Hi Tomasz, On 08/08/2018 05:55 AM, Tomasz Figa wrote: > On Tue, Aug 7, 2018 at 4:37 PM Hans Verkuil <hverkuil@xxxxxxxxx> 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
