Help with all this digital stuff?

[Paul Mather]

On Thu, May 06, 2004 at 03:25:01PM +0100, M Holmes wrote:

=> So after 3 hours of reading manuals, I have questions. Mainly these are
=> about MP3's and what form CD tracks normally arrive in. There appear to
=> be different kinds of MP3 based on bitrates, sampling frequencies, and
=> lord knows what else. Is there a site with a non-geek level of
=> explanation of all this, codecs and whatnot? Basically I want to now
=> what settings to use the microphone on, and what settings to use to
=> store music on the hard disc. I'm told that Itunes converts between all
=> these different formats anyway?

I don't know about "non-geek" :-), but CD players ultimately work with
16-bit stereo samples @ 44.1 KHz sample rate.  MPEG audio (somewhat
erroneously lumped into the grab-bag catch-all category of "MP3" in
the popular mainstream) allows quite a bit of flexibility in encoding.
Normally, though, it comes down to the bitrate you decide to use: the
rate of MPEG data into which your original digital audio must be
squeezed.  The lower the bitrate, the more quality you throw away to
fit things in (but the smaller the resultant encoded file size).

Another important encoding setting is whether to use constant bitrate
(CBR) or variable bitrate (VBR).  VBR is better, though CBR is older
and hence likely to be universal.  VBR will dynamically alter the
bitrate used on a frame-by-frame basis depending upon the complexity
of the music.  So, "simple" things like "quiet bits" are encoded using
a lower bitrate than "complex" things like "noisy whooshy bits." :-)

I have a Panasonic "walkman" that also supports "MP3" CD-ROM/R/RW
discs.  It seems to accept VBR-encoded MPEG audio on a standard ISO
9660 disc.  I encoded about 7 hours of my Bevis Frond studio discs to
provide a nice sample disc for when programming, and it will play it
no bother.  I used the freeware "LAME" encoder encoding CDDA WAV files
using VBR mode on high quality setting (128--320 kbps bitrate).  You
can get a version of LAME for Windows.  EAC can even rip CDs to MPEG
audio using LAME as the encoder.

=> Of course I'm then faced with 5 different recording formats for DVD
=> (only 5?). Anywhere I can find out about those?

How about the DVD FAQ?  (http://www.dvddemystified.com/dvdfaq.html)

=> flashcards much more quickly? However the HDD/DVD units that I've seen
=> seem to record in MP2 format rather than MP4. The Archos won't play MP2.
=> Am I likely to find a DVD/HDD which records in MP4 or is there some
=> reason why the companies won't do that?

I'm guessing they'll be loathe to do that because MP2 is standard,
whereas MP4 subjects you to to "codec hell."  The Archos is
undoubtedly using MP4 so it can use a (possibly proprietary)
high-compression codec to maximise the amount of video they can fit on
the installed hard disc/flash card.

Note that "high compression codec" does not necessarily equate to
"high quality codec." :-)

Cheers,

Paul.

e-mail: paul at gromit.dlib.vt.edu

"Without music to decorate it, time is just a bunch of boring production
 deadlines or dates by which bills must be paid."
        --- Frank Vincent Zappa