n5ac
The "AVT90" mode: wrong the first three bits of the synchronization data
In the AVT90 there is an additional header, containing synchronization data. It consists of 32 sixteen bits words. According to the "Image Communication on Short Waves, page 54" (https://www.sstv-handbook.com/download/sstv-handbook.pdf), the first three bits shall be 101, while in the application it was implemented 010 sequence, which is reserved for the AVT 24 mode.
In the Main.cpp file, line 7108 the is:
int sd = 0x5fa0;
which sets the first word to: 010 11111 101 00000 (bin). This value is reserved for the AVT24. For the AVT90 the value shall be set to: 101 11111 010 00000 (bin), which is BF40 (HEX). Concluding, to correct the error the above line shall be changed into the following:
int sd = 0xbf40;
which solves the issue.
According to aforementioned documentation, the initial values of the first three bits of the synchronization word shall be as follows for various modes:
⊳ 010 – AVT 24, ⊳ 011 – AVT 94, AVT 188, AVT 125 BW, ⊳ 101 – AVT 90.
The affected application version is 1.13A
