Peter Chen wrote: > On Fri, Sep 7, 2012 at 11:44 PM, Alan Stern <st...@rowland.harvard.edu> wrote: >> On Fri, 7 Sep 2012, Peter Chen wrote: >>> If the feedback is supported, the device will know host sends data slowly, >>> it will give speed up feedback information after it receives packet 5 or >>> other >>> packets depends on its interval at descriptor. At this information, it can >>> tell >>> the host to increase the packet size, then the transaction length and >>> transaction >>> numbers at iTD can be increased(Assume it was not maximum). >> >> Clemens pointed out that this won't work if the delay is too long. > > Clements said "In such a situation, the delay is much bigger than the > device's buffer, > so just sending more samples afterwards will not help." before. > > I don't understand what will not be helped?
The frequency feedback mechanism is designed to compensate for small differences in the host's and the device's clocks; it is not suitable for situations where the host sends less data than it should (or none at all). Devices have a buffer that is no larger than two or three milliseconds. Furthermore, the maximum packet size usually is only about 10 % larger than needed for the nominal sample rate, so it would in no case be possible to compensate for even a single lost packet. Regards, Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
