Antex Electronics SX-33e Digital Audio Adapter - Manual (Page 41)

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.