FL001 Preallocated headers

Preallocated headers (near-empty corrupt files) #

Problem ID Manufacturer Affected Firmware Affected Hardware Status
FL001 Frontier Labs unknown: at least most versions of v3.0+ BAR Minor problem

Often when a sensor is interrupted - through a fault, lack of space, or a power failure, fragments of files produced and left in the file system.

These fragments are often:

  • Occurs for both WAVE and FLAC files
  • small but not empty; usually around 153 bytes for FLAC files and 44 bytes for WAVE files
  • contain a RIFF and WAVE header, even if the recording format is FLAC
  • and often contain incoherent or misplaced data
    • for example: a FLAC comment could be in the data section of a WAVE struct FL001 header

    • Or fragments of a header that are mostly null bytes but still have some data in them


There is no usable information in these files and they cannot be reliably repaired.

Since these files are regularly produced, and for we suspect a variety of reasons this issue may be reflective of several smaller issues.

Status #

Minor problem: most tools fail to process these files, they are mainly an annoyance, especially since at a surface level they look like small but valid files.

Status with vendor #

It was suggested to FL they should attempt to clean up or delete such files, but this was a long time ago. No recent contact about this issue has been attempted.

Effects of the problem on common tools #


Emu has support for detecting this problem and renaming problem files: https://github.com/QutEcoacoustics/emu/blob/master/docs/fixes.md#rename-stub-files-fix-fl001

Acoustic Workbench (Ecosounds, A2O) #

Currently fail - ungracefully - to harvest files

ffmpeg/ffprobe #

Will generally produce a variety of errors such as:

[pcm_s16le @ 0x5575904db580] PCM channels out of bounds
    Last message repeated 1 times
[wav @ 0x5575904d9ac0] Failed to open codec in avformat_find_stream_info
[wav @ 0x5575904d9ac0] Estimating duration from bitrate, this may be inaccurate
[wav @ 0x5575904d9ac0] Could not find codec parameters for stream 0 (Audio: pcm_s16le ([1][0][0][0] / 0x0001), 11264 Hz, 0 channels): unspecified number of channels
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, wav, from '/data/harvester_to_do/harvest_28/sdfsdf/20211129_79/314/785/20200711_STUDY/20200711T033015+0000_REC.flac':
  Duration: 00:00:00.00, bitrate: 492 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 11264 Hz, 0 channels
[pcm_s16le @ 0x5575904de800] PCM channels out of bounds
Could not open codec for input stream 0

The metadata command will also report roughly correct values (0 duration, 0 samples) for these files.

Examples #