SkeyeRTSPLive高效转码之SkeyeVideoDecoder高效软解码解决方案（附源码)

在我之前写的一篇文章《SkeyeRTSPLive传统视频监控互联网+实现利器解决方案》中提到RTSP转RTMP的转流过程，简化流程就是通过SkeyeRTSPClient拉RTSP流，获取音视频编码数据，然后再通过SkeyeRTMP推出去，流程非常简单；然后再实际开发过程中，我们发现其实这个过程并没有想象中那么简单；首先，RTSP协议支持多种音视频编码格式，如音频支持AAC,G711，G726,等，视频支持H264，H625，MJPEG, MPEG等等各种格式，而SkeyeRTMPPusher推流只支持H264（已扩展支持H265）格式，这时，音频我们可以通过SkeyeAACEncoder将音频转码成AAC格式，而视频我们可以通过SkeyeVideoDecoder解码成原始数据，然后再通过SkeyeVideoEncoder将原始数据转码成RTMP推送指定的格式，本文，我们将重点讲述SkeyeVideoDecoder的软解码流程。

1. SkeyeVideoDecoder软解码接口声明如下：

#ifndef __SKEYE_DECODER_API_H__
#define __FF_DECODER_API_H__


#include <windows.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define SKEYEDECODER_API  __declspec(dllexport)
//=======================================================
//Decoder
#ifndef DECODER_H264
#define DECODER_H264            0x1C            //28
#endif
#ifndef DECODER_MPEG4
#define DECODER_MPEG4            0x0D            //13
#endif
#ifndef DECODER_MPEG2
#define DECODER_MPEG2            0x02            //2
#endif
#ifndef DECODER_MJPEG
#define DECODER_MJPEG            0x08            //8
#endif

#ifndef DECODER_MP3
#define DECODER_MP3                0x15001            //86017
#endif

#ifndef DECODER_AAC
#define DECODER_AAC                0x15002            //86018
#endif

//=======================================================
//输出格式
#ifndef OUTPUT_PIX_FMT_YUV420P
#define OUTPUT_PIX_FMT_YUV420P        0
#endif
#ifndef OUTPUT_PIX_FMT_YUYV422
#define OUTPUT_PIX_FMT_YUYV422        1
#endif
#ifndef OUTPUT_PIX_FMT_RGB565LE
#define OUTPUT_PIX_FMT_RGB565LE        44
#endif
#ifndef OUTPUT_PIX_FMT_RGBA
#define OUTPUT_PIX_FMT_RGBA            28
#endif

//=======================================================
//图像处理
//=======================================================
typedef enum __VIDEO_FILTER_TYPE
{
    VIDEO_ROTATION_90_0                =        0,    //顺时针旋转90度
    VIDEO_ROTATION_90_1,                        //逆时针旋转90度
    VIDEO_ROTATION_90_0_FLIP,                    //顺时针旋转90度,再水平翻转
    VIDEO_ROTATION_90_1_FLIP,                    //逆时针旋转90度,再垂直翻转

    VIDEO_TEXT,

}VIDEO_FILTER_TYPE;




//=======================================================
typedef void *SKEYEDEC_HANDLE;


//=======================================================
extern "C"
{
    int    SKEYEDECODER_API    SKEYEDECODER_Init(SKEYEDEC_HANDLE *_handle);
    int    SKEYEDECODER_API    SKEYEDECODER_Deinit(SKEYEDEC_HANDLE *_handle);

    int SKEYEDECODER_API    SKEYEDECODER_SetVideoDecoderParam(SKEYEDEC_HANDLE _handle, int _width, int _height, int _decoder, int _outformat);
    int SKEYEDECODER_API    SKEYEDECODER_SetAudioDecoderParam(SKEYEDEC_HANDLE _handle, unsigned char _channel, unsigned int _sample_rate, unsigned int _decoder);

    int    SKEYEDECODER_API    SKEYEDECODER_GetVideoDecoderInfo(SKEYEDEC_HANDLE _handle, int *_decoder, int *_width, int *_height);

    int    SKEYEDECODER_API    SKEYEDECODER_DecodeVideo(SKEYEDEC_HANDLE _handle, char *pInBuf, int inputSize, char **pOutBuf, int dstW, int dstH);

    //desc:                解码后的数据，直接送到指定的内存中
    int    SKEYEDECODER_API    SKEYEDECODER_DecodeVideo2Buf(SKEYEDEC_HANDLE _handle, char *_inbuf, int _bufsize, void *_outbuf[8], int _pitch);

    int    SKEYEDECODER_API    SKEYEDECODER_DecodeVideo3(SKEYEDEC_HANDLE _handle, char *_inbuf, int _bufsize, void *yuvbuf, int dstW, int dstH);
    int    SKEYEDECODER_API    SKEYEDECODER_DecodeVideoPacket(SKEYEDEC_HANDLE _handle, char *pCodecCtx, unsigned char *avPacket, char **_outbuf);


    int    SKEYEDECODER_API    SKEYEDECODER_DecodeAudio(SKEYEDEC_HANDLE _handle, char *pInBuf, int inputSize, char *pOutBuf, int *outSize);
    int    SKEYEDECODER_API    SKEYEDECODER_DecodeAudioPacket(SKEYEDEC_HANDLE _handle, char *pCodecCtx, unsigned char *avPacket, char *pOutBuf, int *outSize);
};

#endif

2. 软解码通过ffmpeg解码实现流程

和网上大多数的ffmpeg解码示例调用相似。软解码实现分四步走，详细流程如下：

• 第一步，全局注册ffmpeg编解码器

    avcodec_register_all();/*注册所有的编码解码器*/
    av_register_all();// //注册所有可解码类型
  

• 第二步，初始化视频解码参数

int    InitVideoDecoder(int _width, int _height, int _videoCodec, int _outformat)
{
    if (NULL != decoderObj.pVideoCodecCtx)        return -1;    //or call DeinitVideoDecoder();

    AVCodec            *pAVCodec;
    pAVCodec = avcodec_find_decoder((AVCodecID)_videoCodec);
    if (NULL == pAVCodec)        return -1;

    decoderObj.pVideoCodecCtx = avcodec_alloc_context3(pAVCodec);
    decoderObj.pVideoCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
    decoderObj.pVideoCodecCtx->width   = _width;
    decoderObj.pVideoCodecCtx->height  = _height;
    //decoderObj.pVideoCodecCtx->thread_count = 2;
    //decoderObj.pVideoCodecCtx->active_thread_type = decoderObj.pVideoCodecCtx->thread_type = FF_THREAD_FRAME;

    int ret = avcodec_open2(decoderObj.pVideoCodecCtx, pAVCodec, NULL);
    if (ret < 0)                goto $fail;

    int numBytes = avpicture_get_size(AV_PIX_FMT_YUV420P, _width, _height);
    decoderObj.pBuffYuv420 = (uint8_t *)av_malloc(numBytes * sizeof(uint8_t));
    decoderObj.mVideoFrame420    = av_frame_alloc();
    if (avpicture_fill((AVPicture *)decoderObj.mVideoFrame420, decoderObj.pBuffYuv420, AV_PIX_FMT_YUV420P,
        decoderObj.width, decoderObj.height) < 0)
    {
    }
#ifdef ADD_VIDEO_FILTER
    SetVideoFilter(VIDEO_TEXT, NULL);
#endif
    av_init_packet(&decoderObj.avVidPacket);
    decoderObj.outputFormat = _outformat;
    decoderObj.codec    =    _videoCodec;
    decoderObj.width    =    _width;
    decoderObj.height    =    _height;    
    return 0;

$fail:
    {
        DeinitVideoDecoder();
        return -1;
    }
}

• 第三步，直接解码视频帧并输出指定色彩格式

int    DecodeVideo(char *_inbuf, int _bufsize, char **_outbuf, int dstW, int dstH)
{
    if (NULL == _inbuf)            return -1;
    if (1 > _bufsize)            return -1;

    //if (NULL == decoderObj.pSws_ctx)    return -2;

    if (NULL == decoderObj.mVideoFrame420)    decoderObj.mVideoFrame420 = av_frame_alloc();
    
    decoderObj.avVidPacket.size = _bufsize;
    decoderObj.avVidPacket.data    = (uint8_t*)_inbuf;

    int frameFinished = 0;
    int nDecode = avcodec_decode_video2(decoderObj.pVideoCodecCtx, decoderObj.mVideoFrame420, &frameFinished, &decoderObj.avVidPacket);//(uint8_t*)pInBuffer, inputSize);
    if (nDecode < 0)    return -3;
    if (!frameFinished)    return -4;

    if (NULL == decoderObj.pAvFrameYuv)
    {
        int numBytes = avpicture_get_size((AVPixelFormat)decoderObj.outputFormat,  dstW, dstH);
        decoderObj.pBuffYuv = (uint8_t *)av_malloc(numBytes * sizeof(uint8_t));
        decoderObj.pAvFrameYuv = av_frame_alloc();
        if (avpicture_fill((AVPicture *)decoderObj.pAvFrameYuv, decoderObj.pBuffYuv, (AVPixelFormat)decoderObj.outputFormat,
            dstW, dstH) < 0)
        {

        }
    }

    if (NULL == decoderObj.pSws_ctx)
    {
        decoderObj.pSws_ctx = sws_getCachedContext(decoderObj.pSws_ctx, decoderObj.width, decoderObj.height, (AVPixelFormat)AV_PIX_FMT_YUV420P, 
            //decoderObj.width/2, decoderObj.height/2, (PixelFormat)PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
            dstW, dstH, (AVPixelFormat)decoderObj.outputFormat, SWS_BICUBIC, NULL, NULL, NULL);
    }

    if (NULL == decoderObj.pSws_ctx)        return -1;

    sws_scale(decoderObj.pSws_ctx, decoderObj.mVideoFrame420->data, decoderObj.mVideoFrame420->linesize, 0, decoderObj.pVideoCodecCtx->height, 
        decoderObj.pAvFrameYuv->data, decoderObj.pAvFrameYuv->linesize);

    //sws_freeContext(decoderObj.pSws_ctx);
    //decoderObj.pSws_ctx = NULL;

    *_outbuf = (char*)decoderObj.pAvFrameYuv->data[0];

    return 0;
}

• 第四步，停止解码后，销毁解码器申请的资源

void DeinitVideoDecoder()
{
    if (NULL != decoderObj.mVideoFrame420)
    {
        av_frame_free(&decoderObj.mVideoFrame420);
        decoderObj.mVideoFrame420 = NULL;
    }
    if (NULL != decoderObj.pBuffYuv420)
    {
        av_free(decoderObj.pBuffYuv420);
        decoderObj.pBuffYuv420 = NULL;
    }
    if (NULL != decoderObj.pAvFrameSws)
    {
        av_frame_free(&decoderObj.pAvFrameSws);
        decoderObj.pAvFrameSws = NULL;
    }
    if (NULL != decoderObj.pAvFrameYuv)
    {
        av_frame_free(&decoderObj.pAvFrameYuv);
        decoderObj.pAvFrameYuv = NULL;
    }
    if (NULL != decoderObj.pBuffYuv)
    {
        av_free(decoderObj.pBuffYuv);
        decoderObj.pBuffYuv = NULL;
    }

    if (NULL != decoderObj.pSws_ctx)
    {
        sws_freeContext(decoderObj.pSws_ctx);
        decoderObj.pSws_ctx = NULL;
    }

    if (NULL != decoderObj.pVideoCodecCtx)
    {
        avcodec_close(decoderObj.pVideoCodecCtx);
        av_free(decoderObj.pVideoCodecCtx);
        decoderObj.pVideoCodecCtx = NULL;
    }
}

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