[Ardour-Dev] 2.8.12 export problem

[John Rigg]

I've just tried exporting a stereo file from a 48kHz session in Ardour
2.8.12 to 44.1Hz 16-bit and encountered some very odd behaviour.
In 2.8.11 this procedure used to produce a file without any audio in it
for the first 3 or 4 attempts, but it would eventually export successfully.

In 2.8.12 this has changed. The exported file contains audio but the
file is truncated. Subsequent exports truncate the file to a different
length, which appears to be random. Sometimes only a few MB are exported,
other times 90% of what should be a 32MB file get exported. I gave up
after 30 or so attempts failed to produce a full length file.

Exporting to a 48kHz floating point file works fine.
Exporting to 48kHz 16-bit with triangular dither also works.
Add in sample rate conversion and the problem appears.

System is Debian testing amd64 with jack-0.121.3 and 3.2.16 kernel with
preempt but no rt-patch. Command line used to start jackd couldn't be
simpler:
jackd -d alsa

For the time being I can work around it by exporting to 48kHz
and then convert using sndfile-resample from the command line.

Any ideas about what is causing this?

John