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，而后再通过SkeyeRTMP推出去，流程非常简单；而后再理论开发过程中，咱们发现其实这个过程并没有设想中那么简略；首先，RTSP协定反对多种音视频编码格局，如音频反对AAC,G711，G726,等，视频反对H264，H625，MJPEG, MPEG等等各种格局，而SkeyeRTMPPusher推流只反对H264（已扩大反对H265）格局，这时，音频咱们能够通过SkeyeAACEncoder将音频转码成AAC格局，而视频咱们能够通过SkeyeVideoDecoder解码成原始数据，而后再通过SkeyeVideoEncoder将原始数据转码成RTMP推送指定的格局，本文，咱们将重点讲述SkeyeVideoDecoder的软解码流程。
1. SkeyeVideoDecoder软解码接口申明如下：
#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//=======================================================//输入格局#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,再程度翻转 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，间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);};#endif2. 软解码通过ffmpeg解码实现流程
和网上大多数的ffmpeg解码示例调用类似。软解码实现分四步走，具体流程如下：
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，间接解码视频帧并输入指定色调格局
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，进行解码后，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; }}有任何技术问题，欢送大家和我技术交换：
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