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Wiki > Main > AudioAPIEnhancement

---+!! Enhancements to the Audio API

%TOC%

---++ 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 mutexes 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 SVN

---+++ 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

r6 - 10 Oct 2007 - 06:52:23 - SteveBavin