Jack Audio Bugs

Hello Shotcut and mlt devs!

First, thanks a million to have implemented Jack support. I’m a recording engineer and I’m making a lot of music videos. Until now it was a pain to work with music AND video on linux… But thank to the Jack implementation in Shotcut now it’s absolutely amazing. So creating complex mixes in Ardour with a lot of automations, routing, surround and this all synced with the video timeline of shotcut is now an really big step forward. Thank you!!!

Now, I was trying around with Ardour-Jack-Shotcut sync and I figured out 2 small bugs:

  1. MLT is creating a stereo output and a stereo input in jack, which is fine, but it connects shotcut’s output to shotcut’s input automatically (which doesn’t make sense), instead of connecting the output to the system playback (and input with system capture).

  2. in Jack sync mode, the play button (Shotcut or Ardour or Jack, doesn’t matter) sends “play” to Jack (and Shotcut), but the real timeline start occurs 4-5 sec later… so Shotcut starts but Ardour waits 4-5 sec to the start of the jack timeline. Shotcut and Ardour are synced, but with 4-5 sec delay. I don’t think this is the wanted behaviour, since hitting play should start all Jack clients at the same time with the same timeline.

I hope I could help, just waiting for these bugfixes to start the new AV revolution on Linux :wink:

All the best and thanks a million for Shotcut!!


OS: LinuxMint 17, Shotcut 17.04, Ardour 5.8

Oh that is great news you managed to connect Ardour with Shotcut through Jack. Could you write a tutorial om how to do it?

[You might want to add your bug reports to github too]

Hey tin2tin,

Syncing Shotcut with Jack and Ardour ist straightforward;

  1. start jack, ardour and shotcut
  2. set ardour in jack sync mode and shotcut “use jack”
  3. connect the audio output of shotcut to the system out in jack (qjackctl)
  4. that’s it :slight_smile:

If everything worked properly, hitting the play button in ardour, in jack or in shotcut will start the jack transport and all applications will start playing (for now with a delay like in this bug report, which has to be corrected).

I’ve install both Shotcut (20.02.21) and Ardour (5.12.0) and I’m experiencing the same problem as @vince.

Sometimes when I press play in Ardour the Shotcut playhead won’t move at all, even after a 4-5 second delay. Other times when I press play in Shotcut the playhead takes up to 10 seconds to move and the audio is out of sync.

See the release notes for latest version 20.04 has fix. Closing this old thread.

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