[solved] Dolby Pro Logic - waste of time if used on headphones only?

[Prototype v1.0]

Hi.

When encoding vdeos - in some programs there are options under audio to encode using Dolby Pro Logic.

The thing I want to ask here:
I plan to use mostly headphones (no surround or even center speakers) when I'm hearing on the recordings. Therefore - does it makes any sense usind Dolby Pro Logic when only 2 speakers/headset will be used to listen at recordings ?

Also - I have a Logitech G35 headset (without drivers). Should one expect any difference in audio experience if audio track is encoded in Dolby Pro Logic ?

And for the record : All source video audio are recorded as stereo only.

[jagabo]

Don't ruin a decent stereo track by adding Pro Logic nonsense. All it's going to do is add echo/reverb effects.

[Ennio]

For listening in stereo, I would agree with jagabo. Specially for music.

In the past I had some experience with listening to Pro Logic headphones. As for movies, it will add something, but is wasn't my cup of tea.

[Cornucopia]

ProLogic encoding is a matrixing method of going from 4 (or 5 or 5.1) channels to 2 for transport & storage using normal stereo bandwidth constraints.
PL decoding does the reverse. It works properly when the content was originally designed to be multichannel.
Adding PL to plain stereo just ends up making it worse than stereo.
If you're going to not follow the proper guidelines, you could just as well take a mono signal and put the lows on the left and highs on the right, and you'd get the same fake mush as the Beatles did over 50 years ago.

Scott

[Ennio]

ProLogic encoding is a matrixing method of ...

Would you be so kind to explain what "matrixing" means, regarding this subject?

[pandy]

No, there is no sense in using Dolby Pro Logic for headphone listening (unless your headphones are equipped with Dolby Pro Logic decoder or you feed your headphones with decoded Dolby Pro Logic) - but there is sense to use Dolby Headphone or HRTF to encode multichannel (for example 7.1) into binaural. I use in ffmpeg something like this:

"aformat=channel_layouts=7.1,aresample=resampler=soxr:osr=48000:cutoff=0.99:dither_method=0,sofalizer=sofa=dodeca_and_7channel_3DSL_HRTF.sofa:gain=11:lfegain=9"

It gives nice, quite realistic impression of 7.1 layout, highly recommends for headphone listening.

[Prototype v1.0]

Thanks a lot for explaining

[jagabo]

Listen to this with headphones (especially near the end): https://www.youtube.com/watch?v=IUDTlvagjJA

[Cornucopia]

There are 2 basic types of multichannel audio: Discreet and Matrixed.

Discreet 5.1 audio uses 5.1 separate channels throughout with no inter-mixing.
Matrixed 5.1 audio uses 5.1 channels MIXED & FOLDED INTO 2 channels (temporarily), to save on bandwidth, storage space, and to provide for backward compatibility.
The recipe for the mixing/folding follows a specific matrix of amplitude values & phase angle/delay correllations.
Matrixed multichannel audio that has been folded down to 2 will then be ultimately UNFOLDED back to 5.1. However, there is never a way to totally "unmix" something, and there will be inter-mixing/crosstalk artifacts and quality losses.

For headphone use, even though there are (expensive) headphones with more than 2 (main) drivers, for all intents and purposes, you are left with 2 channel output going to your ears. Basically, 1 per ear.
Thus, discreet MC would be wasted unless you had one of those expensive headphone sets, and I question the claims of increased imaging/spaciousness with them, regardless.
Similarly, matrixed MC is giving you something you cannot take advantage of. Thought there are only 2 channels, what is in them is comprised of more than 2 channels' worth of material, more than the normal amount of which is ambient. So you will experience more reverberation, as well as muddiness due to the unfolded intermixing.

What pandy mentioned WOULD be good: Dolby Headphone/HRTF/Binaural. I am a strong proponent of Binaural! You could also benefit from Inter-Aural Crosstalk cancellation processing (of regular stereo material). This opens up headphones so the soundstage appears no longer between your ears.

Scott

[azmoth]

Excellent explanations. You are getting your money's worth from the tech guys here. I'll add Dolby Headphone technology has come a long way too. The track on T2 extreme edition using this technology was very good at the time with virtual surround techniques, and since then aacPlus is the in thing now.

For me plain vanilla stereo is unbeatable or just having a 2.1 setup with a subwoofer is more than adequate. Headphone stereo is enough without that prologic fancy spin. He-aacv1 or v2 is excellent through headphones.

[Ennio]

Indeed good explanations, for which I take my hat off. Thanks everybody.

Matrixed multichannel audio that has been folded down to 2 will then be ultimately UNFOLDED back to 5.1.

I always understood that Dolby Pro Logic would carry a full-range center channel and a limited-range monaural surround channel. No subwoofer channel.
Can you confirm this and, are there more types of Pro Logic that are capable of more channels?

[jagabo]

Indeed good explanations, for which I take my hat off. Thanks everybody.

Matrixed multichannel audio that has been folded down to 2 will then be ultimately UNFOLDED back to 5.1.

I always understood that Dolby Pro Logic would carry a full-range center channel and a limited-range monaural surround channel. No subwoofer channel.
Can you confirm this and, are there more types of Pro Logic that are capable of more channels?

Original Prologic, yes. Prologic II encoded 5 separate full range channels. The sub is just R+L through a low pass filter.

https://en.wikipedia.org/wiki/Dolby_Pro_Logic

[Cornucopia]

1. 1982 Dolby Surround = 4->2->4, limited freq on surround/back channel
2. 1987 Dolby ProLogic = 4->2->4, with separation-increased vario steering "logic" (hence the name), NR, surr delay (for Haas effect), also limited freq surr
3. 2000 Dolby ProLogicII = 5->2->5, full freq on surround/back channel (add .1 with no real separation)
4. 201x? Dolby ProLogicIIx = 6/7->2->6/7 (same trick with .1), additional channels are extracted using extended cues, but not much separation with normal surrounds
5. 201x? Dolby ProLogicIIz = 8/9->2->8/9, includes height, similar extraction tricks

Scott

[Ennio]

Wow, never thought ProLogic was taken up that far. Again, thanks for great explanation

[azmoth]

The below NPR loudness tool is now free of charge for those who like to analyse their beloved audio files to see if they meet industry standards.

http://www.prss.org/loudness-tool