From 7aae316869feda22d86406bc900e12a5b7029c05 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Sun, 25 Apr 2004 13:30:21 +0000 Subject: [PATCH] ring buffer fix by (Luca Abeni ) Originally committed as revision 3067 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavformat/grab.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/libavformat/grab.c b/libavformat/grab.c index d8a1ce6fcb..755680ec29 100644 --- a/libavformat/grab.c +++ b/libavformat/grab.c @@ -66,6 +66,7 @@ static int grab_read_header(AVFormatContext *s1, AVFormatParameters *ap) struct video_tuner tuner; struct video_audio audio; const char *video_device; + int j; if (!ap || ap->width <= 0 || ap->height <= 0 || ap->frame_rate <= 0) return -1; @@ -229,6 +230,10 @@ static int grab_read_header(AVFormatContext *s1, AVFormatParameters *ap) } goto fail; } + for (j = 1; j < s->gb_buffers.frames; j++) { + s->gb_buf.frame = j; + ioctl(video_fd, VIDIOCMCAPTURE, &s->gb_buf); + } s->frame_format = s->gb_buf.format; s->use_mmap = 1; } @@ -273,8 +278,14 @@ static int v4l_mm_read_picture(VideoData *s, uint8_t *buf) { uint8_t *ptr; + while (ioctl(s->fd, VIDIOCSYNC, &s->gb_frame) < 0 && + (errno == EAGAIN || errno == EINTR)); + + ptr = s->video_buf + s->gb_buffers.offsets[s->gb_frame]; + memcpy(buf, ptr, s->frame_size); + /* Setup to capture the next frame */ - s->gb_buf.frame = (s->gb_frame + 1) % s->gb_buffers.frames; + s->gb_buf.frame = s->gb_frame; if (ioctl(s->fd, VIDIOCMCAPTURE, &s->gb_buf) < 0) { if (errno == EAGAIN) av_log(NULL, AV_LOG_ERROR, "Cannot Sync\n"); @@ -283,14 +294,8 @@ static int v4l_mm_read_picture(VideoData *s, uint8_t *buf) return -EIO; } - while (ioctl(s->fd, VIDIOCSYNC, &s->gb_frame) < 0 && - (errno == EAGAIN || errno == EINTR)); - - ptr = s->video_buf + s->gb_buffers.offsets[s->gb_frame]; - memcpy(buf, ptr, s->frame_size); - /* This is now the grabbing frame */ - s->gb_frame = s->gb_buf.frame; + s->gb_frame = (s->gb_frame + 1) % s->gb_buffers.frames; return s->frame_size; }