Re: [linux-audio-dev] So, what to do about it? (was: Still I cannot understand why...)

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Subject: Re: [linux-audio-dev] So, what to do about it? (was: Still I cannot understand why...)
From: Paul Davis (pbd_AT_Op.Net)
Date: Tue Dec 18 2001 - 15:58:29 EET


>> the rate at which data arrives over s/pdif *is* the exact sample rate
>> that the CD is burning at (well, unless you're insane). there is no
>> need for throttling, pitch control or anything like that.
>
>??? dats are 48000, and cds are 44100. doesn't some sort of resampling
>need to occur here?

sure. but thats totally different than dealing with pitch
control. FWIW, i think the tascam units do the resampling themselves,
and in addition, many DATs can be set to resample before output.

a diagram to try to make this clear once and for all:

Collecting data from input:

  data src at some sample rate + bit depth
                   |
                   v
   (resample and format convert as necessary)
                   |
                   v
   store in buffer of a few seconds duration

Burn to CD:

       read from buffer
            |
            v
       deliver to burner

Now just run these two things with the second one starting slightly
after the first. Voila.

As i mentioned, i wrote a highly graphical RT CD burner last year. it
worked, and really worked quite nicely, but it ran into ugly design
problems because of the need for full duplex operation, meaning that
we had to have cdda2av and cdrecord running as joint subprocesses. i
wanted a library do to CD reading and burning, and people pointed me
at paranoia, but this has never matured, the mailing list is all but
dead. at this point, there is no easy to use solution for burning cds
if you want to write a program to do it. cdrecord is full of globals
and design assumptions that prevent its effective use a library, and
its author intends to keep it that way given his response when i asked
him about this.

--p


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