Strange: I see no reason why any major MP3 player manufacturer out there would NOT support variable bit rate, for two reasons: 1) It's in the spec. Layer I and II are not required to support it, but Layer III is, and 2) Manufacturers rarely, if ever, roll their own implementation of the decoder...it's usually purchased from some third party, and there aren't that many out there. Since each of those third parties is trying to support as wide a market as possible, they will always put in as many options as possible, hence, everyone gets those options.

SO, it doesn't surprise me that your Alpine played it. I'll take a look at that website and report back what I find.

 

Oh, I figured they would. I just do not want to make the statement that all mp3 units or even all Alpine units definitely do and then have someone be disappointed when/if they find out it doesn't.

 

The LAME website isn't too shabby. It's a GPL version of an MP3 codec (decoder AND coder), so the source is there to scrutinize. It looks like they're adding in some fresh, new ideas to the psychoacoustic model from time to time, so I'll probably check back from time to time to see what they've come up with.

 

I think there is little need to save space, given the high capacity disks of today. I have just ordered a iPOP (MP3-Player from Apple, 10GB-Disk). I plan to use it in my S2000 too.

 

That sounds like a comment straight out of Bill Gates' mouth At one point, he said "Why would anyone need more than 640kB of memory?!" Obviously he was dead wrong.

While I agree that high-capacity disks are quite cheap these days, does that negate the requirement of smaller files? Probably not. With smaller files, I can begin to use other means of storage media, such as flash cards to hold the same amount of data. Smaller files may also mean reduced system complecity, which could also mean longer battery life, reduced cost, etc.

The project I'm currently working on is in line to be about the size of the i-POD. However, I intend mine to support quite a few things the i-POD doesn't, such as the ability to update its software to accept new standards as they are released. I want the ability to use not only HDs, but flash, USB, Bluetooth, etc. Any reduction in filesize is welcome for a lot of the options I just mentioned.

 

BTW, the iPod is capable of software update. They recently added support for Audible content (mostly spoken word books etc.) Presumably they could add something like MP3Pro, or more likely AAC support.

 

Ted, can you clarify what audible content is? The MP3 spec supports extremely low bitrates, something perfect for voice only, book readings, etc. Never knew the i-PODs were updatable, but it seemed more odd to me that they WOULDN'T add that feature in, considering the technology.

 

You can find out about it at:

http://www.audible.com/

It may actually be the same encoding as MP3, I'm not sure, but they do have security stuff going on, since they sell the content, and it's usually copyrighted by other people . Apple added support for it in a recent software update. I've never used the Audible stuff, so I don't know much about it.

Apple has also added other features to the iPod since it was introduced, like abiity to store contacts (phone, addresss, etc.) and events, with clock and alarm features. Plus you have always been able to use the iPod as a FireWire hard disk.

 

OK, gotcha...Audible isn't a format, it's merely content you can purchase, most likely in MP3 format. The MP3 format supports two bits within the header, one to specify if the material is copyrighted, and the other to specify if "this" bitstream is an original, or a copy.

Voice tends to be monophonic (i.e., no multi-instrument orchestrations playing at once), which lends itself to high compression with the Huffman coding used in MP3. Reading books are perfect material for this sort of medium.

 

Here's a description I found and some more info on the MP3PRO format...

=======================================
How does Spectral Band Replication work?

SBR does not really encode the highest part of the frequency spectrum; it reconstructs this part. In a 64 kbps Mp3Pro encoded file, around 60 kbps are used for the conventional Mp3 data. The Mp3 encoder encodes the music signal up to 8kHz in a conventional way. This part of the resulting Mp3 file can be decoded by any Mp3 decoder, so compatibility is kept with conventional decoders.
The SBR technique will use this part of the decoded signal to reconstruct the missing high frequency part, from 8kHz up to 16kHz, by duplicating the spectrum. This kind of trick was already used by Kenwood (D.R.I.V.E.) and Pioneer (Legato-Link). So what does make SBR better than those other solutions? A simple fact: while previous solutions were blind, SBR knows better how to reconstruct the missing parts.
During the encoding stage, the SBR encoder stores some information to in order to try reconstructing properly during the decoding stage. It stores from which part of the original band-limited signal the upper frequencies should be replicated, and also the scale of those frequencies. That information is very small compared to a conventional encoding, and are stored into ancillary data of the Mp3 file. This way, an SBR-enhanced decoder will be able to use this info.


The results:

The first thing is that this SBR reconstruction needs some processing power. So current SBR-enhanced Mp3 decoders need 3 times (yes, 300%) the power of a conventional Mp3 decoder. If this is not a problem for a computer, it could be a problem for hardware decoders, like those found in portable devices.
For low bitrates, the sound result is quite good (The interest of SBR with high bitrates is limited). Of course Mp3pro won't give you CD quality at only 64 kbps. Such a 64 kbps file gives a result similar to a 100 kbps Mp3 file, but according to the bitrate, this is a good result. With SBR, Mp3Pro is now able to compete against Windows Media Audio for low bitrates.
=======================================

This description also brings up a good point which I think I missed in my original description...with some decoders (actually, quite a few more than I expected, including commercial software), information above 16kHz is not even encoded into the final bitstream. The MP3 spec actually leaves this band of the spectrum open to interpretation and doesn't require coding there. With the MP3PRO format, audio data above 8kHz ISN'T encoded in such a way that it can be decoded with a standard MP3 decoder.

I'm not sure if too many would disagree with me or not, but there's a LOT of good music above 8kHz.