MMB 2x2
MIDI Merge Box
Model 8-252 ver. 1.2
Copyright © 2009 CHD Elektroservis
All rights reserved. No part of this publication may be reproduced in any form without the written permission of CHD Elektroservis, s.r.o.
10
APPENDIX: FAQ
Question :
Our arranges are relatively “dense”. Will not resulting sound “choke”, with regard to
stated possible delay of 0.3-0.9 ms?
Answer :
This delay is caused by the fact that the device needs to receive complete MIDI
message, before it is processed and sent further. Size of messages ranges from one to three bytes,
one byte takes 0.32 ms to transfer – this is where the stated delay results from. The delay is absolutely
imperceptible by human senses. Interestingly, even synthesizers from higher price categories take
approx. 5 to 20 ms to emit sound after receiving "Note On" command. In comparison to this, delay of
Merge Box is one rank lower.
Question :
I cannot judge how dense the data have to be, in order to overfill buffer (how large it
is)? How large is the density of data that can be safely transmitted through the device?
Answer :
The principle of merging of data from more serial buses with constant transfer rate
into one bus with the same transfer rate implies that in case of data flow on input buses being dense,
accumulation of data can take place. Output bus might not be able to handle the transmission in this
case. MMB 2x2 is provided with caching data buffers on each MIDI input and on MIDI output for this
reason. These buffers capture data from this signal route for the duration of time period when
controlling processor of MMB 2x2 processes data from other signal routes. The capacity of these
buffers is substantial despite the fact sometimes the data can be delayed. In extreme cases the buffers
can be overfilled. In case of one input bus being extremely loaded, it is therefore recommended to load
other input buses lightly or not at all. This is of course applicable only for transmissions of extremely
large data blocks, which can be for example SysEx memory dumps, transfer of sound samples (SDS)
or MIDI files (MFD), and the like. However, caching buffers cannot be realistically overfilled by common
musical data.
Let us suppose following example – merging data from two sequencers, all of them broadcast on
all 16 channels. Four voiced accords in
1
/
16
notes are played on each channel of each sequencer,
tempo is 120 BPM. Therefore 1024 tones sound during one second. In this example, Merge Box is
used (while in "Running Status" regime) to 55 to 65 % of its capacity. There is still plenty of room for
data of commands Pitch Bend, Key / Channel Aftertouch, Control Change, etc.
Question :
Is it possible to filter Control Changes 00 and Control Changes 32 information ?
Answer :
Filters of controllers 0 and 32 (Bank Select MSB and LSB) are included in filters of
program changing (filter No. 2 - Program Change).
Summary of Contents for 8-252
Page 12: ...7...
