Date: Thu, 18 Jan 2001 10:08:53 -0500 From: Bob Johnson <bob@eng.ufl.edu> To: Mike Meyer <mwm@mired.org> Cc: questions@freebsd.org, r.j.steehouder@student.utwente.nl, dhagan@colltech.com Subject: Re: [FBSD-Q] Re: Burning Audio CD's w/ IDE CD-RW drive Message-ID: <3A670705.ABEF177F@eng.ufl.edu> References: <14950.32096.857110.50397@guru.mired.org>
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Mike Meyer wrote: > > Bob Johnson <bob@eng.ufl.edu> types: > > Rogier Steehouder wrote: > > > > > 2) Burn that track onto a cd-r (burncd -f /dev/acd1c audio filename > > > > > fixate?) > > > > That's right. burncd will accept wildcards, so all of the files > > > > generated by dagrab can be burned with something like: > > > > $ burncd -f /dev/acd1c -e -s4 audio track*.wav fixate > > > Have you tried this? Does burncd convert .wav to CD audio format? > > > I suspect the result of the procedure above will sound like random noise. > > It works fine. I've done it several times. > > The cdrecord man page implies that wav files are in the right format, > but the header needs to be skipped. Failing to skip the header will > cause a click at the start of the track (as it plays the > header). Do you get such a click on the track? > I started thinking about it after my previous message and realized that is probably what is happening. A wave file is basically raw audio with a header added. I had never noticed it before, but if I listen very carefully I can hear the click at the start of the track. It's at the start of the silent lead-in, and is an extremely short click. I would have never noticed it if I had not been looking for it. Someone with better ears or better equipment might notice it, though. I would think that it would be very easy to strip off the header (with dd, for example) if you knew the details of the wave file format. It turns out that the headers add up to 42 bytes at the start of the file. Raw CD audio is 44,100 samples/second, 32 bits per sample (16 for each channel), so that 42 byte header will produce about 0.2 ms of audio, and because it is relatively random audio, it doesn't produce a click that is as loud as it would be if the data were, for example, all ones. When I get a chance I'll see what happens if I try to strip the header off before I record the CD. For those who are interested, http://www.technology.niagarac.on.ca/courses/comp630/WavFileFormat.html has some information about the wave file format, and http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio2/95x7.htm has a lot of information about how audio is recorded on a CD. The page following it has info about CD data formats, the difference between mode 1 and mode 2, and other neat stuff. - Bob > <mike > -- > Mike Meyer <mwm@mired.org> http://www.mired.org/home/mwm/ > Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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