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IDCategoryLast Update
0008750bugs2021-06-19 17:04
Reporterccr5-delta32Assigned To 
Reproducibilityalways 
Status newResolutionopen 
PlatformMicrosoftOSWindowsOS Version10
Product Version6.7 
Fixed in Version 
Summary0008750: Transport malfunction when synced to continuous external midi clock
DescriptionI am experiencing a bug where Ardour will not run properly when synced to external midi clock. Although I am reporting for Win10, the same happens in the Linux(Debian) version.

In my case the incoming midi clock signal is continuous rather than only on after a midi start until a midi stop, something I require for my boxes with internal sequencers. The clock source is an E-RM MIDIclock+ through an simple midi - USB converter, but not a cheap one with all kinds of design compromises. I have made the necessary "MIDI Connections" to route the incoming midi clock.

When Ardour is not running, as soon as I switch Ardour to external sync using the button below the transport buttons Ardour immediately starts to run from some seemingly arbitrary point in the song. Note that this does not require a midi start. I did set up the Transport Master "Active Commands" to accept start/stop. In fact, Ardour does not react to midi start/stop/reset commands at all when synced to my external midi clock.

In Edit>Preferences>Transport>Chase>Transport Masters I notice that the "Sync Position + Delta" is continuously increasing regardless of whether Ardour is running. This value is determining where Ardour will start playback when external sync is activated.

Now, if I press start on the midiclock+ followed by stop, while Ardour was running due to the above, Ardour does not stop. But the "Sync Position + Delta" in the "Transport Masters" resets and starts incrementing from 0 again.

I am not sure if the following is part of the problem because it seems sensible. If the song position pointer is stopped at a timepoint in the track that is greater than the "Sync Position + Delta", Ardour does not immediately start playback as soon as external sync is activated. But when "Sync Position + Delta" catches up to the song position pointer it Ardour will start to run. But in any case midi start and stop commands do nothing.

Only in Linux using Jack and a2jmidid the above behavior is associated with glitches such as tooltip balloons flickering rather than being displayed properly. I have also had crashes to desktop in Linux while experiencing the issue described above but cannot provide more details now.
Steps To Reproduce(1) Connect an external midi clock source that sends continuous midi clock data.
(2) Make the necessary connections in "MIDI Connections"
(3) Setup or verify "Edit>Preferences>Transport>Chase>Transport" to select 'MIDI Clock' from the respective source, and select "Accept start/stop commands" and "Accept locate commands" in "Active Commands".
(4) Note how "Sync Position + Delta" in "Edit>Preferences>Transport>Chase>Transport" is continuously increasing according to the continuous incoming midi clock.
(5) Move the song position pointer to the start of the session.
(6) Select 'M-Clk' by pressing the 'Int.' button near the transport buttons.
(7) Watch Ardour immediately start playback from whatever the value of "Sync Position + Delta" in "Edit>Preferences>Transport>Chase>Transport Masters" was.
(8) Press start/stop/reset on the midi master
(9) See Ardour do nothing while other slaves do start/stop/reset. But the "Sync Position + Delta" in "Edit>Preferences>Transport>Chase>Transport Masters" does reset upon receiving midi stop.
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Issue History

Date Modified Username Field Change
2021-06-19 17:00 ccr5-delta32 New Issue