From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from lo.gmane.org ([80.91.229.12]:33420 "EHLO lo.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751981Ab0FJDZH (ORCPT ); Wed, 9 Jun 2010 23:25:07 -0400 Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1OMYO7-0003QO-H3 for linux-media@vger.kernel.org; Thu, 10 Jun 2010 05:25:03 +0200 Received: from 216-239-45-4.google.com ([216.239.45.4]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 10 Jun 2010 05:25:03 +0200 Received: from zhujiajun by 216-239-45-4.google.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 10 Jun 2010 05:25:03 +0200 To: linux-media@vger.kernel.org From: jiajun Subject: V4L Camera frame timestamp question Date: Thu, 10 Jun 2010 03:24:05 +0000 (UTC) Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Hi, I'm currently using the V4L-DVB driver to control a few logitech webcams and playstation eye cameras on a Gubuntu system. Everything works just fine except one thing: the buffer timestamp value seems wrong. The way I get the timestamp value is through the v4l2_buffer struct like this: struct v4l2_buffer buf; CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; assert(ioctl(fd_, VIDIOC_DQBUF, &buf)); printf("timestamp = %.3f", buf.timestamp.tv_sec + buf.timestamp.tv_usec / 1000000); this should be the timestamp of when the image is taken (similar to gettimeofday() function) but the value I got is something way smaller (e.g. 75000) than what it should be (e.g. 1275931384) Is this a known problem? Thanks!