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AVT mode

Amiga Video Transceiver AVT24

Historical Amiga Video Transceiver compatibility and reference decoding.

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, 24.88 s.

AVT24 SSTV BBC-style colour test card
AVT24 test card, 128 x 120

Mode spec

Short nameAVT24
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.
Duration22.502 s
Frame128 x 120
Data lines120
Public VISVIS 64 (0x40; AVT normal code from public 64/65/66/67 set)
Standard VIS code0x40 (64)
Extended/N-VISNo
Color modelRGB
Component sequenceR-G-B
Line rate319.977 lpm
Public timing profileNo implementation-grade public line timing was found in checked sources; app implementation fields are listed separately.
App duration22.502 s
App frame128 x 120
App raw VIS0xC0 (192)
App timing profileApp RX line fields: sync 5 ms; front porch 0.8 ms; back porch 0.5 ms; separator/blank 0.5 ms; video tones 1500-2300 Hz around 1900 Hz.
App RX sync5 ms
App RX front porch0.8 ms
App RX back porch0.5 ms
App RX separator/blank0.5 ms
App subcarrier1900 Hz
App deviation400 Hz
App tone range1500-2300 Hz

Strengths

  • AVT24 is a fast compact AVT mode: 22.502 s, 128 x 120, RGB.
  • AVT24 preserves AVT R-G-B RGB ordering while publishing the normal-code label VIS 64 (0x40; AVT normal code from public 64/65/66/67 set) separately from the app raw VIS value.
  • AVT24 has explicit app timing fields: 5 ms sync, 0.8 ms front porch, 0.5 ms back porch, 0.5 ms separator/blank, and 1500-2300 Hz around 1900 Hz video tones.
  • AVT24 is documented from the app timing row; the line fields are explicit even where checked public sources do not publish every porch value.

Tradeoffs

  • AVT24's 22.502 s airtime is practical for casual contacts, while the 128 x 120 frame still gives less margin than the longer high-detail modes.
  • AVT24 AVT public tables vary by source; use the app-generated sample audio when checking exact receive timing.

Source notes

AVT public mode tables vary and Dayton N7CXI excludes AVT timing because it did not have solid author data. This row presents the app-supported implementation with the public normal VIS label where available. App raw VIS 0xC0 and app timing fields are generated from sstv/sstv/sstv/sstvparam.swift during the website build.