WINSAC: Scalable Audio Coding Demonstration Software
----------------------------------------------------

Version 1.2
Scala Technology Ltd
2 November 2005

web: http://www.scalatech.co.uk
email: help@scalatech.co.uk

WINSAC demonstrates Scala's proprietary scalable audio coding technology. This Win32 windows application 
comprises a scalable-bitrate decoder, and also a bitstream scaling function. The decoding process 
decompresses a .SAB bitstream file to an output .WAV file, while the scaling function can extract a 
lower-rate bitstream from a coded bitstream file. The effect of random bit errors within a coded 
bitstream can be simulated in the decoding process.

Scalable decoding is achieved by selecting appropriate input bitstream and output wav file names 
using the File Menu, choosing an appropriate output bitrate and bit error rate from the Decode Menu, and 
then selecting [decode bitstream] from the Decode Menu. After decoding to the chosen wav file is 
complete, decoding bitrate statistics are displayed in the main section of the WINSAC window.

A scalable bitstream can be decoded at a bitrate that is equal to or less than the encoded bitrate 
of the bitstream. The [output bitrate] switch on the Decode Menu selects either the encoded bitrate, 
or a scaled bitrate that can be equal to or less than the encoded rate.

The effect of random bit errors within a coded bitstream can be simulated in the decoding process by 
setting a target error rate with the [bit error rate] item on the Decode Menu. This determines the rate
at which bits within the selected bitstream are randomly corrupted during decoding. 

Bitstream scaling is invoked by selecting appropriate input bitstream and output bitstream file names 
using the File Menu, choosing an appropriate output bitrate from the Decode Menu, and then selecting 
[scale bitstream] from the Decode Menu. After scaling to the chosen output file is complete, scaling 
bitrate statistics are displayed in the main section of the WINSAC window.

The default input / output file directory is set relative to the location of the WINSAC application 
(winsac.exe) as 'wav', and this directory must exist and include a valid .sab bitstream file before 
decoding or scaling can take place.

Details about each of the menu options can be found below.


File Menu
---------

File | input bitstream

Sets the input bitstream file name (type in the file root name only, omitting the file extension).
Setting the input bitstream file name also sets default output wav and output bitstream file names, 
based on the input file root name. For example, if the input file is set to harp(.sab), then the 
output wav file will be set to harp.wav and the output bitstream file to harp_s.sab


File | output wav

Sets the output wav file name to which the input bitstream will be decoded (type in the file root 
name only, omitting the file extension - this is automatically set to .wav). This menu item overrides 
the default output wav filename set from [File | input bitstream]. 


File | output bitstream

Sets the output bitstream file name to which the input bitstream will be scaled (type in the file 
root name only, omitting the file extension - this is automatically set to .sab). This menu item 
overrides the default output bitstream file name set from [File | input bitstream], but it cannot be
the same filename as the input bitstream file. 


File | directory

Sets the common directory location for input bitstream, output wav and output bitstream files. 
The directory name can either be input as an absolute path (eg 'C:\scalademo\wav'), or relative to 
the location of the winsac.exe application (eg 'wav'). 


Decode Menu
-----------

Decode | decode bitstream

Decodes the selected input bitstream file to the selected output wav file.


Decode | scale bitstream

Extracts a scaled bitrate version of the selected input bitstream file and writes the result to the 
selected output bitstream file.


Decode | output bitrate

Switches the output bitrate between the encoded bitrate of the input bitstream file, or a scaled rate
set by [Decode | scaled bitrate], for bitstream decoding or scaling.


Decode | scaled bitrate

Sets the scaled output bitrate in kbit/s, which determines the quality of wav decoding or size of the 
scaled output bitstream, when [Decode | output bitrate: scaled] is selected. If the scaled bitrate is 
higher than the encoded bitrate of the input bitstream file, then the output bitrate is set to the 
encoded rate.


Decode | bit error rate

Sets a target bit error rate for bitstream decoding, where the signs of bits within the selected input 
bitstream file are randomly changed prior to decoding to the selected output wav file. Each bit within 
the input bitstream file has an equal chance of being corrupted in this way. After decoding is complete 
the measured bit error rate is displayed in the main section of the WINSAC window - this can differ 
slightly from the target rate due to the random nature of corruption. Note that the chosen bit error 
rate only affects the decoding process, and has no effect on bitstream scaling.






