2010/2/21 Kai Vehmanen kvehmanen@eca.cx
Hi,
On Mon, 15 Feb 2010, Raymond Yau wrote:
Even using a high resolution timer , the application still cannot achieve
latency better than the configured period size
For USB case , the driver cannot give accurate hw pointer position , hw pointer increase in steps for the current implementation, (i.e. the graph is
... but that's a real hardware limitation for the USB-driver, right? And even in the USB case, hw pointer is incremented in steps of URB transfer size, so even in this case, latency of a highres timer based application is not limited by the set period-size.
I don't think so since the sound card still use interrupt driven , the latency cannot be better than the period size
To achieve lower latency , you have to set a smaller period size even if you are using high resoultion timer
The glitch is most likely underrun since the watermark may be too low on machine with slow CPU since you assume all CPU have enough power and disk I/O to write ( buttfer time - 20ms ) audio data in 20ms