home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Amiga MA Magazine 1998 #6
/
amigamamagazinepolishissue1998.iso
/
datatypes
/
fp_adpcm
/
hifi2adpcm
/
hifi2adpcm.doc
< prev
next >
Wrap
Text File
|
1997-07-30
|
4KB
|
142 lines
-----------------------------------
*** Flowerpower's ADPCM package ***
-----------------------------------
Hifi2ADPCM documentation
This software package is in the public domain.
Do with it whatever you want.
Introduction
------------
This program can convert HIFI Stereo and Mono music data to ADPCM format.
Its main purpose is to convert CD-DA data and decoded MPeg audio file to
ADPCM format.
Technical Info
--------------
This program will either read RAW PCM or 8 and 16 bit AIFF files. The
CD-DA data will be converted to MONO. An optional scaling can be done as
well. Then the data will be compressed using ADPCM2 or ADPCM3. The ADPCM
algorithm is taken from example sourcecodes for the ZyXEL modem's voice
files.
Usage
-----
This is a Shell-only program. Do not try to start it from Workbench. A
user interface may be added in the future.
FROM/A
The name of the source RAW PCM or AIFF file.
FREQ=FREQUENCY/K/N
Define or override the sampling frequency of the input file.
TRK=TRACKS/K/N
The number of audio tracks of the input file. 1 for Mono. 2 for Stereo.
BPS=BITSPERSAMPLE/K/N
The number of bits the input file is quantized with. Either 8 or 16.
TO/K/A
This keyword must exist. After that you must specify a file name to save
the ADPCM sample to.
FD=FREQDIV/K/N
The factor to downsample the input frequency with. Any number >1 allowed.
BITS/K/N
Either specify 2 or 3 for ADPCM2 or ADPCM3 compression. Other values might
be added in the future (e.g. 8 or 16 for saving as IFF or WAV file)
MAXIMIZE/S
If you give this parameter, the program will first scan through the audio
track(s) and try to find the maximum peak (similar to PEAK SEARCH on your
CD-Player). Then it will scale the sample to maximum 8 bit dynamics. This
will reduce the quantisation noise level. Your sample will be louder and
clearer. But it will take twice the time to convert the track.
BOOST/S
Here you can give a scaling factor for your sample in percent. 100 will
mean no scaling, 50 means half the volume, 200 will double the volume
etc... You can also combine this parameter with the MAXIMIZE switch.
The boost factor can further improve the sound quality as it improves the
signal-to-noise ratio. Values between 100 and 400 usually give best
results. Using too high boost values may lead to audible distortion,
similar to overmodulating an audio amplifier.
INTEL/S
Defines the byte ordering of 16 bit PCM files. The INTEL switch will allow
you to read little endian byte order.
Examples
--------
This example will convert an AIFF file to 2 Bit ADPCM. Easy, isn't it?
Hifi2ADPCM Around_the_World.AIFF to Around_the_World.ADPCM
This is an example script for converting HIFI MPegAudio streams to ADPCM
format with a frequency downscaling of 2. Note that you require the MPega
program V2.9 or 3.x by Stephane Tavenard. The frequency downscaling is
done by the mpega program. This avoids the creation of aliasing
frequencies that will be caused by the simple downscaling algorithm of
Hifi2ADPCM. Not that your T: volume should be assigned to your hard disk
because the AIFF file can become very large.
Save this to your S: or script file directory and don't forget to set the
s bit in the protection flags.
.KEY From/A,To/A
mpega -s -q2 -d2 -A -T -b64 "<From>" T:MPeg.TMP
Hifi2ADPCM T:MPeg.TMP BITS=3 MAXIMIZE BOOST=150 To "<To>"
Delete T:MPeg.TMP quiet
To Do
-----
-implement a loader for uncompressed AIFC files.
-implement a 8SVX format reader.
-implement a WAVE format reader.
The Author
----------
Christian Buchner
Steinbergstraße 2
82110 Germering
Germany
Tel.: +49-89-849868
EMAIL: flowerp@eikon.e-technik.tu-muenchen.de
<flowerp> on irc #amiga and #amigager
//
\X/ Flowerpower