海思输出bt656视频流代码

以下是一个基本的海思输出BT656视频流的代码：

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <asm/ioctl.h>
#include <linux/fb.h>
#include <linux/videodev2.h>

#define VIDEO_DEVICE "/dev/video0"
#define VIDEO_WIDTH 640
#define VIDEO_HEIGHT 480
#define VIDEO_FORMAT V4L2_PIX_FMT_YUYV
#define FB_DEVICE "/dev/fb0"

int main(void) {
    int fd_fb = open(FB_DEVICE, O_RDWR);
    if(fd_fb == -1) {
        printf("Error: could not open framebuffer device.\n");
        return -1;
    }

    struct fb_var_screeninfo var_info;
    if(ioctl(fd_fb, FBIOGET_VSCREENINFO, &var_info) == -1) {
        printf("Error: could not get variable screen info.\n");
        close(fd_fb);
        return -1;
    }

    uint32_t width = var_info.xres;
    uint32_t height = var_info.yres;
    uint32_t bytes_per_pixel = var_info.bits_per_pixel / 8;

    uint32_t fb_size = width * height * bytes_per_pixel;
    uint8_t *fbp = (uint8_t *)mmap(0, fb_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_fb, 0);
    if(fbp == MAP_FAILED) {
        printf("Error: could not mmap framebuffer device.\n");
        close(fd_fb);
        return -1;
    }

    int fd_video = open(VIDEO_DEVICE, O_RDWR);
    if(fd_video == -1) {
        printf("Error: could not open video device.\n");
        munmap(fbp, fb_size);
        close(fd_fb);
        return -1;
    }

    struct v4l2_capability cap;
    if(ioctl(fd_video, VIDIOC_QUERYCAP, &cap) == -1) {
        printf("Error: could not query video device capabilities.\n");
        munmap(fbp, fb_size);
        close(fd_fb);
        close(fd_video);
        return -1;
    }

    struct v4l2_format fmt;
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width = VIDEO_WIDTH;
    fmt.fmt.pix.height = VIDEO_HEIGHT;
    fmt.fmt.pix.pixelformat = VIDEO_FORMAT;
    fmt.fmt.pix.field = V4L2_FIELD_ANY;
    if(ioctl(fd_video, VIDIOC_S_FMT, &fmt) == -1) {
        printf("Error: could not set video format.\n");
        munmap(fbp, fb_size);
        close(fd_fb);
        close(fd_video);
        return -1;
    }

    struct v4l2_requestbuffers req;
    req.count = 1;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;
    if(ioctl(fd_video, VIDIOC_REQBUFS, &req) == -1) {
        printf("Error: could not request video buffers.\n");
        munmap(fbp, fb_size);
        close(fd_fb);
        close(fd_video);
        return -1;
    }

    struct v4l2_buffer buf;
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = 0;
    if(ioctl(fd_video, VIDIOC_QUERYBUF, &buf) == -1) {
        printf("Error: could not query video buffer.\n");
        munmap(fbp, fb_size);
        close(fd_fb);
        close(fd_video);
        return -1;
    }

    void *video_buffer = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd_video, buf.m.offset);
    if(video_buffer == MAP_FAILED) {
        printf("Error: could not mmap video buffer.\n");
        munmap(fbp, fb_size);
        close(fd_fb);
        close(fd_video);
        return -1;
    }

    if(ioctl(fd_video, VIDIOC_STREAMON, &buf.type) == -1) {
        printf("Error: could not start video streaming.\n");
        munmap(video_buffer, buf.length);
        munmap(fbp, fb_size);
        close(fd_fb);
        close(fd_video);
        return -1;
    }

    // Write BT656 video data to framebuffer
    uint8_t *video_data = (uint8_t *)video_buffer;

    for(uint32_t y = 0; y < height; y++) {
        for(uint32_t x = 0; x < width; x++) {
            uint32_t fb_offset = (y * width + x) * bytes_per_pixel;
            uint32_t video_offset = (y * width + x) * 2;

            // Convert YCbCr to RGB
            uint8_t y_data = *(video_data + video_offset);
            uint8_t cb_data = *(video_data + video_offset + 1);
            uint8_t cr_data = *(video_data + video_offset + 3);
            uint8_t r = y_data + 1.402 * (cr_data - 128);
            uint8_t g = y_data - 0.34414 * (cb_data - 128) - 0.71414 * (cr_data - 128);
            uint8_t b = y_data + 1.772 * (cb_data - 128);

            *(fbp + fb_offset) = r;
            *(fbp + fb_offset + 1) = g;
            *(fbp + fb_offset + 2) = b;
        }
    }

    if(ioctl(fd_video, VIDIOC_STREAMOFF, &buf.type) == -1) {
        printf("Error: could not stop video streaming.\n");
    }

    munmap(video_buffer, buf.length);
    munmap(fbp, fb_size);
    close(fd_fb);
    close(fd_video);
    return 0;
}

这个代码假设你的海思芯片已经捕获了BT656格式的视频流，并将其输出到/dev/video0设备上。它将使用 mmap() 函数来映射视频和帧缓冲设备，并将YCbCr格式的视频转换为RGB格式并写入帧缓冲设备。