Re: SysEx overflow when using the MIDI sequencer event interface

[Haakon Riiser <haakon.riiser@fys.uio.no>]

A little followup to my previous post:  I just placed a printk()
in snd_emu10k1_midi_output_trigger() that prints the number of
bytes just sent to the SB Live's MPU-401.  I also also increased
the dmesg size to 512 KiB to make sure that nothing was lost.

I had expected that by summing the entries in dmesg after having
run 'amidi -s <sysex-file>', I would get the same number as the
number of in bytes of the sysex file, but that didn't happen.

When I try to insert a 18584 byte long sysex file using amidi,
dmesg shows a byte count of approx. 10868 (+/- a few bytes).
My own toy-version of amidi that uses the event interface gets
consistently less than ten(!) bytes in the dmesg log.  If I insert
a delay between each sysex event of about 100 ms, the byte count
increases to almost 300.

That is _far_ too low a number to explain how the MIDI tunes
can sound the same as when I load the sysex data with amidi.
If only 300 sysex bytes were actually sent to the MIDI device,
I would obviously hear the difference between that and amidi's
method that got over 10000 bytes through.

None of this makes any sense to me.  I thought all bytes pushed onto
the MPU-401 were sent through snd_emu10k1_midi_output_trigger(), but
this experiment contradicts that.  I'm having trouble getting the
big picture of how the MIDI parts in ALSA works, so a little help
would be appreciated. :-)

-- 
 Haakon

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