Update on my attempt to record 8 stereo audio feeds.
It worked! I recorded for 43 minutes at which point I noticed the file was 3.5GB which is approaching the 4GB file size limit of FAT32. So I stopped the recording and loaded it into audio player. It played and I could select each of the 16 tracks individually as well as listen to the stereo mixdown. I observed these issues:
- Xruns: There were a few xruns but all were short (reporting 0.0us) without noticable impact on the audio. They were concentrated on a particular time which I think corresponds with me dicking around with something.
- Audio Player could not display the waveform and incorrectly shows “File not loaded”. This is due to an overly simplistic waveform display mechanism. (We can’t fit 4GB samples into 3GB RAM!) I will work on a better waveform display.
- Slowing down playback too much caused an unrecoverable exception. This doesn’t surprise me. This is very new functionality and I have a fair idea of the cause - again an overly simplistic approach to time stretching. (I think the buffers automatically resize and this is not handled gracefully.
- The multichannel file was imported into Ardour okay but I didn’t change the import rule so it put all 16 tracks in a single Ardour track. I remove the track and reimported with the correct setting to get 16 individual tracks. (I wish it offered to import as stereo pairs.)
- There is 24ms between the synthesised drums and the recording of the same track sent out to direct output, looped physically back into an analogue input and recorded through a chain. (44100 sps, 2x256 frame buffers through a Behringer 1820 connected via USB.) That is just over 2 processing periods which is cool - one period to get the audio out and another to capture it back in. Of course I could use latency correction in the DAW to correct this but it was a contrived experiment.
- Audacity also imported the multchannel file. FYI: Recordings are 16-bit signed PCM WAV files at the native sample rate of the Zynthian which is pretty portable but maybe we could offer an option to record in any of the other supported formats (WAV, AIFF, FLAC, OGG, MP3, AAC, etc.). Audacity stuggled more than Ardour on my old laptop. (I gave up on the Chromebook - too little memory.)
- I stopped before hitting a file size limit but had forgotten that we use jack_capture which automatically splits files to avoid this issue.
- It would be advantagous to be able to record mono tracks. If there is a mono source it just wastes disk space and processing to record stereo.
Overall I am quite pleased with this experiment. It shows that Zynthian can be used as a multitrack recorder, mixer, sequencer and multi-instrument softsynth simultaneously to a reasobable quantity of channels.
Zynthasia uses these chains:
- LinuxSampler->Roomy
- LinuxSampler
- Helm
- Arpegiatore->Helm
- LinuxSampler->Roomy
- MDA DX10->MDA Delay