If you have MENU>Setup>TV>Auto language>Prefer audio track stored by service enabled, then disabling Prefer AC3 track (same setup screen) won't help by itself with switching back from the AD soundtrack to the plain soundtrack.
In any case, I recommend changing Audio language selection 1 (same setup screen again) from None to English instead of disabling Prefer AC3 track, because that operates on something that is directly related to whether a soundtrack carries AD or not: some commercial broadcasts have their plain soundtrack in AC3 and some SBS and ABC channels have both the plain and AD soundtracks in MPEG.
But that has exactly the same problem as disabling Prefer AC3 track: it won't change the stored default soundtracks if Prefer audio track stored by service is enabled.
There are two ways of fixing the problem in live TV and for new recordings: change either of the settings that will fix the problem, and then re-scan, or make the settings changes and then visit all the channels with AD on an AC3-encoded soundtrack and press AUDIO to change the soundtrack to MPEG English. Having changed the setting, you won't be affected by the problem next time you scan.
Recordings made from a channel that has the AD soundtrack selected will also default to the AD soundtrack. You can only change that by pressing AUDIO when you play the recording back, and use that to change the soundtrack (you could also edit the recording's .ts.meta file to remove the saved soundtrack, but that's a bit messy).
For people who'd prefer the non-AD soundtarck, the following channels will have pre-selected the AD soundtrack if Prefer AC3 track was enabled, Audio language selection 1 was set to None and Prefer audio track stored by service was enabled (the factory defaults) when the last scan was done:
ABC TV HD, ABCKids/TV Plus, ABC ME, ABC News, SBS One HD, SBS Viceland HD, SBS World Movies, NITV.
I'm working on a fix that will make it clearer that a soundtrack has AD (even when it's on an MPEG-encoded stream), have English as the default for Audio language selection 1, and allow that setting to also be able to select Audio Description as the "language", so that people with visual impairment can have an option to prefer Audio Description, including on channels where both the plain soundtrack and the Audio Described soundtrack are encoded using MPEG.
The only holdup is about another feature that I want to add that peteru is reluctant to include.
Here's an example of what the AUDIO popup will look like (from ABC TV, where both the plain and the AD soundtracks are MPEG):
And here's an example of Audio language selection 1 set to show Audio Description as the preferred "language". You'd use that setting if you wanted AD to be pre-selected on all channels that have it (something that's not actually possible in the current firmware).
- Screen Shot 2021-08-17 at 10.50.49.png (55.56 KiB) Viewed 2054 times