URec384k - Underwater Acoustic Recorder
CONTINUOUS RECORDING OVER DAYS
One customer reported the need to program a repeated recording scheme with continuous recording over days.
The android programming software does NOT allow a pause, between repeated recordings, of less than one minute.
The same software does NOT allow to schedule repeated tasks for recordings longer than 23:59 hours with a trailing 00:01 pause.
We have been searching for alternative solutions in order to deliver the required feature quickly without having to recompile and re-test a new firmware.
What we have tested
Manually editing the XML file written on the mSD can help in solving this issue.
We have tested two changes:
1. manually setting the pause to 0 - zero DOES NOT work. The system correctly starts and follows the schedule until the end of the first round. Then meets the zero pause and stops due to the zero value, which is considered as an error.
2. manually setting the duration of the repeated cycle to a period longer than 23 hrs. This solution worked and allowed to set a recording cycle of 72 continuous hours. The system did not meet any error during the tests and nearly all files resulted identical in duration (set to 1 hour in the example).
The sample code used (to be edited by the end-user) is reported here.
At the same link you can find two directory listings showing the list of files obtained with the provided XML.
The error in file length shown in one shorter file is probably due to a delay in file writing on the mSD. It corresponds to a negligible 0.3 sec of missing data.
The firmware is designed to preserve the integrity of recorded data.
This could lead, under some circumstances, to a fragmentation of the recorded files within the sampled period.
WHEN THIS HAPPENS:
This behavior is rarely predictable. It depends on both the mSD card used for acoustic recording (brand, model, production batch), its capacity and its level of free space.
The issue happens when a DATA WRITE DELAY event is detected.
HOW IT IMPACTS DATA:
When a delay in writing data is detected by the firmware, the file is closed to preserve data integrity, and a subsequent file is opened. The pending data are written to the new file, which is timestamped accordingly.
WHAT SHOULD I DO TO ANALYZE DATA:
If your analysis is statistical then there should be not problem in keeping the files fragmented. Files will be correctly timestamped and the period to be statistically analyzed can be selected independently from the total number of files in the range.
If you need to stitch the files in order to have a consistent duration set of files then we have checked a simple procedure you can follow. See below.
CURRENT STATUS OF THE ISSUE:
We are testing to find a radical solution to solve this issue.
The software you can use to stitch file together and the tested procedure.
1. download and install FRE:AC software. It's free and reliable.
2. in the main window, on the bottom right, select ENCODE TO A SINGLE FILE (YES)
3. select WRENCH (setup) —ENCODER — WINDOWS WAVE FILE OUTPUT
4. USE INPUT FOLDER AS OUTPUT IF POSSIBLE
5. FILENAME PATTERN: FILENAME (and specify the filename scheme you prefer)
6. on the right: ENCODE TO A SINGLE FILE
Check the files you want to stitch (concatenate)
Select the name of the first file in the group and copy it in the clipboard (CTRL-C)
Drag and drop the group of files into FRE:AC
Run the software.
The program asks for a filename for the generated file. Paste the name of the first file and add a suffix you like (we use _CONC)
the generated file will have the name of the first file of the group xxx+_CONC.WAV and will contain the stitched audio of the whole group.