Sound Channels ?

[puffdragon]

Any info on what sound channels, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14 stand for and how sound behavior change when you switch between them?

 

[Dr Super Good]

By sound channel might they be referring to the number of sound channels that can be devoted to playing the sound? In real time audio synthesis sounds are attached to "channels" which are then blended together by software to produce output sound channels for the playback device. The number of sound channels for blending at any given time is finite and once the pool is depleted it becomes impossible to blend in any more sounds.

In the case of games like WC3 this means that after a certain number of sounds start playing back new sounds cannot start to be played back until one or more of the current sounds finish which can cause certain expected sounds to be missing from the playback device output. The results can sound quite bad if an expected loud effect, eg an explosion, is missing due to all channels being depleted by quiet effects, eg burn sounds. To minimize the effects I can assume one can limit the number of channels available for a sounds playback, so that loud sounds can be given more channels than quite sounds so as to guarantee their inclusion in the playback.

In theory today there is no limit to the number of sound channels one can blend at once as all consumer level blending is done by software which can be scaled to any required number. It has been like this since Windows Vista was released and standardized audio playback devices in Windows and dropped wide spread support for audio accelerator cards. Before then the channel limit was defined by the audio accelerator card, dedicated hardware which performed sound blending. Such hardware was capable of blending a finite, and often small, number of sounds simultaneously so had a finite number of sound channels. Non standardized and often crash prone drivers would then expose these sound channels to applications which could direct sound data to them.

In reality there still is a limit to the number of sound channels one can blend at once. Although the software mixers that perform blending are very fast, they still eat up CPU and memory bandwidth to perform the mixing. The amount of resources used depends on the number of active channels in use, with an extra performance penalty once caching becomes inefficient. Blending sounds is not the only operation the mixer performs, resampling, 3D sound and audio effects like reverb all have to be performed. Although modern games like StarCraft II and Diablo III can have up to 128 sound channels for audio playback, it is well known that using that many can lead to poor in game performance on some systems when a lot of sounds are being played back at the same time.

As I have mostly looked into image processing I refer to the process of merging 2 audio streams into a single output audio stream as blending as with images this refers to merging 2 images into a single output image. It is probably more correct to call it "mixing" within the field of audio processing instead.

 

[puffdragon]

So, if I play a sound on all 15 wc3 channel, its going to silence all wc3 sounds? Interesting