Re: Attn Muse: Your current duties

Andrew Stephenson <ames@xxxxxxxxxxxxxxxxxxx> wrote:

In article <1i3vr52.1e63cp61dkp2c1N%spam@xxxxxxxxxxxxxxxxxxxx>
spam@xxxxxxxxxxxxxxxxxxxx "Jonathan L Cunningham" writes:

Andrew Stephenson <ames@xxxxxxxxxxxxxxxxxxx> wrote:

That was the basis of my grouse: it's a simple format, yet "they"
manage to screw it up _and_ call it WAV. (If the player can play
normal commercial CDs but has problems with WAV files made by the
recorder, I infer dishonourable misconduct by the Sanyo-machino.)
Unless I missed a detail somewhere, that is.

It can play all files in the format it records in. It can't play .WAV
files recorded in a different format. Possibly the detail you are
missing is that the .WAV file format isn't a single format.

I really should look this up but am entangled in OtherStuff: are
you saying there is no clear definition of the WAV format? That

I have a very-out-of-date description of the file format. It may have
been extended (such things often have a field "reserved for future
enhancements" which has to be set to 0 in this version. Off the top
of my head, I can't remember if there are such fields in the WAV
file header).

it is not, in fact, a standard? What you go on to say about BMP
illustrates my question: an image format will contain all manner
of info, beyond dimensions and version codes (including "finger-
prints", such as TIFF's code to say which order multibyte values
are stored in (Intel vs Motorola) and Unicode Byte Order Mark to
achieve the same effect). Do WAV files really not contain basic
info like that?

Yes, they do. But suppose one of the basic pieces of info is a code
indicating a compression algorithm to use?

Take MPEG files as an example. A lot of programs can play MPEGs. A lot
less can play MPEG2 (which is the basic format for unencrypted DVDs).

I don't know any that can play MPEG9. Probably because MPEG9 hasn't been
invented yet ...

What is your player to do, if it encounters an MPEG file, and the header
says it's compressed according to MPEG compression standard 53? Wait
twenty (or a hundred) years until it can download a suitable codec? :-)

If not, I am duly boggled. But IMHO the bl**dy
recorder/reader should at least use the CD WAV format, so common
software can be sure of being able to manipulate it. </grump>

I'm not sure that CD's *do* use WAV files. As I said, the *basic* WAV
format doesn't use compression. Neither does the CD format (after error
correction and low-level stuff to do with actually reading the data off
the disc). So converting a sequence of numbers into another sequence of
numbers isn't very difficult, i.e. reading a CD and storing a track as a
WAV file is just a question of writing a different (very short) header
(I think).

But, while CD's use a fixed encoding (I think) WAV files *do* contain
all that information you were talking about in a header i.e.
no. of channels (mono or stereo)
samples per second (there are a few common sample rates)
bits per sample

Multiply those three numbers together, to get an idea of how much
processing power is needed to play the file.

If you are running a processor off a single 1.5v AAA battery, it's
probably not going to be as powerful as your desktop Pentium churning
out enough heat to cook sausages ... so it's not unreasonable if your
little voice recorder can't process 24 bit stereo at 44,000 samples a
second, but *can* process 8 bit mono at 11,000 samples a second (or
whatever the actual format is).

If you want to play CD's, you probably need *two* AAA batteries ... :-)

Jonathan

--
"I think too much - therefore I am mad!"
Agatha Clay playing Lucrezia Mongfish.
.

Relevant Pages

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