B2M latency issues

The B2M™ Universal Bass to MIDI Converter.

B2M latency issues

Postby squizzercrow » Wed Feb 27, 2013 9:28 pm

Hi

Just received a B2M yesterday and eagerly set about trying it out. Works pretty well - there are a few issues where the note played seems to drop down an octave - however, and after testing directly through recording a simple 1 - 2 - 3 - 4 into Cubase and Ableton using different MIDI interfaces (EWS64 and midisport 8x8) and computers, it is consistently 1 tenth of a second out. I tried the same set ups with a keyboard and all recordings spot on the beat. Is it likely I have a duff unit or are there other things I should try?

TIA

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Re: B2M latency issues

Postby james » Thu Feb 28, 2013 10:27 am

What notes are you playing?

Lower notes will have more latency than higher-pitched notes. But even so, a tenth of a second (100ms) is much longer than it should be.

It is not possible for the B2M to have a delay as long as 100ms after a note is detected. So, I'm assuming it's the start of the note that is taking time to be detected, and then the MIDI data is sent out correctly thereafter. To get lowest latency, the B2M has to "see" the start of the note with an obvious increase in level (a transient). On low bass strings, this doesn't usually happen when you play (you can hear the notes but there isn't much level change), so trying to accentuate the start of notes and damp the strings to stop the string between notes can really help here.

As a test, try the higher notes: not only do these have lower latency because they are higher pitch, but the level change on the notes is much more obvious, particularly if you use a pick rather than fingers to pluck the strings.
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Re: B2M latency issues

Postby squizzercrow » Thu Feb 28, 2013 5:22 pm

Hi

Its consistent all over the neck - the problem with lower notes is quite intuitive and so the timing test against the click track into the DAW was using the e above the octave on the d string using a single note on the first beat of each bar and stopping the string straight away. I'm a finger player.

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Re: B2M latency issues

Postby james » Thu Feb 28, 2013 5:28 pm

I'm not sure what's going on here.

When you play a note, do you see the MIDI LED on the B2M light immediately? That's showing that it is sending MIDI data, and it there should be no obvious lag between the LED blinking and you playing a high note.
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Re: B2M latency issues

Postby squizzercrow » Thu Feb 28, 2013 6:02 pm

Hi

checked that last night - the midi light does seem to lag too - though obviously I can't time that quite as accurately as I can the signal received at the daw ;-) Is it possible I've just got a dodgy pedal?

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Re: B2M latency issues

Postby james » Thu Feb 28, 2013 6:06 pm

If the MIDI notes are correct (most of the time), its unlikely there is a fault.

Can you record a simple section of audio of what you're playing (and ideally the MIDI at the same time) and I'll take a look at it and see if I can replicate it on a B2M here.
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Re: B2M latency issues

Postby squizzercrow » Thu Feb 28, 2013 6:17 pm

can do that later this evening - I'll do the same first beat of bar for 8 bars - email address to send to?

oh, do you want the midi sounds and data or just the data?
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Re: B2M latency issues

Postby james » Thu Feb 28, 2013 7:57 pm

I've sent you a PM with the email address.

MIDI data is fine, with the original bass audio as a WAV (so it's not been compressed).
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Re: B2M latency issues

Postby squizzercrow » Thu Feb 28, 2013 10:08 pm

thanks email sent - apologies for the first with mp3's, I hadn't read your reply above!

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Re: B2M latency issues

Postby james » Fri Mar 01, 2013 10:53 am

Thanks for emailing the files.

I can certainly see that the MIDI sound is lagging behind the bass by more than you'd expect (30-55ms which is a lot for the note being measured). However, this latency is still possible if the signal level the B2M is seeing isn't quite right. In which case the "transient" sometimes can't be used and it has to wait a bit longer to work out the note.

So, first check the input level to the B2M. Can you make the signal clip (the CLIP LED will light)? If not, maybe the B2M has a problem and it's only seeing a small signal level. Similarly, if it's clipping all the time it can cause problems.
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