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Get Metadata

Retrieves detailed metadata information from an audio segment including duration, quality settings, and amplitude metrics.

Common Properties​

  • Name - The custom name of the node.
  • Color - The custom color of the node.
  • Delay Before (sec) - Waits in seconds before executing the node.
  • Delay After (sec) - Waits in seconds after executing node.
  • Continue On Error - Automation will continue regardless of any error. The default value is false.
info

If the ContinueOnError property is true, no error is caught when the project is executed, even if a Catch node is used.

Inputs​

  • Audio Segment ID - The ID of the audio segment to retrieve metadata from.

Options​

This node does not have any configurable options.

Output​

  • metadata - An object containing detailed audio metadata with the following properties:
    • length_ms - Duration of the audio in milliseconds
    • frame_rate - Sample rate in Hz (e.g., 44100, 48000)
    • channels - Number of audio channels (1=mono, 2=stereo)
    • frame_width - Size of each frame in bytes
    • sample_width - Size of each sample in bytes
    • dbfs - Average loudness in dBFS (decibels relative to full scale)
    • max_dbfs - Peak loudness in dBFS
    • rms_amplitude - Root mean square amplitude value

How It Works​

The Get Metadata node analyzes an audio segment and extracts technical information. When executed, the node:

  1. Validates the segment ID is not empty
  2. Retrieves the audio segment from memory
  3. Analyzes the segment's properties
  4. Calculates amplitude and loudness metrics
  5. Handles special cases (like infinite values for silent audio)
  6. Returns a metadata object with all information

Requirements​

  • Valid audio segment ID (from Create, Slice, Concatenate, etc.)
  • Segment must exist in memory

Understanding Metadata Properties​

length_ms (Duration)​

  • Audio duration in milliseconds
  • Example: 5000 = 5 seconds
  • Use for: Timing calculations, validation, progress tracking

frame_rate (Sample Rate)​

  • Number of samples per second
  • Common values:
    • 8000 Hz - Telephone quality
    • 22050 Hz - Low quality
    • 44100 Hz - CD quality (standard)
    • 48000 Hz - Professional audio/video
    • 96000 Hz - High-resolution audio
  • Use for: Quality assessment, conversion planning

channels​

  • Number of audio channels
  • Values:
    • 1 = Mono (single channel)
    • 2 = Stereo (left and right)
    • 5.1, 7.1 = Surround sound (rare in typical processing)
  • Use for: Format determination, conversion decisions

frame_width​

  • Number of bytes per frame
  • Calculated as: sample_width × channels
  • Use for: Technical analysis, memory calculations

sample_width​

  • Number of bytes per sample
  • Common values:
    • 1 byte = 8-bit audio
    • 2 bytes = 16-bit audio (standard)
    • 3 bytes = 24-bit audio
    • 4 bytes = 32-bit audio
  • Use for: Quality assessment, compatibility checks

dbfs (Average Loudness)​

  • Decibels relative to full scale
  • Range: -∞ to 0 dB
  • Values closer to 0 are louder
  • Example values:
    • 0 dBFS = Maximum possible level (clipping)
    • -3 dBFS = Very loud
    • -12 dBFS = Moderate volume
    • -20 dBFS = Quiet
    • 0 = Complete silence (converted from -∞)
  • Use for: Loudness normalization, quality control

max_dbfs (Peak Loudness)​

  • Maximum loudness level in the audio
  • Same scale as dbfs
  • Should be < 0 to avoid clipping
  • Use for: Detecting peaks, preventing distortion

rms_amplitude (Root Mean Square)​

  • Average signal strength
  • Linear scale (not decibels)
  • Higher values = louder audio
  • 0 = Silence
  • Use for: Loudness calculations, normalization

Error Handling​

The node will return specific errors in the following cases:

  • Audio segment ID is empty or null
  • Audio segment with the specified ID does not exist
  • Segment has been deleted

Usage Examples​

Example 1: Check Audio Duration​

Verify audio length before processing:

  1. Create audio segment from file
  2. Use Get Metadata to retrieve metadata
  3. Use Condition node to check if {{msg.metadata.length_ms}} > 10000 (10 seconds)
  4. Process accordingly

Example 2: Validate Audio Quality​

Ensure audio meets quality requirements:

  1. Create segment from uploaded file
  2. Get Metadata
  3. Check if frame_rate 4 or greater4100
  4. Check if channels == 2 (stereo required)
  5. Accept or reject based on criteria

Example 3: Calculate Processing Time​

Estimate how long operations will take:

Duration in seconds = metadata.length_ms / 1000
Estimated processing time = duration × complexity_factor

Example 4: Detect Silent Audio​

Check if audio is actually silent:

  1. Create segment
  2. Get Metadata
  3. If dbfs == 0 or rms_amplitude == 0, audio is silent
  4. Handle accordingly (skip, reject, etc.)

Example 5: Loudness Normalization Decision​

Determine if loudness adjustment is needed:

  1. Get Metadata from segment
  2. If max_dbfs > -1, audio may be clipping
  3. If dbfs < -20, audio is too quiet
  4. Apply appropriate processing based on values

Example 6: Format Information Display​

Show audio properties to users:

Duration: {{msg.metadata.length_ms / 1000}} seconds
Quality: {{msg.metadata.frame_rate}} Hz, {{msg.metadata.channels}} channel(s)
Loudness: {{msg.metadata.dbfs}} dBFS average

Usage Notes​

  • Metadata extraction is very fast (milliseconds)
  • The operation is non-destructive - doesn't modify the segment
  • Metadata reflects the current state of the segment
  • For transformed segments (sliced, sped up), metadata shows the result
  • Infinite values (for silent audio) are automatically converted to 0
  • Use metadata for validation, decision-making, and quality control
  • Metadata can be logged for auditing and debugging

Practical Applications​

Quality Assurance​

1. Get Metadata
2. Check frame_rate >= 44100 (CD quality)
3. Check channels == 2 (stereo)
4. Check max_dbfs < -1 (no clipping)
5. Accept/reject based on criteria

Conditional Processing​

1. Get Metadata
2. If length_ms < 60000, skip processing (too short)
3. If length_ms > 3600000, split into chunks (too long)
4. Otherwise, process normally

Batch Processing Statistics​

1. Process multiple files
2. Get Metadata for each
3. Calculate:
   - Total duration
   - Average quality
   - Format distribution
4. Generate report

Loudness Analysis​

1. Get Metadata
2. Check dbfs value:
   - > -6: Too loud, needs reduction
   - -12 to -6: Good level
   - < -20: Too quiet, needs boost
3. Apply appropriate gain adjustment

Understanding Audio Levels​

dBFS Scale​

  • 0 dBFS = Maximum possible level (digital ceiling)
  • Every -6 dB represents approximately half the amplitude
  • Professional standards:
    • Podcasts: -16 to -20 dBFS average
    • Music: -9 to -13 dBFS average
    • Broadcast: -23 dBFS average (LUFS)

Preventing Clipping​

  • Keep max_dbfs below -1 dBFS
  • Leave headroom for processing
  • Use metadata to detect potential clipping

Common Use Cases​

  • Validating uploaded audio files
  • Checking audio duration for scheduling
  • Ensuring audio quality meets requirements
  • Detecting silent or corrupt audio files
  • Calculating processing estimates
  • Generating audio file reports
  • Quality control in batch processing
  • Conditional workflow routing
  • Loudness normalization preparation
  • Format compatibility checks
  • Generating audio inventories
  • Debugging audio processing issues

Best Practices​

  • Check metadata before heavy processing operations
  • Use duration to estimate processing time
  • Validate audio quality early in workflows
  • Log metadata for troubleshooting
  • Set clear quality thresholds for your use case
  • Handle edge cases (silent audio, corrupt files)
  • Use metadata for conditional branching
  • Store metadata with processed files for documentation
  • Create validation rules based on your requirements
  • Monitor loudness levels to prevent clipping

Metadata in Decision Making​

Example Decision Tree​

Get Metadata
↓
Check length_ms:
  < 1000ms → Too short, reject
  > 7200000ms → Too long, split
  Otherwise → Continue
↓
Check frame_rate:
  < 44100 → Convert to higher quality
  >= 44100 → Accept
↓
Check channels:
  1 → Convert to stereo if needed
  2 → Accept
↓
Check max_dbfs:
  > -1 → Apply limiter to prevent clipping
  < -1 → Continue
↓
Process audio

Integration with Other Nodes​

Works seamlessly with:

  • Create - Get metadata immediately after loading
  • Convert - Verify conversion success
  • Slice - Check duration of sliced segments
  • Concatenate - Verify combined segment properties
  • Speedup - Confirm duration changes
  • Condition - Use metadata for branching logic
  • Log - Record metadata for auditing

Performance Tips​

  • Get metadata once and store in variables
  • Use metadata early to avoid processing invalid files
  • Cache metadata for repeated checks
  • Metadata extraction has minimal overhead
  • No need to worry about performance impact

Troubleshooting​

All values are 0​

  • The audio segment is silent or empty
  • Use Create with Silent format if intended

Unexpected frame_rate​

  • Audio was converted from another format
  • Check source file specifications

High max_dbfs (close to 0)​

  • Audio may be clipping (distorted)
  • Consider applying gain reduction

Very low dbfs (< -30)​

  • Audio is very quiet
  • May need amplification or boost