输出bt656视频流代码

以下是一个基本的BT656视频流输出代码：

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

#define VIDEO_BASE_ADDR 0x10000000
#define VIDEO_SIZE 0x10000000
#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("/dev/mem", O_RDWR | O_SYNC);
    if(fd_video == -1) {
        printf("Error: could not open /dev/mem.\n");
        munmap(fbp, fb_size);
        close(fd_fb);
        return -1;
    }

    uint8_t *video_base = (uint8_t *)mmap(0, VIDEO_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd_video, VIDEO_BASE_ADDR);
    if(video_base == MAP_FAILED) {
        printf("Error: could not mmap video memory.\n");
        munmap(fbp, fb_size);
        close(fd_fb);
        close(fd_video);
        return -1;
    }

    // Write BT656 video data to framebuffer
    uint32_t y_addr = VIDEO_BASE_ADDR;
    uint32_t cbcr_addr = VIDEO_BASE_ADDR + (width * height);

    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;

            uint8_t y_data = *(video_base + y_addr);
            uint8_t cb_data = *(video_base + cbcr_addr);
            uint8_t cr_data = *(video_base + cbcr_addr + 1);

            // Convert YCbCr to RGB
            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;
        }

        y_addr += width;
        if(y % 2 == 1) {
            cbcr_addr += width;
        }
    }

    munmap(video_base, VIDEO_SIZE);
    munmap(fbp, fb_size);
    close(fd_fb);
    close(fd_video);
    return 0;
}

这个代码假设你的BT656视频流已经被存储在物理内存地址0x10000000开始的位置，并且你想将它输出到Linux帧缓冲设备/dev/fb0上。它将使用 mmap() 函数来映射帧缓冲设备和视频内存，然后将YCbCr格式的视频转换为RGB格式并写入帧缓冲设备。