Changing default Mixdown from Dolby Prologic II to Stereo

[thejuergen]

Hi,

I'm about to rip some of my TV-Show Collections from DVD to mkv to take them with me when I'm on business trips. I was able to set the default languages that should be selected (German and English) - but the default setting is to mixdown (or in some cases "mixup") to Dolby Prologic II. I would rather like to have plain Stereo only - but I just can't seem to find the way to do this. I'm using a custom preset that has default languages set but no track added so loading a DVD selects the first German and English track - but with Prologic II.

Any help?

Thanks in Advance!
Juergen

[moneymatt4life]

keep it DPLII if it want to downmix 5.1ch to stereo
if the source is stereo handbrake will automatically change the mixdown to stereo, which you will see in the log, as it'll say "sanitizing mixdown to stereo" or something like that

[Deleted User 13735]

Really no need to do so.
The PLII phase shift is transparent when the material is played on a non-matrix device or amp.
This is described in the Dolby White Paper if you care to dig for it.

[thejuergen]

Thanks for the reply!

Oh ok. I guess it's a bit tricky on my Laptop then - I ripped a bunch of TV episodes in Stereo and then in DPLII and they are a bit more silent... (Hope that's the right way to describe it in English since it's not my native language - I mean to say that the Stereo version is a bit louder overall). Following musicvid this means my VLC on my Laptop is a matrix device that's recognized as PLII capable. Guess this will have to do then and I'll tick the volume up a bit.

[Deleted User 13735]

It's not VLC, it's your laptop sound card. I can promise you it is not PLII capable, and if you can hear a difference, you must have some other effect / DSP / environment causing it. Stereo "enhancement" and fake "surround" environments are real baddies.

We would need to see encode logs and output samples for BOTH audio versions to carry this any further, but unless something's changed recently, I would not expect to find anything except a trivial difference.

[thejuergen]

I'll re-try to do the same episode in stereo and PLII and compare them again. If there is a difference I'll upload it and post a log - since I'm currently not at home until the weekend it will take some days.
Thanks!

[moneymatt4life]

... again, choosing dpl2 shouldn't do anything to stereo as handbrake will automatically change the mixdown to stereo for stereo sources

[thejuergen]

Understood, the episodes I'm talking about were 5.1ch however. I'll report on the weekend.

Thanks!

[moneymatt4life]

ah
i forget how regular stereo downmix works, i kinda want to say it's something along the lines of just the FR and FL or something? again, no clue and am most likely wrong but i can tell a difference between a stereo vs dpl2 downmix on a 5.1ch source, not exactly sure what that difference would be however, hoping it's just not volume i like the dpl2 one better but's that's just the one test i did just now on a music video

[Deleted User 13735]

If the stereo and PLII down mixes from Dolby 5.1 source sound different, then there "may" be a phase shift bug.
Are the differences consistent across different audio encoders in Handbrake?

Encode logs, and in this case, file samples are required.
I can analyze this stuff, but I can't do it blind.

[Deleted User 11865]

HandBrake's Pro Logic mixes will have a weaker left channel whenever there is strong correlation between the front and rear channels. Not much we can do about it.

The Mac and Linux UIs should let you save a Stereo mixdown in the preset; I haven't checked the Windows GUI in a while.

[thejuergen]

@Rodeo: For Linux/Mac: Is this in the defaults tab for audio or by saving individual languages in the preset? Haven't found a thing in the Windows gui

But I'm glad to see that I'm not crazy and that there is a difference. Now a way to set is default to stereo would be great in the windows gui. Or by hand by editing the preset file maybe?

[moneymatt4life]

mine was from a DTS source, should that make a difference? only thing that really stands out is the dpl2 is louder than the simple stereo, otherwise i can't notice much difference... except, i wonder if i'm paying enough attention? *after typing that* actually, i can now... a portion of the vocals are different on the dl2, as it's more confined to the right side whereas in regular stereo i can hear it clearly in both sides... can't really tell which one i like better though... *again after typing* Rodeo seemed to have given an answer as to why that would be... so no logs
and i don't use anything but AAC, as i can't thanks to my iPoop so i generally don't test the others...

... now i'm wondering if i should be using regular stereo instead of dpl2 suppose i have some testing to do...

[Deleted User 13735]

That "louder right channel" behavior is very typical in my work, but I only see it in stereo downmixes from 5.1 Dolby Digital where the phase shift flag was not set correctly in the original encode. It "may" be widespread practice, but not setting the 90 deg. phase shift flag for PLII mixdown in the Dolby 5.1 encoder is not correct, and in fact is noncompliant for BluRay encoding.

This is the Preprocessing panel in the licensed Dolby Digital Pro AC-3 surround encoder.

The behavior Rodeo describes is almost certainly a result of a similar occurrence somewhere from door to door (maybe a redundant phase shift)?

WITH THOSE EXAMPLES AND LOGS and a pristine SOURCE EXAMPLE I can track it down; I did the same identifying the same bug in DVD Architect years ago. I just don't have the time now to run the encoding tests and necessary documentation for you guys.I can't decode DTS in my NLE, so that will not work as a source. Let me know your level of interest in this; otherwise I won't bother pursuing it.

[Deleted User 11865]

@Rodeo: For Linux/Mac: Is this in the defaults tab for audio or by saving individual languages in the preset? Haven't found a thing in the Windows gui

In the "Configure Defaults" panel, yes.

[Deleted User 11865]

That "louder right channel" behavior is very typical in my work, but I only see it in stereo downmixes from 5.1 Dolby Digital where the phase shift flag was not set correctly in the original encode.

What about if the source isn't AC-3?

Also, this is actual processing, or if it really is a flag it's nowhere to be found in the official A/52 specification.

Finally, if it's a flag and we figure out where to look for it, HandBrake can't apply the 90° shift anyway…

[Deleted User 13735]

What about if the source isn't AC-3?

I was kind of hoping one of you guys would check that.

I will post Dolby's explanation later when I can dig it up. It's in their whitepaper.
I think it's an actual phase shift. I thought the mixdown decoder was alerted with a corresponding flag, but I can't be sure.
Maybe Friday when things aren't so busy.

In the meantime, here is the stock tooltip:

[thejuergen]

@Rodeo: For Linux/Mac: Is this in the defaults tab for audio or by saving individual languages in the preset? Haven't found a thing in the Windows gui

In the "Configure Defaults" panel, yes.

Is there a chance that this will find it's way in the windows gui, too? Seems like the setting I'm looking for

Edit:
After taking a look at the linux gui: There is the setting I was looking for and it's working the way it should. Too bad that there isn't this good "add all" / "add selectection" button Otherwise I would switch the encoding to linux.. but then I'll have to select every single episode by hand instead of batch adding them. Guess I'll have to stick with one thing or the other

[JeffePgh]

Sorry if I'm hijacking this thread but it addresses the exact thing I was about to make a topic for...so I just want to summarize/verify I understand what is being said here.

When trying to encode from the Doctor Who season 5 Blu-Rays, I was going nuts hearing most of the sound in the right channel, I see it must be this encoding mistake musicvid mentions. And Rodeo saying HB can't apply a 90 degree shift anyway means, even if one could say "oh, that flag is wrong", HB cannot and never will be able to work around the error? So then it would not be a waste of time for me to just mixdown to plain ol' stereo, there's no worry that I'll be kicking myself in a year or two if it's fixed/worked around?

FWIW, I think I've detected this slightly with Iron Man 3, also. I try to listen for it by flipping between the stereo and passed-thru audio in VLC to point out the differences if they're too subtle.

If my summary is not entirely correct and it would be helpful to either of you to see a log of this if this IS something you can work around someday, please let me know, I'll rerip and post a log (I deleted the mkvs out of frustration thinking it was my fault and moved on to other discs

Thanks!