On Tue, Jun 21, 2011 at 10:07:43PM +0400, Kirill Smelkov wrote: > The camera there identifeis itself as being manufactured by Cheng Uei > Precision Industry Co., Ltd (Foxlink), and product is titled as "HP > Webcam [2 MP Fixed]". > > I was trying to get 2 USB video capture devices to work simultaneously, > and noticed that the above mentioned webcam always requires packet size > = 3072 bytes per micro frame (~= 23.4 MB/s isoc bandwidth), which is far > more than enough to get standard NTSC 640x480x2x30 = ~17.6 MB/s isoc > bandwidth. > > As there are alt interfaces with smaller MxPS > > T: Bus=01 Lev=01 Prnt=01 Port=03 Cnt=01 Dev#= 2 Spd=480 MxCh= 0 > D: Ver= 2.00 Cls=ef(misc ) Sub=02 Prot=01 MxPS=64 #Cfgs= 1 > P: Vendor=05c8 ProdID=0403 Rev= 1.06 > S: Manufacturer=Foxlink > S: Product=HP Webcam [2 MP Fixed] > S: SerialNumber=200909240102 > C:* #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=500mA > A: FirstIf#= 0 IfCount= 2 Cls=0e(video) Sub=03 Prot=00 > I:* If#= 0 Alt= 0 #EPs= 1 Cls=0e(video) Sub=01 Prot=00 Driver=uvcvideo > E: Ad=83(I) Atr=03(Int.) MxPS= 16 Ivl=4ms > I:* If#= 1 Alt= 0 #EPs= 0 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo > I: If#= 1 Alt= 1 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo > E: Ad=81(I) Atr=05(Isoc) MxPS= 128 Ivl=125us > I: If#= 1 Alt= 2 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo > E: Ad=81(I) Atr=05(Isoc) MxPS= 512 Ivl=125us > I: If#= 1 Alt= 3 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo > E: Ad=81(I) Atr=05(Isoc) MxPS=1024 Ivl=125us > I: If#= 1 Alt= 4 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo > E: Ad=81(I) Atr=05(Isoc) MxPS=1536 Ivl=125us > I: If#= 1 Alt= 5 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo > E: Ad=81(I) Atr=05(Isoc) MxPS=2048 Ivl=125us > I: If#= 1 Alt= 6 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo > E: Ad=81(I) Atr=05(Isoc) MxPS=2688 Ivl=125us > I: If#= 1 Alt= 7 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo > E: Ad=81(I) Atr=05(Isoc) MxPS=3072 Ivl=125us > > UVC_QUIRK_FIX_BANDWIDTH helps here and NTSC video can be served with > MxPS=2688 i.e. 20.5 MB/s isoc bandwidth. > > In terms of microframe time allocation, before the quirk NTSC video > required 60 usecs / microframe and 53 usecs / microframe after. > > > P.S. Now with tweaked ehci-hcd to allow up to 90% isoc bandwith (instead of > allowed for high speed 80%) I can capture two video sources -- PAL 720x576 > YUV422 @25fps + NTSC 640x480 YUV422 @30fps simultaneously. Hooray! > > Signed-off-by: Kirill Smelkov <kirr@xxxxxxxxxx> Silence... though even the above-mentioned EHCI tweak was merged already: http://git.kernel.org/?p=linux/kernel/git/gregkh/usb-2.6.git;a=commitdiff;h=cc62a7eb6396e8be95b9a30053ed09191818b99b Hope this patch is not lost and thanks, Kirill -- 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
