[ale] [OT] Help! burned cd playback wave clipped, original wave perfect
Ron Frazier (ALE)
atllinuxenthinfo at techstarship.com
Thu Aug 29 01:14:06 EDT 2013
Hi all,
I need some help with an audio cd production I'm working on for a
private family event. This is a little complex.
I've been working hard to pull some quality master audio waveform files
from cassettes that I own. The audio is as good as can be expected from
a cassette tape, and is very decent to listen to. I've worked hard to
edit the files, set the levels, eliminate the clipping, and silence the
space between songs.
I saved the MASTER files as signed 24 bit pcm wav files, which are
lossless. I then burn the wav files to cd (standard cd audio) using
Windows Media Player. Bear with me, this is NOT Windows centric.
Next I rip the cd I burned back to lossless wav files. I then import
the two waves, my master, and the ripped wave into audacity. The waves
look identical, as they should.
So, I know that my master wav file and the wave file on the cd, ripped
back into wav are exactly the same.
Then I play the cd on a cd player and record back into audacity. I make
sure the volume on the input is NOT too high. However, the waveform
coming out of the cd headphone jack is visually severely distorted and
clipped.
Look at this file.
https://dl.dropboxusercontent.com/u/9879631/cd_playback_clipping.png
The top waveform, titled ripped, is the file that was ripped from the
cd. It looks very nice and there is no clipping or excursions beyond
the +/- 1 amplitude levels. It's just like the master file.
The bottom file, titled played, is what was obtained by playing that
same file (track) back and rerecording it. Note that it is severely
clipped, BUT, its excursions are nowhere near the +/- 1 limits. This
proves I don't have the input volume too loud. This is something that's
happening in the playback circuit of the cd player. I've confirmed the
behavior on 2 cd players and observed the same thing on a commercially
recorded cd.
Also, I've compared the audio playing back the ripped file, versus the
played file from the cd player. The ripped version sounds better and
fuller.
I wonder if they're doing some dynamic range compression on the output
of the dac. Whatever it is, it's not stored in the raw cd data.
Does anyone know what this is and if there is a way to eliminate this,
so that the true waveform on the cd, which is the same as my master, is
what comes out of the speakers.
Any help is appreciated.
Sincerely,
Ron
--
(PS - If you email me and don't get a quick response, you might want to
call on the phone. I get about 300 emails per day from alternate energy
mailing lists and such. I don't always see new email messages very quickly.)
Ron Frazier
770-205-9422 (O) Leave a message.
linuxdude AT techstarship.com
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