1.1 海思3518 H264编码
海思的SDK里其实有H264编码的sample，但因为要匹配很多东西，代码有点复杂，让初学都感到有点混乱。我根据sample自己修改了一下代码，从最简单的情况(确定摄像头类型，只选一种尺寸的图片，只用一个通道)来说明海思HI3518是怎么编码为H264的。
先把源代码下载下来，再分析程序。
下载链接：https://download.csdn.net/download/zhanshenrui/10324766
首先从main函数开始。
//./myvenc
int main(int argc, char *argv[])//main()
{
HI_S32 s32Ret;
signal(SIGINT, SAMPLE_VENC_HandleSig);//ctrl+c,delete
signal(SIGTERM, SAMPLE_VENC_HandleSig);//shell命令kill缺省产生这个信号.
s32Ret = H264_Venc();
if(s32Ret==HI_SUCCESS)
printf("normally\n");
else
printf("unnormally\n");
return -1;
}main函数里先是用signal定义了两个信号来中断程序的运行，在板子上输入./myvenc 执行程序，按ctrl+c来中断程序，然后再往下就是H264编码函数H264_Venc()。
在H264_Venc()函数里先去初始化MPI系统，然后根据摄像头设置参数。我这里是AR030摄像头，其拍摄图片大小为720P,编码为H264,为了简单只输出一路。在初始化MPI系统时要计算视频缓存池VB_CONF_S的大小，然后填充VB_CONF_S结构体。填充完VB_CONF_S结构体后再用HI_MPI_VB_SetConf设置，最后初始化视频视频缓存池HI_MPI_VB_Init。这里注意的是基本上每个函数调用后都会判断返回值并作出错出理，后面很多函数也是这样处理的，这样利于程序排错。
//为了简单点，编码类型就选择PT_H264，图片大小就选择PIC_HD720，通道也只用1路s32ChnNum=1
PAYLOAD_TYPE_E enPayLoad=PT_H264;//264编码
PIC_SIZE_E enSize=PIC_HD720;//摄像头拍摄图片的大小，这里只用720P
HI_S32 s32ChnNum=1;//支持一路摄像
HI_S32 s32Ret=HI_FAILURE;
/******************************************
mpp system init.
******************************************/
HI_MPI_SYS_Exit();
HI_MPI_VB_Exit();
VB_CONF_S stVbConf;//缓存池参数结构体
HI_U32 u32BlkSize;//一张图片占多少字节
memset(&stVbConf,0,sizeof(VB_CONF_S));
//根据制式，图片大小，图片格式及对齐方式确定图片缓存大小
//这里用NTSC,720P,YUV420,64字节对齐
u32BlkSize=SAMPLE_COMM_SYS_CalcPicVbBlkSize(gs_enNorm,enSize, PIXEL_FORMAT_YUV_SEMIPLANAR_420, SAMPLE_SYS_ALIGN_WIDTH);
printf("u32BlkSize=%d\n",u32BlkSize);
stVbConf.u32MaxPoolCnt = 128;//用默认值，3518默认是128
stVbConf.astCommPool[0].u32BlkSize = u32BlkSize;
stVbConf.astCommPool[0].u32BlkCnt = g_u32BlkCnt;
s32Ret = HI_MPI_VB_SetConf(&stVbConf);//设置 MPP 视频缓存池属性
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_VB_SetConf failed!\n");
return HI_FAILURE;
}
s32Ret = HI_MPI_VB_Init();//初始化 MPP 视频缓存池
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_VB_Init failed!\n");
return HI_FAILURE;
}
//定义结构体，对结构体赋值，然后设置，最后初始化
MPP_SYS_CONF_S stSysConf = {0};
stSysConf.u32AlignWidth = SAMPLE_SYS_ALIGN_WIDTH;
s32Ret = HI_MPI_SYS_SetConf(&stSysConf);//配置系统控制参数
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_SYS_SetConf failed\n");
return HI_FAILURE;
}
s32Ret = HI_MPI_SYS_Init();//初始化 MPP 系统
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_SYS_Init failed!\n");
return HI_FAILURE;
}
HI_S32 fdmipi;
combo_dev_attr_t *pstcomboDevAttr = NULL;
fdmipi = open("/dev/hi_mipi", O_RDWR);
if (fdmipi < 0)
{
printf("warning: open hi_mipi dev failed\n");
return -1;
}
pstcomboDevAttr = &MIPI_CMOS3V3_ATTR;//AR0130模组属性
if (ioctl(fdmipi, HI_MIPI_SET_DEV_ATTR, pstcomboDevAttr))
{
printf("set mipi attr failed\n");
close(fdmipi);
return HI_FAILURE;
}
close(fdmipi);
HI_S32 i,ViChn=0;//只有一路输出，所以ViChn=0
//设置输入配置参数
SAMPLE_VI_CONFIG_S stViConfig = {0};
stViConfig.enViMode = APTINA_AR0130_DC_720P_30FPS;//摄像头是AR0130模组
stViConfig.enRotate = ROTATE_NONE;//不翻转
stViConfig.enNorm = VIDEO_ENCODING_MODE_AUTO;//编码模式自动
stViConfig.enViChnSet = VI_CHN_SET_NORMAL;//普通
stViConfig.enWDRMode = WDR_MODE_NONE;//不设置宽动态
VI_DEV_ATTR_S stViDevAttr;
VI_DEV ViDev=0;//只有一个摄像头设备，所以设备序号为0
ISP_DEV s32IspDev=0;//同样，ISP序号也为0
memset(&stViDevAttr,0,sizeof(stViDevAttr));
memcpy(&stViDevAttr,&DEV_ATTR_9M034_DC_720P_BASE,sizeof(stViDevAttr));
/******************************************
step 1: mipi configure
******************************************/
/*
s32Ret = SAMPLE_COMM_VI_StartMIPI(&stViConfig);
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("%s: MIPI init failed!\n", __FUNCTION__);
return HI_FAILURE;
}
*/
/******************************************
step 2: configure sensor and ISP (include WDR mode).
note: you can jump over this step, if you do not use Hi3516A interal isp.
//虽然说了不用，但还要需要，因为后面HI_MPI_ISP_GetWDRMode函数会调用ISP_CHECK_MEM_INIT
//检测内存，所以还是在这里使用
******************************************/
s32Ret = SAMPLE_COMM_ISP_Init(stViConfig.enWDRMode);
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("%s: Sensor init failed!\n", __FUNCTION__);
return HI_FAILURE;
}
/******************************************
step 3: run isp thread
note: you can jump over this step, if you do not use Hi3516A interal isp.
******************************************/
s32Ret = SAMPLE_COMM_ISP_Run();
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("%s: ISP init failed!\n", __FUNCTION__);
/* disable videv */
return HI_FAILURE;
}
s32Ret=HI_MPI_VI_SetDevAttr(ViDev, &stViDevAttr);//只有一个设备，所以设备号为0
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VI_SetDevAttr failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
ISP_WDR_MODE_S stWdrMode;
s32Ret = HI_MPI_ISP_GetWDRMode(s32IspDev, &stWdrMode);
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_ISP_GetWDRMode failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
VI_WDR_ATTR_S stWdrAttr;
stWdrAttr.enWDRMode = stWdrMode.enWDRMode;
stWdrAttr.bCompress = HI_FALSE;
s32Ret = HI_MPI_VI_SetWDRAttr(ViDev, &stWdrAttr);
if (s32Ret)
{
SAMPLE_PRT("HI_MPI_VI_SetWDRAttr failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VI_EnableDev(ViDev);
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VI_EnableDev failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
RECT_S stCapRect;
SIZE_S stTargetSize;
stCapRect.s32X = 0;
stCapRect.s32Y = 0;
stCapRect.u32Width = 1280;
stCapRect.u32Height = 720;//AR030输出1280*720图像
stTargetSize.u32Width = stCapRect.u32Width;
stTargetSize.u32Height = stCapRect.u32Height;
//设置通道属性
VI_CHN_ATTR_S stChnAttr;
memcpy(&stChnAttr.stCapRect, &stCapRect, sizeof(RECT_S));
stChnAttr.enCapSel = VI_CAPSEL_BOTH;
stChnAttr.stDestSize.u32Width = stTargetSize.u32Width;
stChnAttr.stDestSize.u32Height = stTargetSize.u32Height;
stChnAttr.enPixFormat = PIXEL_FORMAT_YUV_SEMIPLANAR_420;
stChnAttr.bMirror = HI_FALSE;
stChnAttr.bFlip = HI_FALSE;
stChnAttr.s32SrcFrameRate = -1;
stChnAttr.s32DstFrameRate = -1;
stChnAttr.enCompressMode = COMPRESS_MODE_NONE;
s32Ret = HI_MPI_VI_SetChnAttr(ViChn, &stChnAttr);//设置通道属性
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("in HI_MPI_VI_SetChnAttr failed with %#x!\n", s32Ret);
SAMPLE_COMM_ISP_Stop();
return HI_FAILURE;
}
s32Ret = HI_MPI_VI_EnableChn(ViChn);//使能通道
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VI_EnableChn failed with %#x!\n", s32Ret);
SAMPLE_COMM_ISP_Stop();
return HI_FAILURE;
}设置VPSS组过程如下：定义结构体，给结构体赋值，设置(创建的同时就设置了)，启动
SIZE_S stSize;
stSize.u32Width = 1280;
stSize.u32Height = 720;
VPSS_GRP_ATTR_S stVpssGrpAttr;
VPSS_NR_PARAM_U unNrParam = {{0}};
VPSS_GRP VpssGrp=0;//只有一个设备，序号为0
stVpssGrpAttr.u32MaxW = stSize.u32Width;
stVpssGrpAttr.u32MaxH = stSize.u32Height;
stVpssGrpAttr.bIeEn = HI_FALSE;
stVpssGrpAttr.bNrEn = HI_TRUE;
stVpssGrpAttr.bHistEn = HI_FALSE;
stVpssGrpAttr.bDciEn = HI_FALSE;
stVpssGrpAttr.enDieMode = VPSS_DIE_MODE_NODIE;
stVpssGrpAttr.enPixFmt = PIXEL_FORMAT_YUV_SEMIPLANAR_420;
s32Ret = HI_MPI_VPSS_CreateGrp(VpssGrp, &stVpssGrpAttr);//创建组的同时将组的属性设置进去
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VPSS_CreateGrp failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VPSS_GetNRParam(VpssGrp, &unNrParam);
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VPSS_GetNRParam failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VPSS_SetNRParam(VpssGrp, &unNrParam);
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VPSS_SetNRParam failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VPSS_StartGrp(VpssGrp);//启动VPSS组
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VPSS_StartGrp failed with %#x\n", s32Ret);
return HI_FAILURE;
}一个通道，目的源设置为VPSS的一个通道
SAMPLE_VI_PARAM_S stViParam;
stViParam.s32ViDevCnt = 1;
stViParam.s32ViDevInterval = 1;
stViParam.s32ViChnCnt = 1;
stViParam.s32ViChnInterval = 1;
MPP_CHN_S stSrcChn;
MPP_CHN_S stDestChn;
stSrcChn.enModId = HI_ID_VIU;
stSrcChn.s32DevId = 0;
stSrcChn.s32ChnId = ViChn;
stDestChn.enModId = HI_ID_VPSS;
stDestChn.s32DevId = VpssGrp;
stDestChn.s32ChnId = 0;
s32Ret = HI_MPI_SYS_Bind(&stSrcChn, &stDestChn);//将VI的0通道与VPSS的组的0通道绑定起来
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("failed with %#x!\n", s32Ret);
return HI_FAILURE;
}//设置VPSS通道，只有一个通道，所以VpssChn=0
VPSS_CHN VpssChn=0;
VPSS_CHN_ATTR_S stVpssChnAttr;
VPSS_CHN_MODE_S stVpssChnMode;
stVpssChnMode.enChnMode = VPSS_CHN_MODE_USER;
stVpssChnMode.bDouble = HI_FALSE;
stVpssChnMode.enPixelFormat = PIXEL_FORMAT_YUV_SEMIPLANAR_420;
stVpssChnMode.u32Width = stSize.u32Width;
stVpssChnMode.u32Height = stSize.u32Height;
stVpssChnMode.enCompressMode = COMPRESS_MODE_SEG;
memset(&stVpssChnAttr, 0, sizeof(stVpssChnAttr));
stVpssChnAttr.s32SrcFrameRate = -1;
stVpssChnAttr.s32DstFrameRate = -1;
s32Ret = HI_MPI_VPSS_SetChnAttr(VpssGrp, VpssChn, &stVpssChnAttr);
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VPSS_SetChnAttr failed with %#x\n", s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VPSS_SetChnMode(VpssGrp, VpssChn, &stVpssChnMode);
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("%s failed with %#x\n", __FUNCTION__, s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VPSS_EnableChn(VpssGrp, VpssChn);
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VPSS_EnableChn failed with %#x\n", s32Ret);
return HI_FAILURE;
}
//定义结构体，给结构体赋值，创建通道同时将结构体设置进去
SAMPLE_RC_E enRcMode= SAMPLE_RC_CBR;
VENC_CHN VencChn=0;
VENC_CHN_ATTR_S stVencChnAttr;
VENC_ATTR_H264_S stH264Attr;
VENC_ATTR_H264_CBR_S stH264Cbr;
stVencChnAttr.stVeAttr.enType =enPayLoad;
stH264Attr.u32MaxPicWidth =stSize.u32Width;
stH264Attr.u32MaxPicHeight = stSize.u32Height;
stH264Attr.u32PicWidth = stSize.u32Width;/*the picture width*/
stH264Attr.u32PicHeight = stSize.u32Height;/*the picture height*/
stH264Attr.u32BufSize = stSize.u32Width * stSize.u32Height;/*stream buffer size*/
stH264Attr.u32Profile = 0;/*0: baseline; 1:MP; 2:HP; 3:svc_t */
stH264Attr.bByFrame = HI_TRUE;/*get stream mode is slice mode or frame mode?*/
stH264Attr.u32BFrameNum = 0;/* 0: not support B frame; >=1: number of B frames */
stH264Attr.u32RefNum = 1;/* 0: default; number of refrence frame*/
memcpy(&stVencChnAttr.stVeAttr.stAttrH264e, &stH264Attr, sizeof(VENC_ATTR_H264_S));
stVencChnAttr.stRcAttr.enRcMode = VENC_RC_MODE_H264CBR;
stH264Cbr.u32Gop = (VIDEO_ENCODING_MODE_PAL== gs_enNorm)?25:30;
stH264Cbr.u32StatTime = 1; /* stream rate statics time(s) */
stH264Cbr.u32SrcFrmRate = (VIDEO_ENCODING_MODE_PAL== gs_enNorm)?25:30;/* input (vi) frame rate */
stH264Cbr.fr32DstFrmRate = (VIDEO_ENCODING_MODE_PAL== gs_enNorm)?25:30;/* target frame rate */
stH264Cbr.u32BitRate = 1024*2;
stH264Cbr.u32FluctuateLevel = 0; /* average bit rate */
memcpy(&stVencChnAttr.stRcAttr.stAttrH264Cbr, &stH264Cbr, sizeof(VENC_ATTR_H264_CBR_S));
s32Ret = HI_MPI_VENC_CreateChn(VencChn, &stVencChnAttr);//创建通道同时将结构体设置进去
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_VENC_CreateChn [%d] faild with %#x!\n",VencChn, s32Ret);
return s32Ret;
}
//将VPSS通道作为源通道与VENC通道作为目的通道绑定起来
stSrcChn.enModId = HI_ID_VPSS;
stSrcChn.s32DevId = VpssGrp;
stSrcChn.s32ChnId = VpssChn;
stDestChn.enModId = HI_ID_VENC;
stDestChn.s32DevId = 0;
stDestChn.s32ChnId = VencChn;
s32Ret=HI_MPI_SYS_Bind(&stSrcChn, &stDestChn);
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("failed with %#x!\n", s32Ret);
return HI_FAILURE;
}gs_stPara.bThreadStart = HI_TRUE;
gs_stPara.s32Cnt = s32ChnNum;
pthread_create(&gs_VencPid, 0, VENC_GetVencStreamProc, (HI_VOID*)&gs_stPara);
printf("please press twice ENTER to exit this sample\n");
getchar();
getchar();
if (HI_TRUE == gs_stPara.bThreadStart)
{
gs_stPara.bThreadStart = HI_FALSE;
pthread_join(gs_VencPid, 0);
}
stSrcChn.enModId = HI_ID_VPSS;
stSrcChn.s32DevId = VpssGrp;
stSrcChn.s32ChnId = VpssChn;
stDestChn.enModId = HI_ID_VENC;
stDestChn.s32DevId = 0;
stDestChn.s32ChnId = VencChn;
s32Ret = HI_MPI_SYS_UnBind(&stSrcChn, &stDestChn);//先解绑VPSS和VENC的绑定，后面再解绑VPSS和VI的绑定
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VENC_StopRecvPic(VencChn);//前面开启了接收图片，这里就要停止
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_VENC_StopRecvPic vechn[%d] failed with %#x!\n",VencChn, s32Ret);
return HI_FAILURE;
}
/******************************************
Distroy Venc Channel
******************************************/
s32Ret = HI_MPI_VENC_DestroyChn(VencChn);
//前面创建了VENC通道，这里就要销毁VENC通道，而且最先销毁，后面再销毁VI通道
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_VENC_DestroyChn vechn[%d] failed with %#x!\n",VencChn, s32Ret);
return HI_FAILURE;
}
stSrcChn.enModId = HI_ID_VIU;
stSrcChn.s32DevId = ViDev;
stSrcChn.s32ChnId = ViChn;
stDestChn.enModId = HI_ID_VPSS;
stDestChn.s32DevId = VpssGrp;
stDestChn.s32ChnId = 0;
s32Ret = HI_MPI_SYS_UnBind(&stSrcChn, &stDestChn);
//后面再解绑VPSS和VI的绑定,在解绑VPSS和VENC的绑定之后，顺序与绑定顺序相反
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("failed with %#x!\n", s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VPSS_DisableChn(VpssGrp, VpssChn);//失能VPSS组和VPSS通道
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("%s failed with %#x\n", __FUNCTION__, s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VPSS_StopGrp(VpssGrp);//停止VPSS组
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("%s failed with %#x\n", __FUNCTION__, s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VPSS_DestroyGrp(VpssGrp);//销毁组
if (s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("%s failed with %#x\n", __FUNCTION__, s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VI_DisableChn(ViChn);//失能通道
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_VI_DisableChn failed with %#x\n",s32Ret);
return HI_FAILURE;
}
s32Ret = HI_MPI_VI_DisableDev(ViDev);//失能VI设备即摄像头
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_VI_DisableDev failed with %#x\n", s32Ret);
return HI_FAILURE;
}
SAMPLE_COMM_ISP_Stop();//停止ISP
HI_MPI_SYS_Exit();//去初始化
HI_MPI_VB_Exit();
//由以上几个步骤可以看出，设置与销毁顺序相反，而且是成对出现
return HI_SUCCESS;
HI_VOID* VENC_GetVencStreamProc(HI_VOID *p)
{
SAMPLE_VENC_GETSTREAM_PARA_S *pstPara;
HI_S32 s32ChnTotal;
VENC_CHN VencChn;
HI_S32 s32Ret;
PAYLOAD_TYPE_E enPayLoadType[VENC_MAX_CHN_NUM];
HI_CHAR aszFileName[VENC_MAX_CHN_NUM][64];
VENC_CHN_ATTR_S stVencChnAttr;
struct timeval TimeoutVal;
fd_set read_fds;
HI_S32 VencFd[VENC_MAX_CHN_NUM],maxfd;
VENC_STREAM_S stStream;
VENC_CHN_STAT_S stStat;
FILE *pFile[VENC_MAX_CHN_NUM];
HI_S32 i;
pstPara = (SAMPLE_VENC_GETSTREAM_PARA_S*)p;
s32ChnTotal = pstPara->s32Cnt;//pstPara->s32Cnt是由参数传进来的，为1
for (i = 0; i < s32ChnTotal; i++)
{
VencChn = i;
s32Ret = HI_MPI_VENC_GetChnAttr(VencChn, &stVencChnAttr);
//这里是为了取得是什么编码类型，以便确定保存文件的后缀名
//比如这里是H264编码，所以保存文件的后缀后就是.h264
if(s32Ret != HI_SUCCESS)
{
SAMPLE_PRT("HI_MPI_VENC_GetChnAttr chn[%d] failed with %#x!\n", \
VencChn, s32Ret);
return NULL;
}
enPayLoadType[i] = stVencChnAttr.stVeAttr.enType;
gettime(filename);//获取时间如20171101085639为文件名
sprintf(aszFileName[i], "%s_%d%s",filename, i, ".h264");//20171101085639.h264
pFile[i] = fopen(aszFileName[i], "wb");
if (!pFile[i])
{
SAMPLE_PRT("open file[%s] failed!\n", aszFileName[i]);
return NULL;
}
VencFd[i] = HI_MPI_VENC_GetFd(i);//获取文件句柄，以便后面能用select来IO复用
if (VencFd[i] < 0)
{
SAMPLE_PRT("HI_MPI_VENC_GetFd failed with %#x!\n", VencFd[i]);
return NULL;
}
if (maxfd <= VencFd[i])
{
maxfd = VencFd[i];
}
}
while (HI_TRUE == pstPara->bThreadStart)
//当main函数所在的线程接收到两个键盘字符或ctrl+c时，pstPara->bThreadStart会为假，跳出while循环
//然后往下执行关闭前面打开的文件，执行完这个VENC_GetVencStreamProc线程函数，线程结束
{
/*IO复用4步骤
1.清空文件集合FD_ZERO(&read_fds);
2.将文件加入文件集合FD_SET(VencFd[i], &read_fds);
3.设置超时时间并用select(maxfd + 1, &read_fds, NULL, NULL, &TimeoutVal)来等待文件状态有变化唤醒线程
或超时唤醒
4.FD_ISSET查询文件状态是否有变化，有变化则处理
*/
FD_ZERO(&read_fds);
for (i = 0; i < s32ChnTotal; i++)
{
FD_SET(VencFd[i], &read_fds);
}
TimeoutVal.tv_sec = 2;
TimeoutVal.tv_usec = 0;
s32Ret = select(maxfd + 1, &read_fds, NULL, NULL, &TimeoutVal);
if (s32Ret < 0)
{
SAMPLE_PRT("select failed!\n");
break;
}
else if (s32Ret == 0)
{
SAMPLE_PRT("get venc stream time out, exit thread\n");
continue;
}
else
{
for (i = 0; i < s32ChnTotal; i++)
{
if (FD_ISSET(VencFd[i], &read_fds))
{
memset(&stStream, 0, sizeof(stStream));
s32Ret = HI_MPI_VENC_Query(i, &stStat);//查询是否有码流，并将码流信息填充到stStat结构体中
if (HI_SUCCESS != s32Ret)
{
SAMPLE_PRT("HI_MPI_VENC_Query chn[%d] failed with %#x!\n", i, s32Ret);
break;
}
if(0 == stStat.u32CurPacks)
{
SAMPLE_PRT("NOTE: Current frame is NULL!\n");
continue;
}
stStream.pstPack = (VENC_PACK_S*)malloc(sizeof(VENC_PACK_S) * stStat.u32CurPacks);
//分配内存以便保存码流包数据
if (NULL == stStream.pstPack)
{
SAMPLE_PRT("malloc stream pack failed!\n");
break;
}
stStream.u32PackCount = stStat.u32CurPacks;
//printf("stStream.u32PackCount=%d\n",stStream.u32PackCount);
s32Ret = HI_MPI_VENC_GetStream(i, &stStream, HI_TRUE);//获取码流数据并保存到stStream结构体中
if (HI_SUCCESS != s32Ret)
{
free(stStream.pstPack);//获取失败则要释放前面分配的内存，否则会造成内存溢出
stStream.pstPack = NULL;
SAMPLE_PRT("HI_MPI_VENC_GetStream failed with %#x!\n", s32Ret);
break;
}
HI_S32 u32PackIndex;
for (u32PackIndex= 0;u32PackIndex < stStream.u32PackCount; u32PackIndex++)
{
fwrite( stStream.pstPack[u32PackIndex].pu8Addr+stStream.pstPack[u32PackIndex].u32Offset,\
stStream.pstPack[u32PackIndex].u32Len- stStream.pstPack[u32PackIndex].u32Offset, \
1, pFile[i]);
fflush(pFile[i]);
#if 1
printf("stStream.u32PackCount=%d,stStream.pstPack[%d].pu8Addr=0x%08x,\
stStream.pstPack[%d].u32Offset=%d,stStream.pstPack[%d].u32Len=%d\n",\
stStream.u32PackCount,u32PackIndex,stStream.pstPack[u32PackIndex].pu8Addr,\
u32PackIndex,stStream.pstPack[u32PackIndex].u32Offset,u32PackIndex,stStream.pstPack[u32PackIndex].u32Len);
//添加打印信息，查看保存码流内容的内存是怎么样的
#endif
}
s32Ret = HI_MPI_VENC_ReleaseStream(i, &stStream);//保存后要释放码流
if (HI_SUCCESS != s32Ret)
{
free(stStream.pstPack);//获取失败则要释放前面分配的内存，否则会造成内存溢出
stStream.pstPack = NULL;
break;
}
free(stStream.pstPack);//释放码流后，也要释放分配的内存，避免内存溢出
stStream.pstPack = NULL;
}
}
}
}
for (i = 0; i < s32ChnTotal; i++)
{
fclose(pFile[i]);
}
return NULL;
}综合整个程序，在创建线程函数前都是对系统设置，按照海思SDK里的文档步骤设置就行，基本上就是定义结构体，给结构体赋值，然后设置进系统。到后面创建线程后就有两个线程函数了，一个main函数所在线程，一个VENC_GetVencStreamProc函数所在线程。main函数所在线程创建VENC_GetVencStreamProc线程后就调用getchar();函数进入休眠状态，只有当键盘有输入时getchar()函数有返回值时才会唤醒main函数所在线程，所以CPU就切换到VENC_GetVencStreamProc线程，VENC_GetVencStreamProc线程在调用select函数时，如果读文件集合read_fds有要读的内容则会往下执行，如果没有VENC_GetVencStreamProc线程也会休眠，CPU会切换到别的线程，当read_fds有要读的内容内容时或超时VENC_GetVencStreamProc线程会唤醒，往下执行去进行读码流的处理过程。
程序写完后，在sample文件夹里创建个子文件夹如myvenc,然后将这个文件保存到myvenc里，从sample\venc里复制makefile到sample\myvenc里，这个makefile都不要我们改些什么东西，只要位置放对了位置(跟源代码文件在同一个目录里)就直接可以用，然后make clean,make编译，如果没问题的话会生成myvenc可执行文件，将这个可执行文件拷贝到HI3518开发板(可通过SD卡从PC拷贝到开发板，也可挂载根文件系统直接复制过去，方法多样)，然后执行./myvenc就会运行程序，过一会就会在myvenc同级目录下生成一个以时间为名的，后缀名为h264的文件，这个文件就是H264码流保存的文件，将这文件从Hi3518里复制到PC机上，用VLC播放器就可以播放出摄像头拍摄的内容。
编译运行程序后生成了h264文件，这个文件及程序运行时打印的输出内容有助于我们分析h264,下一篇我们将分析h264以便后期怎么将h264数据打包到rtp中进行rtsp传送数据。
这个程序比较简单，只是为了让大家了解海思芯片是怎么进行多媒体开发，所以很多功能没有写成函数，感觉内容很多，但避免了sample里复杂的函数调用，有助于将了解各个数据结构及海思SDK各个函数的用法。程序从前往后看，流程一目了然，各个数据结构、函数对应哪个模块很清楚，对入门很有好处。我将代码上传到github,欢迎朋友们下载，一起讨论学习。
最后看一下程序运行效果，用VLC打开H264文件，可以看到摄像头拍摄界面：
项目源代码及工具:Hi3518编码H264