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MPecker Encoder 1.0b1 ƒ
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1998-04-01
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MPecker Encoder 1.0 Directions
-------------------------------
Mpecker will run on any MacOS PPC machine, and will encode AIFF files
sampled at appropriate frequencies into mpeg files. It will also encode
44100 Hz PCM files as well. Supported sampling frequencies are:
44100, 48000, 32000, 24000, 22050, and 16000 Hz.
To start the program, double click on the MPecker Icon, or drag your aiff
file(s) onto the icon. The program will start. If you have used MPecker
Encoder before, your previously used preferences will automatically be loaded
and set.
To add more files for encoding, either drag their icons onto the application's
icon, or use option-M or Modify Batch List from the Menu, and add files there.
The program will hold 256 different file names for encoding.
To open and encode just one file, you can use option-O, or Open File. After
you select the file, it will start encoding.
To start encoding the batch list, choose option-E, or Encode Batch List from
the File menu. All files in the list will be encoded, no matter what type of
file they are. Warning: This means text files, binary files, ANYTHING you add
to the list will be encoded.
Converting CDDA to AIFF files
-----------------------------
Select this option from the files menu. IMPORTANT: Be sure to select the
options button at least the first time you use this feature, or you will
get some random conversion. Your converted files MUST BE 16 BIT!
Mono or stereo is up to you. Your sampling frequency must be one of the
supported sampling frequencies mentioned above.
NOTE: THE OPTIONS BUTTON IS ON THE SAVE MENU DIALOG (The Second one), NOT THE SELECTION
MENU DIALOG (The initial one)!
Next select a place and a name for the file and the computer will do the rest.
The Priority Menu
-----------------
You can change the amount of processor time the encoder uses by selecting
one of the three options in this menu. The default is "Run like a good mac
proggie" and this will "yield" to most every other process running. It will
also considerably lengthen your encoding time.
The two other options increase the number of encoded frames between CPU
"yields", and also increases the amount of time between encoder window updates.
It will also make other programs a bit "jerky" as interrupts are serviced less
frequently.
The Options Menu
----------------
Here, you can choose several different options for encoding your file.
If you know nothing about MPEG, use joint stereo, 128 kbps, layer III.
---Layer II or III
These are different means for encoding music files. Layer II is
less complex, but sounds better at higher bitrates. Stereo reproduction in
this layer is very good for bitrates of 128 kbps and up. Layer III is the
most complex of the implementations. It combines the features of layer II,
plus a modified FFT and a Modified Discrete Cosine Transform (MDCT) to the
encoding process, and also "packs" each frame using Huffman encoding, thus
it takes ALOT of computation time to encode in layer III.
There is a great deal of debate on whether layer II or layer III is the more
robust of the encoding implementations. At bitrates of 128 kbps and higher,
arguably layer II is better at reproduction in my opinion. Nevertheless, there
is a bias toward layer III on the internet, probably only because it is
more complex, and because III comes after II, rather than any real audio
difference between the two. Certainly, however, at bitrates lower than
128 kbps, layer III has the upper hand.
---Bitrates
The bitrate is the number of bits used to encode the audio sample for each
second of music. For example, a bitrate of 128 kbps means that there are
128,000 bits (16,000 bytes) used to encode each second of music. While
that sounds like alot, realize that there are 176,200 BYTES (1,409,600 bits!)
for every second of music in a 44.1 kHz stereo AIFF file. Thus you can see
the significant advantage of encoding in MPEG audio.
In general, most people will leave the bitrate at 128 kbps, as most people are
encoding stereo files. Mono files can be encoded at lower bitrates - 64 kbps
will probably work nicely. For both stereo and mono files, if you find your
particular file sounds "distorted" or like music is "missing," try a higher
bitrate.
---Modes
There are three modes of encoding: Mono, stereo, and joint stereo. Mono is just
an encoding of a one channel file. Stereo makes an encoding of a two channel
stereo file. Do not worry too much about mono vs stereo if you are using
AIFF files, as the program detects mono files and will adjust the encoding
accordingly.
The term that may sound unfamiliar is "joint stereo." Joint stereo is an
encoding algorithm used to increase the quality of the encoding. If the
total distortion of the music exceeds an implementation dependent value,
then subbands of the audio are combined, highest frequencies first, so
that less space is required to encode the entire file. This tends to make
the treble sound a bit flatter than a stereo encoding would, but improves
the reproduction of the mid and lower range frequencies.
===================================
The most common encoding settings found in MPEG files on the internet are:
128 kbps, joint stereo, layer III. See my layer discussion above.
For your own purposes, you may want to experiment with different settings to
generate your favorite "flavor" of MPEG files. My personal preferences are
either layer II stereo 128 kbps, or layer III stereo 128kbps.
Do not confuse MPEG layer III with MPEG-3. There is no MPEG-3 as an IS.
MPEG-1 is the original MPEG audio standard, and has layer I, II and III
encoding. It supports 32 kHz, 44.1 kHz, and 48 kHz sampling rates.
Thus, all files encoded from a 44.1 kHz sampled file are MPEG-1 Layer I, II
or III files. MPEG-2 was developed after MPEG-1 with the goal of supporting
lower sampling frequencies. MPEG-2 supports 16 kHz, 22.05 kHz, and 24 kHz
sampling frequencies, thus all files encoded from a 22.05 kHz sampled file
are MPEG-2 layer I, II or III files. The commonly used suffix ".mp3" is
commonly referred to as "MPEG 3" files, but really, it is an MPEG-1 or MPEG-2
layer III file, depending on the sampling frequency as discussed above.