On Wed 20 June 2012 12:25:09 Sakari Ailus wrote: > Hi Scott, > > Scott Jiang wrote: > >>>>>> I would expect that the combination of v4l2_mbus_framefmt + > >>>>>> v4l2_dv_timings > >>>>>> gives you the information you need. > >>>>>> > >>>>> I can solve this problem in HD, but how about SD? Add a fake > >>>>> dv_timings ops in SD decoder driver? > >>>>> > >>>> > >>>> No, you add g/s_std instead. SD timings are set through that API. It is > >>>> not so > >>>> much that you give explicit timings, but that you give the SD standard. > >>>> And from > >>>> that you can derive the timings (i.e., one for 60 Hz formats, and one for > >>>> 50 Hz > >>>> formats). > >>>> > >>> Yes, it's a solution for decoder. I can convert one by one. But how > >>> about sensors?They can output VGA, QVGA or any manual resolution. > >>> My question is why we can't add these blanking details in > >>> v4l2_mbus_framefmt? This structure is used to describe frame format on > >>> media bus. And I believe blanking data also transfer on this bus. I > >>> know most hardwares don't care about blanking areas, but some hardware > >>> such as PPI does. PPI can capture ancillary data both in herizontal > >>> and vertical interval. Even it works in active video only mode, it > >>> expects to get total timing info. > >> > >> > >> Since I don't know what you are trying to do, it is hard for me to give > >> a good answer. > >> > >> So first I'd like to know if this is related to the adv7842 chip? I think > >> you are talking about how this is done in general, and not specifically in > >> relationship to the adv7842. At least, I can't see how/why you would > >> hook up a sensor to the adv7842. > > Yes, I want to have a general solution. > > > >> > >> Sensor configuration is a separate topic, and something I am not an > >> expert on. People like Sakari Ailus and Laurent Pinchart know much > >> more about that than I do. > >> > >> I know that there is some support for blanking through low-level image > >> source > >> controls: > >> > >> http://hverkuil.home.xs4all.nl/spec/media.html#image-source-controls > >> > >> This is experimental and if this is insufficient for your requirements than > >> I suggest posting a message where you explain what you need, CC-ing the > >> people > >> I mentioned, > >> > >> Most of these APIs are quite new and by marking them as experimental we can > >> make changes later if it turns out it is not good enough. > > I remember I have discussed this topic with Sakari before but without > > working out a solution. > > In conclusion, my current solution is: > > if (HD) > > dv_timings > > else if (SD) > > fill in according to PAL/NTSC timings > > else > > get control of V4L2_CID_HBLANK/V4L2_CID_VBLANK > > > > I guess this can solve my problem. But it's a bit complicated. If > > v4l2_mbus_framefmt contains thes members, it's convenient and simple. > > Adding horizontal and vertical blanking as fields to struct > v4l2_mbus_framefmt was discussed long ago --- I even sent a patch doing > that AFAIR. It'd have been a simple solution, yes. The resulting > discussion concluded, however, that as the horizontal or vertical > blanking are not really a property of the image format, and generally > only affect timing (frame rate, they do not belong to this struct. > > Also changing them while streaming is almost always possible (except in > your case, I believe) whereas the rest of the fields are considered > static. It'd be difficult for the user to know which fields can be > actually changed while streamon, and which can't. > > For these reasons (AFAIR) we chose to use controls instead. > > I think the right solution to the problem when it comes to sensors, is > to mark these controls busy from the bridge driver if the bridge > hardware can't cope with changes in blanking. The control framework > doesn't support this currently but it might not be that much of work to > implement it. Such feature would definitely have to be used with care. > > Hans, what do you think? That's already supported for a long time. If the control flag V4L2_CTRL_FLAG_GRABBED is set, then the control is marked busy. There aren't many drivers that use this flag, but some do. 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
