[MPlayer-dev-eng] Real Time Clock into timer-lx.c?
Sidik Isani
lksi at cfht.hawaii.edu
Sun Sep 22 16:31:00 CEST 2002
Hello Dominik -
On Sun, Sep 22, 2002 at 11:50:27AM +0200, Dominik Mierzejewski wrote:
> On Sunday, 22 September 2002, Sidik Isani wrote:
> > Hello -
> >
> > I'm still planning to send you that timing patch this weekend!
> > (The one which makes video smooth with network audio and broken
> > sound drivers.) Please tell me what you think about the following
> > though, so if needed I can back out other changes that are now in
> > my tree before generating this patch. This has to do with RTC.
> > I get good results with it, but only if:
> >
> > 1. Some previous program happens to have left it at >= 256Hz.
>
> This is not required.
>
> > 2. I'm running as root, or setuid-root
>
> And this isn't either, if you have a recent kernel (i.e. 2.4.19
> or so, check DOCS).
Ah, the *mplayer* DOCS. I found it now. The kernel docs had
not been updated with /proc/sys/dev/rtc/max-user-freq yet.
> > Even if 1. is true, kernel will not allow a normal user to enable
> > the interrupt until they select something <= 64Hz.
>
> Not true for recent kernels.
I see. So it is still true for an unmodified system. The FAQ
says how to modify it, but if someone doesn't, then since -rtc
is the default now, non-optimal things can happen.
> [...]
> > I'd like to propose three things... and the patch if you like ;-)
> >
> > 1. *Set* the RTC to 256Hz rather than accepting whatever frequency
> > it was left at, ... or if that somehow causes a problem, set the
> > frequency to 256Hz only if the old frequency happens to be lower
> > than that. Since only one application can use the RTC at a time,
> > does anyone see a problem with just putting a value in?
>
> What's wrong with current 1024Hz?
Well, there is no "current 1024Hz", but 1024 works just as well as
256 on mine, so why not. I don't know what the overhead for a hw
interrupt is on a powerPC (it has the RTC also), but it is still
probably insignificant at 1KHz. I have 2.4.19, and the CVS mplayer.
Try compiling and running the RTC example in
/usr/src/linux/Documentation/rtc.txt and then run mplayer . . .
It runs at 64Hz! :-(
- Sidik
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