On Thu, 18 Dec 2014, Udo van den Heuvel wrote: > On 2014-12-18 16:23, Alan Stern wrote: > >>> The bug report says there should be 10 M samples per second. How many > >>> bytes are in a sample? 2? > >> > >> I and Q samples are two bytes each. > > > > What is an I sample? What is a Q sample? > > I and Q samples describe the radio signal received by the airspy. > > > Are there any samples that > > aren't two bytes? > > No that I am aware. > > > You need to keep in mind that the people reading this mailing list know > > a lot about USB but don't know anything about Airspy devices. > > In fact the airspy samples at 20 MSPS with 2 bytes per sample, but the > host converts that to the I/Q pairs at 10 MSPS, with 2 bytes for each I > and Q. (I was explained in #airspy) I don't know what "#airspy" is. If the airspy sends 20 million samples per second to the host and each sample is 2 bytes, then the host would have to receive 40 MB/s of data from the airspy. As I mentioned before, the usbmon trace showed that the actual transfer rate was about 24 MB/s. 40 MB/s is a little beyond the limit of what most EHCI host controllers are able to handle, although an xHCI host controller ought to be able to do it. In your lsusb -t listing, bus 10 is EHCI. Maybe you should try plugging the airspy into an xHCI port. For example, you could use one of the ports currently occupied by the webcam or the video device. Alan Stern -- 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
