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Subject:Where's 0dB in SF 5.0? Attn: Engineering
Posted by: Rednroll
Date:2/28/2001 4:02:30 PM

I was doing some testing on 1Khz 0dB Sinewaves today for
engineering test purposes. 1 ripped from a Abex test CD
(TCD-782 track#2), 1 ripped from a Ford Audio System Test
CD, and then 1 generated in SF 4.5 simple synthesis
generator. I wanted to verify that all these sinewaves
were truly at a 0dB peak. I did a normalize on each using
Sound Forge 4.5 using peak level set at 0dB. When SF 4.5
did a scan on all 3 waveforms it detected that they all
where at 0dB and did no further processing. I then
reopened all 3 of the same waveforms in SF 5.0 and did the
same test. All three of them did processing and raised the
levels. So why would v5.0 detect that there was available
headroom and 4.5 wouldn't? Which program is correct?
Seeing I did a digital rip of 2 engineering test CD's, I
would suspect 4.5 to be correct. Why is there this
discrepancy?

regards,
Brian Franz

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: Itna
Date:3/2/2001 9:26:54 AM

Hey Ted,

Seems to be a very important topic here !
Any answer ?

Itna

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: SonyEPM
Date:3/2/2001 5:12:03 PM

Quote from the SF5 lead developer:

If he was working on a 16 bit source file as a float temp
file, then there actually would be a bit of extra headroom
in the temp file.

Of course, when you convert back to 16 bit on the save,
that change would get truncated back to the original
waveform. (in theory).

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: Rednroll
Date:3/2/2001 8:10:16 PM

Yikes, did anyone here understand what that meant? You
just introduced me to a new term, "float temp file". I
don't know what that means,I'm sure it has something to do
with floating point integers. I opened the file as I
normally would, which I know does create a new temporary
file and it was a 16 bit file. In any case, as everyone
knows this breaks all laws of audio conservation (ie don't
do any unnecessary processing of audio if it is not
needed). This is what the scanning process is suppose to
do for you, (ie scan audio.....if a peak is at 0dB, no
processing is necessary...cancel operation). This also
waste time by processing unnecessary files, that have been
already normalized. Well anyways, I'm sure there's a lot
of down sides to this, I hope someone fixes it correctly
though.

FYI
I found this by mistake. I was just trying to compare the
two test CD's to verify that 1Khz @ 0dB was just that,
because some engineers at ford found different RMS output
levels from the 2 test CD's, on CD mechanisms I design. So
to verify this on the two CD's I did a normalization test
and then measured the frequency. I know this is anal, but
this is the kind of precision engineering I have to deal
with, I guess I just won't use the v5.0 downgrade to do
this kind of test. :-)
I'll do some further testing Monday also. I'll try opening
these same files in 5.0, do the normalization and then save
them, then close them. I'll re-open and then try
normalization again. If the developer is correct, then it
should actually process it and normalize it again when I re-
open it.

Thanks for the reply,
Brian Franz

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: sreams
Date:3/2/2001 10:08:13 PM

Go to Options/Preferences and click on the File tab. There
should be a checkbox labelled "Use 32-bit (IEEE Float)
temporary files". Be sure it is unchecked.

-S

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: Rednroll
Date:3/3/2001 6:54:10 PM

Thanks for the info, I will check this out.

Brian Franz

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: Rednroll
Date:3/5/2001 11:58:55 AM

Update:
First I opened the Abex sinewave and Normalized it in 5.0.
I then saved it as another file. I reopened this file and
normalized it again. SF 5.0 did no further processing to
it, (IE IT DETECTED THAT IT WAS AT PEAK LEVEL). So the
statement of re-truncating it didn't hold up under this
test, because if it disregarded this information, then it
should have therectically normalized it again.

Next, I went to option-properties-File. I checked "use
same bit depth for temp files as the original file". I
unchecked "enable 64bit internal processing". Again I
opened the Abex sinewave and normalized, again it raised
the level. Here's the format of the file under the file
menu-properties menu.

SOURCE: 44,100 HZ,16 BIT ,STEREO
TEMPORARY: 44,100 HZ,16 BIT ,STEREO
PROCESS/DSP: 44,100 HZ, 32 BIT (IEEE FLOAT),STEREO
PLAYBACK: 44,100 HZ,16 BIT ,STEREO

So where is 0dB in v5.0? Is there something I'm missing
here or is it, "back to the drawing board?"

regards,
Brian Franz

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: SonicCaleb
Date:3/6/2001 11:47:39 AM

This may be a silly question, but exactly how are you
determining that Sound Forge is raising the level of the
audio?

Thanks,
Caleb

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: Rednroll
Date:3/6/2001 1:48:37 PM

Just do to the fact that in the bottom left hand corner it
shows the "normalize" status as it is processing and in the
normalize setup menu it is set to "peak level" and is set
to 0dB. So from this I would have to conclude that Sound
Forge detected that the waveform wasn't at 0dB and raised
the level. When I open this same file in v4.5 with the
same settings, it does the scan of the waveform and detects
that it's at 0dB and does no further processing, as
expected. This is a 10meg file, if you would like me to
upload it for you to further investigate I will happily do
that. My email address is REDNROLL@HOTMAIL.COM. Or SF
could purchase an Abex audio test CD (TCD-782).

Regards,
Brian Franz

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: SonicCaleb
Date:3/7/2001 2:43:04 PM

I can't seem to reproduce the problem with 0 dB files
generated by 4.5. Now, i am using the soon-to-be-released
5.0a update version, but nothing to my knowledge has
changed with regards to the normalize function.

There may have been differences between the beta version
and the final retail version. So, if you are using the
beta, i'd suggest downloading the demo version of the final
and seeing if that does the same thing.

Let me know.
Thanks,
Caleb

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: Rednroll
Date:3/7/2001 3:32:31 PM

Yes, I am using the Beta version and FYI it is installed on
a Win2k Pro OS. I will download the demo and retry the
tests.

Thanks for the response,
Brian Franz

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: CDM
Date:3/7/2001 5:48:37 PM

I am also able to create a 0dB sine wave in Forge 4.5 and
normalize it in Forge 5.0. It doesn't seem to really change
anything but it does process. Forge 5.0 Retail

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: SonicCaleb
Date:3/8/2001 12:21:37 PM

Ok, so this is all figured out. It is, in fact, the
difference between processing in floating point math (SF
5.0) and processing in integer math (SF 4.5) for
normalization as posted earlier.

The reason it keeps normalizing after saves is because
everytime the file goes back to 16-bit, the same problem
exists. A max level of 32767 in a 16-bit integer when
converted to 32-bit floating point is 0.9999694. That means
that there is an incredibly small amount of headroom left
to get to 1.0. It is inpercievable, but it still exists.

So, we are going to add a little fudge in the normalize
code to detect this situation and not do anything. You
won't notice any sonic differences at all.

Hopefully that is all cleared up now.

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: Rednroll
Date:3/8/2001 12:29:16 PM

Thanks for the explanation and the good work Sonic
Foundry. I think most of us realized this was not a big
difference, just wondered where the discrepencancy was and
where the extra headroom came from.

Thank you,
Brian Franz

Subject:RE: Where's 0dB in SF 5.0? Attn: Engineering
Reply by: CDM
Date:3/8/2001 2:17:33 PM

Thanks Caleb. I wasn't particularly worried. :)

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