Hi, first of all thank you for your detailed answer. Mauro Carvalho Chehab wrote: > Hi Németh, > > Em Sun, 23 Aug 2009 11:30:42 +0200 > Németh Márton <nm127@xxxxxxxxxxx> escreveu: > >> From: Márton Németh <nm127@xxxxxxxxxxx> >> >> Change the handling of the case when vdev->tvnorms == 0. >> > > This patch (together with a few others related to tvnorms and camera drivers) > reopens an old discussion: should webcams report a tvnorm? > > There's no easy answer for it since: > > 1) removing support for VIDIOC_G_STD/VIDIOC_S_STD causes regressions, since > some userspace apps stops working; > > 2) It is a common scenario to use cameras connected to some capture only devices > like several bttv boards used on surveillance systems. Those drivers report STD, > since they are used also on TV; > > 3) There are even some devices that allows cameras to be connected to one input and > TV on another input. This is another case were the driver will report a TV std; > > 4) Most webcam formats are based on ITU-T formats designed to be compatible > with TV (formats like CIF and like 640x480 - and their multiple/sub-multiples); > > 5) There are formats that weren't originated from TV on some digital webcams, > so, for those formats, it makes no sense to report an existing std. > > Once people proposed to create an special format for those cases > (V4L2_STD_DIGITAL or something like that), but, after lots of discussions, > no changes were done at API nor at the drivers. > > While we don't have an agreement on this, I don't think we should apply a patch > like this. I was reading the V4L2 specification and based my patch on the specification. Maybe the specification is wrong at that point? (see Chapter 1.7 Video Standards at http://v4l2spec.bytesex.org/spec/x448.htm , starting with paragraph 6: "Special rules apply to USB cameras...") Regards, Márton Németh -- 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
