Antex electronic SX-3 Stereo System User Manual


 
38
ISO/MPEG-1 BITRATES & FORMAT EXTENSIONS
ISO/MPEG supports several compression rates and encodes
flags that describe the audio data. The flags and other options
are selected by typing MPEG with[extensions] switches in the
Format text box of the DOS demo. (The bitrates in the Windows
demo are selected by double-clicking on MPEG in the
Compression list to get a bitrate drop-down menu)
MPEG[
extensions
]"
where [extensions] is a concatenation (in any order) of:
/L =1
(layer 1) or
=2
(layer 2),
/sr =32000
=44100
or
=48000
(to specify the sample
rate),
/M =st
(mode = stereo)
=js
(mode = joint-stereo) or
=dc
(mode = dual channel) or
=sc
(mode = single channel)
/kB=
Kbits per second per channel
/E=1
(crc error checking) or
=0
(no crc error checking),
/C=1
(copyright protected) or
=0
(not copyright protected)
,
/O=1
(original)
or
=0
(copy),
/Em =0
(no emphasis) or
=1
(emphasis 50/15ms) or
=2
(reserved)
=3
(CCITT J17)
For example to get a 5.5:1 compression ratio, layer II and joint
stereo in a 44.1kHz file:
1. Select 44100 from the
SampleRate
menu
2. Click on the text box lableled
Format
3. Type MPEG/kb=128/m=js/l=2
MPEG-1 has a range of compression ratios that are user select-
able. The compression ratio selected will depend upon the audio
quality required. The MPEG-1 format specifies the compression
ratio by defining the desired bitrate. The compression ratio ob-
tained for a given output bitrate therefore changes with sample
rate.