Is it just me, or does Sox deemph overdo the de-emphasis? - diyAudio
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Old 16th June 2012, 05:50 PM   #1
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Default Is it just me, or does Sox deemph overdo the de-emphasis?

I've been using Sox v.14.3.2 to de-emphasise CDs that have the emphasis flag set. After a couple of dozen or so such discs, I reckon that the resulting music file sounds rather flat - i.e. with reduced top end - compared to other CDs where the preemphasis flag is not set. Am I alone in thinking this? My implementation is Sox inputfile.flac outputfile.flac deemph. What do others think?
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Old 16th June 2012, 06:12 PM   #2
kevinkr is offline kevinkr  United States
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I've yet to run into any CDs with the de-emphasis flag set, was not very commonly used except on a few early CD classical recordings.

I guess I am wondering why you are manually applying de-emphasis to those flac files? Most dacs afaik still do this automatically if the flag is set and it doesn't need to be done twice.

Perhaps I've missed something, can you elaborate on why you are doing this? I've been ripping to flac via EAC or J River for about 7yrs now and never used sox or any other tool to manually de-emphasize anything.

(Also have used sox as a player in linux...)
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Old 16th June 2012, 06:15 PM   #3
Wombat is offline Wombat  Germany
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The biquad filter sox uses is working correctly if you donīt use some very old buggy version.
From the sox page: "The current deemph effect works fine and is accurate to 0.06dB"
This is correct. Depending on the reference curve used sox is always correct. Beware of the iTunes implementation. In some version the de-emphasing dips ~1dB to low.
I have done some graphs a while back and posted in other forums for this one iTunes version. I donīt know about later versions.

After all it does matter more what way was used to apply pre-emphasis. It seems every curve with sample sinuids i collected over time for testing was way more off as the sox de-emphasis itself.
In the end i decided to apply a de-empasis that is more like +0,10 dB to be on the safe side. Better a tiny bit to much highs as to less.
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Old 16th June 2012, 06:17 PM   #4
Wombat is offline Wombat  Germany
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Quote:
Originally Posted by kevinkr View Post
Perhaps I've missed something, can you elaborate on why you are doing this? I've been ripping to flac via EAC or J River for about 7yrs now and never used sox or any other tool to manually de-emphasize anything.
PC playback doesnīt know about a flag and applying de-emphasis until you have an application that reads the "FLAGS PRE" info in a CUE file. So the played files will be most likely played back horrible sounding.
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Old 16th June 2012, 06:29 PM   #5
phofman is online now phofman  Czech Republic
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Quote:
Originally Posted by kevinkr View Post
Most dacs afaik still do this automatically if the flag is set and it doesn't need to be done twice.
The dacs have the ability, but have to be told by the driver/playback software to deemph.
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Old 16th June 2012, 06:35 PM   #6
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Originally Posted by kevinkr View Post
I guess I am wondering why you are manually applying de-emphasis to those flac files? Most dacs afaik still do this automatically if the flag is set and it doesn't need to be done twice.

Perhaps I've missed something, can you elaborate on why you are doing this? I've been ripping to flac via EAC or J River for about 7yrs now and never used sox or any other tool to manually de-emphasize anything.
I was under the impression that FLAC files have no facility for storing pre-emphasis information. If I don't use Sox preemph, it usually sounds too bright, so I don't think it's being applied twice.
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Old 16th June 2012, 06:42 PM   #7
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Originally Posted by Wombat View Post
After all it does matter more what way was used to apply pre-emphasis. It seems every curve with sample sinuids i collected over time for testing was way more off as the sox de-emphasis itself.
I wonder whether some recordings actually used proper pre-emphasis at all or just sounded a bit bright so the engineer set the preemph flag? (eg. Cala's disc of Franck's Symphonic Variations, rec. 1987)

In a couple of cases I wonder if the flag was set by mistake (eg. BBC Music magazine's CD of Stravinsky's Firebird Suite, rec. 2006)

Surely someone else has noticed this sort of thing?
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Old 16th June 2012, 06:49 PM   #8
Wombat is offline Wombat  Germany
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I donīt have many cds with pre-emphasis but the ones that were detected by EAC were absolutely right.
I think it is more the other way around and many people play back files that never were checked for it.
Most likely on many so called Audiophile systems it shouldnīt matter, the system itself will color the sound more as the de-emphasis.
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Old 16th June 2012, 07:44 PM   #9
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Originally Posted by Wombat View Post
Most likely on many so called Audiophile systems it shouldnīt matter, the system itself will color the sound more as the de-emphasis.
This misses the point that if de-emphasis is applied incorrectly, these recordings will acquire a different tonal balance from the rest of the music collection.

My observations are that without de-emphasis, these recordings sound brighter than the norm, but with sox de-emphasis they end up sounding noticeably duller than the norm. Why should this be?
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Old 16th June 2012, 07:57 PM   #10
Wombat is offline Wombat  Germany
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Originally Posted by CastleJohn View Post
This misses the point that if de-emphasis is applied incorrectly, these recordings will acquire a different tonal balance from the rest of the music collection.

My observations are that without de-emphasis, these recordings sound brighter than the norm, but with sox de-emphasis they end up sounding noticeably duller than the norm. Why should this be?
This shouldnīt be. When i listen the non-de-emphasis version directly before the de-emphasised version i also feel it cuts to much highs. That is normal. We like highs and will prefer it. Also you may prefer the unmodified simply because it seems louder!? When i am at it i also normalize my resutling files.
If i listen the recording without direct comparison on my system the mofified files sound right to me with the ones i have.

Edit: maybe you want to share a test sample of 20 seconds, either with a music part you hear to be totaly wrong or simply a silent part with obvious noisefloor. The shape of the noisefloor if no straight line can hint to a degree but this needs some fiddling and luck to check.
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Last edited by Wombat; 16th June 2012 at 08:12 PM.
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