Subject: RE: [linux-audio-user] Mastering; Rezound, fir filter, digital clipping
From: Mark Knecht (mknecht_AT_controlnet.com)
Date: Fri Jun 13 2003 - 20:38:55 EEST
> Hi,
>
> I'm doing a study on audio mastering. Hopefully this
> letter will generate some correspondance from which
> I'll learn enough to augment a GFDL licensed document
> that I've been working on.
Great! I wish you the best of luck and I'm certainly
interested in hearing about what you learn.
(And maybe hearing some results along the way!) ;-)
>
> The test job is an album I recorded several years ago.
> The source I've decided to use is 16bit 44100 audio
> CD. I'm restricting the applications I use to jack
> clients.
>
> I guess the process of copying audio and data from CD
> doesn't introduce any opportunity to compromise the
> sonic quality of the source. Am I right or wrong?
According to one guy, you're wrong. (In a very minimal
sense...) There is a tool called 'Exact Audio Copy'
that is very interesting. It's a pretty cool little tool.
I think you might be looking for it's 'Glitch Removal'
section on the Sound Editor page.
>
> Having opened the songs in Rezound, I've discovered
> that some of the songs have an inordinate amount of
> clipping--represented by vertical red lines on the
> time line. For the purposes of testing this is
> excellent because they're an opportunity to solve a
> common problem. The clips cause a series of questions
> for which I absolutely do not have definitive answers.
>
> Is what I am seeing clipping or is there a more
> accurate term to describe what I'm seeing?
These may be clipping, but the might be incorrectly
written bits on the CD you're ripping, as described above.
As an experiment, I've burned multiple CDRs with the
same database, and then used EAC to see what happened.
None of the CDRs were identical, even when burned at
a lower speed.
It could also be just plain clipping if the levels were
set too hot in the original mix.
A very interested CD for you to look at sometime is
Pilgrim by Eric Clapton. That CD looks like it went
through an overaggressive compressor. Most songs, when
viewed in their entirety, look like a big rectangle
of data. Very weird, and not his most successful.
Other CDs I've run across with strange results might
be something like SMPTE by Transatlantic which seems
to drive my CD player crazy with clipping.
I've spend time looking visually at CDs I like the sound
of, and a few I dislike, just to get an impression of
what's going on. Weird hobby of mine, but I have others
too... ;-)
>
> Perhaps someone could provide a technical explanation
> of clipping or a link to a definition.
>
> What tools do you use for eliminating clipping that
> already exists in a source? I don't care at all about
> preventing the problem.
Waves has some stuff in their Restoration package for
clicks and pops, and then their Master's package has a
look-ahead limiter/compressor which is quite good at
this sort of stuff.
<SNIP>
> *can engineers safely ignore inaudible clips and tell
> their clients that there's room to fudge and not to
> worry
>
That's a business question! ;-)
- Mark
This archive was generated by hypermail 2b28 : Fri Jun 13 2003 - 20:49:43 EEST