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Wiki > Main > AudioAPIEnhancement (r4)

Enhancements to the Audio API

Goals

Simpler to understand

  • The interfaces are currently bloated, this makes knowing who the consumers of a particular function or variable are very difficult.
  • The names of functions need to clearly identify not only what they do, but also what context they are to be called in

Thread safety

  • The Codec and Audio thread should share zero state-modifying code. Any state modifying function that one calls should never be called on the other. -- Known problem areas:
    • pcmbuf_flush_fillpos
    • pcmbuf_play_stop
    • pcmbuf_play_start
    • skip_next_track
  • In the off chance that there is some data that must be modified by both threads, it must not be performance sensitive, and may be protected by a mutex
  • Existing use of mutex's to protect functions can be eliminated to improve performance once the above is done.

Performance

The following apply only to performance sensitive sections of code.
  • Functions should have specific behavior, rather than conditional branches.
  • Some sacrifices to readability for performance is acceptable in these areas
  • Keep register usage to a minimum (check in the asm how many registers the compiler is using)

Progress

Steps that I've so far taken are in CVS

PCMBuffer

  • now behaves more like a typical buffer where consumers are told how much space is left if they reach the end
  • now uses linked lists instead of circular buffer for the buffer descriptors
  • performance sensitive code optimized by reading compiled code
  • trimmed down the API exposed to consumers

PCM

  • Reduced usage of pcm_ function calls outside of pcmbuf.c (this probably wants more doing)
  • Reduce latency by only holding the currently playing chunk in PCM.c not the next one too

Playback

Not much done yet
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r4 - 17 Feb 2006 - 16:19:00 - JeffNemic
Copyright by the contributing authors.