Overview

The Scanner module is the entry point for your subs in ALS.

It is responsible for:

• Monitoring the appearance of subs in the scan folder
• Loading the detected subs

Configuration

	Source	Data Type	Required	Default Value
Scan Folder	Preferences: General Tab	Path to a folder	Yes	∅
Profile	Preferences: General Tab	Choice: EAA / photo	Yes	EAA
Memory Use	Preferences: General Tab	fuzzy	Yes	“Unfair”

Control

Source	Type	Response
Interface: Session Controls	Command: STOP	Scan folder monitoring: OFF
Interface: Session Controls	Command: START	Scan folder monitoring: ON
System event	sub detected in the scan folder	Load the detected sub

Input

Data	Type
Path to the detected sub	Path to a file

Behavior

flowchart LR
    START([Sub detected])
    
    WAIT_FILE[Wait for file<br><br>According to profile:<br>EAA: 10ms<br>Astrophoto: 1500ms]
    WAIT_RAM[Wait 20ms]
    
    CHECK_RAM{{Check available RAM<br><br>According to preferences:<br>Greedy: 256 MiB<br>Unfair: 512 MiB<br>Fair: 1 GiB<br>Cautious: 2 GiB<br><br>OK?}}
    CHECK_SIZE{{Check file size<br><br>OK?}}
    TEST_FORMAT{{Check file format}}
    
    FITS[Load FITS]
    STANDARD[Load standard]
    RAW[Load Raw]
    
    METADATA[Extract metadata]
    
    END((End))
    
    START ---> CHECK_RAM   
    WAIT_RAM <-->|NO| CHECK_RAM
 
    
    CHECK_RAM --->|YES| CHECK_SIZE
    WAIT_FILE <-->|NO| CHECK_SIZE   
    CHECK_SIZE -->|YES| TEST_FORMAT

    TEST_FORMAT -->  FITS
    TEST_FORMAT -->  STANDARD
    TEST_FORMAT -->  RAW
    

    RAW --> METADATA
    FITS --> METADATA
    
    STANDARD ---> END
    METADATA --> END
    
    classDef bounds fill: #333, stroke: #666, stroke-width: 2px, color: #BBB, font-family: 'Poppins', sans-serif
    classDef step fill: #444, stroke: #662, stroke-width:2px, color: #c6c6c6, font-family: 'Poppins',sans-serif
    classDef wait  fill: #444, stroke: #262,stroke-width: 2px, color: #c6c6c6, font-family:'Poppins', sans-serif
    classDef test fill: #444, stroke: #226, stroke-width: 2px, color: #c6c6c6, font-family: 'Poppins', sans-serif
    
    class START bounds
    class WAIT_FILE wait
    class WAIT_RAM wait
    class CHECK_RAM test
    class CHECK_SIZE test
    class TEST_FORMAT test
    class FITS step
    class STANDARD step
    class RAW step
    class METADATA step
    class END bounds

RAM Test

Wait until the available RAM is greater than the configured value:

Memory Use	Amount of Memory Left for the System
Greedy	256MiB
Unfair	512MiB
Fair	1GiB
Scared	2GiB

Wait for Complete File

Files are detected as soon as they appear in the scan folder.

To ensure file is complete before loading it:

• Poll the size of the detected file in a loop
  • Verify that the file size is stable over 2 consecutive polls

The polling interval depends on the configured profile:

Profile	Polling Interval
EAA	10ms
Astrophoto	1500ms

Image Loading

Compatible Formats

The file is loaded into memory using the format matching its filename extension.

Extension	Format
.jpg .jpeg	JPEG
.png	PNG
.tiff .tif	TIFF
.fits .fit .fts	FITS
All other extensions	Raw

Raw files are loaded using the libRaw library. See the list of supported cameras

Metadata Extraction

Supported for:

• FITS
• Raw

Metadata extracted from file and incorporated into the loaded image:

• Exposure Time
• Bayer Matrix (for subs from a color sensor)
  • FITS files: BAYERPAT header
  • Raw files: standard Exif header

Output

The loaded image is broadcast to whoever listens.

⚙️ ALS will put the image in the Preprocess module’s input queue for calibration