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

    pkt->size = 0;
}

static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
{
    struct video_data *s = ctx->priv_data;
    struct v4l2_buffer buf;
    struct buff_data *buf_descriptor;
    int res;

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

    /* FIXME: Some special treatment might be needed in case of loss of signal... */
    while ((res = ioctl(s->fd, VIDIOC_DQBUF, &buf)) < 0 && (errno == EINTR));
    if (res < 0) {
        if (errno == EAGAIN) {
            pkt->size = 0;

            return AVERROR(EAGAIN);
        }
        av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_DQBUF): %s\n", strerror(errno));

        return -1;
    }
    assert (buf.index < s->buffers);
    if (buf.bytesused != s->frame_size) {
        av_log(ctx, AV_LOG_ERROR, "The v4l2 frame is %d bytes, but %d bytes are expected\n", buf.bytesused, s->frame_size);

        return -1;
    }

    /* Image is at s->buff_start[buf.index] */
    pkt->data= s->buf_start[buf.index];
    pkt->size = buf.bytesused;
    pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec;
    pkt->destruct = mmap_release_buffer;
    buf_descriptor = av_malloc(sizeof(struct buff_data));
    if (buf_descriptor == NULL) {
        /* Something went wrong... Since av_malloc() failed, we cannot even
         * allocate a buffer for memcopying into it
         */
        av_log(ctx, AV_LOG_ERROR, "Failed to allocate a buffer descriptor\n");
        res = ioctl (s->fd, VIDIOC_QBUF, &buf);

        return -1;
    }
    buf_descriptor->fd = s->fd;
    buf_descriptor->index = buf.index;
    pkt->priv = buf_descriptor;

    return s->buf_len[buf.index];
}

static int read_frame(AVFormatContext *ctx, AVPacket *pkt)
{
    return -1;
}

static int mmap_start(AVFormatContext *ctx)
{
    struct video_data *s = ctx->priv_data;
    enum v4l2_buf_type type;
    int i, res;

    for (i = 0; i < s->buffers; 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_QBUF, &buf);
        if (res < 0) {
            av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", strerror(errno));

            return -1;
        }
    }

    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    res = ioctl (s->fd, VIDIOC_STREAMON, &type);
    if (res < 0) {
        av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_STREAMON): %s\n", strerror(errno));

        return -1;
    }

    return 0;
}

static void mmap_close(struct video_data *s)
{
    enum v4l2_buf_type type;
    int i;

    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    /* We do not check for the result, because we could
     * not do anything about it anyway...
     */
    ioctl(s->fd, VIDIOC_STREAMOFF, &type);
    for (i = 0; i < s->buffers; i++) {
        munmap(s->buf_start[i], s->buf_len[i]);
    }
    av_free(s->buf_start);
    av_free(s->buf_len);
}

static int v4l2_set_parameters( AVFormatContext *s1, AVFormatParameters *ap )
{
    struct video_data *s = s1->priv_data;
    struct v4l2_input input;
    struct v4l2_standard standard;
    int i;

    if(ap->channel>=0) {
        /* set tv video input */
        memset (&input, 0, sizeof (input));
        input.index = ap->channel;
        if(ioctl (s->fd, VIDIOC_ENUMINPUT, &input) < 0) {
            av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl enum input failed:\n");
            return AVERROR(EIO);
        }

        av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set input_id: %d, input: %s\n",
               ap->channel, input.name);
        if(ioctl (s->fd, VIDIOC_S_INPUT, &input.index) < 0 ) {
            av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set input(%d) failed\n",
                   ap->channel);
            return AVERROR(EIO);
        }
    }

    if(ap->standard) {
        av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set standard: %s\n",
               ap->standard );
        /* set tv standard */
        memset (&standard, 0, sizeof (standard));
        for(i=0;;i++) {
            standard.index = i;
            if (ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {
                av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set standard(%s) failed\n",
                       ap->standard);
                return AVERROR(EIO);
            }

            if(!strcasecmp(standard.name, ap->standard)) {
                break;
            }
        }

        av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set standard: %s, id: %"PRIu64"\n",
               ap->standard, standard.id);
        if (ioctl(s->fd, VIDIOC_S_STD, &standard.id) < 0) {
            av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set standard(%s) failed\n",
                   ap->standard);
            return AVERROR(EIO);
        }
    }

    return 0;
}

static int v4l2_read_header(AVFormatContext *s1, AVFormatParameters *ap)
{
    struct video_data *s = s1->priv_data;
    AVStream *st;
    int width, height;
    int res, frame_rate, frame_rate_base;
    uint32_t desired_format, capabilities;

    if (ap->width <= 0 || ap->height <= 0 || ap->time_base.den <= 0) {
        av_log(s1, AV_LOG_ERROR, "Missing/Wrong parameters\n");

        return -1;
    }

    width = ap->width;
    height = ap->height;
    frame_rate = ap->time_base.den;
    frame_rate_base = ap->time_base.num;

    if((unsigned)width > 32767 || (unsigned)height > 32767) {
        av_log(s1, AV_LOG_ERROR, "Wrong size %dx%d\n", width, height);

        return -1;
    }

    st = av_new_stream(s1, 0);
    if (!st) {
        return AVERROR(ENOMEM);
    }
    av_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */

    s->width = width;
    s->height = height;
    s->frame_rate      = frame_rate;
    s->frame_rate_base = frame_rate_base;

    capabilities = 0;
    s->fd = device_open(s1, &capabilities);
    if (s->fd < 0) {
        av_free(st);

        return AVERROR(EIO);
    }
    av_log(s1, AV_LOG_INFO, "[%d]Capabilities: %x\n", s->fd, capabilities);

    desired_format = fmt_ff2v4l(ap->pix_fmt);
    if (desired_format == 0 || (device_init(s1, &width, &height, desired_format) < 0)) {
        int i, done;

        done = 0; i = 0;
        while (!done) {
            desired_format = fmt_conversion_table[i].v4l2_fmt;
            if (device_init(s1, &width, &height, desired_format) < 0) {
                desired_format = 0;
                i++;
            } else {
               done = 1;
            }
            if (i == sizeof(fmt_conversion_table) / sizeof(struct fmt_map)) {
               done = 1;
            }
        }
    }
    if (desired_format == 0) {
        av_log(s1, AV_LOG_ERROR, "Cannot find a proper format.\n");
        close(s->fd);
        av_free(st);

        return AVERROR(EIO);
    }
    s->frame_format = desired_format;

    if( v4l2_set_parameters( s1, ap ) < 0 )
        return AVERROR(EIO);

    st->codec->pix_fmt = fmt_v4l2ff(desired_format);
    s->frame_size = avpicture_get_size(st->codec->pix_fmt, width, height);
    if (capabilities & V4L2_CAP_STREAMING) {
        s->io_method = io_mmap;
        res = mmap_init(s1);
        if (res == 0) {
            res = mmap_start(s1);
        }
    } else {
        s->io_method = io_read;
        res = read_init(s1);
    }
    if (res < 0) {
        close(s->fd);
        av_free(st);

        return AVERROR(EIO);
    }
    s->top_field_first = first_field(s->fd);

    st->codec->codec_type = CODEC_TYPE_VIDEO;
    st->codec->codec_id = CODEC_ID_RAWVIDEO;
    st->codec->width = width;
    st->codec->height = height;
    st->codec->time_base.den = frame_rate;
    st->codec->time_base.num = frame_rate_base;
    st->codec->bit_rate = s->frame_size * 1/av_q2d(st->codec->time_base) * 8;

    return 0;
}

static int v4l2_read_packet(AVFormatContext *s1, AVPacket *pkt)
{
    struct video_data *s = s1->priv_data;
    int res;

    if (s->io_method == io_mmap) {
        av_init_packet(pkt);
        res = mmap_read_frame(s1, pkt);
    } else if (s->io_method == io_read) {
        if (av_new_packet(pkt, s->frame_size) < 0)
            return AVERROR(EIO);

        res = read_frame(s1, pkt);
    } else {
        return AVERROR(EIO);
    }
    if (res < 0) {
        return res;
    }

    if (s1->streams[0]->codec->coded_frame) {
        s1->streams[0]->codec->coded_frame->interlaced_frame = 1;
        s1->streams[0]->codec->coded_frame->top_field_first = s->top_field_first;
    }

    return s->frame_size;
}

static int v4l2_read_close(AVFormatContext *s1)
{
    struct video_data *s = s1->priv_data;

    if (s->io_method == io_mmap) {
        mmap_close(s);
    }

    close(s->fd);
    return 0;
}

AVInputFormat v4l2_demuxer = {
    "video4linux2",
    "video grab",
    sizeof(struct video_data),
    NULL,
    v4l2_read_header,
    v4l2_read_packet,
    v4l2_read_close,
    .flags = AVFMT_NOFILE,
};