SSTV.org.uk

Wraase mode

Wraase SC2 30

Wraase family analog SSTV operation and compatibility reference.

Supported in app

Mode sample

BBC-style colour test card and app-generated audio

The image is generated locally for this mode's raster. For supported modes, the audio sample is encoded from that image with the SSTV Signal Desk transmitter code, then published as lossless FLAC for static playback.

FLAC, 48 kHz, 16-bit mono, 33.079 s.

SC2-30 SSTV BBC-style colour test card
SC2-30 source card, 320 x 128
SC2-30 SSTV round-trip decoded test card
Receiver decoded SC2-30 from the FLAC-restored WAV, 128 lines.

Round-trip decode evidence

Encoded, compressed losslessly, restored, then decoded.

The published FLAC is restored to WAV and passed through the SSTV Signal Desk receiver sample harness. The receiver decoded SC2-30 from the FLAC-restored WAV and wrote 128 image lines for this SC2-30 test card.

Open the generated decode report

Mode spec

Short nameSC2-30
Support statusSupported in app
Spec statusSupported in app; public line-level timing was not found in checked sources, so app timing fields are labeled separately.
Duration30.769 s
Frame320 x 128
Data lines128
Public VISVIS 51 (0x33)
Standard VIS code0x33 (51)
Extended/N-VISNo
Color modelRGB
Component sequenceR-G-B
Line rate249.6 lpm
Public timing profileNo implementation-grade public line timing was found in checked sources; app implementation fields are listed separately.
App duration30.769 s
App frame320 x 128
App raw VIS0x33 (51)
App timing profileApp RX line fields: sync 5 ms; front porch 0 ms; back porch 2.385 ms; separator/blank 0 ms; video tones 1500-2300 Hz around 1900 Hz.
App RX sync5 ms
App RX front porch0 ms
App RX back porch2.3846153846154 ms
App RX separator/blank0 ms
App subcarrier1900 Hz
App deviation400 Hz
App tone range1500-2300 Hz

Strengths

  • SC2-30 is a fast compact Wraase mode: 30.769 s, 320 x 128, RGB.
  • SC2-30 uses R-G-B RGB component order and VIS 51 (0x33), giving receivers enough mode identity to separate it from neighbouring Wraase rows.
  • SC2-30 has explicit app timing fields: 5 ms sync, 0 ms front porch, 2.385 ms back porch, 0 ms separator/blank, and 1500-2300 Hz around 1900 Hz video tones.
  • SC2-30 is documented from the app timing row; the line fields are explicit even where checked public sources do not publish every porch value.

Tradeoffs

  • SC2-30's 30.769 s airtime is practical for casual contacts, while the 320 x 128 frame still gives less margin than the longer high-detail modes.
  • SC2-30 sends colour sequentially in RGB; sync drift can appear as colour fringing before the whole frame becomes unreadable.

Source notes

Public VIS/timing labels are normalized from checked SSTV references where available. App raw VIS 0x33 and app timing fields are generated from sstv/sstv/sstv/sstvparam.swift during the website build.