On Tue, Apr 13, 2010 at 11:15 AM, Subbrathnam, Swaminathan <[email protected]> wrote: > > >> -----Original Message----- >> From: Markus Rechberger [mailto:[email protected]] >> Sent: Tuesday, April 13, 2010 2:39 PM >> To: Subbrathnam, Swaminathan >> Cc: Andreas Auer; [email protected] >> Subject: Re: UVC webcam problem >> >> 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 > > I have personally verified the exact use case you have mentioned and seen it > working just fine (with Haupaugue 1950 device as I remember). ISO functions > as spec'ed and so does Bulk. 4.5MBps is too low pl. refer to DM644x release > data sheets and you can see much higher numbers for throughput in the USB MSC > contexts. >
> The problem could have been with the older drivers and I do acknowledge that > there were instability issues with them. > the problem we had with 45mbit was USB BUS resets and occasional hangups when the transfer stopped (although we were also using 2.6.18 back then). Maybe things improved... a customer got a patch from TI back then the reset recovered but it still caused glitches in the stream. Maybe things improved a little bit further in the meantime (last time we tested it was exactly 1 year ago). DVB-C gains a much higher bandwidth than ATSC or DVB-T devices (clearQAM might be near but I'm not sure). Just in case as a reference: http://support.sundtek.com/index.php/topic,4.0.html (DVB-T/DVB-C) http://support.sundtek.com/index.php/topic,87.0.html (ATSC/Qam) Markus _______________________________________________ Davinci-linux-open-source mailing list [email protected] http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
