v4l2 test

Makefile

v4l2: v4l2.cpp
	g++ v4l2.cpp -o v4l2 -ljpeg

v4l2.cpp

// http://blog.csdn.net/shaolyh/article/details/6583226
// http://www.linuxidc.com/Linux/2011-03/33022p3.htm
// http://blog.csdn.net/kevin_li_823/article/details/5280521

#include <iostream>
#include <vector>
#include <cstring>
#include <cstdio>

#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <linux/videodev2.h>

#include <jpeglib.h>
using namespace std;

int main()
{
    int fd = open("/dev/video0", O_RDWR);

    struct v4l2_capability cap;
    memset(&cap, 0, sizeof(cap));
    ioctl(fd, VIDIOC_QUERYCAP, &cap);

    cout << "Driver = " << cap.driver << "\n"
         << "Card = " << cap.card << "\n"
         << "Bus info = " << cap.bus_info << endl;

    struct v4l2_input input;
    memset(&input, 0, sizeof(input));

    ioctl(fd, VIDIOC_G_INPUT, &input);
    cout << "Input index = " << input.index << endl;
    ioctl(fd, VIDIOC_ENUMINPUT, &input);
    cout << "Input name = " << input.name << endl;

    // http://kongping.blog.hexun.com/46900639_d.html
    struct v4l2_standard standard;
    memset(&standard, 0, sizeof(standard));

    while(ioctl(fd, VIDIOC_ENUMSTD, &standard) == 0)
    {
        if (standard.id & input.std)
        {
            cout << standard.name << endl;
        }
        standard.index++;
    }

    v4l2_std_id std = 0;
    ioctl(fd, VIDIOC_QUERYSTD, &std);

    switch(std)
    {
        case V4L2_STD_NTSC:
            cout << "Standard: NTSC" << endl;
            break;
        case V4L2_STD_PAL:
            cout << "Standard: PAL" << endl;
            break;
    }

    v4l2_fmtdesc fmt, target_fmt;
    memset(&fmt, 0, sizeof(fmt));
    fmt.index = 0;
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    char fourcc[5];
    while(ioctl(fd, VIDIOC_ENUM_FMT, &fmt) == 0)
    {
        memset(fourcc, 0, sizeof(fourcc));
        memcpy(fourcc, &fmt.pixelformat, 4);
        cout << "pixelformat = " << fourcc << ", description = " << fmt.description << endl;

        if(strcmp(fourcc, "YUYV") == 0)
        {
            memcpy(&target_fmt, &fmt, sizeof(fmt));
        }

        fmt.index++;
    }

    ioctl(fd, VIDIOC_S_FMT, &target_fmt);
    cout << "Format set as YUYV" << endl;

    // http://www.cs.fsu.edu/~baker/devices/lxr/source/2.6.31.13/xawtv-3.95/console/v4l-info.c
    v4l2_format format;
    memset(&format, 0, sizeof(format));
    format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    ioctl(fd, VIDIOC_G_FMT, &format);
    unsigned int width = format.fmt.pix.width, height = format.fmt.pix.height;
    cout << "Width = " << width << ", height = " << height << endl;

    v4l2_requestbuffers req;
    memset(&req, 0, sizeof(req));

    req.count = 1;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;

    ioctl(fd, VIDIOC_REQBUFS, &req);

    cout << req.count << " buffered requested" << endl;

    unsigned char* buffer_addr = NULL;
    unsigned int buffer_length = 0;

    struct v4l2_buffer buf;
    memset(&buf, 0, sizeof(buf));
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = 0;
    ioctl(fd, VIDIOC_QUERYBUF, &buf);

    buffer_length = buf.length;
    buffer_addr = (unsigned char*)mmap(NULL, buf.length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
    cout << "Buffer starts at 0x" << hex << (void*)buffer_addr << ", length = " << buffer_length << endl;

    ioctl(fd, VIDIOC_QBUF, &buf);

    // http://www.linuxidc.com/Linux/2011-03/33022p4.htm
    v4l2_buf_type v4l2type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    ioctl(fd, VIDIOC_STREAMON, &v4l2type);

    memset(&buf,0,sizeof(buf));

    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = 0;

    ioctl(fd, VIDIOC_DQBUF, &buf);

    // http://stackoverflow.com/questions/16390783/how-to-save-yuyv-raw-data-to-jpeg-using-libjpeg
    FILE* output = fopen("output.jpeg", "wb");

    // "base" is an unsigned char const * with the YUYV data
    // jrow is a libjpeg row of samples array of 1 row pointer
    struct jpeg_error_mgr jerr;
    jpeg_compress_struct cinfo;
    jpeg_create_compress(&cinfo);
    JSAMPROW jrow[1];
    cinfo.image_width = width & -1;
    cinfo.image_height = height & -1;
    cinfo.input_components = 3;
    cinfo.in_color_space = JCS_YCbCr;
    // http://stackoverflow.com/questions/4664087/write-a-jpeg-with-libjpeg-seg-fault
    cinfo.err = jpeg_std_error(&jerr);
    jpeg_stdio_dest(&cinfo, output);
    jpeg_set_defaults(&cinfo);
    jpeg_set_quality(&cinfo, 100, TRUE);
    jpeg_start_compress(&cinfo, TRUE);
    unsigned char *buf2 = new unsigned char[width * 3];
    while (cinfo.next_scanline < height)
    {
        for (unsigned int i = 0; i < cinfo.image_width; i += 2)
        {
            buf2[i*3] = buffer_addr[i*2];
            buf2[i*3+1] = buffer_addr[i*2+1];
            buf2[i*3+2] = buffer_addr[i*2+3];
            buf2[i*3+3] = buffer_addr[i*2+2];
            buf2[i*3+4] = buffer_addr[i*2+1];
            buf2[i*3+5] = buffer_addr[i*2+3];
        }
        jrow[0] = buf2;
        buffer_addr += width * 2;
        jpeg_write_scanlines(&cinfo, jrow, 1);
    }
    jpeg_finish_compress(&cinfo);
    jpeg_destroy_compress(&cinfo);
    delete [] buf2;

    fclose(output);

    ioctl(fd, VIDIOC_QBUF, &buf);

    ioctl(fd, VIDIOC_STREAMOFF, &v4l2type);

    close(fd);

    return 0;
}