[LAD] Tests directly routing pc's midi-in to midi-out

[Clemens Ladisch]

Robin Gareus wrote:
> On 07/15/2010 01:07 PM, Ralf Mardorf wrote:
>> On Thu, 2010-07-15 at 12:55 +0200, Clemens Ladisch wrote:
>>> Ralf Mardorf wrote:
>>>> dev.hpet.max-user-freq
>>>
>>> This parameter will not have any effect on anything because there is no
>>> program that uses the HPET timers from userspace. 
> 
> That'd be correct if Ralf would stick to 'amidiplay' and friends for his
> tests.
> 
> There are a couple of audio-tools who can use either RTC or HPET for
> timing, although most of them need an option to explicitly enable it.

Jack can read the current time from /dev/hpet, but it does not use it to
generate interrupts.  As far as I know, there is no program that does.

> BTW. Do you know the unit of these values?
>   cat /sys/class/rtc/rtc0/max_user_freq
>   cat /proc/sys/dev/hpet/max-user-freq
> are they Hz?

Yes.

>> IIRC someone on jack-devel mailing list had issues when using mplayer
>> with the value 64 and it was solved when using the value 1024.

This has nothing to do with MIDI timing; mplayer can use the RTC (not
HPET) for audio/video synchronization to work around the 100 Hz limit of
the system timer on old Linux kernels.


Regards,
Clemens