XXHighEnd

Has anyone else noticed the drastic contracting of the soundstage when upsampling either to double or quad, or is it just me?

Mani.

No, that is not my experience. It seems a bit softer though. I think I like it better. But more listening has to be done. I can live with that:)
Leo

Persnonally I don't like it at all. But then I can only listen to Quad via the Fireface as the DAC. And that's not really it. :nea:

I'm with you Peter - I don't like it. (Actually, my strong preference is 'DAC is 16 bits 44.1 KHz' when I'm not listening to 24 bit files.)

Using my headphones, the stereo imaging has definitely contracted.

I agree Leo, it's softer... but lost the transient edge IMO.

Mani.

Mani, I assume that you don't mean that things changed for the worse since 0.9u-4 ? (for Doubling of course)
If you do mean that, then something else is going on, because such a change is not intentional.

Btw, don't forget to set the buffer of the soundcard accordingly (like in your case the Fireface);
For Double it needs 96 samples, and for Quad 128 (native can deal with 32 when your driver allows).

Also, when you (all) can listen to it through the same DAC (hence capable of 176400), give it some (tweak) time; Just as you needed experience with 44.1 or doubled to 88.2 for that matter, this needs that experience just the same, and the settings (like Q1) probably won't be the same.

Keep in mind that a DAC always performes worse on a higher sample rate than on the lower.
But then also try to imagine that the increased (though calculated) resolution works for movies, and therefore it should work for audio as well. Sadly so many parameters are in effect with audio (like the larger buffer needed, which destroys by itself).

And yes Mani, I still have to look into the aliasing. :)

No, things haven't changed for the worse. I preferred no upsampling then and now.

Have a look at these two images on the RME Vector Audio Scope. Guess which one is quad upsampled...

Mani.

Wow. But I guess it's the one which says SR 176.4 KHz and is called Quad Upsampled.jpg. :grazy:

Uhhm ... does Double/Upsampled looks so as well ?

Yes, I realised the files names as I pressed post.

Here's another pretty picture...

Mani.

Actually, my P70 transport is also capable of double and quad upsampling. But it's part of my other system. If I have time, I'll connect it's dig output to the RME and see what happens.

Mani.

If your last pisture is, say, stable, then sure something is wrong there.
I'll dive into that this week. Something else for a change.

Hahaha, not good. A clear case of program(er) error.
The Double-Upsampling part contains an error somewhere. The used bith depth can be the other way around just the same.
Smart ... :swoon:

Very nice graphics Mani, but what do they represent ? 

Leo

ps

In highschool days  my father gave me an old copy of the book "How to lie with statistics". Very usefull it turned out to be..

Leo, they're not just pretty pictures. These things are taken very seriously in broadcast studios and in the post-pro and mastering field.

A Vector Audio Spectrum shows the level and phase differences between the left and right channel (often referred to as a Goniometer).

From the second you see the double upsampled image, you know something is wrong - it should be symmetrical when fed, as it was, a mono signal.

The quad upsampled image shows the effects of aliasing...

Hope this helps.

Mani.

Actually, thinking about it, the quad upsampled image suggested a 90 degree phase shift between left and right channels... I think.

Any other ideas anyone?

Mani.

Thanks Mani,

And will this kind of output allways be there with oversampling (if without error, like the quad) . I mean the soundlevel effect and the aliasing 'noise', Or are some oversampling algorithmes better than others employing this test.
Funny to see that the soundlevel impression is confirmed by the test.

I ask this because, this seems a very easy test for the quality of oversampling, whereas all kinds of semi-religious wars are being fought on the fora about which up-sampling method is better (software, (and then which...),  hardware, realtime or not) .

Leo

If it is 90 degrees off, than DSP can deal with it . At least that is a function on the Behringer DCX (and DEQ I think).

Well Peter, there you go, DSP corrections for double and quad...... :)

:rofl: If it's 90 degrees of, it's 50% wrong. :(

The kernel code producing the sound is some 6000 lines of program code now, which kind of makes you dizzy about the bits and pieces looking alike but are not. You could say the "smartness" in there to provide the good sound on one hand and save cpu cycles on the other, starts to cripple me a bit. Also, checking by listening has become a sheer impossibility because of all the combinations, and actually I am very glad that Mani "found" this means of checking.

Btw, I briefly looked at the aliasing, and things happen only at the other side (above 22050Hz) of the mirror. Only if you think you can hear this or you think it influences, you could call it wrong. Please note that no AA is applied on purpose, that leaving the audible data, say, bit perfect (and otherwise you'd get a roll off in the highs and more side effects).
The "hum" your picture showed in the other topic (http://www.phasure.com/index.php?topic=372.msg2739#msg2739)          , luckily didn't show with me (because *that* would really have been aliases at the wrong side of the mirror).
Careful : this was briefly looking.

I would bet my house that there is more going on than a test like this can reveal.

For my own part, I believe so much is down to phase coherence. I'm just not sure what happens when aliasing etc comes into play. For example, in the quad upsampling case, the left and right are not 90 degrees out of phase... but some of the components are - I suspect those that arise from aliasing (though perhaps these should be 180 degrees out of phase?).

The situation is too complex for me to understand fully, but I do find these sorts of tests to be useful.

Will try get some images using upsampling in Foobar for comparison.

Mani.

My pleasure.

Mani.

Alaising definitely influences the sound below 22.05KHz. It has a filtering effect on the signal as it approaches the 22.05KHz cutoff. That's why there is a lowering in the RMS level of the 15KHz signal in the quad upsampled image.

And perhaps that explains why I hear a softening in the sound and a lowering of transient attack when using quad upsampling? In any event, I think we can all hear some change in the sound, no?

Mani.

Ah, I'm sorry, I wanted to respond to that in the previous post, but got stuck in the 6000 lines of code. :)

Indeed, what will have happened, is that PARTS of the samples (oh yes) have been assigned to the wrong channel, or just aren't upsampled (but repeated = doubled (or quadrupuled)). This may look strange as something which can happen (in decent program code), but it really is not if you know what all has to happen to utilize the additionally available bits (because remember, this is so far about 16 bits only, while 24 are avaialble, and I just use them). All in combination with the digital volume, DACs which allow for 16 bits only *but* where Doubling/Quadding is allowed just the same, and some more stuff like the calculations themselves which may be just wrong.

Anyway Mani, what I see here indeed, is or :
a. a mixture of aliasing and wrongly assigned sample parts or
b. all upsampling just being plain wrong (on that matter I forgot to check "DAC is 16 bits") or
c. aliasing influencing the whole spectrum, but which doesn't show on the frequency plots.

At this moment I can't even see how a. can be in order, but I keep in my mind that the RME software just *will* show the theoretical frequency full range, coming from the sampling frequency, hence up to 44100 Hz at 88K2 sampling. So it will incorporate the anomalies above 22050 just as well (but you can't see them seprately in the Gonio plot I think).

But let me first try to find the now 100% sure culprit in the program. Then we can start looking for other things. :yes:

OK. I've got a small "confession" to make;

Double/Upsample is working OK now here, and I imagine myself to have heard the most undisturbed sound so far. Don't matter higher buffer settings and all, I enjoyed the music VERY much the last couple of hours. Does it work afterall then (my remark about movies where upsampling just visually works for 100 % sure) ?

Quad/Upsample does not work yet other than "wrongly", and it kind of needs the program to be re-written which I will do.

Mani, thank you once more for your remarkable justification on ... well, the title of this topic;
With or without justifying pictures I listen. Now or in the future. :yes:

Peter

What happened to the imaging ? Well, I can tell you.

Quad/Upsample :
First pair (L/R) of samples (out of the total of 4 pairs) was written ok, then 3 interpolated samples went to the left channel, then 3 interpolated samples went to the right channel. So, 25 % of samples was ok, 75% ended up in the wrong channel, implying a high degree of mono sound.

Double/Upsample :
3 wrong lines of code indeed caused that a.o. the part of one sample (think of first 8 bits vs. the last 4 bits) ended up in the wrong channel.
This was expected as per the plot Mani showed (a torned circle).

It's actually fun learning to read these plots related to program errors.
Again, Mani, thank you.
Peter

My pleasure.

Yeah, the genios are fun, aren't they?

I suppose I can speak for all of us; can't wait to get hold of 0.9u-6  :P

Mani.

Yep, me too. Have gotten so used to DoubleOn, UpsampOn that going back to vanilla 44/16 has been quite a chore...

Awaiting version 6 with anticipation.

quad oversampling sounds great with number 6 !