Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[ttirvnet]

Hi,

I'm not getting the results I expect when I try to change the "Dither Mode" in Media Center - I'm using version 26.0.56 (64bit). Most likely I'm not understanding something here, so I hope you guys can shed some light on it for me.

First of all, all is good here:

8bit - Source audio file is not dithered - Dither mode is set to "No dithering" in Media Center.


16bit - Source audio file is not dithered - Dither mode is set to "No dithering" in Media Center.


24bit - Source audio file is not dithered - Dither mode is set to "No dithering" in Media Center.



Also all good here - all these files are "Shape" dithered with Audacity:

8bit - Source audio file is dithered - Dither mode is set to "No dithering" in Media Center.


16bit - Source audio file is dithered - Dither mode is set to "No dithering" in Media Center.


24bit - Source audio file is dithered - Dither mode is set to "No dithering" in Media Center.



Now I wanted to compare the un-dithered tone made in Audacity vs Media Center and its dither modes:

8bit - Source audio file is not dithered - Dither mode is set to "JRiver Bit-exact Dithering" in Media Center.


16bit - Source audio file is not dithered - Dither mode is set to "JRiver Bit-exact Dithering" in Media Center.


24bit - Source audio file is not dithered - Dither mode is set to "JRiver Bit-exact Dithering" in Media Center.


---

8bit - Source audio file is not dithered - Dither mode is set to "TPDF Dithering" in Media Center.


16bit - Source audio file is not dithered - Dither mode is set to "TPDF Dithering" in Media Center.


24bit - Source audio file is not dithered - Dither mode is set to "TPDF Dithering" in Media Center.



Well this is strange, it looks to me like regardless of which Dither Mode I selected in Media Center, it didn't actually apply any dithering ?

Additional information for reference/context:

My AudioPath in Media Center:


Voxengo Span Media Center Plugin settings:



Thanks for your time guys.

[ttirvnet]

Here is an example from foobar2000 media player using the same spectrum analyser plugin and additionally using a plugin to apply dither on my 16bit un-dithered source audio file.

Here is my 16bit un-dithered source audio file: (Dither plugin switched off):


And here is the result with dither plugin switched on:


It works as expected in foobar.

Therefore, I conclude for now that the Dither Mode" option in Media Center is a broken feature unless someone can find a fault in my test methodology.

[Hendrik]

Dithering in Media Center happens on output, as the very last step, as its supposed to, after any DSP plugin sees it.

If you want to visualize the dithering MC uses, you can use PEQ with the Bitdepth Simulator, I believe.

[ttirvnet]

Hi Hendrik,

Thanks, I'll check this out and report back.

As a side note, given that by default, Media Center has the "Dither Mode" enabled and set to "JRiver Bit-exact Dithering", why is the fact that this manipulates the audio signal not listed in the "Audio Path - Changes" window - is it because it is not part of the Media Center DSP processing stage like you seem to suggest? How can I be confident that there isn't any other "hidden" processing going on by Media Center?

[Hendrik]

The Audio Path will indicate the input and output bitdepth, and we don't consider dithering "additional processing", but the only and right way to reduce a signals bitdepth to the output bitdepth. It makes no sense to list something in the audio path thats simply always going to be there. Media Center will never not dither by itself - the only way to make it not dither on a bitdepth reduction is when you tell it to.

[ttirvnet]

Dithering in Media Center happens on output, as the very last step, as its supposed to, after any DSP plugin sees it.

If you want to visualize the dithering MC uses, you can use PEQ with the Bitdepth Simulator, I believe.

Here are my results:

PEQ settings:


JRiver Bit-exact Dithering enabled:


TPDF Dithering enabled:



TPDF dithering result looks as expected, however the JRiver Bit-exact Dithering doesn't look like it worked at all?

[Hendrik]

The bit-exact dithering is called that way because its designed to not modify an input signal if you do not do any audio processing. If you play an input file at 16 or less bits, and output to 16-bits, the output will be bit-exact to the file.

[ttirvnet]

Ah, I see, the puzzle is starting to make sense - thank you so much for detailing the internal behaviour. I appreciate being able to gain some understanding of what is actually going on under the hood.

So I reduced volume by -1dB:


And now I see evidence of the JRiver Bit-exact Dithering being applied to my 16bit undithered source audio:

[ttirvnet]

Here some additional observations at lowered volume levels, comparing JRiver dither vs TPDF dither:

-12dB:


-32dB


Why would I want these unwanted artefacts in my signal from the JRiver dither, when TPDF has cleaner output every time? So for now I'll stick with TPDF when not having volume at 100%.

Given what I know now, I wish there was 5 dither mode options:

• JRiver bit perfect dither (Always applies JRiver dither, except if there are no DSP changes - current behaviour)
• JRiver dither (would apply JRiver dither always, regardless of whether there are any DSP changes or not)
• TPDF bit perfect dither (Would always apply TPDF dither, except if there are no DSP changes)
• TPDF dither (would apply TPDF dither always, regardless of whether there are any DSP changes or not - current behaviour)
• None

I would go as far as to say that TPDF bit perfect dither would be the better/more correct default dither mode.

[wer]

Ttirvnet, I'm not sure what your main thrust is here, other than wondering why the JRiver Bit Exact dither exists if TPDF is better....

Since you're new to the forums perhaps you're not aware that the JRiver dither was the original dither approach that has existed in the software for many years.

TPDF was added more recently as an enhancement.

[Hendrik]

I would go as far as to say that TPDF bit perfect dither would be the better/more correct default dither mode.

That is not a possible mode of operation. The JRiver Dither mode is designed to give this behavior, which sacrifices a bit higher distortions for lower noise, which as a positive side-effect gives you the bit-exact behavior.

[ttirvnet]

Ttirvnet, I'm not sure what your main thrust is here, other than wondering why the JRiver Bit Exact dither exists if TPDF is better....

I'm trying to get an understanding of what Media Center is doing when I set one of the dither mode options and how it really affects the final output - I will admit without hesitation that I'm not an expert in this area, just presenting my findings as I go and trying to interpret them with the help of users here.

Since you're new to the forums perhaps you're not aware that the JRiver dither was the original dither approach that has existed in the software for many years.
TPDF was added more recently as an enhancement.

From what I've seen looking at older threads, the TPDF dither mode was put into Media Center in 2015 as an additional option after a request from a forum member.

[JimH]

... I will admit without hesitation that I'm not an expert in this area, just presenting my findings as I go and trying to interpret them

Good to know.  I'm closing this thread now.