CD de-emphasis

[Clegane]

All Japanese CDs printed in the 80's have pre-emphasis, boosted high frequencies which were attenuated on playback to improve the S/N ratio in early CD players. It would therefore be really nice if dbPoweramp offered de-emphasis amongst its DSP effects.

I have spent a fortune collecting these CDs, I am not about to use some free 3rd party utility with no reputation to de-emphasize them. The alternative is to spend a few hundred dollars purchasing Sony Sound Forge and the Waves Q10 plugin and creating my own de-emphasis filter.

The de-emphasis filter is simple and easily within bounds of what dbPoweramp could do.

[EliC]

Re: CD de-emphasis

Clegane, can you explain more about this to those of us (me) that don't know about de-emphasis on CDs?

[Spoon]

Re: CD de-emphasis

There is the EQ DSP effect, I am sure de-emphasis could be applied with it.

[EliC]

Re: CD de-emphasis

But is this something encoded on the disc in some way that is not being "ripped"?

[Clegane]

Re: CD de-emphasis

But is this something encoded on the disc in some way that is not being "ripped"?

Of course not, not any more than pre-emphasis on an FM broadcast prevents you from listening to the signal. There is some sort of bit flag on the disc that signals the presence of pre-emphasis, but nothing reads it anymore. All you need to do is look for the presence of "TO" after the catalog and matrix number of the CD on the inner ring.

[Clegane]

Re: CD de-emphasis

There is the EQ DSP effect, I am sure de-emphasis could be applied with it.

That isn't going to come even close to cutting it. First off, it has to be parametric to get the correct frequencies, and then there is the matter that the attenuation levels off after a certain frequency - it's not a simple lowpass, highpass, or bandpass filter.

[Tigerman]

Re: CD de-emphasis

I find this

I have spent a fortune collecting these CDs, I am not about to use some free 3rd party utility with no reputation to de-emphasize them.

and this

The de-emphasis filter is simple and easily within bounds of what dbPoweramp could do.

a bit contradictory.

If it's so easy why is sox (see point 6) or even this program not good enough?

Both programs are freeware. I think the people at sourceforge normally have a good reputation (imho). Don't know the reputation of Dipl.-Ing. Th. Ahlersmeyer, but his references (see "My background") don't look too bad


But then again, if DBpoweramp could do it, it would be even better

[Porcus]

Re: CD de-emphasis

But then again, if DBpoweramp could do it, it would be even better

Quite a bit annoying that it doesn't, nor does it even log that a disc is pre-emph'ed.

sox is free open source (available under GPL and LGPL), so Spoon won't even have to write the filter, only invoke sox -- and make sure the output is written to a 24-bit file (just as HDCD files are).

[EliC]

Re: CD de-emphasis

This is why it would be nice if the DSP development were opened so others could develop DSPs for dbpoweramp.

[Clegane]

Re: CD de-emphasis

I find this

If it's so easy why is sox (see point 6) not good enough?

The art is in the phase manipulation.

The Waves Q10 plugin only uses 32 bit floats internally, so SOX is the best alternative, for better or worse.

The most important CD to de-emphasize are the early issues of the Wall, the Japanese 50dp and 48dp issues, as well as the original "made in Japan" American issues.

MFSL totally blew it when they made The Wall, thus forcing everyone to pursue these archaic issues if they want good sound.

[Clegane]

Re: CD de-emphasis

Given sox, the difficulty is in detecting the presence of pre-emphasis. There's an easy way that doesn't always work and a hard way that always works.
It might be a good idea to have a beta version that doesn't always detect the presence of pre-emphasis successfully. EAC once implemented it.

[Rollo]

Re: CD de-emphasis

Not ALL Japan CDs from the 80s have Pre Emphasis.

"TO" in the matix only indicates the CDs were pressed at the Toshiba plant in Japan. The CDs may or may not have PE applied.

EAC only detects PE if the signal is properly included in the Q sub channel. These Japan pressings [apparently] do not, as the flag is included in the disc TOC.

Audacity, as I recall, has a proper de-emphasis filter.

Unless you have a vintage CD player with a PE indicator, its difficult to determine for absolute certain whether the disc included PE or not. Typically, the sound will be much brighter and harsher, and you may hear a pronounced tape hiss.

[EliC]

Re: CD de-emphasis

Spoon, since this is already detected is there any reason discs with pre-emphasis can't be flagged in the meta-data?

Also agree that a sox dsp would be nice for de-emphasis, though rare enough to be low on the priority list.