SPDIF Audio via Bluetooth Transmitter

[CRMS]

Q about BT audio, and hopefully someone here will know.

I'm using the Quad 4K AC3 SPDIF optical output into an Elegiant BTI-066 BT transmitter. This is BT5. 0 and has AAC, SBC, APTX HD and LL codecs.
https://www.elegiants.com/ELEGIANT-BTI-066-Bluetooth-Audio-Transmitter-Receiver-p-187466.html

I have recently got 2 Tribit XSound Go which are paired to provide stereo. They are also BT 5.0 but only SBC codec. The Elegiant is in SBC mode. The Quad is in AC3 Downmix for HD TV and all the other audio options are downmix. I'm currently on 5.4.016, but will update to the latest.

The stereo sound hasn't been as good as I expected after using an earlier non stereo XSound Go and is breaking up. Picture/audio sync is fine. It affects both live SD or HD TV and recordings.
Turning off 1 speaker back to mono, and the quality is good.

With the Go's linked to my phone/tablet BT the stereo is fine.

Before getting the Elegiant, I did try a Broadcom USB BT dongle in 2020, but I had to reset the Quad box each time to use the BT audio.

So, I'm searching for where the issue is - Elegiant or Quad 4K.

Any pointers gratefully received.

[CRMS]

So I've been through the audio settings for AC3, and others, but I don't know what Freesat channels transmit other than AC3 on HD.

force_dts - audio stutters but good volume. Assume forcing AC3 to DTS.
use_hdmi_cap audio seems fine and good volume. Don't know what this means - nothing with google.
downmix - stutters but good volume. Assume AC3 downmixed to stereo.
pass through - no sound. Assume AC3 straight through.
mutichannel - audio seems fine but quiet. Again don't know what it is.

So as I asked in the guides section, some information on audio would be useful?? Even better explanation in OpenVix as the options are scrolled through.

[twol]

So I've been through the audio settings for AC3, and others, but I don't know what Freesat channels transmit other than AC3 on HD.

force_dts - audio stutters but good volume. Assume forcing AC3 to DTS.
use_hdmi_cap audio seems fine and good volume. Don't know what this means - nothing with google.
downmix - stutters but good volume. Assume AC3 downmixed to stereo.
pass through - no sound. Assume AC3 straight through.
mutichannel - audio seems fine but quiet. Again don't know what it is.

So as I asked in the guides section, some information on audio would be useful?? Even better explanation in OpenVix as the options are scrolled through.

So they are straight out of the receiver procs - set by the manufacturer
So as defined by you above, your assumptions are accurate. Probably be corrected but multichannel -> PCM
use_hdmi_cap----> use hdmi capabilities?

[CRMS]

So solved issue with new Bluetooth transmitter. A 1MII B06TX. Great long range sound as well. Elegiant was fine for mono, but fell down with stereo.

Anyway, I now discover that AC3 is the code name for good old Dolby Digital. Quite why it is not called DD in the audio settings I know not.

So is there any benefit changing DD to DTS if an audio amp can accept both??