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View Full Version : Feature request: Audio format of the future - ISO?



paulkmoore
2007-01-10, 15:36
All

First post so please let me know if I've posted wildly in the wrong place.

I have been using SBs and Slim for about a year and have now decided that I'm going to do away with my Hi-Fi altogether. Not amazing you may suggest, but I've gone through the what format should I settle on thinking and concluded that I need to be as close to the original as possible - wav (PCM).

This spurred some further thought... why not take ISO backups of my original CDs and use that as the source file format. Yes there would be some work to be done about how to get / process / update the metadata (remoteDB), but this would mean that for the same disk utilisation you would have a full backup of your prized CDs and would not be committing to any format outside the ISO standard itself.

I have done a little research and obviously you can mount ISO images as file systems, but this gets labourious with vast numbers of CDs (and hence mount points).

Does anybody know if this is in the art of the possible / worth investigation / or reasons why it shouldn't be pursued?

Cheers, Paul

Robin Bowes
2007-01-10, 16:25
paulkmoore wrote:
> All
>
> First post so please let me know if I've posted wildly in the wrong
> place.
>
> I have been using SBs and Slim for about a year and have now decided
> that I'm going to do away with my Hi-Fi altogether. Not amazing you
> may suggest, but I've gone through the what format should I settle on
> thinking and concluded that I need to be as close to the original as
> possible - wav (PCM).
>
> This spurred some further thought... why not take ISO backups of my
> original CDs and use that as the source file format. Yes there would
> be some work to be done about how to get / process / update the
> metadata (remoteDB), but this would mean that for the same disk
> utilisation you would have a full backup of your prized CDs and would
> not be committing to any format outside the ISO standard itself.
>
> I have done a little research and obviously you can mount ISO images as
> file systems, but this gets labourious with vast numbers of CDs (and
> hence mount points).
>
> Does anybody know if this is in the art of the possible / worth
> investigation / or reasons why it shouldn't be pursued?

I'm sure I won't be the first to suggest this, but would suggest you
investigate flac format more closely.

Benefits:

1. lossless encoding - decodes to exactly same as original .wav
2. Tagging support - .wav doesn't support tagging
3. Native support in SB2/3 + Transporter
4. Open source format - if that's important to you.

Hope that gives you some food for thought.

R.

JJZolx
2007-01-10, 16:34
this would mean that for the same disk utilisation you would have a full backup of your prized CDs

How many people backup their CDs? This makes almost no sense to me... it would be like keeping a copy of your TV set or silverware in case of fire or theft. That's what insurance is for.

Ben Sandee
2007-01-10, 17:02
On 1/10/07, paulkmoore <
paulkmoore.2k7uon1168468801 (AT) no-mx (DOT) forums.slimdevices.com> wrote:
>
>
> This spurred some further thought... why not take ISO backups of my
> original CDs and use that as the source file format. Yes there would
> be some work to be done about how to get / process / update the
> metadata (remoteDB), but this would mean that for the same disk
> utilisation you would have a full backup of your prized CDs and would
> not be committing to any format outside the ISO standard itself.


Well, it's pretty simple -- you can't do that. ISO (aka ISO-9660) is not an
audio CD format but rather a data CD format. There are techniques that can
be used to back up audio CD's, but they all involve backing up to WAV/CUE or
FLAC/etc. Look up redbook audio for more info.

Ben

paulkmoore
2007-01-10, 18:58
Firstly - thanks for all the responses - awesome!

Robin - I have indeed investigated FLAC (and the joy of EAC!) and understand the benefits you suggest. I didn't see amazing compression rates - approx 40%. I'm therfore not entirely convinced it's worth using given the balance of storage savings against non-PCM format and ripping effort. Useful though.

Jim - on the backing up CDs point - if I'm going to do lossless ripping (without compression) then the storage used for the CD is approx the same as the ISO anyway. To some degree, anybody who's ripping without compression is backing up their CDs. I was just thinking that given I would be using equivalent space why would I not use a format that would allow me to re-create the CD bit-perfectly. I hear the insurance point though!

Ben - I understand the data vs audio format issue. I can't believe it's beyond the wit of man to have an architecture layer doing the translation on the fly. Given that the data format on the CD is still PCM (chunks) I can't see that something inline would need to be that advanced either - it would have to deal with the meta-data though (non-trivial).

Anyway - thanks to all - will continue pondering - maybe I'll have a go at a plug-in (he said naievely)

Thanks again, Paul

totoro
2007-01-10, 20:25
Firstly - thanks for all the responses - awesome!

Robin - I have indeed investigated FLAC (and the joy of EAC!) and understand the benefits you suggest. I didn't see amazing compression rates - approx 40%. I'm therfore not entirely convinced it's worth using given the balance of storage savings against non-PCM format and ripping effort. Useful though.

Jim - on the backing up CDs point - if I'm going to do lossless ripping (without compression) then the storage used for the CD is approx the same as the ISO anyway. To some degree, anybody who's ripping without compression is backing up their CDs. I was just thinking that given I would be using equivalent space why would I not use a format that would allow me to re-create the CD bit-perfectly. I hear the insurance point though!

Ben - I understand the data vs audio format issue. I can't believe it's beyond the wit of man to have an architecture layer doing the translation on the fly. Given that the data format on the CD is still PCM (chunks) I can't see that something inline would need to be that advanced either - it would have to deal with the meta-data though (non-trivial).

Anyway - thanks to all - will continue pondering - maybe I'll have a go at a plug-in (he said naievely)

Thanks again, Paul

But if you get a good rip when putting it into flac, you _will_ be able to get bit-perfect wav files back if you want to.

I don't think I understand what the advantage of saving the cd as it is would be over this, which probably means I've missed something. Is it the cue sheet you're worried about? I've never messed with those, but I _think_ eac will export it. I'm sure someone here will know the facts about that.

smc2911
2007-01-10, 21:04
Robin - I have indeed investigated FLAC (and the joy of EAC!) and understand the benefits you suggest. I didn't see amazing compression rates - approx 40%. I'm therfore not entirely convinced it's worth using given the balance of storage savings against non-PCM format and ripping effort. Useful though.
Flac is not a non-PCM format, it's just compressed PCM. 40-50% compression may not seem like much, but for me it does mean that I can get my entire music collection on a single 250G drive, which would not be possible uncompressed. Finally, of course, as has often been noted in threads comparing WAV and flac, flac has the added advantage of supporting tags, which means that you actually have more information than you had on the original CD.

Ben Sandee
2007-01-10, 22:18
On 1/10/07, paulkmoore <
paulkmoore.2k83y01168480802 (AT) no-mx (DOT) forums.slimdevices.com> wrote:
>
>
> Jim - on the backing up CDs point - if I'm going to do lossless ripping
> (without compression) then the storage used for the CD is approx the
> same as the ISO anyway. To some degree, anybody who's ripping without
> compression is backing up their CDs. I was just thinking that given I
> would be using equivalent space why would I not use a format that would
> allow me to re-create the CD bit-perfectly. I hear the insurance point
> though!
>
> Ben - I understand the data vs audio format issue. I can't believe it's
> beyond the wit of man to have an architecture layer doing the
> translation on the fly. Given that the data format on the CD is still
> PCM (chunks) I can't see that something inline would need to be that
> advanced either - it would have to deal with the meta-data though
> (non-trivial).


There is no way to do bit-perfect audio CD backups. The audio CD format is
designed with more redundancy on the disc than the data formats have. They
are more resistant to scratches and also laid out in a fashion more
conducive to 'streaming' off the disc. If you do a bit of googling you can
get more information about the unique characteristics of audio CD's,
compared to ISO-9660 data discs.

Further, there is no standard audio CD image format that preserves all of
the data on an audio cd (including CD-TEXT, track boundaries, gaps, etc).
Pretty much the closest you can get is WAV coupled with CUE sheets (ripped
by EAC). This is similar to BIN/CUE sheets too. Using these two tools you
can recreate discs that, for all practical purposes, will sound identical to
the original (however it won't be bit-perfect, it just isn't possible --
google it if you don't believe me).

If you really want a single-file-per-disc backup solution, probably your
best bet is FLAC + embedded CUE sheets, I guess.

Ben

Gregory P. Smith
2007-01-12, 02:27
On Wed, Jan 10, 2007 at 11:18:17PM -0600, Ben Sandee wrote:
> The audio CD format is designed with more redundancy on the disc
> than the data formats have. They are more resistant to scratches
> and also laid out in a fashion more conducive to 'streaming' off the
> disc. If you do a bit of googling you can get more information
> about the unique characteristics of audio CD's, compared to ISO-9660
> data discs.

Audio CDs have -less- redundancy (i'm assuming you mean error
correction bits when you say that) on the disc as bit errors matter
less in audio streams than they do in data. Thats how audio CDs can
get >72 minutes of audio on the same size disc that can only hold
650-700mb of data.

2352 bytes per CD sector for redbook audio. Data CDs have 2048 bytes
per sector.