I'm interested in SACD technology. But I'm puzzled by this:

http://interprod5.imgusa.com/son-637/technology.asp

"Unfortunately, the PCM process exposes the music to a "decimation"
filter during recording and an "interpolation" filter during playback.
These two filters can smear the sound, corrupt the sense of space
around the instruments and sacrifice the subtleties of live music."

- What do the quotation marks signify?

- "Decimation" means "killing every tenth man", according to my
dictionary. What's that all about?

- I think I understand "Interpolation" which is about filling in
a missing value with a guessed value. Isn't that more to do
with error handling?

Or this:

"The Direct Stream DigitalT pulse train "looks" remarkably
like the analog waveform it represents. More pulses point
up as the wave goes positive and down as the wave goes negative."

- How do I "look" at a pulse train?

- What are the benefits of this "look" to the audible results?

Or is this mumbo-jumbo to impress those who do not understand
it? Having said which, I don't understand it, but I'm not impressed
either.

Tim

In article , Tim Anderson wrote:
I'm interested in SACD technology. But I'm puzzled by this:

http://interprod5.imgusa.com/son-637/technology.asp

"Unfortunately, the PCM process exposes the music to a "decimation"
filter during recording and an "interpolation" filter during playback.
These two filters can smear the sound, corrupt the sense of space
around the instruments and sacrifice the subtleties of live music."

I won't comment on the "unfortunately" bit. Someone else may.

- What do the quotation marks signify?

It means that amongst the DSP (Digital Signal Processing) community
the words have a conventional (jargon) meaning intended for brief but
accurate communication between experts which is different from the
dictionary meaning. Unfortunately these words are then (mis-)appropriated
for marketing purposes despite the retention of the quotation marks.

- "Decimation" means "killing every tenth man", according to my
dictionary. What's that all about?

Start by translating that as "killing every tenth sample". But it
isn't just used about getting rid of every tenth - the DSP world uses
the word for any process which removes samples from the digital audio
stream leaving a lower sample rate.

- I think I understand "Interpolation" which is about filling in
a missing value with a guessed value. Isn't that more to do
with error handling?

It can be used for handling errors where a sample is genuinely missing
due to an error and has to be re-created but interpolation is also
used (more often) for any process which increases the sample rate by
introducing more samples continuously.

Or this:

"The Direct Stream DigitalT pulse train "looks" remarkably
like the analog waveform it represents. More pulses point
up as the wave goes positive and down as the wave goes negative."

- How do I "look" at a pulse train?

You actually don't because SACD is encrypted, but I have seen diagrams
which draw the analogue representation of the stream's 1s and 0s on a
page with a pen whose line width is a reasonable fraction of the maximum
data rate. It does seem to create a visual approximation of the original
signal's amplitude.

- What are the benefits of this "look" to the audible results?

Ah. That's more difficult.

--
John Phillips

In article , Tim Anderson wrote:
I'm interested in SACD technology. But I'm puzzled by this:

http://interprod5.imgusa.com/son-637/technology.asp

"Unfortunately, the PCM process exposes the music to a "decimation"
filter during recording and an "interpolation" filter during playback.
These two filters can smear the sound, corrupt the sense of space
around the instruments and sacrifice the subtleties of live music."

I won't comment on the "unfortunately" bit. Someone else may.

- What do the quotation marks signify?

It means that amongst the DSP (Digital Signal Processing) community
the words have a conventional (jargon) meaning intended for brief but
accurate communication between experts which is different from the
dictionary meaning. Unfortunately these words are then (mis-)appropriated
for marketing purposes despite the retention of the quotation marks.

- "Decimation" means "killing every tenth man", according to my
dictionary. What's that all about?

Start by translating that as "killing every tenth sample". But it
isn't just used about getting rid of every tenth - the DSP world uses
the word for any process which removes samples from the digital audio
stream leaving a lower sample rate.

- I think I understand "Interpolation" which is about filling in
a missing value with a guessed value. Isn't that more to do
with error handling?

It can be used for handling errors where a sample is genuinely missing
due to an error and has to be re-created but interpolation is also
used (more often) for any process which increases the sample rate by
introducing more samples continuously.

Or this:

"The Direct Stream DigitalT pulse train "looks" remarkably
like the analog waveform it represents. More pulses point
up as the wave goes positive and down as the wave goes negative."

- How do I "look" at a pulse train?

You actually don't because SACD is encrypted, but I have seen diagrams
which draw the analogue representation of the stream's 1s and 0s on a
page with a pen whose line width is a reasonable fraction of the maximum
data rate. It does seem to create a visual approximation of the original
signal's amplitude.

- What are the benefits of this "look" to the audible results?

Ah. That's more difficult.

--
John Phillips

In article , Tim Anderson
wrote:
I'm interested in SACD technology. But I'm puzzled by this:

http://interprod5.imgusa.com/son-637/technology.asp

"Unfortunately, the PCM process exposes the music to a "decimation"
filter during recording and an "interpolation" filter during playback.
These two filters can smear the sound, corrupt the sense of space around
the instruments and sacrifice the subtleties of live music."

- What do the quotation marks signify?

Not seen the page, but I'd assume the quote marks either genuinely mean
they are a quote from somewhere else, or the author is using them to imply
something - e.g. that he is writing in a descriptive manner that may not be
reliable. The comment seems to include some opinions after the "can..."
which may be of debatable relevance or reliability in any given case.


I could just as easily write something like "The SACD approach tends
to inherently produce large amounts of ultrasonic/hf hash/noise
that can cause problems for amplifiers and loudpeakers and hence
smear the sound." Putting this in quotes means I could then say
I'd expressed an opinion qualified with "can" that can be argued
to be supported by some evidence.


- "Decimation" means "killing every tenth man", according to my
dictionary. What's that all about?

In this context I suspect it means that the analog original has been
sampled at a high sampling rate, and this data steam is then reprocessed
and filtered to provide a lower sample rate output. By implication the
output may have a lower bandwidth. The historic meaning of decimation has
been ovetaken by engineers who now use the word for their own purposes. :-)

- I think I understand "Interpolation" which is about filling in a
missing value with a guessed value. Isn't that more to do with error
handling?

Not necessarily. It can mean inserting samples at intermediate instants
between the input data samples, but these do not have to be 'guesses', nor
are they just to correct errors. The idea may be to (using methods based
upon information theory) to produce the values *you would genuinely have
obtained* if you'd actually sampled the original input waveform more
frequently, but limited it beforehand to the bandwidth implied by the
sampling rate to which you are applying the 'interpolation'. The purpose is
to aid the filtering/processing process. It can make the task of the DAC
and following analog filters less demanding, so give (nominally) a 'better'
result.

Above said, It *can* mean attempts to replace values which have been lost
due to errors, so this will depend upon the context.

Or this:

"The Direct Stream DigitalT pulse train "looks" remarkably like the
analog waveform it represents. More pulses point up as the wave goes
positive and down as the wave goes negative."

- How do I "look" at a pulse train?

In a diagram or on the screen of something like a 'scope. :-)

- What are the benefits of this "look" to the audible results?

The closer the output of the DAC approaches the shape of the original
analog waveform, the less work the following filters have to do.

Or is this mumbo-jumbo to impress those who do not understand it? Having
said which, I don't understand it, but I'm not impressed either.

It just sounds to me to be unclearly expressed. However I've not had a
chance to examine the page, so can't say for sure.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Tim Anderson
wrote:
I'm interested in SACD technology. But I'm puzzled by this:

http://interprod5.imgusa.com/son-637/technology.asp

"Unfortunately, the PCM process exposes the music to a "decimation"
filter during recording and an "interpolation" filter during playback.
These two filters can smear the sound, corrupt the sense of space around
the instruments and sacrifice the subtleties of live music."

- What do the quotation marks signify?

Not seen the page, but I'd assume the quote marks either genuinely mean
they are a quote from somewhere else, or the author is using them to imply
something - e.g. that he is writing in a descriptive manner that may not be
reliable. The comment seems to include some opinions after the "can..."
which may be of debatable relevance or reliability in any given case.


I could just as easily write something like "The SACD approach tends
to inherently produce large amounts of ultrasonic/hf hash/noise
that can cause problems for amplifiers and loudpeakers and hence
smear the sound." Putting this in quotes means I could then say
I'd expressed an opinion qualified with "can" that can be argued
to be supported by some evidence.


- "Decimation" means "killing every tenth man", according to my
dictionary. What's that all about?

In this context I suspect it means that the analog original has been
sampled at a high sampling rate, and this data steam is then reprocessed
and filtered to provide a lower sample rate output. By implication the
output may have a lower bandwidth. The historic meaning of decimation has
been ovetaken by engineers who now use the word for their own purposes. :-)

- I think I understand "Interpolation" which is about filling in a
missing value with a guessed value. Isn't that more to do with error
handling?

Not necessarily. It can mean inserting samples at intermediate instants
between the input data samples, but these do not have to be 'guesses', nor
are they just to correct errors. The idea may be to (using methods based
upon information theory) to produce the values *you would genuinely have
obtained* if you'd actually sampled the original input waveform more
frequently, but limited it beforehand to the bandwidth implied by the
sampling rate to which you are applying the 'interpolation'. The purpose is
to aid the filtering/processing process. It can make the task of the DAC
and following analog filters less demanding, so give (nominally) a 'better'
result.

Above said, It *can* mean attempts to replace values which have been lost
due to errors, so this will depend upon the context.

Or this:

"The Direct Stream DigitalT pulse train "looks" remarkably like the
analog waveform it represents. More pulses point up as the wave goes
positive and down as the wave goes negative."

- How do I "look" at a pulse train?

In a diagram or on the screen of something like a 'scope. :-)

- What are the benefits of this "look" to the audible results?

The closer the output of the DAC approaches the shape of the original
analog waveform, the less work the following filters have to do.

Or is this mumbo-jumbo to impress those who do not understand it? Having
said which, I don't understand it, but I'm not impressed either.

It just sounds to me to be unclearly expressed. However I've not had a
chance to examine the page, so can't say for sure.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

John Phillips wrote in message


"The Direct Stream DigitalT pulse train "looks" remarkably
like the analog waveform it represents. More pulses point
up as the wave goes positive and down as the wave goes negative."

- How do I "look" at a pulse train?

You actually don't because SACD is encrypted, but I have seen diagrams
which draw the analogue representation of the stream's 1s and 0s on a
page with a pen whose line width is a reasonable fraction of the maximum
data rate. It does seem to create a visual approximation of the original
signal's amplitude.

It's not encrypted. It's just a bitstream at 2.8Mb/s.
If you put the digital signal through a simple RC low pass filter
you get something very like the original analogue audio signal.

Roger.

John Phillips wrote in message


"The Direct Stream DigitalT pulse train "looks" remarkably
like the analog waveform it represents. More pulses point
up as the wave goes positive and down as the wave goes negative."

- How do I "look" at a pulse train?

You actually don't because SACD is encrypted, but I have seen diagrams
which draw the analogue representation of the stream's 1s and 0s on a
page with a pen whose line width is a reasonable fraction of the maximum
data rate. It does seem to create a visual approximation of the original
signal's amplitude.

It's not encrypted. It's just a bitstream at 2.8Mb/s.
If you put the digital signal through a simple RC low pass filter
you get something very like the original analogue audio signal.

Roger.

In article , The Old
Fogey wrote:
John Phillips wrote in message


"The Direct Stream DigitalT pulse train "looks" remarkably
like the analog waveform it represents. More pulses point
up as the wave goes positive and down as the wave goes negative."

- How do I "look" at a pulse train?

You actually don't because SACD is encrypted, but I have seen diagrams
which draw the analogue representation of the stream's 1s and 0s on a
page with a pen whose line width is a reasonable fraction of the maximum
data rate. It does seem to create a visual approximation of the original
signal's amplitude.

It's not encrypted. It's just a bitstream at 2.8Mb/s.
If you put the digital signal through a simple RC low pass filter
you get something very like the original analogue audio signal.

I was under the impression you were never going to be allowed to see the
bitstream, through licensing conditions restricting SACD manufacturers
from exposing interfaces where digital copies could be taken. I thought
SACD was going to be like DVD-A in this respect. Have I got this wrong?

John
--
John Phillips

In article , The Old
Fogey wrote:
John Phillips wrote in message


"The Direct Stream DigitalT pulse train "looks" remarkably
like the analog waveform it represents. More pulses point
up as the wave goes positive and down as the wave goes negative."

- How do I "look" at a pulse train?

You actually don't because SACD is encrypted, but I have seen diagrams
which draw the analogue representation of the stream's 1s and 0s on a
page with a pen whose line width is a reasonable fraction of the maximum
data rate. It does seem to create a visual approximation of the original
signal's amplitude.

It's not encrypted. It's just a bitstream at 2.8Mb/s.
If you put the digital signal through a simple RC low pass filter
you get something very like the original analogue audio signal.

I was under the impression you were never going to be allowed to see the
bitstream, through licensing conditions restricting SACD manufacturers
from exposing interfaces where digital copies could be taken. I thought
SACD was going to be like DVD-A in this respect. Have I got this wrong?

John
--
John Phillips

more from the 'Tim Anderson school' of uk.rec.audio-ism:


More pulses point
up as the wave goes positive and down as the wave goes negative."

Is this to say that SACD is vbr?

--
Jim H jh
@333
.org