Sound_Volume (changes)
Showing changes from revision #1 to #2:
Added | Removed | Changed
Programmer's SoundChannels Reference Manuals
» Part 15 – SWI Calls
» Sound_VolumeSound
» Sound_Volume
Sound_Volume
(SWI &40180)
| Entry | |
|---|---|
| R0 | New volume (1-127) |
| Or 0 to read current volume |
| Exit | |
|---|---|
| R0 | Previous volume (1-127) |
Use
This SWI is used to read or set the master volume of the 8 bit sound system.
Notes
Volume is specified using a logarithmic scale, with 127 representing a 1x multiplier. For every 16 you subtract from the base volume of 127, the linear output will be halved. I.e.:
| Volume | Multiplier |
|---|---|
| 127 | 1 |
| 127-16 | 1/2 |
| 127-32 | 1/4 |
| 127-48 | 1/8 |
| 127-64 | 1/16 |
| 127-80 | 1/32 |
| 127-96 | 1/64 |
| 127-112 | 1/128 |
The setting made here or via *Volume influences the return values of SWIs Sound_SoundLog and Sound_LogScale, and it also controls the contents of the linear-to-log and log amplification tables that are available at offsets +8 and +12 of the sound channel handler block (available via Sound_Configure). Well-behaved voice generators should make use of one of the above interfaces to determine the volume scale they should use when they generate their output.
See also
Social
and
ROOL Store
Buy RISC OS Open merchandise here, including SD cards for Raspberry Pi and more.