We had a 2-days live event with my choir, professional audio engineers doing the mixing. I asked to connect to their console for multi-track recording with ardour, and we set things up for 48 kHz recording. First show done, perfect recording.
Second day, I opened the ardour project again and did the recording of the show into the same project, to avoid having to reconfigure inputs and channel names. Unfortunately, did not check the recording right after the show.
Now back home, I find the second day recording much shorter than the first. Raw wav files roughly half the size of the day before. Playback too fast and significantly distorted.
It absolutely seems like a sample rate issue, and I tried importing the raw file to audacity. Using 24000 Hz seems to play back roughly at the right speed, but is still significantly distorted (and does not seem to be a common sample rate, actually). 22050 Hz is proposed by Audacity as a common rate, but seems to play back too slow and still distorted.
Unfortunately, we had another person doing the second show, and I remember that initially, I did not receive a signal in ardour, when he got started for the second day, so he might have somehow changed the setup of the console, which I wasn’t aware of…
Did the console have a USB port which acted as an audio interface? Or you had some other way to connect to the console?
A sample rate mismatch between project and hardware will usually result in a warning message pop-up in Ardour right away.
Can you open the files from the first day in audacity and verify the sample rate is actually 48k as expected? I have never seen a digital console which can operate at 24k sample rate, so very surprising that the files are half the size of the first day.
The console (32 channel digital mixer; don’t remember the exact model, unfortunately) was connected as audio interface via USB. No drivers installed, was immediately detected by my linux machine and in Ardour. Routed the first 20 channels pre-fader to USB out for recording.
Audacity states 48 kHz, 32bit float, mono - as expected and same as Ardour’s project settings. Approx. 2h 40 min show resulted in 1850 Mb wav file - clean audio.
For the second day files, Audacity reports the same. Approx. same duration of show, but 975 Mb wav file, broken audio.
Importing at 24 kHz gives approximately the same duration (2h 45 min). Badly distorted, but I can hear enough to confirm the whole show was recorded, well, somehow :-/
Is there another “common” sample rate close to that? Although it seems unlikely that anyone would consciously use sample rates below 44.1 kHz on a professional console today…
Years ago there was a 32k sample rate sometimes used for extended recording time on digital tape, or for transmitting to a radio transmitter that had low bandwidth and so did not need the full 20kHz available with 44.1k and above sample rates. I haven’t seen that used in years, I would be very surprised if a digital mixer made in the last 10 or 15 years supported that.
Just tried that, but no luck. Playback still too fast, with significant distortion.
Completely strange. What puzzles me, is that I still can here the signal - at 24kHz and behind the distortion - but there’s something, not just mere noise. And it’s consistent across all channel.
You may have to find the exact model of the mixer, and check the user guide for possible configurations which might explain the strange files you have. Possibly it is just an error of some kind and not an explicitly available configuration option, because a USB interface should be able to describe the sample rate and sample format (word length and encoding) which is being used. Ardour should have warned if the USB interface indicated that the sample rate was something other than the project configured rate.