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IDCategoryLast Update
0008153bugs2020-06-01 17:38
ReporterDirk OffringaAssigned Tox42 
Status feedbackResolutionopen 
PlatformWindows 10OSWindowsOS Version10
Product VersionMixbus 6.x 
Fixed in Version 
Summary0008153: Midi Real Time messages are sent too early (Mixbus AND Ardour)
I’m using Mixbus 32c V6.à.655 on Win10, 48k, 1024 buffersize, ASIO. I have an issue with the midiclock and/or the start/continue messages. They start/continue messages are always sent too early in relation to the grid, and this offset seems to be related to some latency compensation: if I insert a plugin that needs PDC (even the limiter on the main bus) the start/continue messages are issued even earlier but I did not identify a clear sample-accurate pattern. I spent countless hours checking every possibility I could think of, and reported the issue to Harrison support. as well. On the other hand, audio latency compensation is spot on: I have correctly calibrated the audio hardware and it’s sample accurate.

When using the midi device calibration results, the offset is worse than when leaving them at default 0.

The Real Time start/continue/stop messages should be sent when the actual audio starts to sound, so that synced external sequencers are synced to the recorded audio. This means that all latency compensation should apply to these RT messages too. This seems not to be the case. When a external sequencer receives a start message, and we record its (audio) metronome, the record metronome shoul be perfectly aligned on the grid.

I downloaded Ardour to doublecheck and it has the same behaviour.

Please note this is MidiClock, not MTC.

Steps To ReproduceMake sure audio and midi have been calibrated. Patch midiclock to the midiport a sequencer is connected to. Patch the sequencer's audio click output into a audio interface input, and connect to a Ardour track. Start Ardour and record that click. Check if the click is aligned on the grid.

Even when routing internally, there's an issue:

Patch Ardour click to an audio track input, record metronome. Check if the click is aligned on the grid.
TagsNo tags attached.


related to 0008154 new Midi clock should stream always 



2020-05-31 22:47

administrator   ~0024331

This should be fixed since Ardour 6.0-44-gef94663d1c

The main problem was that Ardour just sent start/continue message instantly, and not at MIDI Clock downbeats. Nor was the clock every in sync with music-time beats.
In all versions prior to 6.0.44 Ardour just used it to indicate [clock] speed (and state).

Issue History

Date Modified Username Field Change
2020-05-27 11:29 Dirk Offringa New Issue
2020-05-31 22:47 x42 Assigned To => x42
2020-05-31 22:47 x42 Status new => feedback
2020-05-31 22:47 x42 Note Added: 0024331
2020-06-01 17:38 x42 Relationship added related to 0008154