Crappy Soundchips [was Re: [Alsa-user] Re: [linux-audio-dev] ]Re: image problem...

[Takashi Iwai]

At Wed, 23 Oct 2002 15:16:08 +0200,
Werner Schweer wrote:
> 
> On Wednesday 23 October 2002 11:51, Takashi Iwai wrote:
> ...
> > > - SB AWE models (ugh, crap!)
> > > - Yamaha YMF7xx/DS-XG (some have reported that these work ok,
> > >   but in any case they have a max 3 periods limitation
> > >   similar to cs4281, which can confuse apps)
> >
> > no, instead, the interrupts are generated in the fixed time-length,
> > not at the period boundary or the end of buffer.
> > thus, this chip doesn't suit for low-latency purpose at all.
> >
> > the similar case is ESS chips, es1968 and maestro3 (allegro).
> > that is, many on-board chips on notebooks are crap, unfortunately.
> 
> it cost me a day of debugging to find out that my notebook with 
> ES1983S (Maestro3i) chip does not work well with JACK. Sometimes
> all seems to be ok (no underruns) sometimes timing was horrible with
> lots of underruns. Tracing shows that soundcard interrupts (JACK callbacks)
> sometimes are just too late.
> Takashi, are you saying that this cannot be fixed because the driver
> does not get an interrupt on buffer empty?

i'm afraid that it's a driver bug.  i got the similar report from
Steve, and in fact, this delay looks longer than expected.
however, in the case of maestro3, the situation is worse:  we have no
enough technical information to debug this behavior...

regarding to the audio device for notebooks, a USB device is not a bad
choice nowadays.
the latency is fairly good, you'll get 1 or 2ms order response.
but the bandwidth is too narrow, so the i/o channels are limited.
and if you use other usb devices together, the behavior is
unreliable.
but, anyway, it's easy - just hook and run (as long as usb hotplug is
fixed :)


ciao,

Takashi