FFMPEG（YUV编码为H.264）

下面附一张使用FFmpeg编码视频的流程图。使用该流程，不仅可以编码H.264的视频，而且可以编码MPEG4/MPEG2/VP8等等各种FFmpeg支持的视频。图中蓝色背景的函数是实际输出数据的函数。浅绿色的函数是视频编码的函数。

简单介绍一下流程中各个函数的意义：

av_register_all()：注册FFmpeg所有编解码器。

avformat_alloc_output_context2()：初始化输出码流的AVFormatContext。

avio_open()：打开输出文件。

av_new_stream()：创建输出码流的AVStream。

avcodec_find_encoder()：查找编码器。

avcodec_open2()：打开编码器。

avformat_write_header()：写文件头（对于某些没有文件头的封装格式，不需要此函数。比如说MPEG2TS）。

avcodec_encode_video2()：编码一帧视频。即将AVFrame（存储YUV像素数据）编码为AVPacket（存储H.264等格式的码流数据）。

av_write_frame()：将编码后的视频码流写入文件。

flush_encoder()：输入的像素数据读取完成后调用此函数。用于输出编码器中剩余的AVPacket。

av_write_trailer()：写文件尾（对于某些没有文件头的封装格式，不需要此函数。比如说MPEG2TS）

#include 

#define __STDC_CONSTANT_MACROS

#ifdef _WIN32

//Windows

extern "C"

{

#include "libavutil/opt.h"

#include "libavcodec/avcodec.h"

#include "libavformat/avformat.h"

};

#else

//Linux...

#ifdef __cplusplus

extern "C"

{

#endif

#include 

#include 

#include 

#ifdef __cplusplus

};

#endif

#endif

int flush_encoder(AVFormatContext *fmt_ctx,unsigned int stream_index){

    int ret;

    int got_frame;

    AVPacket enc_pkt;

    if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &

        CODEC_CAP_DELAY))

        return 0;

    while (1) {

        enc_pkt.data = NULL;

        enc_pkt.size = 0;

        av_init_packet(&enc_pkt);

        ret = avcodec_encode_video2 (fmt_ctx->streams[stream_index]->codec, &enc_pkt,

            NULL, &got_frame);

        av_frame_free(NULL);

        if (ret < 0)

            break;

        if (!got_frame){

            ret=0;

            break;

        }

        printf("Flush Encoder: Succeed to encode 1 frame!\tsize:%5d\n",enc_pkt.size);

        /* mux encoded frame */

        ret = av_write_frame(fmt_ctx, &enc_pkt);

        if (ret < 0)

            break;

    }

    return ret;

}

int main(int argc, char* argv[])

{

    AVFormatContext* pFormatCtx;

    AVOutputFormat* fmt;

    AVStream* video_st;

    AVCodecContext* pCodecCtx;

    AVCodec* pCodec;

    AVPacket pkt;

    uint8_t* picture_buf;

    AVFrame* pFrame;

    int picture_size;

    int y_size;

    int framecnt=0;

    //FILE *in_file = fopen("src01_480x272.yuv", "rb"); //Input raw YUV data

    FILE *in_file = fopen("output.yuv", "rb");   //Input raw YUV data

    int in_w=480,in_h=272;                              //Input data's width and height

    int framenum=100;                                   //Frames to encode

    //const char* out_file = "src01.h264";              //Output Filepath

    //const char* out_file = "src01.ts";

    //const char* out_file = "src01.hevc";

    const char* out_file = "ds.h264";

    av_register_all();

    //Method1.

    pFormatCtx = avformat_alloc_context();

    //Guess Format

    fmt = av_guess_format(NULL, out_file, NULL);

    pFormatCtx->oformat = fmt;

    //Method 2.

    //avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, out_file);

    //fmt = pFormatCtx->oformat;

    //Open output URL

    if (avio_open(&pFormatCtx->pb,out_file, AVIO_FLAG_READ_WRITE) < 0){

        printf("Failed to open output file! \n");

        return -1;

    }

    video_st = avformat_new_stream(pFormatCtx, 0);

    //video_st->time_base.num = 1;

    //video_st->time_base.den = 25;

    if (video_st==NULL){

        return -1;

    }

    //Param that must set

    pCodecCtx = video_st->codec;

    //pCodecCtx->codec_id =AV_CODEC_ID_HEVC;

    pCodecCtx->codec_id = fmt->video_codec;

    pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;

    pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;

    pCodecCtx->width = in_w;

    pCodecCtx->height = in_h;

    pCodecCtx->bit_rate = 400000;

    pCodecCtx->gop_size=250;

    pCodecCtx->time_base.num = 1;

    pCodecCtx->time_base.den = 25;

    //H264

    //pCodecCtx->me_range = 16;

    //pCodecCtx->max_qdiff = 4;

    //pCodecCtx->qcompress = 0.6;

    pCodecCtx->qmin = 10;

    pCodecCtx->qmax = 51;

    //Optional Param

    pCodecCtx->max_b_frames=3;

    // Set Option

    AVDictionary *param = 0;

    //H.264

    if(pCodecCtx->codec_id == AV_CODEC_ID_H264) {

        av_dict_set(¶m, "preset", "slow", 0);

        av_dict_set(¶m, "tune", "zerolatency", 0);

        //av_dict_set(¶m, "profile", "main", 0);

    }

    //H.265

    if(pCodecCtx->codec_id == AV_CODEC_ID_H265){

        av_dict_set(¶m, "preset", "ultrafast", 0);

        av_dict_set(¶m, "tune", "zero-latency", 0);

    }

    //Show some Information

    av_dump_format(pFormatCtx, 0, out_file, 1);

    pCodec = avcodec_find_encoder(pCodecCtx->codec_id);

    if (!pCodec){

        printf("Can not find encoder! \n");

        return -1;

    }

    if (avcodec_open2(pCodecCtx, pCodec,¶m) < 0){

        printf("Failed to open encoder! \n");

        return -1;

    }

    pFrame = av_frame_alloc();

    picture_size = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);

    picture_buf = (uint8_t *)av_malloc(picture_size);

    avpicture_fill((AVPicture *)pFrame, picture_buf, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);

    //Write File Header

    avformat_write_header(pFormatCtx,NULL);

    av_new_packet(&pkt,picture_size);

    y_size = pCodecCtx->width * pCodecCtx->height;

    for (int i=0; i i++){

        //Read raw YUV data

        if (fread(picture_buf, 1, y_size*3/2, in_file) <= 0){

            printf("Failed to read raw data! \n");

            return -1;

        }else if(feof(in_file)){

            break;

        }

        pFrame->data[0] = picture_buf;              // Y

        pFrame->data[1] = picture_buf+ y_size;      // U

        pFrame->data[2] = picture_buf+ y_size*5/4;  // V

        //PTS

        //pFrame->pts=i;

        pFrame->pts=i*(video_st->time_base.den)/((video_st->time_base.num)*25);

        int got_picture=0;

        //Encode

        int ret = avcodec_encode_video2(pCodecCtx, &pkt,pFrame, &got_picture);

        if(ret < 0){

            printf("Failed to encode! \n");

            return -1;

        }

        if (got_picture==1){

            printf("Succeed to encode frame: %5d\tsize:%5d\n",framecnt,pkt.size);

            framecnt++;

            pkt.stream_index = video_st->index;

            ret = av_write_frame(pFormatCtx, &pkt);

            av_free_packet(&pkt);

        }

    }

    //Flush Encoder

    int ret = flush_encoder(pFormatCtx,0);

    if (ret < 0) {

        printf("Flushing encoder failed\n");

        return -1;

    }

    //Write file trailer

    av_write_trailer(pFormatCtx);

    //Clean

    if (video_st){

        avcodec_close(video_st->codec);

        av_free(pFrame);

        av_free(picture_buf);

    }

    avio_close(pFormatCtx->pb);

    avformat_free_context(pFormatCtx);

    fclose(in_file);

    return 0;

}