From 8db1a7310272d4c9f6d621aa4dacd625d5ea05a4 Mon Sep 17 00:00:00 2001 From: dave Date: Tue, 2 Apr 2013 10:31:02 -0700 Subject: [PATCH] Added v4l2 support for getting capture property CV_CAP_PROP_POS_MSEC --- modules/highgui/src/cap_v4l.cpp | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/modules/highgui/src/cap_v4l.cpp b/modules/highgui/src/cap_v4l.cpp index 829d0ab..a788c90 100644 --- a/modules/highgui/src/cap_v4l.cpp +++ b/modules/highgui/src/cap_v4l.cpp @@ -154,6 +154,11 @@ the symptoms were damaged image and 'Corrupt JPEG data: premature end of data se - USE_TEMP_BUFFER fixes the main problem (improper buffer management) and prevents bad images in the first place +11th patch: April 2, 2013, Forrest Reiling forrest.reiling@gmail.com +Added v4l2 support for getting capture property CV_CAP_PROP_POS_MSEC. +Returns the millisecond timestamp of the last frame grabbed or 0 if no frames have been grabbed +Used to successfully synchonize 2 Logitech C310 USB webcams to within 16 ms of one another + make & enjoy! @@ -320,6 +325,8 @@ typedef struct CvCaptureCAM_V4L struct v4l2_queryctrl queryctrl; struct v4l2_querymenu querymenu; + struct timeval timestamp; + /* V4L2 control variables */ int v4l2_brightness, v4l2_brightness_min, v4l2_brightness_max; int v4l2_contrast, v4l2_contrast_min, v4l2_contrast_max; @@ -836,6 +843,9 @@ static int _capture_V4L2 (CvCaptureCAM_V4L *capture, char *deviceName) capture->v4l2_gain_max = 0; capture->v4l2_exposure_max = 0; + capture->timestamp.tv_sec = 0; + capture->timestamp.tv_usec = 0; + /* Scan V4L2 controls */ v4l2_scan_controls(capture); @@ -1221,6 +1231,9 @@ static int read_frame_v4l2(CvCaptureCAM_V4L* capture) { if (-1 == ioctl (capture->deviceHandle, VIDIOC_QBUF, &buf)) perror ("VIDIOC_QBUF"); + //set timestamp in capture struct to be timestamp of most recent frame + capture->timestamp = buf.timestamp; + return 1; } @@ -2308,6 +2321,13 @@ static double icvGetPropertyCAM_V4L (CvCaptureCAM_V4L* capture, /* initialize the control structure */ switch (property_id) { + case CV_CAP_PROP_POS_MSEC: + if (capture->FirstCapture) { + return 0; + } else { + return 1000 * capture->timestamp.tv_sec + ((double) capture->timestamp.tv_usec) / 1000; + } + break; case CV_CAP_PROP_BRIGHTNESS: capture->control.id = V4L2_CID_BRIGHTNESS; break; -- 2.7.4