
December 2nd 03, 11:48 PM
posted to uk.rec.audio
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Co-ax SPDIF digital out
On Tue, 02 Dec 2003 21:12:25 +0000
Ian Bell wrote:
Actually you can. You just resample. No buffers, no worries about
different clock speeds or source data jitter.
Then input != output though. why bother?
(yes I know about this type of filtering - apps like mplayer use it to
resample audio if your soundcard doesnt 'do' 44k4 or 48k sampling and
the movie does (or is some other odd samplerate / multiple therof.)
And lets not get started on aliasing effects and the derivatives
therof...
--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux
Do not meddle in the affairs of Dragons, for you are tasty and good with
ketchup.
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December 2nd 03, 11:48 PM
posted to uk.rec.audio
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Co-ax SPDIF digital out
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December 2nd 03, 11:48 PM
posted to uk.rec.audio
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Co-ax SPDIF digital out
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December 2nd 03, 11:50 PM
posted to uk.rec.audio
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Co-ax SPDIF digital out
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December 2nd 03, 11:50 PM
posted to uk.rec.audio
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Co-ax SPDIF digital out
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December 3rd 03, 07:55 AM
posted to uk.rec.audio
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Co-ax SPDIF digital out
On Tue, 02 Dec 2003 23:21:13 GMT, "Bedouin"
wrote:
"Stewart Pinkerton" wrote in message
...
Not for digital audio, you don't, or you have altered the pitch.
But this is actually done - there is an analogue devices chip that does
exactly this. It can convert between two totally separate bit rates by
interpolation.
Sure there is, and it's used on all those 'DJ' CD players you'll find
in the new Bullring Selfridges (and elsewhere) for pitch shifting.
However, it's not a good idea if you want *accurate* replay - unless
you re-clock to an accurate 44.1kHz on the output.
I understand that this is very effective at cleaning up jitter signals
although of course it can't cope perfectly with long term clock instability.
Sure it can - you just lock its output to a low-noise clock. Remember,
it's the *output* clock accuracy which determines the pitch - and we
already know that the *recording* had an accurate 44.1kHz clock on it.
This *is* an effective jitter removal method, and is used by Bel Canto
among others. As previously noted however, true re-clocking is still
*extremely* rare in linear PCM such as audio DACs, although it is of
course a basic feature of the compressed multi-channel formats such as
DD and DTS.
--
Stewart Pinkerton | Music is Art - Audio is Engineering
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December 3rd 03, 07:55 AM
posted to uk.rec.audio
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Co-ax SPDIF digital out
On Tue, 02 Dec 2003 23:21:13 GMT, "Bedouin"
wrote:
"Stewart Pinkerton" wrote in message
...
Not for digital audio, you don't, or you have altered the pitch.
But this is actually done - there is an analogue devices chip that does
exactly this. It can convert between two totally separate bit rates by
interpolation.
Sure there is, and it's used on all those 'DJ' CD players you'll find
in the new Bullring Selfridges (and elsewhere) for pitch shifting.
However, it's not a good idea if you want *accurate* replay - unless
you re-clock to an accurate 44.1kHz on the output.
I understand that this is very effective at cleaning up jitter signals
although of course it can't cope perfectly with long term clock instability.
Sure it can - you just lock its output to a low-noise clock. Remember,
it's the *output* clock accuracy which determines the pitch - and we
already know that the *recording* had an accurate 44.1kHz clock on it.
This *is* an effective jitter removal method, and is used by Bel Canto
among others. As previously noted however, true re-clocking is still
*extremely* rare in linear PCM such as audio DACs, although it is of
course a basic feature of the compressed multi-channel formats such as
DD and DTS.
--
Stewart Pinkerton | Music is Art - Audio is Engineering
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December 3rd 03, 07:55 AM
posted to uk.rec.audio
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Co-ax SPDIF digital out
On Tue, 2 Dec 2003 23:48:47 +0000, Ian Molton wrote:
On Tue, 2 Dec 2003 22:51:16 +0000 (UTC)
(Stewart Pinkerton) wrote:
Actually you can. You just resample. No buffers, no worries about
different clock speeds or source data jitter.
Not for digital audio, you don't, or you have altered the pitch.
No, hes right, you can resample, but you dont preserve the original data, so its a bit pointless.
True, but you can also use a data-rate converter, which may be what he
meant. I confess that I hadn't even considered the possibility that he
was referring to D/A-A/D resampling, which would indeed be terminally
brain-dead as a jitter suppression technique!
--
Stewart Pinkerton | Music is Art - Audio is Engineering
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