Re: [MacPerl] Querying audio CD for track pre-play times

[Alan Fry <ajf@afco.demon.co.uk>]

At 8:26 pm -0500 18/04/00, Ken Williams wrote:

>I've been looking at the AudioCD::Mac module and wondering whether I can get
>the "pre-track pause" information about a CD.  I'm not sure what the official
>name is for this information (Toast simply calls it the "pause").

In the last few days I have been looking at AudioCD::Mac (with Chris 
Nandor's assent I hasten to add -- he broke the ice on this one) with 
a view to tackling some of the things on his 'ToDo' list (see Mac.pm 
POD). So the question comes at a timely moment.

What exactly do you mean by "pre-track pause"? To the best of my 
knowledge the only information on the disc about the contents of the 
disc is the absolute start time (in minutes, seconds and frames) of 
each track. This is returned by Mac.pm in 'cd_toc' ( and in 
alternative format by 'cddb_toc').

In practice there is a period of silence between the physical 
track-start and the beginning of the sound and similarly between the 
last sound and the physical track-end. However the duration of the 
recorded sound itself is certainly not recorded in the CD information 
block, although it might well be printed on the CD 'sleeve'.

>My goal is to get a list of pause timings for copying one CD to another,
>possibly using Disk-At-Once for seamless transitions, so that the copy has the
>same pauses between tracks as the original.  Apparently Toast can't read the
>pauses on a CD, it can only write them.

This makes no sense to me at all. There are no 'end of track' markers 
on the disc. The end of one track is simply defined by the beginning 
of the next. In the case of the last track on the disc, its end is 
determined by the beginning of the 'lead out area', which _is_ a 
defined position. The 'lead out area' descriptor is returned by 
Mac.pm as the last item in the 'cddb_toc' list. Hence if you add up 
all the track playing times on the printed CD 'sleeve' the total will 
generally be less than the 'lead out area' start-time.

In a nutshell, I cannot see why a copy of a disc in which the 
absolute starting times of each track were the same as the original 
disc should not be a mirror image of the original disc. Have I missed 
something here?

At 8:52 pm -0500 18/04/00, Ken Williams wrote:
>Perhaps I'm a step ahead of (behind?) myself.  Actually I'm having trouble
>installing AudioCD::Mac, because when I dropped the .tar.gz file on
>installme.plx, the Mac.xs file didn't get compiled (I don't have a compiler).
>Thus there's no loadable object for the module.

The CPAN distribution of Mac.pm certainly does include the compiled 
binary for Mac.xs and it works fine. There has been quite a lot of 
discussion in these pages in recent times about installing modules on 
the Mac and to say the least I am not the best person to add anything 
to that.

Alan Fry

PS Perhaps this thread ought to be continued on the 'modules' list?

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