How to decode 6-track APTX-100 (cinema DTS) with the correct channel levels

[little-endian]

[...]once the A->D conversion has taken place[...]

You mean "D->A" conversion, don't you?

[zoidberg]

Yes, well spotted

[Dr. Cooper]

Yep, use 32-bit floating point PCM instead in Foobar's export settings and attenuate the levels in an audio editor of your trust. This should avoid the clipping.

Just using "32-bit Float" in the Output Bit Depth-settings in the converter-settings should solve it? Right now it's just set to "Auto" and converts the files to 16 Bit WAV-files.

And just to point it out again, so there's no confusion: It wasn't the LFE that was clipping, it was one of the Surround-channels (IIRC Surround Left).

[little-endian]

Just using "32-bit Float" in the Output Bit Depth-settings in the converter-settings should solve it?

Exactly. As I noted a few pages back here.

Right now it's just set to "Auto" and converts the files to 16 Bit WAV-files.

Yep, and that often leads to clipping.

For the LFE, you'll also notice that you often can't raise that by 6dB without causing clipping either. Better attenuate the rest accordingly (futher, the surrounds anyway).

And just to point it out again, so there's no confusion: It wasn't the LFE that was clipping, it was one of the Surround-channels (IIRC Surround Left).

Yes, since the LFE needs quite some boost anyway, it will most probably never clip during the process (may have some clipping baked in the mix however).

[FoLLgoTT]

Btw, I analyzed the decoder plugin and how it creates the DTS-ES back surround cannel. It is just a simple mix of the other two surrounds: (SL + SR) / 2. That means it doesn't contain any exclusive information. This can be done better by any consumer AVR (DTS-ES uses phase shifting to encode the BS). I suggest to skip this channel or decode without it.

[Dr. Cooper]

Sorry for my late reply.
I just tried to see what happens when I save it as 32 bit float, but the results were the same. The LFE gain is set to +3dB as described in the first post. After setting the surrounds to -3dB in the APT-X1000-preferences the clipping on the Surround Left is gone, but there's still clipping on the LFE (which I just didn't recognize before). So now I'm going to recover that by just applying a gain of let's say -3dB to the entire 5.1 WAV afterwards?

[stwd4nder2]

Btw, I analyzed the decoder plugin and how it creates the DTS-ES back surround cannel. It is just a simple mix of the other two surrounds: (SL + SR) / 2. That means it doesn't contain any exclusive information. This can be done better by any consumer AVR (DTS-ES uses phase shifting to encode the BS). I suggest to skip this channel or decode without it.

That's good to know. I thought it would actually extract the matrixed channel. Guess there's no need to encode those syncs as 6.1 then.

[FoLLgoTT]

Btw, I analyzed the decoder plugin and how it creates the DTS-ES back surround cannel. It is just a simple mix of the other two surrounds: (SL + SR) / 2. That means it doesn't contain any exclusive information. This can be done better by any consumer AVR (DTS-ES uses phase shifting to encode the BS). I suggest to skip this channel or decode without it.

That's good to know. I thought it would actually extract the matrixed channel. Guess there's no need to encode those syncs as 6.1 then.

The need is there. The information for the Backsurround channel is encoded phase shifted ("ES pre-mixed" as stated in the DTS Encoder Suite Manual), but the decoder doesn't know anything about it during decoding. You have to encode it as DTS-HD MA 6.1 Matrix so set the flag. Then it can be decoded correctly. But you only need the 5.1 channels for encoding. There is no need to extract the channel before encoding.

There are even a few (old) Blu-rays which are "ES pre-mixed", but only encoded in 5.1. "The Pantom Menace", "Fight Club" or "Gladiator" for example. I noticed the same phase shift when listening to their surrounds in Stereo mode. To fix it they can be encoded with the 6.1 Matrix flag, too.