v4l2.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

/*
 * Video4Linux2 grab interface
 * Copyright (c) 2000,2001 Fabrice Bellard.
 * Copyright (c) 2006 Luca Abeni.
 *
 * Part of this file is based on the V4L2 video capture example
 * (http://v4l2spec.bytesex.org/v4l2spec/capture.c)
 *
 * Thanks to Michael Niedermayer for providing the mapping between
 * V4L2_PIX_FMT_* and PIX_FMT_*
 *
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
#include "avformat.h"
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <asm/types.h>
#include <linux/videodev2.h>
#include <time.h>

static const int desired_video_buffers = 256;

enum io_method {
    io_read,
    io_mmap,
    io_userptr
};

struct video_data {
    int fd;
    int frame_format; /* V4L2_PIX_FMT_* */
    enum io_method io_method;
    int width, height;
    int frame_rate;
    int frame_rate_base;
    int frame_size;
    int top_field_first;

    int buffers;
    void **buf_start;
    unsigned int *buf_len;
};

struct buff_data {
    int index;
    int fd;
};

struct fmt_map {
    enum PixelFormat ff_fmt;
    int32_t v4l2_fmt;
};

static struct fmt_map fmt_conversion_table[] = {
    {
        .ff_fmt = PIX_FMT_YUV420P,
        .v4l2_fmt = V4L2_PIX_FMT_YUV420,
    },
    {
        .ff_fmt = PIX_FMT_YUV422P,
        .v4l2_fmt = V4L2_PIX_FMT_YUV422P,
    },
    {
        .ff_fmt = PIX_FMT_YUYV422,
        .v4l2_fmt = V4L2_PIX_FMT_YUYV,
    },
    {
        .ff_fmt = PIX_FMT_UYVY422,
        .v4l2_fmt = V4L2_PIX_FMT_UYVY,
    },
    {
        .ff_fmt = PIX_FMT_YUV411P,
        .v4l2_fmt = V4L2_PIX_FMT_YUV411P,
    },
    {
        .ff_fmt = PIX_FMT_YUV410P,
        .v4l2_fmt = V4L2_PIX_FMT_YUV410,
    },
    {
        .ff_fmt = PIX_FMT_BGR24,
        .v4l2_fmt = V4L2_PIX_FMT_BGR24,
    },
    {
        .ff_fmt = PIX_FMT_RGB24,
        .v4l2_fmt = V4L2_PIX_FMT_RGB24,
    },
    /*
    {
        .ff_fmt = PIX_FMT_RGB32,
        .v4l2_fmt = V4L2_PIX_FMT_BGR32,
    },
    */
    {
        .ff_fmt = PIX_FMT_GRAY8,
        .v4l2_fmt = V4L2_PIX_FMT_GREY,
    },
};

static int device_open(AVFormatContext *ctx, uint32_t *capabilities)
{
    struct v4l2_capability cap;
    int fd;
    int res;
    int flags = O_RDWR;

    if (ctx->flags & AVFMT_FLAG_NONBLOCK) {
        flags |= O_NONBLOCK;
    }
    fd = open(ctx->filename, flags, 0);
    if (fd < 0) {
        av_log(ctx, AV_LOG_ERROR, "Cannot open video device %s : %s\n",
                 ctx->filename, strerror(errno));

        return -1;
    }

    res = ioctl(fd, VIDIOC_QUERYCAP, &cap);
    // ENOIOCTLCMD definition only availble on __KERNEL__
    if (res < 0 && errno == 515)
    {
        av_log(ctx, AV_LOG_ERROR, "QUERYCAP not implemented, probably V4L device but not supporting V4L2\n");
        close(fd);

        return -1;
    }
    if (res < 0) {
        av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYCAP): %s\n",
                 strerror(errno));
        close(fd);

        return -1;
    }
    if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == 0) {
        av_log(ctx, AV_LOG_ERROR, "Not a video capture device\n");
        close(fd);

        return -1;
    }
    *capabilities = cap.capabilities;

    return fd;
}

static int device_init(AVFormatContext *ctx, int *width, int *height, int pix_fmt)
{
    struct video_data *s = ctx->priv_data;
    int fd = s->fd;
    struct v4l2_format fmt;
    int res;

    memset(&fmt, 0, sizeof(struct v4l2_format));
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width = *width;
    fmt.fmt.pix.height = *height;
    fmt.fmt.pix.pixelformat = pix_fmt;
    fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
    res = ioctl(fd, VIDIOC_S_FMT, &fmt);
    if ((*width != fmt.fmt.pix.width) || (*height != fmt.fmt.pix.height)) {
        av_log(ctx, AV_LOG_INFO, "The V4L2 driver changed the video from %dx%d to %dx%d\n", *width, *height, fmt.fmt.pix.width, fmt.fmt.pix.height);
        *width = fmt.fmt.pix.width;
        *height = fmt.fmt.pix.height;
    }

    return res;
}

static int first_field(int fd)
{
    int res;
    v4l2_std_id std;

    res = ioctl(fd, VIDIOC_G_STD, &std);
    if (res < 0) {
        return 0;
    }
    if (std & V4L2_STD_NTSC) {
        return 0;
    }

    return 1;
}

static uint32_t fmt_ff2v4l(enum PixelFormat pix_fmt)
{
    int i;

    for (i = 0; i < sizeof(fmt_conversion_table) / sizeof(struct fmt_map); i++) {
        if (fmt_conversion_table[i].ff_fmt == pix_fmt) {
            return fmt_conversion_table[i].v4l2_fmt;
        }
    }

    return 0;
}

static enum PixelFormat fmt_v4l2ff(uint32_t pix_fmt)
{
    int i;

    for (i = 0; i < sizeof(fmt_conversion_table) / sizeof(struct fmt_map); i++) {
        if (fmt_conversion_table[i].v4l2_fmt == pix_fmt) {
            return fmt_conversion_table[i].ff_fmt;
        }
    }

    return -1;
}

static int mmap_init(AVFormatContext *ctx)
{
    struct video_data *s = ctx->priv_data;
    struct v4l2_requestbuffers req;
    int i, res;

    memset(&req, 0, sizeof(struct v4l2_requestbuffers));
    req.count = desired_video_buffers;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;
    res = ioctl (s->fd, VIDIOC_REQBUFS, &req);
    if (res < 0) {
        if (errno == EINVAL) {
            av_log(ctx, AV_LOG_ERROR, "Device does not support mmap\n");
        } else {
            av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_REQBUFS)\n");
        }

        return -1;
    }

    if (req.count < 2) {
        av_log(ctx, AV_LOG_ERROR, "Insufficient buffer memory\n");

        return -1;
    }
    s->buffers = req.count;
    s->buf_start = av_malloc(sizeof(void *) * s->buffers);
    if (s->buf_start == NULL) {
        av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer pointers\n");

        return -1;
    }
    s->buf_len = av_malloc(sizeof(unsigned int) * s->buffers);
    if (s->buf_len == NULL) {
        av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer sizes\n");
        av_free(s->buf_start);

        return -1;
    }

    for (i = 0; i < req.count; i++) {
        struct v4l2_buffer buf;

        memset(&buf, 0, sizeof(struct v4l2_buffer));
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = i;
        res = ioctl (s->fd, VIDIOC_QUERYBUF, &buf);
        if (res < 0) {
            av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYBUF)\n");

            return -1;
        }

        s->buf_len[i] = buf.length;
        if (s->buf_len[i] < s->frame_size) {
            av_log(ctx, AV_LOG_ERROR, "Buffer len [%d] = %d != %d\n", i, s->buf_len[i], s->frame_size);

            return -1;
        }
        s->buf_start[i] = mmap (NULL, buf.length,
                        PROT_READ | PROT_WRITE, MAP_SHARED, s->fd, buf.m.offset);
        if (s->buf_start[i] == MAP_FAILED) {
            av_log(ctx, AV_LOG_ERROR, "mmap: %s\n", strerror(errno));

            return -1;
        }
    }

    return 0;
}

static int read_init(AVFormatContext *ctx)
{
    return -1;
}

static void mmap_release_buffer(AVPacket *pkt)
{
    struct v4l2_buffer buf;
    int res, fd;
    struct buff_data *buf_descriptor = pkt->priv;

    memset(&buf, 0, sizeof(struct v4l2_buffer));
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = buf_descriptor->index;
    fd = buf_descriptor->fd;
    av_free(buf_descriptor);

    res = ioctl (fd, VIDIOC_QBUF, &buf);
    if (res < 0) {
        av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF)\n");
    }
    pkt->data = NULL;