Hi Pawel, > From: Pawel Osciak [mailto:posciak@xxxxxxxxxxxx] > Sent: Tuesday, April 22, 2014 9:46 AM > To: Kamil Debski > Cc: Arun Kumar K; linux-media@xxxxxxxxxxxxxxx; linux-samsung-soc; > Sylwester Nawrocki; Hans Verkuil; Laurent Pinchart > Subject: Re: [PATCH v2 1/2] v4l: Add resolution change event. > > Hi Kamil, > > On Tue, Apr 22, 2014 at 4:34 PM, Kamil Debski <k.debski@xxxxxxxxxxx> > wrote: > > > Hi Pawel, > > > From: Pawel Osciak [mailto:posciak@xxxxxxxxxxxx] > > Sent: Monday, April 21, 2014 12:27 PM > > To: Arun Kumar K > > Cc: linux-media@xxxxxxxxxxxxxxx; linux-samsung-soc; Kamil > Debski; > > Sylwester Nawrocki; Hans Verkuil; Laurent Pinchart > > Subject: Re: [PATCH v2 1/2] v4l: Add resolution change event. > > > > > As a side note, because this is not really codified in the API, > I would > > like this event to indicate not only resolution change mid- > stream, but > > also detection of initial resolution, which should be a subset > of > > resolution change. I think this would make sense for the codec > > interface: > > > > Video decode: > > 1. S_FMT to given codec on OUTPUT queue. > > 2. REQBUFS(n) and STREAMON on OUTPUT queue. > > 3. Keep QBUFing until we get an resolution change event on the > CAPTURE > > queue; until then, the driver/codec HW will operate on the > OUTPUT queue > > only and try to detect relevant headers in the OUTPUT buffers, > and will > > send resolution change event once it finds resolution, profile, > etc. > > info). DQEVENT. > > 4. G_FMT on CAPTURE to get the discovered output format > (resolution), > > REQBUFS and STREAMON on the CAPTURE queue. > > 5. Normal mem-to-mem decoding. > > 6. If a resolution change event arrives on CAPTURE queue, > DQEVENT, > > STREAMOFF, REQBUFS(0) only on CAPTURE queue, and goto 4. OUTPUT > queue > > operates completely independently of this. > > > > Also, this event should invariably indicate all of the below: > > - all output buffers from before resolution change are already > ready on > > the CAPTURE queue to DQBUF (so it's ready to REQBUFS(0) after > DQBUFs), > > and > > - there will be no more new ready buffers on the CAPTURE queue > until > > the streamoff-reqbufs(0)-g_fmt-reqbufs()-streamon is performed, > and > > - OUTPUT queue is completely independent of all of the above > and can be > > still used as normal, i.e. stream buffers can still keep being > queued > > at any stage of the resolution change and they will be decoded > after > > resolution change sequence is finished; > > > > If we all agree to the above, I will prepare a subsequent patch > for the > > documentation to include the above. > > > If I understand correctly this will keep the old application > working. > By this I mean application that do not use events and rely on the > current > mechanism to detect initial header parsing and resolution change. > > If backward compatibility is kept I am all for the changes > proposed by you. > > > > MFC codec depends on the userspace to parse the stream and pass the > stream header with resolution info before calling G_FMT. So if it > ignores the events but keeps doing this, things should keep working I > think, as the G_FMT should still work as before. > > This event will help userspace that doesn't want to bother itself with > parsing the stream to know if the right header was queued and rely on > events to know when to call G_FMT instead. > > What do you think? Am I missing something? Do you think this will work with all MFC versions? I guess that your focus is on the newer MFC version such as v6 or even v7. I had worked mostly with the v5 version and I am not sure how well it will handle the situation when it does not receive the header as the first frame. Do you have a target with v5 of MFC at hand? I really like your idea. If you haven't got the possibility to check how it works on v5 then I suggest you go ahead with patches and later I will do some testing on MFC v5. Best wishes, -- Kamil Debski Samsung R&D Institute Poland -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
