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discontinuous recording XR18 / HTC10

I have done a first attempt in recording using the USB Audio Recorder Pro, with the following:

- Behringer XR18 "Stagebox"-style Mixing desk, offering 18 Channels of USB I/O
- USB-Type B to USB-C OTG adapter cable
- HTC 10 running Android 8.0.0,fast SD-Card
- USB Audio recorder Pro (paid version) with default settings, selected Multi-channel recording

I have recorded a live band for around 2 hours. The resulting WAV files (9 files) contain 32-bit float stereo tracks, and are around 2GB each

This all went smooth. However, in post procesing, I noted, that every few minutes, there is a ~5 second long audio segment missing, and replcaed with a later  segment (and hence duplicated).

To illustrate:

I would expect 
   [...][t-2][t-1][t  ][t+1][t+2][...]
but I get
(each "[]" denotes a 5-scond audio block):

This happens on all 18 channels at the very same instant, and reappears every 4-5 minutes. 

At this stage, I am asking where you would suspect the issue to come from, and recommendations/experience how to work around this:

- Could this "buffer skip and repeat next buffer" be on the phone side? The phone was not used for anything else during the recording  time, but was connected to both Wifi and 4G. 
- Could a buggy OTG cable cause this?
- Would increasing buffer size in the App, or any other tweaking cure this?
Would it help to activate airplane mode on the phone?

Any help appreciated

We are sorry to hear that. Basically, the more channels an interface has, the more chance there is on problems unfortunately, since the app/driver does not run in a real-time thread. Increasing the buffer size to the max. should help, as will activating airplane mode. However, if you are talking about 5 second long audio segments, that means something went wrong with the disk buffers not writing fast enough to the SD card. I'm not sure if that can be solved. I assume you selected the external SD card in the app's base directory setting? Please also note that /mnt/sdcard is the internal storage.
Thank you for your reply and thoughts on this.

(yes, I am storing to the external SD card - albeit this is a bit cumbersome as I have not been able to store anywhere outside of the app's directory due to Android app permissions, and the app's directory is a bit deep down in the folder hierarchy)

I take from your response 
  • that the OTG cable can be ruled out as the culprit
  • that I should try again with both airplane mode and a larger buffer size
  • that your are sceptical that this works, as the symptoms would point more towards a too slow sd card
I have benchmarked the SD Card, and it gives my around 28MB/s, so I would think that this should be plenty for the ~4MB/s I would expect from recording 18 x 48kHz 32-bit Channels

I will report back after the next attempt with increased buffers and airplane mode and see whether this has improved

following up on this, I am happy to report success.

After having increased the buffer size to the maximum and enabling airplane mode, I have successfully recorded 2 gigs two hours each with multitrack, and all the glitches I had reported earlier are gone. Really happy to have such a handy and well-functioning available now

Thanks for your help


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