Re: [linux-audio-dev] USB-MIDI Transfer rate

On Fri, 2005-09-16 at 17:10 +0200, Clemens Ladisch wrote:

>
>
> It would be interesting to know what the maximum data rate is.
>

Well, as said elsewhere; (in this case) it is 16 times higher than you
(by default) allow for in usbmidi.c

While trying to catch up, I noticed that there is a "FIXME" in

---------------------
   static void snd_usbmidi_standard_output
                      (snd_usb_midi_out_endpoint_t* ep)
    ...

   // FIXME: lower-numbered ports can starve higher-numbered ports
------------------------

Uhmm ... I have been meditating on this function all evening. There are
implications surrounding it.

You have decided to go for the worst case scenario where an USB
4byte-frame == a 3byte-midi-msg == 1 milisecond. The obvious anvantage
is that this will not break.

Although, for a physical cable there are best case scenarioes where you
can get 3 messages across/milisecond (ie: channel aftertouch)

I also noticed that the driver envestigates quite a few vendor/product
IDs to get around various "quirks". This route might be a way to go?

mvh // Jens M Andreasen

>
> Regards,
> Clemens
>

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