Re: Proposal: new audio framework

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	hello.  How does the latency and overhead of the audio2 framework
compare with the latency and overhead of NetBSD-5?  If you don't know the
answer, can you tell me how you did the tests so I can provide that
information?  I use NetBSD-5 on a daily basis and  it is critical that the
audio be as quick and efficient as it can be.  

-thanks
-Brian

On Apr 1,  1:23pm, Tetsuya Isaki wrote:
} Subject: Proposal: new audio framework
} Hi all,
} 
} I'd like to propose a new audio framework (which I call AUDIO2).
} 
}  http://www.netbsd.org/~isaki/audio2-20190401.diff.gz
} 
} Audio driver since 8.0 has in-kernel mixing feature and it's really
} exciting.  But also has so many problems.
}  * unstable including locking issues.
}  * bad playback quality and high load (especially on slow machines).
}  * high latency.
}  * does not support drivers with uncommon characteristics.
}    For example, vs(4) hardware frequency is 15625Hz but audio.c can
}    not attach such devices (as it is).
}  * interface was silently changed so several hardware drivers have
}    no longer worked.
}  * There is a lot of unmaintained(no longer used) code.
} 
} So I've reimplemented whole audio framework to fix them.  It is mostly
} worked fine for me.
}  * stable.
}  * good playback quality and lightweight even on 68030.
}    The average of system load ("sy" column by vmstat) on playing single
}    1ch/8000Hz mulaw on x68k (68030/30MHz/12MB real machine) is:
}    about 50% on -current,
}    about 10% on AUDIO2.
}    (FYI, it's about 4% on NetBSD7.)
}  * better latency.
}    current latency is normally about 3*50=150msec in default,
}    AUDIO2  latency is normally about 2*40=80msec  in default.
}  * smaller textsize (and probably memory usage).
}    For example, amiga/GENERIC kernel has three old-style audio drivers and
}    AUDIO2 modifies two of these already.  At this moment it reduces kernel
}    size about 35KB.  In the end we will be able to reduce it more.
}  * well support for non-PCM hardware.
}  * well consideration about half duplex hardware.
}  * provide many tests.
}  * introduce sysctl hw.wsbellN.mute to be able to mute individually.
} 
} AUDIO2 requires explicit few interface changes, so all hardware drivers
} must be catched up.  Current status is:
}  * works: arcofi(4), auich(4), bba(4), eap(4), hdafg(4), uaudio(4),
}           vs(4), vsaudio(4)
}  * compiled but not tested: audioamd(4), aucc(4), melody(4), repulse(4)
}  * works but more works are required: sb(4), pad(4), spkr_audio
} Other drivers not listed here are not supported yet.
} 
} There is one thing I'm worried about.  AUDIO2 requires more strict
} blocksize and buffersize for hardware drivers.  It will be a hard
} work if there are any hardware that does not satisfy the requirements.
} # Although I believe there are no such hardware...
} 
} Some of TODOs:
}  * remove all ifdef AUDIO2.
}    It was needed to confirm non-AUDIO2 kernel build.
}  * support all hardware drivers. (need your help!)
}  * support NetBSD8-like multiuser mode?
}  * mmap is not well tested.
}  * translate or cleanup Japanese comments which is left in source code.
}  * convert my local tests (which is not included in the patch) into ATF.
} 
} Any comments?
} ---
} Tetsuya Isaki <isaki%pastel-flower.jp@localhost / isaki%NetBSD.org@localhost>
>-- End of excerpt from Tetsuya Isaki