Em Wed, 22 Jul 2009 11:06:12 -0400 Devin Heitmueller <dheitmueller@xxxxxxxxxxxxxx> escreveu: > On Wed, Jul 22, 2009 at 11:01 AM, Jelle de > Jong<jelledejong@xxxxxxxxxxxxx> wrote: > > Funky timing of those mails :D. > > > > I saw only after sending my mail that Steve was talking about analog and > > that this is indeed different. Dual analog tuner support should be > > possible right? Maybe with some other analog usb chipsets? I don't know > > what the usb blocksize is or if they are isochronous transfers or bulk > > or control. > > > > I assume the video must be uncompressed transferred over usb because the > > decoding chip is on the usb device is not capable of doing compression > > encoding after the analog video decoding? Are there usb devices that do > > such tricks? > > There were older devices that did compression, mainly designed to fit > the stream inside of 12Mbps USB. However, they required onboard RAM > to buffer the frame which added considerable cost (in addition to the > overhead of doing the compression), and as a result pretty much all of > the USB 2.0 designs I have seen do not do any on-chip compression. > > The example which comes to mind is the Hauppauge Win-TV USB which uses > the usbvision chipset. pvrusb2 also has compression, provided by an external mpeg encoder. Those devices are USB 2.0 Cheers, Mauro -- 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
