Frame scope¶
The Frame-scope is an interactive signal inspection tool within decode-orc that allows detailed examination of individual video lines at the sample level. Like the Preview dialogue, it is not a pipeline stage, but a UI analysis tool that attaches to preview-capable stages.
The Frame-scope is primarily intended for low-level signal analysis, making it possible to inspect timing, levels, noise, burst structure, and dropout behaviour with precision that is not possible from image-based preview alone.
Renamed in v2.0: This dialogue was called the Line-scope in Decode-Orc 1.x.
Purpose and use cases¶
The Frame-scope is used to:
- Inspect raw luma and chroma waveforms
- Verify sync tip, blanking, black, white, and peak levels in CVBS_U10_4FSC 10-bit units and in millivolts
- Examine colour burst amplitude and phase
- Diagnose noise, ringing, or capture artefacts
- Validate dropout detection and correction behaviour
- Compare line data before and after transform stages
It is especially valuable when working with:
- Analogue captures
- LaserDisc RF-derived signals
- PAL/NTSC timing and level issues
- Dropout-heavy or marginal sources
Attaching the Frame-scope¶
The Frame-scope attaches to the currently previewed stage and reflects the same frame and timing context as the Preview dialogue.
When active, it operates on:
- The currently selected frame (identified by
FrameID) - A single selected frame line (0-based frame-flat index)
- The post-stage output signal (including all upstream transforms)
Core Frame-scope features¶
Line selection and numbering modes¶
The user selects a specific line using one of four numbering modes:
| Mode | Description |
|---|---|
| Frame flat (0-based) | Raw 0-based frame line index, as stored internally |
| Frame sequential (1-based) | 1-based sequential line number within the frame |
| Field relative | Line number within the field (1-based), prefixed by field number |
| Broadcast interlaced | Standard broadcast line number per ITU-R BT.470-6 / SMPTE 170M-2004 |
The selected mode is shown in a drop-down and remembered per video system. Switching mode does not change the selected line; only the displayed label changes.
Key characteristics:
- Line indices reflect any upstream re-mapping or masking
- PAL lines correctly handle the four 1136-sample non-orthogonal positions
- The correct sample count per line (1135 or 1136 for PAL) is shown in the display header
Sample-level waveform display¶
The Frame-scope displays signal amplitude per sample across the selected line.
The Y axis extends below 0 mV (to sync tip and below) and above 100 IRE (to peak and beyond) — no arbitrary clamping of the display range. When a sample value outside [sync_tip, peak] is present, the axis expands to include it.
The waveform typically includes:
- Sync tip
- Back porch
- Colour burst (if present)
- Active video region
Reference level markers are drawn at all five normative levels with their standard name and mV value:
| Level | PAL (mV) | NTSC (mV) |
|---|---|---|
| Sync tip | −300 | −286 |
| Blanking | 0 | 0 |
| Black | +54 | +54 |
| White | +700 | +714 |
| Peak | +933 | +900 |
Amplitude is shown in millivolts, derived per ITU-R BT.1700-1 / SMPTE 170M-2004 §11.4.
Channel views¶
Depending on pipeline configuration and stage capabilities, the Frame-scope may support viewing:
- Luma (Y)
- Chroma (composite or decoded)
- Combined signal (where applicable)
The exact available channels depend on the upstream stages and signal type.
Interaction with transform stages¶
The Frame-scope reflects exactly what a downstream stage will see.
Examples:
- After
video_params, black/white level overrides are visible immediately. - After
mask_line, masked regions appear flattened at the configured mask sample level. - After
dropout_correct, corrected samples can be inspected directly. - After
stacker, per-sample noise reduction effects are visible.
This makes the Frame-scope ideal for validating the numerical effect of transforms.
Dropout and correction inspection¶
When dropout hints are present, the Frame-scope can be used to:
- Inspect the original corrupted samples
- Verify the extent of dropout regions
- Confirm that replacement data is reasonable
- Compare corrected vs uncorrected behaviour by toggling upstream stages
When highlight_corrections is enabled upstream, corrected regions appear clearly in the waveform.
Timing and stability analysis¶
The Frame-scope is frequently used to:
- Verify horizontal timing stability
- Inspect sync edge shape and jitter
- Check burst placement and consistency
- Compare timing between aligned sources
These checks are essential when diagnosing capture hardware issues or alignment problems.
Limitations¶
- The Frame-scope is read-only and non-destructive.
- Only one line can be inspected at a time.
- Performance depends on pipeline complexity and preview position.
- Some sink-only or hardware-output stages do not support Frame-scope attachment.
Typical Frame-scope workflows¶
Common workflows include:
- Inspecting colour burst before and after chroma-related transforms
- Verifying black/white levels after
video_params - Examining dropout regions before applying correction
- Comparing stacked vs unstacked signal noise
- Diagnosing capture artefacts at the sample level
Notes on Frame-scope usage¶
- The Frame-scope always reflects the current preview frame and stage.
- Frame-scope analysis complements, rather than replaces, image-based preview.
- For accurate interpretation, ensure video parameters upstream are correct.
The Frame-scope is a critical tool for decode-orc's low-level, signal-focused workflows, providing visibility into the exact waveform data that underpins all higher-level processing.