tag.argc = 0;

这是一个C++语言中的语句，它的作用是将`tag`对象的`argc`成员变量的值设置为0。

在C++中，结构体（`struct`）或类（`class`）可以拥有成员变量和成员函数。`tag`可能是一个结构体或类的实例对象，在这个对象中，`argc`是一个成员变量。通过`tag.argc = 0`这个语句，将`tag`对象的`argc`成员变量设置为0。

需要注意的是，这个语句只有在`tag`对象的定义中，`argc`成员变量被声明为公有（public）时才能使用，否则会编译错误。

相关问题

生成一个rk3399 mpi接口使用mppencrccfg 的h264编码 包含#define TAG "mpi_h264enc_test" 完整程序

很抱歉，我无法提供完整的程序代码。但我可以给出一些参考:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <linux/videodev2.h>
#include "rk_mpi.h"
#include "rk_venc.h"

#define TAG "mpi_h264enc_test"

#define VIDEO_WIDTH     1920
#define VIDEO_HEIGHT    1080
#define VIDEO_FPS       30

#define FRAME_NUM       1000

typedef struct
{
    int fd;
    void *start;
    size_t length;
} camera_t;

static camera_t *camera_open(int id)
{
    camera_t *camera = (camera_t *)malloc(sizeof(camera_t));
    if (camera == NULL)
    {
        printf("[%s] malloc camera_t failed\n", TAG);
        return NULL;
    }

    char dev_name[16];
    sprintf(dev_name, "/dev/video%d", id);
    camera->fd = open(dev_name, O_RDWR);
    if (camera->fd < 0)
    {
        printf("[%s] open %s failed\n", TAG, dev_name);
        free(camera);
        return NULL;
    }

    struct v4l2_capability cap;
    if (ioctl(camera->fd, VIDIOC_QUERYCAP, &cap) < 0)
    {
        printf("[%s] VIDIOC_QUERYCAP failed\n", TAG);
        close(camera->fd);
        free(camera);
        return NULL;
    }

    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE))
    {
        printf("[%s] %s is not a video capture device\n", TAG, dev_name);
        close(camera->fd);
        free(camera);
        return NULL;
    }

    if (!(cap.capabilities & V4L2_CAP_STREAMING))
    {
        printf("[%s] %s does not support streaming i/o\n", TAG, dev_name);
        close(camera->fd);
        free(camera);
        return NULL;
    }

    struct v4l2_format fmt;
    memset(&fmt, 0, sizeof(fmt));
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width = VIDEO_WIDTH;
    fmt.fmt.pix.height = VIDEO_HEIGHT;
    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
    fmt.fmt.pix.field = V4L2_FIELD_NONE;
    if (ioctl(camera->fd, VIDIOC_S_FMT, &fmt) < 0)
    {
        printf("[%s] VIDIOC_S_FMT failed\n", TAG);
        close(camera->fd);
        free(camera);
        return NULL;
    }

    struct v4l2_requestbuffers req;
    memset(&req, 0, sizeof(req));
    req.count = 4;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;
    if (ioctl(camera->fd, VIDIOC_REQBUFS, &req) < 0)
    {
        printf("[%s] VIDIOC_REQBUFS failed\n", TAG);
        close(camera->fd);
        free(camera);
        return NULL;
    }

    struct v4l2_buffer buf;
    for (int i = 0; i < req.count; i++)
    {
        memset(&buf, 0, sizeof(buf));
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = i;
        if (ioctl(camera->fd, VIDIOC_QUERYBUF, &buf) < 0)
        {
            printf("[%s] VIDIOC_QUERYBUF failed\n", TAG);
            close(camera->fd);
            free(camera);
            return NULL;
        }

        camera->start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, camera->fd, buf.m.offset);
        if (camera->start == MAP_FAILED)
        {
            printf("[%s] mmap failed\n", TAG);
            close(camera->fd);
            free(camera);
            return NULL;
        }

        camera->length = buf.length;
        if (ioctl(camera->fd, VIDIOC_QBUF, &buf) < 0)
        {
            printf("[%s] VIDIOC_QBUF failed\n", TAG);
            munmap(camera->start, camera->length);
            close(camera->fd);
            free(camera);
            return NULL;
        }
    }

    enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if (ioctl(camera->fd, VIDIOC_STREAMON, &type) < 0)
    {
        printf("[%s] VIDIOC_STREAMON failed\n", TAG);
        close(camera->fd);
        free(camera);
        return NULL;
    }

    return camera;
}

static void camera_close(camera_t *camera)
{
    if (camera != NULL)
    {
        enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        ioctl(camera->fd, VIDIOC_STREAMOFF, &type);

        for (int i = 0; i < 4; i++)
        {
            munmap(camera->start, camera->length);
        }

        close(camera->fd);
        free(camera);
    }
}

static int camera_capture(camera_t *camera, unsigned char *buffer, int *length)
{
    struct v4l2_buffer buf;
    memset(&buf, 0, sizeof(buf));
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    if (ioctl(camera->fd, VIDIOC_DQBUF, &buf) < 0)
    {
        return -1;
    }

    memcpy(buffer, camera->start, buf.bytesused);
    *length = buf.bytesused;

    if (ioctl(camera->fd, VIDIOC_QBUF, &buf) < 0)
    {
        return -1;
    }

    return 0;
}

static void *camera_thread(void *arg)
{
    camera_t *camera = (camera_t *)arg;

    unsigned char *buffer = (unsigned char *)malloc(camera->length);
    if (buffer == NULL)
    {
        printf("[%s] malloc buffer failed\n", TAG);
        return NULL;
    }

    int length = 0;
    while (1)
    {
        if (camera_capture(camera, buffer, &length) == 0)
        {
            // do something with captured frame
        }

        usleep(1000);
    }

    free(buffer);
    return NULL;
}

int main(int argc, char **argv)
{
    RK_MPI_SYS_Init();

    RK_U32 u32Width = VIDEO_WIDTH;
    RK_U32 u32Height = VIDEO_HEIGHT;
    RK_U32 u32Fps = VIDEO_FPS;
    RK_U32 u32BitRate = u32Width * u32Height * 3 / 2 * u32Fps;
    RK_U32 u32KeyFrameInterval = u32Fps;
    RK_U32 u32Profile = 66; // H264 PROFILE_HIGH

    MPP_CHN_S stChnAttr;
    stChnAttr.mChnId = 0;
    stChnAttr.mModId = RK_ID_VENC;
    stChnAttr.mDevId = 0;
    stChnAttr.mWidth = u32Width;
    stChnAttr.mHeight = u32Height;
    stChnAttr.mFps = u32Fps;
    stChnAttr.mBitRate = u32BitRate;
    stChnAttr.mProfile = u32Profile;
    stChnAttr.mLevel = 41; // H264 LEVEL4_1
    stChnAttr.mPixelFormat = RK_FMT_YUV420SP;
    stChnAttr.mRotation = 0;
    stChnAttr.mMirror = 0;
    stChnAttr.mFlip = 0;
    stChnAttr.mDrmMode = 0;
    stChnAttr.mDrmFd = -1;

    if (RK_MPI_VENC_CreateChn(0, &stChnAttr) != RK_SUCCESS)
    {
        printf("[%s] create venc chn failed\n", TAG);
        return -1;
    }

    if (RK_MPI_VENC_RegisterChn(0, 0, 0) != RK_SUCCESS)
    {
        printf("[%s] register venc chn failed\n", TAG);
        return -1;
    }

    MPP_CHN_S stSrcChn;
    stSrcChn.mModId = RK_ID_VI;
    stSrcChn.mDevId = 0;
    stSrcChn.mChnId = 0;

    MPP_CHN_S stDestChn;
    stDestChn.mModId = RK_ID_VENC;
    stDestChn.mDevId = 0;
    stDestChn.mChnId = 0;

    RK_MPI_SYS_Bind(&stSrcChn, &stDestChn);

    camera_t *camera = camera_open(0);
    if (camera != NULL)
    {
        pthread_t tid;
        pthread_create(&tid, NULL, camera_thread, camera);
    }

    RK_S32 s32Ret = RK_SUCCESS;
    MPP_FRAME_S stFrame;
    memset(&stFrame, 0, sizeof(stFrame));
    stFrame.mModId = RK_ID_VENC;
    stFrame.mChannelId = 0;
    stFrame.mWidth = u32Width;
    stFrame.mHeight = u32Height;
    stFrame.mField = RK_FIELD_NONE;
    stFrame.mFrameType = RK_CODEC_FRAME_SPS_PPS_I;
    stFrame.mCompressMode = COMPRESS_MODE_NONE;
    stFrame.mBitWidth = 10;
    stFrame.mColor = MPP_FMT_YUV420SP;

    for (int i = 0; i < FRAME_NUM; i++)
    {
        s32Ret = RK_MPI_VENC_GetFrm(0, &stFrame, RK_TRUE);
        if (s32Ret != RK_SUCCESS)
        {
            printf("[%s] venc get frame failed\n", TAG);
            goto done;
        }

        unsigned char *y = (unsigned char *)stFrame.mVirAddr[0];
        unsigned char *uv = (unsigned char *)stFrame.mVirAddr[1];
        int y_len = stFrame.mWidth * stFrame.mHeight;
        int uv_len = stFrame.mWidth * stFrame.mHeight / 2;

        RK_MPI_VENC_RcCfg rc_cfg;
        memset(&rc_cfg, 0, sizeof(rc_cfg));
        rc_cfg.mRcMode = VENC_RC_MODE_H264CBR;
        rc_cfg.mBitRate = u32BitRate;
        rc_cfg.mFrmRate = u32Fps;
        rc_cfg.mGop = u32KeyFrameInterval;
        rc_cfg.mQpMin = 30;
        rc_cfg.mQpMax = 51;
        rc_cfg.mQpInit = 35;
        rc_cfg.mMaxReEncodeTimes = 5;
        rc_cfg.mMaxQPDelta = 10;
        rc_cfg.mMaxBitRateTolerance = 1000;

        RK_MPI_VENC_SetRcCfg(0, &rc_cfg);

        RK_MPI_VENC_H264Cfg h264_cfg;
        memset(&h264_cfg, 0, sizeof(h264_cfg));
        h264_cfg.mProfile = u32Profile;
        h264_cfg.mLevel = 41;
        h264_cfg.mEntropyMode = VENC_ENTROPY_MODE_CABAC;
        h264_cfg.mCabacInitIdc = 0;
        h264_cfg.mSliceNum = 2;
        h264_cfg.mSliceMode = VENC_H264_SLICEMODE_SINGLE;

        RK_MPI_VENC_SetH264Cfg(0, &h264_cfg);

        RK_MPI_VENC_H264Vui h264_vui;
        memset(&h264_vui, 0, sizeof(h264_vui));
        h264_vui.mAspectRatioIdc = 0;
        h264_vui.mOverScanInfo = 0;
        h264_vui.mBitstreamRestriction = 0;

        RK_MPI_VENC_SetH264Vui(0, &h264_vui);

        RK_MPI_VENC_H264Sei h264_sei;
        memset(&h264_sei, 0, sizeof(h264_sei));
        h264_sei.mRecoveryPoint = 0;
        h264_sei.mRecoveryPointInfoPresent = 0;
        h264_sei.mBufferingPeriod = 0;
        h264_sei.mPictureTiming = 0;

        RK_MPI_VENC_SetH264Sei(0, &h264_sei);

        MPP_ENC_CFG_S stMppEncCfg;
        memset(&stMppEncCfg, 0, sizeof(stMppEncCfg));
        stMppEncCfg.mRcCfg = &rc_cfg;
        stMppEncCfg.mGopCfg = NULL;
        stMppEncCfg.mH264Cfg = &h264_cfg;
        stMppEncCfg.mH264VuiCfg = &h264_vui;
        stMppEncCfg.mH264SeiCfg = &h264_sei;
        RK_MPI_VENC_SetMppCfg(0, &stMppEncCfg);

        MPP_ENC_SEI_S stEncSei;
        memset(&stEncSei, 0, sizeof(stEncSei));
        stEncSei.mEncSeiMode = MPP_ENC_SEI_MODE_ALL;
        RK_MPI_VENC_SetExtCfg(0, ENC_CFG_SEI, &stEncSei);

        RK_MPI_VENC_SendFrame(0, y, uv, y_len, uv_len);

        RK_MPI_VENC_ReleaseFrm(0, &stFrame);

        usleep(1000 * 1000 / u32Fps);
    }

done:
    if (RK_MPI_VENC_UnRegisterChn(0, 0, 0) != RK_SUCCESS)
    {
        printf("[%s] unregister venc chn failed\n", TAG);
    }

    if (RK_MPI_VENC_DestroyChn(0) != RK_SUCCESS)
    {
        printf("[%s] destroy venc chn failed\n", TAG);
    }

    RK_MPI_SYS_UnBind(&stSrcChn, &stDestChn);

    if (camera != NULL)
    {
        camera_close(camera);
    }

    RK_MPI_SYS_Exit();

    return 0;
}

这是一个基于 Rockchip RK3399 平台的 H.264 编码程序，程序中包含了使用 MPP 接口对 H.264 编码器进行配置的相关代码，可以根据需要进行修改。注意，本程序只是一个示例程序，不保证可以直接编译通过并运行。

讲解 napi_value NapiAsyKeyGenerator::CreateJsAsyKeyGenerator(napi_env env, napi_callback_info info) { LOGI("enter ..."); size_t expectedArgc = PARAMS_NUM_ONE; size_t argc = expectedArgc; napi_value argv[PARAMS_NUM_ONE] = { nullptr }; napi_get_cb_info(env, info, &argc, argv, nullptr, nullptr); if (argc != expectedArgc) { LOGE("The input args num is invalid."); return NapiGetNull(env); } napi_value instance; napi_value constructor = nullptr; napi_get_reference_value(env, classRef_, &constructor); napi_new_instance(env, constructor, argc, argv, &instance); std::string algName; if (!GetStringFromJSParams(env, argv[0], algName)) { LOGE("failed to get algoName."); return NapiGetNull(env); } HcfAsyKeyGenerator *generator = nullptr; int32_t res = HcfAsyKeyGeneratorCreate(algName.c_str(), &generator); if (res != HCF_SUCCESS) { LOGE("create c generator fail."); return NapiGetNull(env); } NapiAsyKeyGenerator *napiAsyKeyGenerator = new NapiAsyKeyGenerator(generator); napi_wrap( env, instance, napiAsyKeyGenerator, [](napi_env env, void *data, void *hint) { NapiAsyKeyGenerator *napiAsyKeyGenerator = static_cast<NapiAsyKeyGenerator *>(data); delete napiAsyKeyGenerator; return; }, nullptr, nullptr); napi_value napiAlgName = nullptr; napi_create_string_utf8(env, algName.c_str(), NAPI_AUTO_LENGTH, &napiAlgName); napi_set_named_property(env, instance, CRYPTO_TAG_ALG_NAME.c_str(), napiAlgName); LOGI("out ..."); return instance; }

这段代码是一个 N-API 模块中的函数，用于创建一个 JavaScript 对象，该对象包含一个 C++ 对象的实例。函数名为 `CreateJsAsyKeyGenerator`，它接受两个参数：`napi_env` 类型的 `env` 和 `napi_callback_info` 类型的 `info`。

在函数体内，首先获取函数调用时传入的参数数量和参数值。如果参数数量不符合预期，则返回 null。

接下来，使用 `napi_new_instance` 函数创建一个 JavaScript 对象，并将其赋值给变量 `instance`。这个 JavaScript 对象是通过调用一个 C++ 类的构造函数创建的。具体来说，先使用 `napi_get_reference_value` 函数获取一个类的引用值，然后再将这个引用值传递给 `napi_new_instance` 函数，由它来创建 JavaScript 对象。

然后，从 JavaScript 参数中获取一个算法名称，这个名称是一个字符串。如果获取失败，则返回 null。

接下来，调用 C++ 函数 `HcfAsyKeyGeneratorCreate` 来创建一个 C++ 对象的实例。如果创建失败，则返回 null。

接着，将这个 C++ 对象的实例和 JavaScript 对象进行绑定，使得它们可以相互访问。具体来说，使用 `napi_wrap` 函数将它们绑定在一起。在这个过程中，还传递了一个析构函数，以确保 C++ 对象的实例在 JavaScript 对象被垃圾回收时也能被正确地释放掉。

最后，将算法名称作为一个属性设置在 JavaScript 对象中，并返回这个 JavaScript 对象。