First 10 seconds of modified stereo region goes mono-output

Hi all,

Strange thing happens.
If I modify a stereoregion (even trimming and back untrimming the region is enough to make it happen) and then playback the region the first ten seconds sound mono and during playback after those 10 seconds it switches (audibly) to stereo.
It’s just purely the first time the edited region is played that this does happen. It’s not related to the beginning of the region, even starting in the middle of the region it’s outputted mono for ten seconds.
If I quickly push the spacebar three times, like a quick start/stop/start the region sounds ok.

This mono-start of an edited region is happening in version 7.4 and above (also the newest 8.0).
Of the earlier versions I only have 7.3 on my computer and with this version playback is ok.
Jack or ALSA makes no difference. Buffersize makes no difference, DSP is 4%
I don’t know if these 10 seconds is related to something. I tried different tempo’s but it’s allways 10 sec.

Any clues to this (unwanted) behaviour?

Tnx, Coen

Am I really the only one experiencing this?!?
Did I maybe not describe the issue well enough?
I could report a bug if I knew that this is a common error but without any reactions I’m not sure this is the case.

Testing is very easy. Just select a stereo-track (solo) with a region with an obvious stereo sound of the source. Trim (and untrim) the region and listen to it (through headphone).

In my situation it sounds mono for a while. After about ten seconds stereo kicks in. Playing the region again it is in full stereo from the beginning. It’s almost like there has to be put a stereo-label to the region and Ardour needs time to figure out it is a stereo-region.
A newly recorded region also sounds mono when played for the first time.

I hope some of you will try this out. If I’m really the only I can look into my own configuration to solve this.

I can reproduce this (in 8.0-23-gf29130fc7c built from source, at least). Seems like only the left channel of the track plays through both left & right outputs for an amount of time that seems to be related to the “Edit | Preferences | Performance | Disk I/O | Buffering | Playback” setting.

Thanks a lot Colin,

I can confirm your observation, it indeed seems to be related to the disk i/o playback buffering time. For Medium sessions 10 seconds.
If I switch to small sessions it’s indeed 5 seconds
And yes, during this 10 seconds period (or 5, or 20 secs for large sessions) it’s only the left channel output panned to the middle.

As stated earlier, according to my testing possibilities this behaviour is the case since version 7.4
(7.4, 7.5 and 8.0 are mono starting, in 7.3 there is no problem).

I’ve bisected this to 295dbd8e: “Make RCU reader return a const pointer (omnibus commit)”. I’ll make a bug report.

[edit] Bug report now at 0009483: Only left channel of stereo regions is heard for a while after region trim - MantisBT

And this is now fixed by @x42 in 8.0-24-gfd3f475b3f.

1 Like

That’s great!
Thanks for the response and action :+1:

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