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Date: Tue, 21 Aug 2018 14:29:26 +0300 From: Stanimir Varbanov <stanimir.varbanov@...aro.org> To: Tomasz Figa <tfiga@...omium.org>, Hans Verkuil <hverkuil@...all.nl> Cc: Linux Media Mailing List <linux-media@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Stanimir Varbanov <stanimir.varbanov@...aro.org>, Mauro Carvalho Chehab <mchehab@...nel.org>, Pawel Osciak <posciak@...omium.org>, Alexandre Courbot <acourbot@...omium.org>, kamil@...as.org, a.hajda@...sung.com, Kyungmin Park <kyungmin.park@...sung.com>, jtp.park@...sung.com, Philipp Zabel <p.zabel@...gutronix.de>, Tiffany Lin (林慧珊) <tiffany.lin@...iatek.com>, Andrew-CT Chen (陳智迪) <andrew-ct.chen@...iatek.com>, todor.tomov@...aro.org, nicolas@...fresne.ca, Paul Kocialkowski <paul.kocialkowski@...tlin.com>, Laurent Pinchart <laurent.pinchart@...asonboard.com>, dave.stevenson@...pberrypi.org, Ezequiel Garcia <ezequiel@...labora.com> Subject: Re: [PATCH 1/2] media: docs-rst: Document memory-to-memory video decoder interface Hi Tomasz, On 08/08/2018 05:55 AM, Tomasz Figa wrote: > On Tue, Aug 7, 2018 at 4:37 PM Hans Verkuil <hverkuil@...all.nl> wrote: >>>>>>> +7. If all the following conditions are met, the client may resume the >>>>>>> + decoding instantly, by using :c:func:`VIDIOC_DECODER_CMD` with >>>>>>> + ``V4L2_DEC_CMD_START`` command, as in case of resuming after the drain >>>>>>> + sequence: >>>>>>> + >>>>>>> + * ``sizeimage`` of new format is less than or equal to the size of >>>>>>> + currently allocated buffers, >>>>>>> + >>>>>>> + * the number of buffers currently allocated is greater than or equal to >>>>>>> + the minimum number of buffers acquired in step 6. >>>>>> >>>>>> You might want to mention that if there are insufficient buffers, then >>>>>> VIDIOC_CREATE_BUFS can be used to add more buffers. >>>>>> >>>>> >>>>> This might be a bit tricky, since at least s5p-mfc and coda can only >>>>> work on a fixed buffer set and one would need to fully reinitialize >>>>> the decoding to add one more buffer, which would effectively be the >>>>> full resolution change sequence, as below, just with REQBUFS(0), >>>>> REQBUFS(N) replaced with CREATE_BUFS. >>>> >>>> What happens today in those drivers if you try to call CREATE_BUFS? >>> >>> s5p-mfc doesn't set the .vidioc_create_bufs pointer in its >>> v4l2_ioctl_ops, so I suppose that would be -ENOTTY? >> >> Correct for s5p-mfc. > > As Philipp clarified, coda supports adding buffers on the fly. I > briefly looked at venus and mtk-vcodec and they seem to use m2m > implementation of CREATE_BUFS. Not sure if anyone tested that, though. > So the only hardware I know for sure cannot support this is s5p-mfc. In Venus case CREATE_BUFS is tested with Gstreamer. -- regards, Stan
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