On Tuesday, July 26, 2011 13:44:28 Sakari Ailus wrote: > Hi Hans and Guennadi, <snip> > > I realized that it is not clear from the documentation whether it is possible to call > > VIDIOC_REQBUFS and make additional calls to VIDIOC_CREATE_BUFS afterwards. > > That's actually a must if one wants to release buffers. Currently no other > method than requesting 0 buffers using REQBUFS is provided (apart from > closing the file handle). I was referring to the non-0 use-case :-) > > I can't remember whether the code allows it or not, but it should be clearly documented. > > I would guess no user application would have to call REQBUFS with other than > zero buffers when using CREATE_BUFS. This must be an exception if mixing > REQBUFS and CREATE_BUFS is not allowed in general. That said, I don't see a > reason to prohibit either, but perhaps Guennadi has more informed opinion > on this. <snip> > > > > > Future functionality which would be nice: > > > > > > > > > > - Format counters. Every format set by S_FMT (or gotten by G_FMT) should > > > > > come with a counter value so that the user would know the format of > > > > > dequeued buffers when setting the format on-the-fly. Currently there are > > > > > only bytesperline and length, but the format can't be explicitly > > > > > determined from those. > > > > Actually, the index field will give you that information. When you create the > > buffers you know that range [index, index + count - 1] is associated with that > > specific format. > > Some hardware is able to change the format while streaming is ongoing (for > example: OMAP 3). The problem is that the user should be able to know which > frame has the new format. Ah, of course. > Of course one could stop streaming but this would mean lost frames. > > A flag has been proposed to this previously. That's one option but forces > the user to keep track of the changes since only one change is allowed until > it has taken effect. Something to discuss next week, I think. Regards, Hans -- 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
