Huge pop when crossfading every once in a while

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Chauncellor
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Ubuntu 10.10, Ardour 2.8.11 (rev. 7387).

This is a recent thing to happen to me. Possibly there is a bug in a package that I pulled in when upgrading to 10.10 but I do not know what it is.

I have a 10+ track recording that I'm working on in Ardour. 95 percent of the time the crossfade works just dandy. The other five percent yields a loud 'POP' and a random track shooting up to 600+ decibels(!!) as soon as the play head reaches the region. This will happen on the crossfade one time but not the next five.

This wouldn't be that big a deal if it weren't for the fact that exporting the session also includes these pops (which undoubtedly is not acceptable).

Any help would be appreciated. Thank you!

Chauncellor
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I can't see any option to attach a photo and am unsure if ardour will allow links without moderation but here is a screenshot of it in action:

http://ubuntuone.com/p/PUA/

Also, to clarify, the track itself does not shoot up astronomically, the loud pop just throws the monitors way off for about five seconds.

paul
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@Chauncellor: is the inclusion of this sound in the exported file completely reproducible?

Chauncellor
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Yes, sir. The pop does not happen every time but it seems to strangely affect only specific areas all over the piece (my observations tell me).

I honestly don't think this is directly my fault (i.e. poor mixing, automation - There is lot of looping in the piece) but I don't know what to attribute it to. The pop always occurs when the playhead reaches the *start* of the next region right before the crossfade.
Here's a small export of a pop:

http://ubuntuone.com/p/PVk/

If there's anything I can do/report to help I'd be happy.

Thank you :).

the C.L.A.
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I'm not completely sure, but I had discovered similar pops and believe it is fixed in 2.0-ongoing, even though in the corresponding bugreport (#3461) it was said it only happened with a VST enabled build.

Chauncellor
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That's my bug right there. However, I'm not using Ardour VST, just the stock Ardour 2.8.11 from the Ubuntu repos.

I definitely am using the grid and I have imported some tracks.

Should I go ahead and build from source with the patch in the report or will there be a release featured soon with the fix? I'm a little short on time at the moment as it is and the project needs to be done fairly soon.

Thanks for the report!

Chauncellor
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Oh, my god, it got worse :).

I exported something from one session and imported it to another.....

Take a look at the screenshot and listen to this. I suggest you turn your speakers down.

Screenie:
http://ubuntuone.com/p/Paj/

Audio:
http://ubuntuone.com/p/Pak/

Chauncellor
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I spared some time and built ardour with the proposed patch in that report. Problem seems to be solved for me.

anahata
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I've just had the same thing happen, using the Ardour-VST 2.8.11 supplied with AV Linux 4.1.
It seemed to be repeatable - the noise would be trigggered by a particular crossfade each time I played it, and seemed to go away if I randomly adjusted one edge of the crossfade.

Does this apply to Ardour-VST only or not, because I'm not using any VST plugins and don't particularly intend to, so I could download a stock Linux non-VST Ardour 2.8.11 if that would help.
Otherwise what's the best remedy? Do I have to patch the source as described above and rebuild?

GMaq
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@anahata

For the record Ardour-VST has been pulled for future AV Linux versions so if you aren't relying on particular VST's you might as well move to the Ardour-i686 available in the Debian repos, just a suggestion....

Farmer
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I had a similar issue with an old laptop http://tracker.ardour.org/view.php?id=3825 This is one of those annoying and unhelpful cases where everything seem to happen randomly(peaks appearing and then disappearing).. He has used the laptop for audio work before (adobe audition 1.5) and never experienced anything similar. Unfortunately I don't have access to it anymore now and I don't think he'll be able to try and compile that patch, or the svn version.. Hi's that kind of guy who doesn't have an email address :P

I haven't had this issue lately with my own machine.. I remember getting a similar peak once before, a year ago or so but then I didn't send it to a reverb so I was spared being scared to death and just cut around it and didn't think more of it..

anahata
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Since this thread's been revived, I'm happy to report that after downloading the Ardour source, applying the fix referred to earlier and recompiling, the problem (original one about joining regions) has not recurred.
Fingers crossed. Especially as I have paying customers coming in this weekend...

Chauncellor
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@anahata: I can vouch for the patch, I did a massive week-long project using a compiled ardour with the patch. The problem didn't occur again.

plingativator
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I've avoided using the automatic crossfades in the past because of this problem, but I recently purchased Mixbus 2.0 which has it turned on by default. I had the issue happen again. I don't imagine there's any way to patch Mixbus since I can't build it from source. Is it possible that I have some old file lingering in my system causing this issue or is it more likely to be a hardware/software issue with my particular setup?

seablade
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Mixbus2 doesn't use crossfades the same way Ardour does, in fact they don't exist the same way in MBv2. It is very unlikely you are experiencing the same bug really unless it isn't directly related to the crossfades. What MBv2 does is use overlapping region fades for the time being.

Seablade