Hi Hans, On Mon, Sep 23, 2019 at 04:12:55PM +0200, Hans Verkuil wrote: > Hi all, > > Since we have three separate half-day sessions for different topics I decided > to split the announcement for this in three emails as well, so these things > can be discussed in separate threads. > > All sessions are in room Terreaux VIP Lounge - Level 0. > There is a maximum of 15 people. > > The first session deals with the codec API and is on Tuesday morning from > 8:30 (tentative, might change) to 12:00 (we have to vacate the room at that > time). > > Confirmed attendees for this session: > > Boris Brezillon <boris.brezil...@collabora.com> > Alexandre Courbot <acour...@chromium.org> > Nicolas Dufresne <nico...@ndufresne.ca> > Tomasz Figa <tf...@chromium.org> > Ezequiel Garcia <ezequ...@collabora.com> > Daniel Gomez <dan...@qtec.com> > Dafna Hirschfeld <dafna.hirschf...@collabora.com> > Eugen Hristev <eugen.hris...@microchip.com> > Paul Kocialkowski <paul.kocialkow...@bootlin.com> > Helen Koike <helen.ko...@collabora.com> > Michael Tretter <m.tret...@pengutronix.de> > Hans Verkuil <hverk...@xs4all.nl> > > Tentative: > > Laurent Pinchart <laurent.pinch...@ideasonboard.com> > Jacopo Mondi <jac...@jmondi.org> > > Jacopo, please confirm if you want to attend this session. I didn't find > an email with explicit confirmation, so it was probably done via irc. But > since > this session is getting close to capacity I would prefer to keep attendance to > those are actually working with codecs (or will work with it in the near > future).
I'm not really working on codecs, so if you're running almost at full capacity please feel free to re-assign my seat. If there are free seats I might flock in, but without contributing too much to the discussions :) Thanks j > > If I missed someone, or you are on the list but won't attend after all, then > please let me know. > > > > Agenda: > > - Status of any pending patches related to codec support. > > - Requirements of moving codec drivers out of staging. > > - Finalize the stateful encoder API. There are two pieces that need > to be defined: > > 1) Setting the frame rate so bitrate control can make sense, since > they need to know this information. This is also relevant for the > stateless codec (and this may have to change on a per-frame basis > for stateless codecs!). > > This can either be implemented via ENUM_FRAMEINTERVALS for the coded > pixelformats and S_PARM support, or we just add a new control for this. > E.g. V4L2_CID_MPEG_VIDEO_FRAME_INTERVAL (or perhaps FRAME_RATE). If we > go for a control, then we need to consider the unit. We can use a > fraction as well. See this series that puts in the foundation for that: > https://patchwork.linuxtv.org/cover/58857/ > > I am inclined to go with a control, since the semantics don't really > match ENUM_FRAMEINTERVALS/S_PARM. These ioctls still need to be supported > for legacy drivers. Open question: some drivers (mediatek, hva, coda) > require S_PARM(OUTPUT), some (venus) allow both S_PARM(CAPTURE) and > S_PARM(OUTPUT). I am inclined to allow both since this is not a CAPTURE > vs OUTPUT thing, it is global to both queues. > > 2) Interactions between OUTPUT and CAPTURE formats. > > The main problem is what to do if the capture sizeimage is too small > for the OUTPUT resolution when streaming starts. > > Proposal: width and height of S_FMT(OUTPUT) are used to > calculate a minimum sizeimage (app may request more). This is > driver-specific. (Is it? Or is this codec-specific?) > > V4L2_FMT_FLAG_FIXED_RESOLUTION is always set for codec formats > for the encoder (i.e. we don't support mid-stream resolution > changes for now) and V4L2_EVENT_SOURCE_CHANGE is not > supported. See https://patchwork.linuxtv.org/patch/56478/ for > the patch adding this flag. > > Of course, if we start to support mid-stream resolution > changes (or other changes that require a source change event), > then this flag should be dropped by the encoder driver and > documentation on how to handle the source change event should > be documented in the encoder spec. I prefer to postpone this > until we have an encoder than can actually do mid-stream > resolution changes. > > If sizeimage of the OUTPUT is too small for the CAPTURE > resolution and V4L2_EVENT_SOURCE_CHANGE is not supported, > then the second STREAMON (either CAPTURE or OUTPUT) will > return -ENOMEM since there is not enough memory to do the > encode. > > If V4L2_FMT_FLAG_FIXED_RESOLUTION is set (i.e. that should > be the case for all current encoders), then any bitrate controls > will be limited in range to what the current state (CAPTURE and > OUTPUT formats and frame rate) supports. > > - Stateless encoders? > > - Anything else? (I have a feeling I missed a codec-related topic, but > I can't find it in my mailbox) > > Regards, > > Hans
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