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Analysis Sink Stages

Analysis sink stages are terminal stages that generate diagnostics, metrics, and reports rather than producing media or hardware output. They consume processed data from upstream stages and emit analysis results intended for comparison, validation, or debugging.

Analysis sinks:

  • Do not modify video, audio, or metadata
  • Do not produce outputs that can be connected further downstream
  • Display their results in a dialog of their own and write them to a file

They are typically used to:

  • Compare capture quality across multiple sources
  • Validate signal stability and decode quality
  • Quantify the effects of transform stages such as stacking or dropout correction

Every analysis sink works the same way: trigger the stage to compute the dataset, after which its dialog opens automatically. The dataset stays with the stage, so closing the dialog and picking the tool again from the Stage Tools menu re-opens it immediately, reading what the last trigger produced without recomputing. That menu entry only ever reads: on a node that has not been triggered it says so rather than starting a decode, because deciding when to spend that time is what Trigger Stage is for. Editing any stage's parameters rebuilds the graph and discards every stage's results, closing the open viewers with them — trigger again to get a dataset that matches the new settings.

The burst level, dropout and SNR sinks measure the signal and present a chart with an optional CSV export.

A batch-analysis dialog is not the same thing as an analysis sink, and two stages that offer one live elsewhere: the Teletext Sink and the NABTS Sink are documented under Sink Stages because writing the packet stream is their product, and their page and record viewers are by-products of the same pass rather than the reason for it.

CSV output format. Each CSV is written from the full-resolution, canonical per-frame dataset — one row per frame (every analysis sink analyses every frame), with the frame's true (1-based) frame number in the first column. Units are carried in the header names (_samples, _db, _10bit) and values are plain numbers. A metric that was not measured for a frame is written as an empty field (never the string nan). The CSV is independent of the display decimation used to draw the chart, so it always contains every frame regardless of the on-screen point count.

Burst Level Analysis Sink
Stage id burst_level_analysis_sink
Stage name Burst Level Analysis Sink
Connections 1 input → no outputs
Purpose Measure colour burst level stability across fields

Use this stage when:

  • Evaluating chroma signal stability
  • Comparing multiple captures of the same source
  • Diagnosing colour amplitude fluctuations or capture issues

What it does

This stage measures the amplitude of the colour burst for each field and generates statistics describing burst level variation over time (per-field measurements plus aggregate mean, variance, min/max). After triggering, the Burst Level Analysis chart is opened automatically.

Parameters

  • output_path (file path)
    • Destination CSV file for burst metrics. Leave empty to skip file output.
  • write_csv (bool)
    • Enable writing results to CSV at trigger time.

CSV columns

frame_number, median_burst_10bit — median colour-burst amplitude (10-bit sample units) per frame; the value column is empty when not measured.

Stage tools

  • Burst Level Analysis — displays per-frame colour-burst amplitude measurements in a chart window. Opens automatically after triggering, and re-opens from the Stage Tools menu without recomputing.

Notes

  • Results are meaningful only if colour burst timing is correct upstream.
  • Masking or altering the burst region before this stage will invalidate results.
  • Connect one instance before and one after the Stacker stage to compare burst stability across captures.

Dropout Analysis Sink
Stage id dropout_analysis_sink
Stage name Dropout Analysis Sink
Connections 1 input → no outputs
Purpose Produce statistics describing dropout frequency, size, and distribution

Use this stage when:

  • Comparing dropout levels between captures
  • Evaluating the effectiveness of stacking or dropout correction
  • Identifying problematic regions of a capture

What it does

This stage reads dropout hints present in the stream (originating from the source or modified by transform stages such as dropout_map) and generates statistical summaries: total dropout count, per-field counts, size distributions, and line/field density metrics. After triggering, the Dropout Analysis chart is opened automatically.

It does not perform dropout detection or correction itself.

Parameters

  • output_path (file path)
    • Destination CSV file for dropout metrics. Leave empty to skip file output.
  • write_csv (bool)
    • Enable writing results to CSV at trigger time.
  • mode (choice: full, visible, default full)
    • full counts dropouts across the whole field; visible restricts the count to the active picture area.
  • write_report (bool)
    • Enable writing a per-dropout detail report at trigger time (one entry per dropout run).
  • report_path (file path)
    • Destination file for the detail report. Leave empty to skip report output.
  • report_format (choice: csv, text, default csv)
    • csv writes one row per dropout run; text writes a human-readable report grouped by frame.

CSV columns

frame_number, dropout_count, dropout_length_samples — one row for every frame (the sink analyses every frame). A zero row means the frame was analysed and had no dropouts; an absent frame number means the frame was not analysed.

Per-dropout detail report

Separate from the per-frame CSV, the detail report records where each individual dropout sits within its frame. It is written only when write_report is enabled with a report_path, is always full-resolution (never decimated), and honours the same mode. Coordinates are frame-flat: line_number is a 0-based line within the frame and sample_start / sample_end are 0-based, inclusive sample indices within that line, derived from the nominal samples-per-line (PAL 1135, NTSC 910). Unlike the per-frame CSV, frames with no dropouts do not appear.

  • csv — one row per run: frame_number, line_number, sample_start, sample_end, length_samples.
  • text — grouped by frame, e.g. Frame 1: 2 dropouts, 50 samples total followed by one indented line N, samples A-B (L samples) line per run.

Stage tools

  • Dropout Analysis — displays dropout frequency, size, and distribution charts. Opens automatically after triggering, and re-opens from the Stage Tools menu without recomputing.

Where the analysis reads its data

The analysis reports the dropout state at the sink's input — the dropout hints visible on the representation connected to it. To include edits made in the Dropout Map stage (added or removed dropout regions), the sink must be connected downstream of the dropout_map stage. A sink placed upstream of, or on a branch that bypasses, dropout_map sees only the original sidecar hints. Editing the map and re-triggering re-analyses from scratch, so the chart and CSV never show pre-edit data after a re-trigger.

Notes

  • Results depend on the quality of upstream dropout detection.
  • Removing or adding dropouts upstream will directly affect analysis output.
  • Connect one instance before the Stacker and one after to see the dropout reduction achieved by stacking.

SNR Analysis Sink
Stage id snr_analysis_sink
Stage name SNR Analysis Sink
Connections 1 input → no outputs
Purpose Produce signal-to-noise metrics for capture quality comparison

Use this stage when:

  • Comparing multiple captures of the same material
  • Quantifying improvements from stacking or filtering
  • Evaluating capture hardware or settings

What it does

This stage estimates signal-to-noise ratio using spatial and temporal analysis of the incoming video stream, reporting white SNR and black SNR per field along with aggregate statistics. Results are consistent across comparable pipelines, allowing meaningful cross-capture comparison. After triggering, the SNR Analysis chart is opened automatically.

Parameters

  • output_path (file path)
    • Destination CSV file for SNR metrics. Leave empty to skip file output.
  • write_csv (bool)
    • Enable writing results to CSV at trigger time.
  • mode (choice: white, black, both, default both)
    • Selects which SNR metrics to measure.

CSV columns

frame_number, white_snr_db, black_psnr_db — white SNR and black PSNR (dB) per frame. A column is empty when that metric was not measured (for example, mode = white leaves black_psnr_db empty).

Stage tools

  • SNR Analysis — displays white SNR and black SNR metrics over time in a chart window. Opens automatically after triggering, and re-opens from the Stage Tools menu without recomputing.

Notes

  • Meaningful SNR comparison requires aligned sources.
  • Use source_align and stacker appropriately upstream when comparing captures.
  • Stacking improves SNR only where sources contain independent noise; identical sources will not show an SNR improvement on dropout-free areas.

Notes on Analysis Sink Stages

  • Analysis sink stages terminate pipeline branches.
  • Multiple analysis sinks may consume the same upstream output.
  • Analysis sinks are side-effect-free with respect to media data.
  • Results are intended for diagnostics, comparison, and validation—not for further pipeline processing.