Subject: Re: [linux-audio-dev] RFC: API for audio across network - inter-host audio routing
From: Paul Davis (pbd_AT_op.net)
Date: Mon Jun 17 2002 - 22:01:52 EEST
>>i have to say that i can't imagine the use of the setup you've
>>described? why would run a digital signal into a cheap stereo? either
>>use the onboard converters on the CD/DVD player, which will avoid
>>jitter problems, or use an external system that clocks from the data
>>stream.
>>
>A lot of "home theater" equipment manufacturers are trying to generate
>hype for such setups.
>i think they're banking on the general public's assumption that digital
>= good.
ah yes, silly me. i recently bought a new amplifier for in-home use,
and i was amazed at the extent of all these "home theater" systems. i
settled for a nice simple NAD C370, whose only "additional" feature
was two sets of speaker outs. but i did notice all that silly digital
i/o nonsense on the theater systems. ah, fools and their money.
>now has (generally optical)
>s/pdif. but word clock is generally not part of the package. also, i
s/pdif is self-clocking. you don't need word clock to keep *two*
s/pdif devices in sample-clock sync.
>could be wrong on this, but i
>think that adat has a layer of sync support that toslink doesn't. even
toslink is the same protocol as spdif but a different physical
medium. hence, its self-clocking as well.
>so, pro adat-equipped gear
>usually has wordclock and/or adat sync anyway. i don't think adat
>lightpipe is truly sample-accurate
>unless you use wordclock or the 9-pin adat sync.
adat sync is timecode, not sample sync. it doesn't provide a sample
clock source at all. word clock is relevant, but not necessary since
adat is self-clocking.
however, and its a *****HOWEVER****, the adat clock signal is
unreliable because of connector problems. we tried to use the adat
self-clocking in the studio for a while and gave up. it would work
with some cables on some equipment; change the wire or the endpoints,
and it would break. i think the clock frequency signal is more
susceptible to signal degradation from echoes and reflections in the
fiber optic than the actual data, because the same setup with word
clock between the two endpoints and the same wire works just great.
--p
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