To test this, I did the following experiment. Under the same ehci controller, I connected the following devices. 1) USB 2.0 Mass Storage and 2) USB 2.0 Web Cam. Using hard disk utility tool I tried to measure the usb bandwidth of the mass storage device with and with out camera. The read values shown by the tool are: 1) With USB 2.0 Camera: Avg Speed - 13.1 MB/sec 2) With out USB 2.0 Camera: Avg Speed - 13.3 MB/sec There is not much difference between them. Thanks, Vinai. On Wed, May 26, 2010 at 12:20 PM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote: > B.Vinai Kumar wrote: >> I Have a device controller with Control, Bulk, Interrupt endpoints, it >> does not have >> ISOCH endpoint. Can I stream the USB Audio over bulk endpoint. > > Bulk data transfers have an unpredictable latency because of the error > handling and because other transfers might interfere, so you need a > quite large buffer in the device, which increase latency. Furthermore, > you cannot reserve bandwidth for bulk transfers, so there is no > guarantee that any particular buffer size is actually sufficient. > > There are many cheap USB controllers with iso support available, so > doing audio over bulk is a bad idea. (Being a bad idea, however, > guarantees that somebody does it; in this case, it's the M2Tech hiFace.) > >> If we can, then the existing usb audio class drivers will work with >> this kind of device. > > No. > >> If I connect a usb 2.0 webcam(high speed High badwidth isoch endpoint) >> under usb 2.0 Hub, >> Does it will affect the usb audio performance. (it's between Periodic >> vs Asynchronous scheduler) > > Iso bandwidth, when reserved, is guaranteed to be available; bulk is not. > Using the webcam might kill your bulk audio output. > > > Regards, > Clemens > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
