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AVT mode

Amiga Video Transceiver AVT90

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, 92.446 s.

AVT90 SSTV BBC-style colour test card
AVT90 test card, 320 x 240

Mode spec

Short nameAVT90
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.
Duration90.004 s
Frame320 x 240
Data lines240
Public VISVIS 68 (0x44; AVT normal code from public 68/69/70/71 set)
Standard VIS code0x44 (68)
Extended/N-VISNo
Color modelRGB
Component sequenceR-G-B
Line rate159.992 lpm
Public timing profileNo implementation-grade public line timing was found in checked sources; app implementation fields are listed separately.
App duration90.004 s
App frame320 x 240
App raw VIS0x44 (68)
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

  • AVT90 is a standard-length standard colour AVT mode: 90.004 s, 320 x 240, RGB.
  • AVT90 preserves AVT R-G-B RGB ordering while publishing the normal-code label VIS 68 (0x44; AVT normal code from public 68/69/70/71 set) separately from the app raw VIS value.
  • AVT90 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.
  • AVT90 is documented from the app timing row; the line fields are explicit even where checked public sources do not publish every porch value.

Tradeoffs

  • AVT90's 90.004 s frame is a balanced choice, but it still needs a stable path for the full 320 x 240 scan.
  • AVT90 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 0x44 and app timing fields are generated from sstv/sstv/sstv/sstvparam.swift during the website build.