FFmpeg解码H264为YUV420

在这里我们主要用到三个函数实现解码过程，首先是H264解码初期化，其次是进行H264解码，最后 H264解码销毁，具体代码实现如下。

H264Decoder.h

#pragma onceextern "C"{#include <libavformat\avformat.h>#include <libavutil\pixfmt.h>#include <libavcodec\avcodec.h>}#define X264_DECODER_H longtypedef struct{    struct AVCodec *codec;// Codec    struct AVCodecContext *c;// Codec ContextAVCodecParserContext *pCodecParserCtx;    int frame_count;    struct AVFrame *picture;// Frame    AVPacket avpkt;        int iWidth;    int iHeight;    int comsumedSize;    int got_picture;} X264_Decoder_Handle;class H264Decoder{public:H264Decoder(void);~H264Decoder(void);public:    // H264解码初期化    X264_DECODER_H X264Decoder_Init();        /*     H264数据解码，解码后的数据为yuv420格式     dwHandle:初期化时返回的句柄     pDataIn:待解码数据     nInSize:待解码数据长度     pDataOut:解码后的数据，存储空间由调用者申请     nOutSize:存储空间大小          nWidth:解码后的图像宽度     nHeight:解码后的图像高度     */    int X264Decoder_Decode(X264_DECODER_H dwHandle, uint8_t *pDataIn, int nInSize, uint8_t *pDataOut, int *nOutSize, int *nWidth,int *nHeight);/*     H264解码销毁     dwHandle:初期化时返回的句柄     */    void X264Decoder_UnInit(X264_DECODER_H dwHandle);    protected:    void pgm_save2(unsigned char *buf, int wrap, int xsize, int ysize, uint8_t *pDataOut)    {        int i;        for(i = 0; i < ysize; i++)        {            memcpy(pDataOut+i*xsize, buf + /*(ysize-i)*/i * wrap, xsize);        }    }};

H264Decoder.cpp

#include "stdafx.h"#include "H264Decoder.h"H264Decoder::H264Decoder(void){}H264Decoder::~H264Decoder(void){}X264_DECODER_H H264Decoder::X264Decoder_Init(){    X264_Decoder_Handle *pHandle = (X264_Decoder_Handle *)malloc(sizeof(X264_Decoder_Handle));    if (pHandle == NULL)    {        return -1;    }        avcodec_register_all();                pHandle->codec = avcodec_find_decoder(AV_CODEC_ID_H264);    if (!pHandle->codec)    {        return -2;    }        pHandle->c = avcodec_alloc_context3(pHandle->codec);    if (!pHandle->c)    {        return -3;    }        pHandle->c->codec_type = AVMEDIA_TYPE_VIDEO;    pHandle->c->pix_fmt =AV_PIX_FMT_YUV420P;pHandle->c->flags2|=AV_CODEC_FLAG2_CHUNKS;pHandle->pCodecParserCtx=av_parser_init(AV_CODEC_ID_H264);      if (!pHandle->pCodecParserCtx){          printf("Could not allocate video parser context\n");          return -6;      }      if (avcodec_open2(pHandle->c, pHandle->codec, NULL) < 0)    {        return -4;    }        pHandle->picture =av_frame_alloc();    if (!pHandle->picture)    {        return -5;    }        pHandle->frame_count = 0;        return (X264_DECODER_H)pHandle;}void H264Decoder::X264Decoder_UnInit(X264_DECODER_H dwHandle){    if (dwHandle <= 0)    {        return;    }        X264_Decoder_Handle *pHandle = (X264_Decoder_Handle *)dwHandle;        avcodec_close(pHandle->c);    av_free(pHandle->c);av_free(pHandle->picture->data[0]);    av_free(pHandle->picture);        free(pHandle);}int H264Decoder::X264Decoder_Decode(X264_DECODER_H dwHandle, uint8_t *pDataIn, int nInSize, uint8_t *pDataOut, int *nOutSize, int *nWidth, int *nHeight){    if (dwHandle <= 0)    {        return -1;    }unsigned char buf[20*1024]={0};    X264_Decoder_Handle *pHandle = (X264_Decoder_Handle *)dwHandle;av_init_packet(&(pHandle->avpkt));pHandle->avpkt.size = nInSize;pHandle->avpkt.data = pDataIn;    while (pHandle->avpkt.size > 0)    {        pHandle->comsumedSize = avcodec_decode_video2(pHandle->c, pHandle->picture, &pHandle->got_picture, &(pHandle->avpkt));        if (pHandle->comsumedSize < 0)        {            return -2;        }                if (pHandle->got_picture)        {            *nWidth = pHandle->c->width;            *nHeight = pHandle->c->height;if(pHandle->c->width!=0 && pHandle->c->height!=0){*nOutSize=pHandle->c->width*pHandle->c->height*3/2;}else    {*nOutSize=0;}            pgm_save2(pHandle->picture->data[0],                      pHandle->picture->linesize[0],                      pHandle->c->width,                      pHandle->c->height,pDataOut);            pgm_save2(pHandle->picture->data[1],                      pHandle->picture->linesize[1],                      pHandle->c->width/2,                      pHandle->c->height/2,                      pDataOut +pHandle->c->width * pHandle->c->height);            pgm_save2(pHandle->picture->data[2],                      pHandle->picture->linesize[2],                      pHandle->c->width/2,                      pHandle->c->height/2,                      pDataOut +pHandle->c->width * pHandle->c->height*5/4);        }                if (pHandle->avpkt.data)        {            pHandle->avpkt.size -= pHandle->comsumedSize;            pHandle->avpkt.data += pHandle->comsumedSize;        }    }       return 0;}