C3500 USB Recording Glitches

[Ethan]

When processing a USB file recorded on a C3500 (firmware 1.72) the audio sometimes glitches. The problem is intermittent and not easy to reproduce.

I’ve imported glitched files from USB into various audio and video players / editors on both Mac and PC (VLC, Audacity, Davinci Resolve, Final Cut) and the glitches are always evident in recordings that contain the glitches. So it would seem the problem is in the USB recording itself and not in the post/editing process.

I edited and attached a short .mp3 excerpt of an example glitch that occurred 13 minutes into an hour long choral recording at our church. The glitch is heard at approx 8.4 seconds in the attached file, and another glitch at approximately 10 seconds.

Some recordings have no problems. In others it occurs 2 or 3 times during an hour long recording. It sounds as though the audio is jumping around, as though some internal buffers are being sent out of sequence by the C3500 for recording to the USB, or perhaps sent more than once.

The USB is always freshly formatted by the C3500 before a recording is started. The USB drive is a Samsung MUF-32BA/AM – a USB3.0, 32GB flash drive, rated at a write speed of 150MB/s, way faster than required. Not sure what to do to troubleshoot this or otherwise resolve the problem.

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[Ethan]

One other thing: The recording is StMtx1, which contains the L&R mains and some extra ambient mics.

[Scott]

That sounds like write lag which would be the USB device itself not keeping up with the bit rate. Have you tried using a USB stick with a higher write capacity? I think that might solve the problem.

[Ethan]

Hi Scott – and thanks for the reply. Appreciate it!

When you say higher write capacity, do you mean a higher write rate per second? While this might be a solution, the specs tend to suggest otherwise, which is what caused us to get the Samsung USB sticks. The thinking in selecting a USB stick was as follows:

– According to the dLive Firmware Reference Manual the dLive writes stereo .wav data to the USB at a rate of “approximately 34MB per minute.”
– This USB drive was selected because it has fast specifications, rated at 150MB per second (megabytes not megabits, and seconds not minutes).
– 150MB per second is equivalent to 9,000 MB per minute (150 * 60 = 9,000).
– 9,000 MB per minute is 264.7 times faster than the rate at which the dLive is writing data to the USB (9,000 / 34 = 264.7).
– Thus, we though the USB stick would be mare than fast enough.

Granted, the Samsung spec indicates “up to 150MB/sec” and does not differentiate between read and write rates, nor does it specify a sustained / continuous read or write rate. At the time we bought the dLive system, this seemed to be the fastest USB stick we could find. Maybe the sustained write rate is not quite fast enough?

Just in case though, if there’s a USB stick that is known to record dLive audio data with 100% reliability, I’ll gladly switch. Any suggestions?

[SteffenR]

sorry to say that… 100% reliability is not possible with USB sticks…

I had good results with many of them, even some no name unbranded ones but had some failures now and then with some others
you need to test it yourself

btw the needed write rate is around 5 MByte per second, so most USB sticks will provide that… but…

[Author]

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