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Default: Waiting time to consider before removing SD card?

Dear community,

I have used the default switch for continuous outdoor recordings (Nov 12-14) , however, I noticed that from three days two entire days of recordings are missing. Audiomoth created three folders but only one folder contained WAV files.

I switched Audiomoth from Default to USB/OFF and removed the 64 GB SDXC card. So I wondered whether I should have waited a bit longer before removing the SD card to give Audiomoth time to write the WAV files?

Also, there seems to be a mess up with the time and date settings, although I used the Time App and clearly told the Configurator to use "Local time".

For example, on day one (Nov 12) the folder "20221112" has been created, containing a WAV file with zero bytes.

Weirdly, the second folder was named "19700101" with three WAV files of 10GB.

The third folder "19700102" also contained a zero bytes WAV file.

I used three Varta alkaline batteries (each with 2800 mAh)

I would be grateful for any input!!

Thank you

Anton

is missing. it did not using an AudioMoth-Firmware-Basic (1.8.1)

5 comments

5 Comments

anton.baotic

Nov 15, 2022

Alex, thank you so so much for help!!

Alex Rogers

Nov 15, 2022

Hi, The files are written continuously while recording so switching to USB/OFF isn't causing this problem. If you wait until the AudioMoth has stopped flashing the red LED then the SD card is safe to be removed. In this case, the AudioMoth has lost the time setting for some reason. Hence the folder formats have been reset to 19700101 - 1st Jan 1970 00:00 - which is 0 in the 32-bit Unix timestamp format. The fact that there are also 0 length WAV files suggests that either the battery has gone flat, or the SD card is full up. Make sure that you reformat the card, rather than just delete the files, between use as many OS will just hide the files and the file allocation table becomes full. I think in this case it is more likely the battery. If you check the header information on one of the last files recorded, or one that is shorter than expected, you may see it reporting that the battery voltage was low. You can use the AudioMoth Filter Playground for this - https://playground.openacousticdevices.info. In general, you should probably set a 00:00 - 24:00 recording period, and a recording time of 1795 seconds with a sleep period of 5 seconds, and use CUSTOM mode to make these recordings, as then the start will be on round 30 minute intervals (e.g. 00:00, 00:30, etc). What make and model of SD card were you using? We recommend SanDisk Extreme 64GB cards for most deployments. Alex

anton.baotic

Nov 15, 2022

Replying to

Hi Alex,

Thank you so much for swift and helpful response!

The only Wav files written were:

19700101_010003.WAV (4.29 GB)

19700101_132541.WAV (1.93 GB)

19700101_132542.WAV (4.29 GB)

I used the AudioMoth Filter Playground for the 1.93GB as you suggested and it says:

AudioMoth 247475035FDF1F95

Recorded at 13:25:42 01/01/1970 (UTC+1) by AudioMoth

247475035FDF1F95 at low gain while battery was 4.1V and temperature was 25.2C. Recording stopped due to switch position change.

I used a SanDisk Ultra 64GB with ExFat.

If I set the recording period to 00:00 - 24:00 and use CUSTOM, I assume Audiomoth starts at midnight and not immediately?

Would you recommend using a recording time (e.g. 1795s) or would it be OK to disable this function? I was just afraid that Audiomoth might have difficulties with handling a 10-12 GB WAV file

Once again, thank you so much!

Anton

Alex Rogers

Nov 15, 2022

Replying to

Hi Anton, If you use CUSTOM mode, the recording will start immediately but will be aligned to the sleep/record cycle so that all recordings will start on the same nicely rounded timestamp (e.g. every hour, every 30 minutes, etc). WAV files can only be 4.3GB in size due to the use of a 32-bit value to indicate their size. This is about 12 hours and 25 minutes at 48kHz. If you use DEFAULT mode, AudioMoth will make a continuous recording and will close and re-open the file when the 4.3GB file size is reached.

This means that the files will have strange start and stop times, and if there is an SD card write error within that 12-hour period the file may not be readable. It also makes it hard to use the file. Short files tend to work better. Alex

Alex Rogers

Nov 15, 2022

Replying to

If possible use SanDisk Extreme card (not Extreme Pro). They are quieter than SanDisk Ultra cards and we haven't had any issues with these cards.