FFMPEG_DEMO/source/VideoDecode/VideoDecoder/src/VideoReader/NALUParsing.cpp

/**
 * 叶海辉
 * QQ群121376426
 * http://blog.yundiantech.com/
 */

#include "NALUParsing.h"

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

NALUParsing::NALUParsing()
{
    ///初始化一段内存 用于临时存放h264数据
    mH264Buffer = (uint8_t*)malloc(1024*1024*10);
    mBufferSize = 0;
}

int NALUParsing::inputH264Data(uint8_t *buf, int len)
{
    memcpy(mH264Buffer + mBufferSize, buf, len);
    mBufferSize += len;

    return mBufferSize;
}

T_NALU *NALUParsing::getNextFrame()
{

    /*根据h264文件的特性  逐个字节搜索 直到遇到h264的帧头 视为获取到了完整的一帧h264视频数据*/

///    关于起始码startcode的两种形式：3字节的0x000001和4字节的0x00000001
///    3字节的0x000001只有一种场合下使用，就是一个完整的帧被编为多个slice的时候，
///    包含这些slice的nalu使用3字节起始码。其余场合都是4字节的。
///    因此查找一帧的话，只需要查找四字节的起始码即可。

    ///首先查找第一个起始码

    int pos = 0; //记录当前处理的数据偏移量
    int StartCode = 0;

    while(1)
    {
        unsigned char* Buf = mH264Buffer + pos;
        int lenth = mBufferSize - pos; //剩余没有处理的数据长度
        if (lenth <= 4)
        {
            return NULL;
        }

        ///查找起始码(0x00000001)
        if(Buf[0]==0 && Buf[1]==0 && Buf[2] ==0 && Buf[3] ==1)
         //Check whether buf is 0x00000001
        {
            StartCode = 4;
            break;
        }
        else
        {
            //否则 往后查找一个字节
            pos++;
        }
    }


    ///然后查找下一个起始码查找第一个起始码

    int pos_2 = pos + StartCode; //记录当前处理的数据偏移量
    int StartCode_2 = 0;

    while(1)
    {
        unsigned char* Buf = mH264Buffer + pos_2;
        int lenth = mBufferSize - pos_2; //剩余没有处理的数据长度
        if (lenth <= 4)
        {
            return nullptr;
        }

        ///查找起始码(0x00000001)
        if(Buf[0]==0 && Buf[1]==0 && Buf[2] ==0 && Buf[3] ==1)
         //Check whether buf is 0x00000001
        {
            StartCode_2 = 4;
            break;
        }
        else
        {
            //否则 往后查找一个字节
            pos_2++;
        }
    }

    /// 现在 pos和pos_2之间的数据就是一帧数据了
    /// 把他取出来

    ///由于传递给ffmpeg解码的数据 需要带上起始码 因此这里的nalu带上了起始码
    unsigned char* Buf = mH264Buffer + pos; //这帧数据的起始数据(包含起始码)
    int naluSize = pos_2 - pos; //nalu数据大小 包含起始码

    T_NALU * nalu = AllocNALU(naluSize, mVideoType);//分配nal 资源

    if (mVideoType == T_NALU_H264)
    {
        T_H264_NALU_HEADER *nalu_header = (T_H264_NALU_HEADER *)(Buf + StartCode);

        nalu->nalu.h264Nalu.startcodeprefix_len = StartCode;      //! 4 for parameter sets and first slice in picture, 3 for everything else (suggested)
        nalu->nalu.h264Nalu.len = naluSize;                 //! Length of the NAL unit (Excluding the start code, which does not belong to the NALU)
        nalu->nalu.h264Nalu.forbidden_bit = 0;            //! should be always FALSE
        nalu->nalu.h264Nalu.nal_reference_idc = nalu_header->NRI;        //! NALU_PRIORITY_xxxx
        nalu->nalu.h264Nalu.nal_unit_type = nalu_header->TYPE;            //! NALU_TYPE_xxxx
        nalu->nalu.h264Nalu.lost_packets = false;  //! true, if packet loss is detected
        memcpy(nalu->nalu.h264Nalu.buf, Buf, naluSize);  //! contains the first byte followed by the EBSP

//        {
//            char *bufTmp = (char*)(Buf + StartCode);
//            char s[10];
//            itoa(bufTmp[0], s, 2);
//            fprintf(stderr, "%s %08s %x %d\n", __FUNCTION__, s, bufTmp[0] , nalu_header->TYPE);
//        }
    }
    else
    {
        T_H265_NALU_HEADER *nalu_header = (T_H265_NALU_HEADER *)(Buf + StartCode);

        nalu->nalu.h265Nalu.startCodeLen = StartCode;      //! 4 for parameter sets and first slice in picture, 3 for everything else (suggested)
        nalu->nalu.h265Nalu.len = naluSize;                 //! Length of the NAL unit (Excluding the start code, which does not belong to the NALU)
        nalu->nalu.h265Nalu.h265NaluHeader = *nalu_header;
        memcpy(nalu->nalu.h265Nalu.buf, Buf, naluSize);  //! contains the first byte followed by the EBSP

//        {
//            char *bufTmp = (char*)(Buf);
//            fprintf(stderr, "%s %02x%02x%02x%02x%02x%02x %d %d\n", __FUNCTION__, bufTmp[0], bufTmp[1], bufTmp[2], bufTmp[3], bufTmp[4], bufTmp[5], nalu->nalu.h265Nalu.h265NaluHeader.nal_unit_type, nalu_header->nal_unit_type);
//        }
    }

    /// 将这一帧数据去掉
    /// 把后一帧数据覆盖上来
    int leftSize = mBufferSize - pos_2;
    memmove(mH264Buffer, mH264Buffer + pos_2, leftSize);
    mBufferSize = leftSize;

    return nalu;
}

T_NALU *NALUParsing::AllocNALU(int buffersize, T_NALU_TYPE type)
{
    T_NALU *n = NULL;

    n = (T_NALU*)malloc (sizeof(T_NALU));

    n->type = type;

    if (type == T_NALU_H264)
    {
        n->nalu.h264Nalu.max_size = buffersize;	//Assign buffer size
        n->nalu.h264Nalu.buf = (unsigned char*)malloc (buffersize);
        n->nalu.h264Nalu.len = buffersize;
    }
    else
    {
        n->nalu.h265Nalu.buf = (unsigned char*)malloc (buffersize);
        n->nalu.h265Nalu.len  = buffersize;
    }

    return n;
}

void NALUParsing::FreeNALU(T_NALU *n)
{
    if (n == nullptr) return;

    if (n->type == T_NALU_H264)
    {
        free(n->nalu.h264Nalu.buf);
    }
    else
    {
        free(n->nalu.h265Nalu.buf);
    }
}