From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-wi0-f178.google.com ([209.85.212.178]:47445 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753061Ab2IZWaw (ORCPT ); Wed, 26 Sep 2012 18:30:52 -0400 Received: by wibhr7 with SMTP id hr7so1299426wib.1 for ; Wed, 26 Sep 2012 15:30:51 -0700 (PDT) Message-ID: <50638219.7020105@gmail.com> Date: Thu, 27 Sep 2012 00:30:49 +0200 From: Sylwester Nawrocki MIME-Version: 1.0 To: Laurent Pinchart CC: linux-media@vger.kernel.org, Sakari Ailus , Hans Verkuil , remi@remlab.net, Kamil Debski Subject: Re: [RFC] Timestamps and V4L2 References: <20120920202122.GA12025@valkosipuli.retiisi.org.uk> <20120922202814.GA4891@minime.bse> <505F57A4.3040409@gmail.com> <32114057.tIVjSTYujk@avalon> In-Reply-To: <32114057.tIVjSTYujk@avalon> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Hi Laurent, On 09/25/2012 02:35 AM, Laurent Pinchart wrote: > Does the clock type need to be selectable for mem-to-mem devices ? Do device- > specific timestamps make sense there ? I'd like to clarify one thing here, i.e. if we select device-specific timestamps how should the v4l2_buffer::timestamp field behave ? Are these two things exclusive ? Or should v4l2_buffer::timestamp be valid even if device-specific timestamps are enabled ? With regards to your question, I think device-specific timestamps make sense for mem-to-mem devices. Maybe not for the very simple ones, that process buffers 1-to-1, but codecs may need it. I was told the Exynos/ S5P Multi Format Codec device has some register the timestamps could be read from, but it's currently not used by the s5p-mfc driver. Kamil might provide more details on that. I guess if capture and output devices can have their timestamping clocks selectable it should be also possible for mem-to-mem devices. -- Regards, Sylwester