Signal State Preset Definitions¶
This document is part of the CVBS File Format Specification. It contains the normative Signal State Preset definitions referenced in the Signal State Presets section of that specification.
Naming convention: Signal State Preset names follow the pattern <RATE>_<TBC>_<LOCK>, where <RATE> is STANDARD (4×fsc) or NONSTANDARD, <TBC> is TBC or RAW, and <LOCK> is LOCKED or UNLOCKED. The RAW state implies unlocked (a raw signal with no TBC cannot be burst-locked in a stable sense), so <RATE>_RAW presets do not include a _LOCKED / _UNLOCKED suffix.
A Signal State Preset captures three independent axes of the signal's processing state:
| Axis | Standard state | Non-standard state |
|---|---|---|
| Sample rate | Exactly 4×fsc for the declared Video Standard Preset | Non-standard (e.g., oversampled at 28.6 MHz or 40 MHz) |
| TBC applied | Yes — fixed samples per line, stable timing | No — line lengths vary, timing is raw |
| Burst locked | Yes — subcarrier phase is stable and known | No — subcarrier phase drifts or is unknown |
These axes are independent. In particular, a file can be TBC'd but not burst-locked (e.g., standard NTSC .tbc output from ld-decode or vhs-decode: timing is corrected but the subcarrier phase at each field is not anchored to a canonical 0° reference), and a file at a non-standard sample rate can still have TBC applied (oversampled TBC output).
The preset governs several aspects of format interpretation:
- Normative field sizes as defined by the declared Video Standard Preset in video-standard-presets apply only when
tbc_applied = TRUEand the sample rate is the standard 4×fsc. Without TBC there is no guarantee of a fixed sample count per line, so consumers must not infer fixed per-field byte sizes from presets alone. - Signal level compliance is only meaningful when
tbc_applied = TRUEand the Sample Encoding Preset isCVBS_10BIT. A raw RF capture contains signal levels that bear no relation to the preset's reference sample values. - Sample-coordinate anomaly annotations (for example dropout coordinates) are only stable when lines have a fixed, known length, i.e., when TBC has been applied. Such annotations are extension metadata, not part of the core schema.
- Subcarrier phase analysis requires knowing whether burst locking was applied so that consumers can determine whether phase continuity can be assumed between fields.
Preset: STANDARD_TBC_LOCKED¶
| Property | Value |
|---|---|
| Sample rate | Standard 4×fsc for the declared Video Standard Preset |
| TBC applied | Yes |
| Burst locked | Yes |
Typical source: cvbs-encode synthetic output; broadcast-grade capture; ld-decode / vhs-decode PAL .tbc output when Sc/H locked.
Normative field sizes: Apply as defined by the declared Video Standard Preset in video-standard-presets.
Signal level compliance: Required when Sample Encoding Preset is CVBS_10BIT.
Extension anomaly annotations: Valid and meaningful if an extension format provides them.
Preset: STANDARD_TBC_UNLOCKED¶
| Property | Value |
|---|---|
| Sample rate | Standard 4×fsc for the declared Video Standard Preset |
| TBC applied | Yes |
| Burst locked | No |
Typical source: ld-decode / vhs-decode NTSC .tbc output — timing corrected but subcarrier phase not anchored to a canonical reference.
Normative field sizes: Apply as defined by the declared Video Standard Preset in video-standard-presets.
Signal level compliance: Required when Sample Encoding Preset is CVBS_10BIT.
Extension anomaly annotations: Valid and meaningful if an extension format provides them.
Preset: STANDARD_RAW¶
| Property | Value |
|---|---|
| Sample rate | Standard 4×fsc for the declared Video Standard Preset |
| TBC applied | No |
| Burst locked | No |
Typical source: A signal sampled at the standard rate but without time-base correction applied — e.g., a synchronous ADC capture at the standard 4×fsc rate before any TBC processing.
Normative field sizes: Do not apply.
Signal level compliance: Not required.
Extension anomaly annotations: Per-line/sample coordinates are generally not stable and should not be emitted.
Preset: NONSTANDARD_TBC_LOCKED¶
| Property | Value |
|---|---|
| Sample rate | Non-standard (e.g., 28.6 MHz, 40 MHz) |
| TBC applied | Yes |
| Burst locked | Yes |
Typical source: Oversampled TBC output; a burst-locked TBC applied after raw oversampled capture.
Normative field sizes: Do not apply at field sample counts defined for standard 4×fsc presets in video-standard-presets.
Signal level compliance: Not applicable for CVBS_10BIT amplitude values; consumers must use calibration data to map sample values to analogue levels.
Extension anomaly annotations: Valid (sample coordinates are stable because TBC was applied), but coordinates reference samples at the non-standard sample rate.
Preset: NONSTANDARD_TBC_UNLOCKED¶
| Property | Value |
|---|---|
| Sample rate | Non-standard (e.g., 28.6 MHz, 40 MHz) |
| TBC applied | Yes |
| Burst locked | No |
Typical source: Oversampled TBC output where subcarrier phase is not stabilised.
Normative field sizes: Do not apply.
Signal level compliance: Not applicable.
Extension anomaly annotations: Valid for stable sample coordinate references.
Preset: NONSTANDARD_RAW¶
| Property | Value |
|---|---|
| Sample rate | Non-standard (e.g., 28.6 MHz, 40 MHz) |
| TBC applied | No |
| Burst locked | No |
Typical source: DomesdayDuplicator raw RF capture; raw ADC output at any non-standard rate.
Normative field sizes: Do not apply.
Signal level compliance: Not applicable.
Extension anomaly annotations: Per-line/sample coordinates are generally not stable and should not be emitted.