[alsa-devel] MIDI on ice1724 - long delays

[Pavel Hofman]

Pavel Hofman wrote:
> Takashi Iwai wrote:
>> At Tue, 22 Apr 2008 22:23:55 +0200,
>> Pavel Hofman wrote:
>>> Hi,
>>>
> ...........
>>> After the playback stops, the interrupts are gone too. It seems as if 
>>> the playback interrupt initiates the MPU TX interrupt.
>>>
>>> If we could avoid generating the MPU TX interrupt during regular 
>>> playback, I believe the major problem would be resolved.
>>>
>>> Even if I mask the interrupts (CCS01) and do not explicitly unmask them 
>>> (according to proc ice1724 the CCS01 register stays at 0xa0), the 
>>> interrupt gets generated.
>> OK, then the simplest way would be to just ignore the TX bit at the
>> second or later check.
>>
>> How about the patch below?
> 
> Takashi, thanks for the hack idea. The overhead is just one more loop 
> which is nothing. I will test it and post details of further problems 
> (there is a bunch of them :) )
> 

Hi,

The hack works fine, I am finally getting no CPU burning during playback 
and  MIDI input/output.

Now the next problem are delays. amidi through ice1724 prints the 
rawmidi data a fraction of a second later compared to USB midi input. I 
guess there is not much we could do about it. The format is a bit 
different which probably does not matter:

pavel at nahore:~$ amidi -l
Dir Device    Name
IO  hw:0,0    Audiotrak Prodigy 192 MIDI
IO  hw:1,0,0  Keystation Pro 88 MIDI 1
I   hw:1,0,1  Keystation Pro 88 MIDI 2

ice1724 midi:
pavel at nahore:~$ amidi -p hw:0 -d

90 2D 5E
    2D 00
90 30 79
    30 00

USB midi:
pavel at nahore:~$ amidi -p hw:1 -d

90 2D 4C
90 2D 00
90 30 5E
90 30 00

However, what makes a huge delay difference is the next step - aseqdump. 
Here USB still outputs data immediately:

pavel at nahore:~$ aseqdump -p 20:0
Waiting for data. Press Ctrl+C to end.
Source_ Event_________________ Ch _Data__
  20:0   Note on                 0  41  94
  20:0   Note on                 0  41   0
  20:0   Note on                 0  45  80
  20:0   Note on                 0  45   0



Whereas through ice1724 midi it takes several seconds for the same notes 
to appear in aseqdump:

pavel at nahore:~$ aseqdump -p 16:0
Waiting for data. Press Ctrl+C to end.
Source_ Event_________________ Ch _Data__
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Note on                 0  43  86
  16:0   Note on                 0  43   0
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Note on                 0  47 100
  16:0   Note on                 0  47   0
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing
  16:0   Active Sensing

Google told me the "Active Sensing" messages are OK. Still, the whole 
pack of lines appears at once, but with a huge delay.

When hooking Qsynth to the inputs, notes through USB sound immediately, 
Notes through ice1724 get delayed by several seconds, but mostly they 
produce no sound at all. Surprisingly, the few notes which actually make 
it through sound long (just like the piano sustain pedal). USB notes do 
not have this effect.

Please make respective fixes to the enclosed patch as it involves some 
changes that make the MPU401 actually work.

Thanks a lot for advice and suggestions.

Pavel.



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