Re: Advanced Audio CD Functionality under carbon / OSX
Re: Advanced Audio CD Functionality under carbon / OSX
- Subject: Re: Advanced Audio CD Functionality under carbon / OSX
- From: Brian Willoughby <email@hidden>
- Date: Sun, 20 Jan 2002 04:20:15 -0800
Mark Gilbert <email@hidden> asked:
[ ... I need much lower level
[ access to the Audio CD Data. In particular, its vital that I be
[ able to read the P-Q Subcode which runs alongside the Audio Data
[ in each track. I need this in order to read the 'Sub track Index'
[ value for any given position in the audio data.
[
[ Can anyone point us in the right direction ? I am getting the
[ impression we may have to bypass the OSX Audio CD file system in
[ order to get back to the full data. Is there any way to make OSX
[ mount the disk using a different file system ? I presume there
[ is no longer an .AppleCD driver or anything equivalent which we
[ can communicate with.
You might have better luck accessing the CD drive using the SCSI commands for
CD-DA media. They offer the ability to seek my HMSF instead of by SCSI block.
There are also Mode Select commands for CD which allow access to the full Red
Book frames, including the subcodes you need (although you might have to weave
the bits together yourself). Mac OS X does have a SCSI Client library for
sending any possible SCSI command to a target device.
There are a couple of problems with this:
1) not all CD drives are SCSI, but I assume the ATAPI spec has something along
the lines of the capabilities of SCSI CD drives.
2) regular users typically don't have access to the SCSI target ID after a
drive is mounted, because that might allow them to circumvent the security of
the file system. With CD being read-only, I don't know if this would allow for
an exception, otherwise you'll need to run as root or possibly prevent the
auto-mount of the CD in the first place.
3) I writing this from the point of view of NeXTstep, where I've accessed CD
and other SCSI devices directly, using the SCSI client libraries, in order to
access the kind of data that you need. I assume this is all available from
Cocoa, but I'm not sure what services your Carbon app will have available to
it.
Brian Willoughby
Sound Consulting