On 2012-01-09 09:37:05 +0100, Luca Barbato wrote:
> Instead of busy waiting use poll();
> ---
> libavdevice/v4l2.c | 15 +++++++++++++++
> 1 files changed, 15 insertions(+), 0 deletions(-)
>
> diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c
> index e52731d..c649faf 100644
> --- a/libavdevice/v4l2.c
> +++ b/libavdevice/v4l2.c
> @@ -36,6 +36,7 @@
> #include <sys/ioctl.h>
> #include <sys/mman.h>
> #include <sys/time.h>
> +#include <poll.h>
> #if HAVE_SYS_VIDEOIO_H
> #include <sys/videoio.h>
> #else
> @@ -48,6 +49,7 @@
> #include "libavutil/parseutils.h"
> #include "libavutil/pixdesc.h"
> #include "libavutil/avstring.h"
> +#include "libavutil/mathematics.h"
>
> static const int desired_video_buffers = 256;
>
> @@ -61,6 +63,7 @@ struct video_data {
> int frame_format; /* V4L2_PIX_FMT_* */
> int width, height;
> int frame_size;
> + int timeout;
> int interlaced;
> int top_field_first;
>
> @@ -436,12 +439,20 @@ 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;
> + struct pollfd p = { .fd = s->fd, .events = POLLIN };
> int res;
>
> memset(&buf, 0, sizeof(struct v4l2_buffer));
> buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> buf.memory = V4L2_MEMORY_MMAP;
>
> + res = poll(&p, 1, s->timeout);
> + if (res < 0)
> + return AVERROR(errno);
> +
> + if (!(p.revents & (POLLIN | POLLERR | POLLHUP)))
> + return AVERROR(EAGAIN);
> +
> /* 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) {
> @@ -635,6 +646,10 @@ static int v4l2_set_parameters(AVFormatContext *s1,
> AVFormatParameters *ap)
> s1->streams[0]->codec->time_base.den = tpf->denominator;
> s1->streams[0]->codec->time_base.num = tpf->numerator;
>
> + s->timeout = 100 +
> + av_rescale_q(1, s1->streams[0]->codec->time_base,
> + (AVRational){1, 1000});
100ms + frame time seems to be a little excessive, the frame would be
already if poll timeouts after frame time. not that it matters much.
feel free to push
Janne
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