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REAL TIME: why?

For low latency

• write data as close as possible to when it will be audible
• read data as soon as the audio interface makes it available
• tricks with mmap + non-audio-clock source: non-portable, but occasionally useful.

How come so many apps don't do this?

• don't have low latency requirements
• buffer significant amounts of data
• lack real-time parameter control during playback
• even in media players like XMMS, users notice "lag" between modifying the gain/EQ controls and hearing result.

Summary

• low latency/real time programming is always a tradeoff:
  • applications become more sensitive to OS problems
  • applications become more responsive to user control