Alan Stern wrote: > On Thu, 5 Oct 2006, Christopher "Monty" Montgomery wrote: > > Are overrun and underrun synonyms here? > > Sorry, a persistent thinko. s/overrun/underrun/g.
Except when doing input. In ALSA, we just call them xruns. :-) > > What happens when, eg, an application does not submit more audio to > > the usbaudio layer in time to avoid an underrun in playback? In that > > case, all the completion handlers would return and the stream would be > > released. > > I don't know the details of how usbaudio works. If it suffers an underrun > from an application, it has a choice: submit meaningless URBs -- silence, > or repeat the previous data -- or lose its bandwidth reservation. All three choices are possible, depending on how the application has configured the device. Either application xruns get ignored, in which case snd-usb-audio will continue submitting URBs from its completion handlers, or the stream will be stopped (and then must be explicitly restarted, and that can fail for various reasons). > > The intent is that endpoint_disable is called upon close(); in my > > testing (and from the code I read), close would in fact always result > > in an endpoint_disable. > > No, it doesn't. endpoint_disable() happens only at a few specific times: > when an altsetting or configuration is set or when the USB device is > unregistered. Of course, if usbaudio decides to call usb_set_interface() > whenever its device file was closed then you would be okay. snd-usb-audio actually does call usb_set_interface() when closing a device, but snd-usx2y does not because the endpoints of several devices (PCM and MIDI) share the same interface. With the current API, the only reliable way of detecting a stopped stream is indeed the absence of resubmits from the completion handlers. Regards, Clemens ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
