On Tue, Apr 13, 2010 at 11:00 AM, Subbrathnam, Swaminathan <[email protected]> wrote: > > >> -----Original Message----- >> From: [email protected] >> [mailto:[email protected]] On Behalf >> Of Markus Rechberger >> Sent: Tuesday, April 13, 2010 2:24 PM >> To: Andreas Auer >> Cc: [email protected] >> Subject: Re: UVC webcam problem >> >> On Tue, Apr 13, 2010 at 10:27 AM, Andreas Auer <[email protected]> >> wrote: >> > Hi, >> > >> > I'm trying to get a UVC webcam working with the latest khilman kernel >> > (2.6.34) on a Davinci EVM like board with DM6446 processor. >> > >> > I'm able to request the buffers and queue them without errors. But if I >> > switch on the streaming the UVC driver tells me: >> > "uvcvideo: USB isochronous frame lost (-18)." >> > >> > Some time ago, I tried the 2.6.32 kernel from the arago project and >> webcam >> > capturing was working out of the box but WLAN was not working. (so, I >> > switched to the khilman kernel). >> > >> > Maybe, someone can help me with the uvc webcam problem!!! >> > >> >> with our tests the DM6446 only supported up to around 4.5 mbyte of >> isochronous data... > > DM644x USB supports only normal ISO mode hence the max ISO bandwidth > achievable is limited to ~64Mbps. > not even reliable, we have USB DVB-C/T/ATSC/ISDB-T devices which support exactly 60 MBit, the transfer mode is switchable between ISOC and BULK, we finally managed to get those devices work by enabling hardware PID filtering. 45mbit already caused some issues with it, HDTV (720p) usually requeris around 15 mbit (one channel) which works well with our devices. Isochronous used to hang up for no reason (the usb host controller/driver was(is?) quite unstable as well with isochronous and higher data rates) However Bulk works fine with around 4.5 mbyte/sec
Markus >> Raw Analog TV 720x576x25 requires around 170 mbit, I guess webcams are >> near to that level there's no chance to get such a thing work. >> Maybe MJPEG or MPEG based devices can work with it. > > > One could use BULK mode if higher throughput is needed but not may webcams > support such a transport. > >> >> Markus >> _______________________________________________ >> Davinci-linux-open-source mailing list >> [email protected] >> http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source > _______________________________________________ Davinci-linux-open-source mailing list [email protected] http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
