Re: [linux-audio-dev] MMAP + RTC excellent performance , 2.9ms latency during playback !

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Subject: Re: [linux-audio-dev] MMAP + RTC excellent performance , 2.9ms latency during playback !
From: David Olofson (david_AT_gardena.net)
Date: ti maalis 07 2000 - 21:15:21 EST


On Tue, 07 Mar 2000, Juhana Sadeharju wrote:
> >opinions ?
>
> Pretty good!
> After solving your questions, please make code available.
> I'm writing a simple IPC etc. utility library for setting
> A/D & D/A services, communication systems, etc. and extra
> code for study would be nice.
>
> >PS: please don't ask for my RTC + MMAP code for now because it's PATENTED !
> >patents are modern these days :-)
> >just kidding !!
> >:-)
>
> But what is then US Patent 5,435,863????!!!!

Seriously!? This trick (using an external IRQ source + checking the
current position of the DMA) has been used for *ages* in PC demos and
games, in order to avoid having the audio engine interfering with the
retrace sync cludge that many video boards require. (Polling instead
of the IRQ line that *should* have been there on *all* VGA cards, but
was missing on too many.)

//David

.- M u C o S --------------------------------. .- David Olofson ------.
| A Free/Open Multimedia | | Audio Hacker |
| Plugin and Integration Standard | | Linux Advocate |
`------------> http://www.linuxdj.com/mucos -' | Open Source Advocate |
.- A u d i a l i t y ------------------------. | Singer |
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