On Thu, 10 Jul 2003 16:31:28 +0100 James Courtier-Dutton <[EMAIL PROTECTED]> wrote:
> Hi, > > When an application reads the "avail" or "delay" pcm values: - > 1) how accurate are they? > 2) does the accuracy depend on the sound card driver being used. Worst case accuracy is about one period AFAIK. It depends on the sound chip because the low level driver reads the DMA pointer (or something) from some hardware register or it can know the DMA pointer when it receives an interrupt at the end of a period. > This means that the "avail" and "delay" pointers are only accurate to > the nearest 3 ms. > Do any other alsa drivers suffer from this, or are they all sample > accurate and updated as each sample is sent to the speakers. No, for example the DMA pointer of Echoaudio cards has a precision of 32 frames. But from userspace it can be a lot worse than that. You have to take into account process scheduling, disk i/o, network i/o... Bye. ------------------------------------------------------- This SF.Net email sponsored by: Parasoft Error proof Web apps, automate testing & more. Download & eval WebKing and get a free book. www.parasoft.com/bulletproofapps1 _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
