文件读取一帧压缩数据
        if(packet->stream_index==videoindex){
                /*
                 * 在此处添加输出H264码流的代码
                 * 取自于packet，使用fwrite()
                 */
            fwrite(packet->data,1,packet->size,fp_264);
            fprintf(fp,"每一个解码前视频帧参数: 帧大小=%d\n",packet->size);
            
            ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);//解码一帧压缩数据
            if(ret < 0){
                printf("Decode Error.\n");
                return -1;
            }
            if(got_picture){
                //此处是为了将右边多出来的黑边（硬件导致的）裁剪掉，pFrame->pFrameYUV
                sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, 
                    pFrameYUV->data, pFrameYUV->linesize);
                printf("Decoded frame index: %d\n",frame_cnt);
                /*
                 * 在此处添加输出YUV的代码
                 * 取自于pFrameYUV，使用fwrite()
                 */
                fwrite(pFrameYUV->data[0],1,pCodecCtx->width*pCodecCtx->height,fp_yuv);//Y
                fwrite(pFrameYUV->data[1],1,pCodecCtx->width*pCodecCtx->height/4,fp_yuv);//U:宽高均是Y的一半
                fwrite(pFrameYUV->data[2],1,pCodecCtx->width*pCodecCtx->height/4,fp_yuv);//V：宽高均是Y的一半
                fprintf(fp,"每一个解码后视频帧参数: 帧类型=%s\n",pict_type(pFrame));

                frame_cnt++;

            }
        }
        av_free_packet(packet);
    }

    fclose(fp);
    fclose(fp_264);
    fclose(fp_yuv);

    sws_freeContext(img_convert_ctx);

    av_frame_free(&pFrameYUV);
    av_frame_free(&pFrame);
    avcodec_close(pCodecCtx);//关闭解码器
    avformat_close_input(&pFormatCtx);//关闭输入视频文件
    //system("pause");
    return 0;
}