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. > > Thanks, > Pawel 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
