On 23.09.2019 17:12, 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).

Hi Hans,

I am on 'just interested'. If someone is directly involved , they can 
take my place on this topic. I will see at conference time if there are 
still open seats if I will join or not.


> 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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