Antex electronic SX-33 Manuale Utente
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
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)
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),
=48000 (to specify the sample
rate),
/M =st (mode = stereo)
=js (mode = joint-stereo) or
=dc (mode = dual channel) or
=sc (mode = single channel)
=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)
=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:
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.
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.