Le mercredi 23 janvier 2019 à 12:28 +0100, Hans Verkuil a écrit : > On 01/23/19 11:00, Tomasz Figa wrote: > > On Sat, Nov 17, 2018 at 8:37 PM Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > > > On 11/17/2018 05:18 AM, Nicolas Dufresne wrote: > > > > Le lundi 12 novembre 2018 à 14:23 +0100, Hans Verkuil a écrit : > > > > > On 10/22/2018 04:49 PM, Tomasz Figa wrote: > > [snip] > > > > > > + rely on it. The ``V4L2_BUF_FLAG_LAST`` buffer flag should be used > > > > > > + instead. > > > > > > > > > > Question: should new codec drivers still implement the EOS event? > > > > > > > > I'm been asking around, but I think here is a good place. Do we really > > > > need the FLAG_LAST in userspace ? Userspace can also wait for the first > > > > EPIPE return from DQBUF. > > > > > > I'm interested in hearing Tomasz' opinion. This flag is used already, so there > > > definitely is a backwards compatibility issue here. > > > > > > > FWIW, it would add the overhead of 1 more system call, although I > > don't think it's of our concern. > > > > My personal feeling is that using error codes for signaling normal > > conditions isn't very elegant, though. > > I agree. Let's keep this flag. Agreed, though a reminder of the initial question, "do we keep the EOS event ?", and I think the event can be dropped. > > Regards, > > Hans > > > > > > > + > > > > > > +3. Once all ``OUTPUT`` buffers queued before the ``V4L2_ENC_CMD_STOP`` call and > > > > > > + the last ``CAPTURE`` buffer are dequeued, the encoder is stopped and it will > > > > > > + accept, but not process any newly queued ``OUTPUT`` buffers until the client > > > > > > + issues any of the following operations: > > > > > > + > > > > > > + * ``V4L2_ENC_CMD_START`` - the encoder will resume operation normally, > > > > > > > > > > Perhaps mention that this does not reset the encoder? It's not immediately clear > > > > > when reading this. > > > > > > > > Which drivers supports this ? I believe I tried with Exynos in the > > > > past, and that didn't work. How do we know if a driver supports this or > > > > not. Do we make it mandatory ? When it's not supported, it basically > > > > mean userspace need to cache and resend the header in userspace, and > > > > also need to skip to some sync point. > > > > > > Once we agree on the spec, then the next step will be to add good compliance > > > checks and update drivers that fail the tests. > > > > > > To check if the driver support this ioctl you can call VIDIOC_TRY_ENCODER_CMD > > > to see if the functionality is supported. > > > > There is nothing here for the hardware to support. It's an entirely > > driver thing, since it just needs to wait for the encoder to complete > > all the pending frames and stop enqueuing more frames to the decoder > > until V4L2_ENC_CMD_START is called. Any driver that can't do it must > > be fixed, since otherwise you have no way to ensure that you got all > > the encoded output. > > > > Best regards, > > Tomasz > >
