Re: Audio FS Bad Idea

From: Linda Walsh (law@sgi.com)
Date: Fri Apr 07 2000 - 16:28:20 EST


JM Geremia wrote:

> > Wondefull. But there are hundrets of nice ripper/encoder frontends
> > outhere, but that's not related to an fs that makes traks of an audio
> > cd aviable as files.
>
> As someone who has written an extremely sophisticated audio cd filesystem,
> I must say that I completely agree with Jens. It's a BAD IDEA. Actually,
> he yelled at me about this about a year ago :) This would be a great
> topic to add to the FAQ!
>
> There are two schools of thought:
>
> 1) Things like jitter and scratch correction are not obvious kernel
> functionality. They bloat the kernel and can be done just as
> effectively in user space. Implementing corrections for drives
> that do it with hardware is a waste. Not implementing corrections
> is inadequate for the rest. The whole idea behind standards like ide
> and SCSI is that the drivers can be more generic.
>
> 2) The CD-ROM is a device, and doing corrections are the job of the
> driver. However, the audio sector size is bigger than the pagesize
> and this means doing translation if the filesystem is to use the
> normal blkdev approach.
>
> The inodes and superblock would all have to be virtual since the only
> directory structure on an audio cd is the TOC. I have no problem
> with this, personally.
>
> This means that the cd drivers (all of them) would need to be changed
> to translate between pagesized blocks and framesize blocks and then
> have a fairly intricate cache scheme. Otherwise, the audiofs
> implementation would need to make ioctl() calls. I, for one, don't
> think that the kernel should use ioctl's. Personally, I don't like
> them because the kernel has to turn off memory write verification
> using get_FS() and set_FS(). I'm not happy about that.
>
> Now, honestly, do you think Option (2) is worth all that? Having
> implemented it all (for fun, mainly) I can tell you to stick with the
> userspace rippers/encoders. They are the right way to go.

====
    I dunno. IRIX has had the ability to mount audio CD's for about 4 years. It sees the tracks as '.aiff'
format files and seems to
handle conversions fairly well. The mediad even automounts the CD depending on its format.
I've always thought that was 'nifty'. What would be the harm in having a modular driver for it?
It's not kernel bloat unless you want to select in that driver. If you didn't want it -- use a userspace
ripper. The driver can be tweaked until it produces optimal output.

JMO...

--
Linda Walsh @ SGI                | Core Linux - Trust Technology
1200 Crittenden Lane MS:30-3-802 | Voice: (650) 933-5338
Mountain View, CA 94043          | Email: law@sgi.com

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