From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mailout2.w1.samsung.com ([210.118.77.12]:27015 "EHLO mailout2.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751017Ab1LWHKA (ORCPT ); Fri, 23 Dec 2011 02:10:00 -0500 Received: from euspt2 (mailout2.w1.samsung.com [210.118.77.12]) by mailout2.w1.samsung.com (iPlanet Messaging Server 5.2 Patch 2 (built Jul 14 2004)) with ESMTP id <0LWN0078TAKKV1@mailout2.w1.samsung.com> for linux-media@vger.kernel.org; Fri, 23 Dec 2011 07:09:56 +0000 (GMT) Received: from linux.samsung.com ([106.116.38.10]) by spt2.w1.samsung.com (iPlanet Messaging Server 5.2 Patch 2 (built Jul 14 2004)) with ESMTPA id <0LWN00MOFAKK20@spt2.w1.samsung.com> for linux-media@vger.kernel.org; Fri, 23 Dec 2011 07:09:56 +0000 (GMT) Date: Fri, 23 Dec 2011 08:09:25 +0100 From: Marek Szyprowski Subject: RE: MEM2MEM devices: how to handle sequence number? In-reply-to: To: 'javier Martin' , linux-media@vger.kernel.org, laurent.pinchart@ideasonboard.com, s.nawrocki@samsung.com, hverkuil@xs4all.nl, kyungmin.park@samsung.com, shawn.guo@linaro.org, richard.zhao@linaro.org, fabio.estevam@freescale.com, kernel@pengutronix.de, s.hauer@pengutronix.de, r.schwebel@pengutronix.de Cc: 'Pawel Osciak' Message-id: <013f01ccc141$cdf78ed0$69e6ac70$%szyprowski@samsung.com> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii Content-language: pl Content-transfer-encoding: 7BIT References: Sender: linux-media-owner@vger.kernel.org List-ID: Hello, On Thursday, December 22, 2011 3:34 PM Javier Martin wrote: > we have a processing chain composed of three v4l2 devices: > > --------------------- ----------------------- > ---------------------- > | v4l2 source | | v4l2 fixer | | v4l2 encoder | > | (capture) |---------->| (mem2mem)| ------------>| (mem2mem) | > ------------> > |___________| |____________| |____________| > > > "v4l2 source" generates consecutive sequence numbers so that we can > detect whether a frame has been lost or not. > "v4l2 fixer" and "v4l2 encoder" cannot lose frames because they don't > interact with an external sensor. > > How should "v4l2 fixer" and "v4l2 encoder" behave regarding frame > sequence number? Should they just copy the sequence number from the > input buffer to the output buffer or should they maintain their own > count for the CAPTURE queue? IMHO mem2mem devices, which process buffers in 1:1 way (there is always exactly one 'capture'/destination buffer for every 'output'/source buffer) can simply copy the sequence number from the source buffer to the destination. If there is no such 1:1 mapping between the buffers, drivers should maintain their own numbers. video encoder is probably an example of such device. A single destination ('capture') buffer with encoded video data might contain a fraction, one or more source ('output') video buffers/frames. > If the former option is chosen we should apply a patch like the > following so that the sequence number of the input buffer is passed to > the videobuf2 layer: > > diff --git a/drivers/media/video/videobuf2-core.c > b/drivers/media/video/videobuf2-core.c > index 1250662..7d8a88b 100644 > --- a/drivers/media/video/videobuf2-core.c > +++ b/drivers/media/video/videobuf2-core.c > @@ -1127,6 +1127,7 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b) > */ > list_add_tail(&vb->queued_entry, &q->queued_list); > vb->state = VB2_BUF_STATE_QUEUED; > + vb->v4l2_buf.sequence = b->sequence; > > /* > * If already streaming, give the buffer to driver for processing. > Right, such patch is definitely needed. Please resend it with 'signed-off-by' annotation. Best regards -- Marek Szyprowski Samsung Poland R&D Center