Dirty Digital [sic.]
 

Rob wrote:

Eeyore wrote:
Rob wrote:

I'll obviously defer here, but isn't dither a type of
sound 'shaping', in that it changes the sound?

No. It's merely a tiny bit of noise at ~ -90dB. Coul;d be less with modern
24 bit converters. Most real world signals self-dither anyway.

OK fine, it doesn't change the sound. My source is Wikipedia I'd afraid.

And isn't reducing bitrates to 16 something of an art

You mean bit depth. 96dB ? Not enough ?

Have you any idea how many dB vinyl and analogue tape's capable of ? Nowhere
remotely NEAR that. Plus you had to use Dolby A to get multitrack tape to
deliver an acceptable level of noise.

Bits as in amount of information. More bits more information.

Uh ? Even 16 bit audio beats analogue tape and disc hands down.


- or at least algorithmic?

Uh ?

Changing from say 24 to 16 bitrate involves a process, involving one or
more steps, and calculation: an algorithm.

Not it just gives more resolution. More than you can practically use in fact. You
get 6dB of s/n ratio per bit -3dB off the total.


And DACs?

DACs are STUNNING these days. The very early ones were a bit stinky but
they've been fine for a good 20 years or so now.


If you say all current DACs available are stunning and incapable of
differentiation then I'm in no position to mount a scientific challenge.

Example ... state of the art .....
24-Bit Resolution
Analog Performance:
Dynamic Range:
132 dB (9 V RMS, Mono)
129 dB (4.5 V RMS, Stereo)
127 dB (2 V RMS, Stereo)
THD+N: 0.0004%
Differential Current Output: 7.8 mA p-p
8× Oversampling Digital Filter:
Stop-Band Attenuation: –130 dB
Pass-Band Ripple: ±0.00001 dB
Sampling Frequency: 10 kHz to 200 kHz

http://focus.ti.com/docs/prod/folder.../dsd1794a.html

At 1/4 the price ......

24-Bit Resolution
Analog Performance:
Dynamic Range: 123 dB
THD+N: 0.0005%
Differential Current Output: 4 mA p-p
8× Oversampling Digital Filter:
Stop-Band Attenuation: –98 dB
Pass-Band Ripple: ±0.0002 dB
Sampling Frequency: 10 kHz to 200 kHz

http://focus.ti.com/docs/prod/folder...t/pcm1796.html

And that's a mere £1.85 in small production quantities.

Graham

Dirty Digital [sic.]
 

Rob wrote:

Eeyore wrote:
Rob wrote:

You've obviously had a bad experience of vinyl - it's moved on a lot in
last 40 years IMO.

No, I had / have a Garrard 401, Ortofon arm and various cartridges over the
years.

I'm just glad to rid of all the 'faff' with them and to know that I'm not
relying on a random concoction of pieces of kit in the signal chain to get a
flat frequency response, never mind low noise, distortion, lack of clicks etc.

Which is good - you've one less burden. You would have to accpet,
though, that it doesn't bother me. In much the same way as making bread
doesn't bother me.

Well, if you don't mind the loss of quality and I hate to think what you must be
using not to hear it.

Graham

Dirty Digital [sic.]
 

"Rob" wrote in message


Just seemed possibly ironic that digital might have to be
'shaped' to sound decent.

And you think that LPs aren't shaped?

You've obviously had a bad experience of vinyl

Almost 40 years when it was for many practical purposes, all we had to
listen to.

It's moved on a lot in last 40 years IMO.

If you study the professional literature in the field of recording, you will
find that there have been no significant innovations in almost 30 years.

If you read the consumer audio ragazines, a naive person might think
otherwise.

Dirty Digital [sic.]
 

Rob wrote:
Don Pearce wrote:
Rob wrote:
Don Pearce wrote:
Rob wrote:


Just seemed possibly ironic that digital might have to be 'shaped'
to sound decent.


Digital, unlike vinyl, doesn't need any shaping to sound decent. It
is spot-on right out of the box. With vinyl you need to play with
the frequency response, limit the excursion at the bottom end,
minimise acceleration at the top end, watch out for melted cutters.
In fact the mastering process is the sad and sorry business of
trying to minimise the wreckage.


I've no doubt! I'll obviously defer here, but isn't dither a type of
sound 'shaping', in that it changes the sound? And isn't reducing
bitrates to 16 something of an art - or at least algorithmic? And
DACs? So it's not quite 'out of the box'. Or is it your point of the
many boxes out there, all are so minutely different as to make no
difference to what we're capable of hearing?


No. Dither is an integral part of the process - always has been and
always will be. It isn't shaping anything.

Yes, OK, I did say I was coming from a position of ignorance. I thought
dither does shape sound. Is dither a necessary, objective and ubiquitous
component of digital recording then?


You've got it!

And you don't have to reduce
bit depth (not rate) to 16 - you can record that way in the first
place. It offers far more signal to noise ratio than any available
analogue format. 24 bits is available because it is possible, and it
does offer a S/N advantage over 16 bits - not for an audio recording,
of course, but certainly for other things. People do 24 bits because
they can. There is no "algorithm" involved in getting down to 16 bits
from there - simply add the dither and chop off the bottom 8 bits.


Yes, I'd picked up that recording is sometimes done in higher than 16
bits. There must be an algorithm I'd have thought. What you say
contradicts aspects of the Wikipedia entires. Have you never felt
inclined to put these right? It only takes a couple of seconds. Look up
'dither' and 'quantization' and see what you think. If you'd prefer I'll
pick out a few examples.


I've written my own articles on dither, anti-aliasing etc. The problem
with Wikipedia is that the original authors tend to be proprietorial.
You go in to correct an error, and a day later it is back there again.


Digital audio at 16/44.1 has reached what amounts to perfection. I'm
not saying that there are no audible differences between the boxes -
it is still entirely possible to screw up an implementation. But
certainly the best are no different from the competent. the
differences are to be found in features, function and cosmetics, not
the sound.

You've obviously had a bad experience of vinyl - it's moved on a
lot in last 40 years IMO.

Opinions count for nothing when the facts are available. Vinyl
hasn't moved an inch in that time. It was mediocre back then, and it
is still equally mediocre today.

I meant turntables and cartridges rather than the records themselves.
The few records I've bought new over the past ten years have been
pretty rubbish.


It is a matter of diminishing returns.

Yes, I know that better than most. £100 would see you right. I'm
perfectly happy with a (very) old Thorens TT right now, £100 on ebay.


My vinyl is handled by an old Systemdek Iv, an SME 3009 arm which I
bought in the 1960s and an AT OC9 cartridge. I will not improve that at
any price.

You can spend thousands on a deck
with counterweights, glass platters -whatever you like. Mostly this
stuff is for show, but the stuff that isn't is really just striving to
minimise the horribleness of it all - not make it great.


:-)

OK, you hate the sound from records, and that's really an end to it. I
get a lot of enjoyment from records - sound and artefact.


I love the sound from records (or some of it). I just hate aspects of
its quality.

I just bought a 4 CD Stiff back catalogue collection. Compressed and
sort of 'dolbyised', with dull treble. I played the vinyl version of one
of the tracks I have. I honestly fail to believe the vinyl sounds worse.

Of course back then it was all we had, so we
loved it. Our eyes were opened by CD.


I listen to CDs, obviously, but it didn't/doesn't make that much of a
difference to me in terms of listening to music. Variety and
convenience has increased, but in terms of actually enjoying music,
not really.


Music is nothing like as enjoyable now of course. Back then there was
a joy of ownership, there was the ceremonial of cleaning the record,
brushing the stylus, lowering it carefully into place and sinking
ourselves into the hiss and crackles. With CD you get none of that -
just press the button and there's the music.


Not incredibly rational, but I quite like all of that. I find music is
less special nowadays. I used to play records to death. Now, I have 10s
of CDs I've never played.

And of course mastering for CD is now a disgrace - the inventors have
provided the music industry with unparalleled dynamic range and the
music industry has responded by using none of it; this is an utter
disgrace.


I know this is discussed a lot on this NG, but as simply an 'audio
enthusiast' who likes a decent sound, I do find this frustrating. I
can't seem to get out of the habit of going in to these music boutiques,
and ending up disappointed most of the time.

Listening to Amy Winehouse (more her band actually) on the Glastonbury
thing shows what can be done under very difficult conditions - I thought
the sound was superb.

Rob

I thought they made a fair job of a poor situation. I was unhappy with
much of the mixing and balance from Glastonbury - far too much drums for
the most part. Amy has lost it though - barely managed to mumble her way
through her set list; I would have been asking for my money back. I was
wondering if the on-stage monitoring was bad because nobody was singing
well.

d

Dirty Digital [sic.]
 

Don Pearce wrote:
Rob wrote:
Don Pearce wrote:
Rob wrote:
Don Pearce wrote:
Rob wrote:


Just seemed possibly ironic that digital might have to be 'shaped'
to sound decent.


Digital, unlike vinyl, doesn't need any shaping to sound decent. It
is spot-on right out of the box. With vinyl you need to play with
the frequency response, limit the excursion at the bottom end,
minimise acceleration at the top end, watch out for melted cutters.
In fact the mastering process is the sad and sorry business of
trying to minimise the wreckage.


I've no doubt! I'll obviously defer here, but isn't dither a type of
sound 'shaping', in that it changes the sound? And isn't reducing
bitrates to 16 something of an art - or at least algorithmic? And
DACs? So it's not quite 'out of the box'. Or is it your point of the
many boxes out there, all are so minutely different as to make no
difference to what we're capable of hearing?


No. Dither is an integral part of the process - always has been and
always will be. It isn't shaping anything.

Yes, OK, I did say I was coming from a position of ignorance. I
thought dither does shape sound. Is dither a necessary, objective and
ubiquitous component of digital recording then?


You've got it!

You say that! Just one tiny thing - if I record music on my computer, is
that digital recording dithered? If I *know* that I can work backwards.


And you don't have to reduce
bit depth (not rate) to 16 - you can record that way in the first
place. It offers far more signal to noise ratio than any available
analogue format. 24 bits is available because it is possible, and it
does offer a S/N advantage over 16 bits - not for an audio recording,
of course, but certainly for other things. People do 24 bits because
they can. There is no "algorithm" involved in getting down to 16 bits
from there - simply add the dither and chop off the bottom 8 bits.


Yes, I'd picked up that recording is sometimes done in higher than 16
bits. There must be an algorithm I'd have thought. What you say
contradicts aspects of the Wikipedia entires. Have you never felt
inclined to put these right? It only takes a couple of seconds. Look
up 'dither' and 'quantization' and see what you think. If you'd prefer
I'll pick out a few examples.


I've written my own articles on dither, anti-aliasing etc. The problem
with Wikipedia is that the original authors tend to be proprietorial.
You go in to correct an error, and a day later it is back there again.


Yes, that's a problem. A colleague has to keep correcting a student's
bit of fun - s/he keeps putting 'University' in inverted commas. Ahem.

Couple of the Wki things - 24 bit recording isn't always dithered, and
there are different types of dither.


Digital audio at 16/44.1 has reached what amounts to perfection. I'm
not saying that there are no audible differences between the boxes -
it is still entirely possible to screw up an implementation. But
certainly the best are no different from the competent. the
differences are to be found in features, function and cosmetics, not
the sound.

You've obviously had a bad experience of vinyl - it's moved on a
lot in last 40 years IMO.

Opinions count for nothing when the facts are available. Vinyl
hasn't moved an inch in that time. It was mediocre back then, and
it is still equally mediocre today.

I meant turntables and cartridges rather than the records
themselves. The few records I've bought new over the past ten years
have been pretty rubbish.


It is a matter of diminishing returns.

Yes, I know that better than most. £100 would see you right. I'm
perfectly happy with a (very) old Thorens TT right now, £100 on ebay.


My vinyl is handled by an old Systemdek Iv, an SME 3009 arm which I
bought in the 1960s and an AT OC9 cartridge. I will not improve that at
any price.

You can spend thousands on a deck
with counterweights, glass platters -whatever you like. Mostly this
stuff is for show, but the stuff that isn't is really just striving
to minimise the horribleness of it all - not make it great.


:-)

OK, you hate the sound from records, and that's really an end to it. I
get a lot of enjoyment from records - sound and artefact.


I love the sound from records (or some of it). I just hate aspects of
its quality.

I just bought a 4 CD Stiff back catalogue collection. Compressed and
sort of 'dolbyised', with dull treble. I played the vinyl version of
one of the tracks I have. I honestly fail to believe the vinyl sounds
worse.


I have to correct myself here. When I first listened, to a Nick Lowe
track, it didn't fare well in a back to back with a record.

I listened to most of the music last night and most of it is very good
indeed. There's one track which, I would swear, is taken from a record
(a 1980s recording).

Of course back then it was all we had, so we
loved it. Our eyes were opened by CD.


I listen to CDs, obviously, but it didn't/doesn't make that much of
a difference to me in terms of listening to music. Variety and
convenience has increased, but in terms of actually enjoying music,
not really.


Music is nothing like as enjoyable now of course. Back then there was
a joy of ownership, there was the ceremonial of cleaning the record,
brushing the stylus, lowering it carefully into place and sinking
ourselves into the hiss and crackles. With CD you get none of that -
just press the button and there's the music.


Not incredibly rational, but I quite like all of that. I find music is
less special nowadays. I used to play records to death. Now, I have
10s of CDs I've never played.

And of course mastering for CD is now a disgrace - the inventors have
provided the music industry with unparalleled dynamic range and the
music industry has responded by using none of it; this is an utter
disgrace.


I know this is discussed a lot on this NG, but as simply an 'audio
enthusiast' who likes a decent sound, I do find this frustrating. I
can't seem to get out of the habit of going in to these music
boutiques, and ending up disappointed most of the time.

Listening to Amy Winehouse (more her band actually) on the Glastonbury
thing shows what can be done under very difficult conditions - I
thought the sound was superb.

Rob

I thought they made a fair job of a poor situation. I was unhappy with
much of the mixing and balance from Glastonbury - far too much drums for
the most part. Amy has lost it though - barely managed to mumble her way
through her set list; I would have been asking for my money back. I was
wondering if the on-stage monitoring was bad because nobody was singing
well.


I quite like that 'basic' mix, and didn't notice anything overblown -
just sounded like an approximation of what I thought it might have
sounded like if I was there. Amy had clearly had a drink.

Rob

Dirty Digital [sic.]
 

Rob wrote:
Don Pearce wrote:
Rob wrote:
Don Pearce wrote:
Rob wrote:
Don Pearce wrote:
Rob wrote:


Just seemed possibly ironic that digital might have to be
'shaped' to sound decent.


Digital, unlike vinyl, doesn't need any shaping to sound decent.
It is spot-on right out of the box. With vinyl you need to play
with the frequency response, limit the excursion at the bottom
end, minimise acceleration at the top end, watch out for melted
cutters. In fact the mastering process is the sad and sorry
business of trying to minimise the wreckage.


I've no doubt! I'll obviously defer here, but isn't dither a type
of sound 'shaping', in that it changes the sound? And isn't
reducing bitrates to 16 something of an art - or at least
algorithmic? And DACs? So it's not quite 'out of the box'. Or is it
your point of the many boxes out there, all are so minutely
different as to make no difference to what we're capable of hearing?


No. Dither is an integral part of the process - always has been and
always will be. It isn't shaping anything.

Yes, OK, I did say I was coming from a position of ignorance. I
thought dither does shape sound. Is dither a necessary, objective and
ubiquitous component of digital recording then?


You've got it!

You say that! Just one tiny thing - if I record music on my computer, is
that digital recording dithered? If I *know* that I can work backwards.


Yes; dithering is built into every sound card you can buy.


And you don't have to reduce
bit depth (not rate) to 16 - you can record that way in the first
place. It offers far more signal to noise ratio than any available
analogue format. 24 bits is available because it is possible, and it
does offer a S/N advantage over 16 bits - not for an audio
recording, of course, but certainly for other things. People do 24
bits because they can. There is no "algorithm" involved in getting
down to 16 bits from there - simply add the dither and chop off the
bottom 8 bits.


Yes, I'd picked up that recording is sometimes done in higher than 16
bits. There must be an algorithm I'd have thought. What you say
contradicts aspects of the Wikipedia entires. Have you never felt
inclined to put these right? It only takes a couple of seconds. Look
up 'dither' and 'quantization' and see what you think. If you'd
prefer I'll pick out a few examples.


I've written my own articles on dither, anti-aliasing etc. The problem
with Wikipedia is that the original authors tend to be proprietorial.
You go in to correct an error, and a day later it is back there again.


Yes, that's a problem. A colleague has to keep correcting a student's
bit of fun - s/he keeps putting 'University' in inverted commas. Ahem.

Couple of the Wki things - 24 bit recording isn't always dithered, and
there are different types of dither.


It is certainly dithered, but that doesn't necessarily mean that a
specific noise signal has been provided for the purpose. Anything
noise-like will dither, and at 24 bits the inevitable input noise from
the analogue circuitry is already more than big enough for the job. It
is only when native noise levels are below the digital threshold that
you need to dither specifically. And of course when you are creating
music by synth.

d

Dirty Digital [sic.]
 

Eeyore wrote:

Rob wrote:

Eeyore wrote:
Rob wrote:

I'll obviously defer here, but isn't dither a type of
sound 'shaping', in that it changes the sound?
No. It's merely a tiny bit of noise at ~ -90dB. Coul;d be less with modern
24 bit converters. Most real world signals self-dither anyway.
OK fine, it doesn't change the sound. My source is Wikipedia I'd afraid.

And isn't reducing bitrates to 16 something of an art
You mean bit depth. 96dB ? Not enough ?

Have you any idea how many dB vinyl and analogue tape's capable of ? Nowhere
remotely NEAR that. Plus you had to use Dolby A to get multitrack tape to
deliver an acceptable level of noise.
Bits as in amount of information. More bits more information.

Uh ? Even 16 bit audio beats analogue tape and disc hands down.


- or at least algorithmic?
Uh ?
Changing from say 24 to 16 bitrate involves a process, involving one or
more steps, and calculation: an algorithm.

Not it just gives more resolution. More than you can practically use in fact. You
get 6dB of s/n ratio per bit -3dB off the total.


OK, I'll have to put hands up and say you've completely lost me. I would
have thought changing 24 bit to 16 bit involves calculation. Nothing I
can think of is 'just done'. And I would have thought it (24-16) gave
less resolution. Why record at a higher bit rate to get lower resolution?!


And DACs?
DACs are STUNNING these days. The very early ones were a bit stinky but
they've been fine for a good 20 years or so now.

If you say all current DACs available are stunning and incapable of
differentiation then I'm in no position to mount a scientific challenge.

Example ... state of the art .....
24-Bit Resolution
Analog Performance:
Dynamic Range:
132 dB (9 V RMS, Mono)
129 dB (4.5 V RMS, Stereo)
127 dB (2 V RMS, Stereo)
THD+N: 0.0004%
Differential Current Output: 7.8 mA p-p
8â—Š Oversampling Digital Filter:
Stop-Band Attenuation: ñ130 dB
Pass-Band Ripple: ±0.00001 dB
Sampling Frequency: 10 kHz to 200 kHz

http://focus.ti.com/docs/prod/folder.../dsd1794a.html

At 1/4 the price ......

24-Bit Resolution
Analog Performance:
Dynamic Range: 123 dB
THD+N: 0.0005%
Differential Current Output: 4 mA p-p
8â—Š Oversampling Digital Filter:
Stop-Band Attenuation: ñ98 dB
Pass-Band Ripple: ±0.0002 dB
Sampling Frequency: 10 kHz to 200 kHz

http://focus.ti.com/docs/prod/folder...t/pcm1796.html

And that's a mere £1.85 in small production quantities.


Them's the facts, and to my untrained eye there would appear to be very
little 'real world' difference.

All I can say is that I think I can detect differences in real world
sources - computers for example.

Rob

Dirty Digital [sic.]
 

Eeyore wrote:

Rob wrote:

Eeyore wrote:
Rob wrote:

You've obviously had a bad experience of vinyl - it's moved on a lot in
last 40 years IMO.
No, I had / have a Garrard 401, Ortofon arm and various cartridges over the
years.

I'm just glad to rid of all the 'faff' with them and to know that I'm not
relying on a random concoction of pieces of kit in the signal chain to get a
flat frequency response, never mind low noise, distortion, lack of clicks etc.
Which is good - you've one less burden. You would have to accpet,
though, that it doesn't bother me. In much the same way as making bread
doesn't bother me.

Well, if you don't mind the loss of quality and I hate to think what you must be
using not to hear it.


Admittedly the bread's not as good as baker's. I should imagine my audio
system is mid-fi - Dynaudio/Quad electrostatic speakers, REL sub,
amplifiers and CDP irrelevant, TT a Thorens 125, cartridge a cheap MM
right now. Rooms/acoustics are not ideal but reasonable. All in, makes a
good job of whatever it's fed.

Rob

Dirty Digital [sic.]
 

Rob wrote:
Eeyore wrote:

Rob wrote:

Eeyore wrote:
Rob wrote:

I'll obviously defer here, but isn't dither a type of
sound 'shaping', in that it changes the sound?
No. It's merely a tiny bit of noise at ~ -90dB. Coul;d be less with
modern
24 bit converters. Most real world signals self-dither anyway.
OK fine, it doesn't change the sound. My source is Wikipedia I'd afraid.

And isn't reducing bitrates to 16 something of an art
You mean bit depth. 96dB ? Not enough ?

Have you any idea how many dB vinyl and analogue tape's capable of ?
Nowhere
remotely NEAR that. Plus you had to use Dolby A to get multitrack
tape to
deliver an acceptable level of noise.
Bits as in amount of information. More bits more information.

Uh ? Even 16 bit audio beats analogue tape and disc hands down.


- or at least algorithmic?
Uh ?
Changing from say 24 to 16 bitrate involves a process, involving one or
more steps, and calculation: an algorithm.

Not it just gives more resolution. More than you can practically use
in fact. You
get 6dB of s/n ratio per bit -3dB off the total.


OK, I'll have to put hands up and say you've completely lost me. I would
have thought changing 24 bit to 16 bit involves calculation. Nothing I
can think of is 'just done'. And I would have thought it (24-16) gave
less resolution. Why record at a higher bit rate to get lower resolution?!


Lets' start with some terminology so we're all talking about the same thing.

Sampling rate - 44.1k samples/second for CD. For film sound the standard
is 48k. Sound cards offer other rates, like 88.2, 96 and 192.

Bit depth - How many bits make up a sample. for CD it is 16. TV sound
(NICAM) uses 10. Telephones use 8. Sound cards also offer 24. There are
actual advantages to 24 bits, even when the final product will be
released at 16. It allows you to record at a lower level to guarantee
headroom - no clipping. Also if you have many tracks to be mixed
together, you may have less net noise if they are all 24 bits rather
than 16.

Bit rate - this is a data rate used in streaming. Sampling rate x bit
depth x number of channels gives the bit rate. A CD has 441000 x 16 x 2,
or 1.4 megabits per second. An MP3 might be just a tenth of that rate.


And DACs?
DACs are STUNNING these days. The very early ones were a bit stinky but
they've been fine for a good 20 years or so now.

If you say all current DACs available are stunning and incapable of
differentiation then I'm in no position to mount a scientific challenge.

Example ... state of the art .....
24-Bit Resolution
Analog Performance:
Dynamic Range:
132 dB (9 V RMS, Mono)
129 dB (4.5 V RMS, Stereo)
127 dB (2 V RMS, Stereo)
THD+N: 0.0004%
Differential Current Output: 7.8 mA p-p
8â—Š Oversampling Digital Filter:
Stop-Band Attenuation: ñ130 dB
Pass-Band Ripple: ±0.00001 dB
Sampling Frequency: 10 kHz to 200 kHz

http://focus.ti.com/docs/prod/folder.../dsd1794a.html

At 1/4 the price ......

24-Bit Resolution
Analog Performance:
Dynamic Range: 123 dB
THD+N: 0.0005%
Differential Current Output: 4 mA p-p
8â—Š Oversampling Digital Filter:
Stop-Band Attenuation: ñ98 dB
Pass-Band Ripple: ±0.0002 dB
Sampling Frequency: 10 kHz to 200 kHz

http://focus.ti.com/docs/prod/folder...t/pcm1796.html

And that's a mere £1.85 in small production quantities.


Them's the facts, and to my untrained eye there would appear to be very
little 'real world' difference.

All I can say is that I think I can detect differences in real world
sources - computers for example.


It is possible. 44.1/16 is the norm, and it is where most manufacturers
concentrate their design efforts. The result is that some sound cards
perform audibly more poorly at 96/24 which should intuitively be better.
It is all in the filtering.

d

Dirty Digital [sic.]
 

"Don Pearce" wrote in message
et...



Bit depth - How many bits make up a sample. for CD it is 16. TV sound
(NICAM) uses 10. Telephones use 8.

I think I ought to add that NICAM is 14 bit, and telephones 12 bit, before
compressing.


David.