SPDIF delay question.
 

"Jim Lesurf" wrote in message
...
In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...


With a CRT in principle all you have to do is allow the CRT to switch scan
width. No need for any 'pan and scan' or 'letterbox' processing by either
source or display.

In principle yes, I'm talking about what actually happens, not what is
possible. Since the end of 405-line transmissions TV sets (as opposed to
computer monitors) have never had switching for horizontal scan frequency or
width. Quite a lot can switch the vertical frequency between 50 and 60Hz and
a few have a vertical scan amplitude switching for letterbox presentation of
widescreen material.


I had thought we had been discussing lip synch delays caused by
*displays*.
For fairly obvious reasons, if a source like a DVD player or tuner has to
have a process delay for the image it can easily then apply a similar
delay
to the sound. This just requires the designer to know what they are doing.
However when the display has a vision delay, the designer may have no
control over the sound path from an external source feeding video to the
display.


Well we were, I just made the point that just because you are watching on a
CRT that doesn't mean there isn't any "faffing about". Widscreen CRT TV's
all have digital processing to cope with various aspect ratios etc.

But it isn't the faffing about needed to convert the pixel number/layout
(which is in effect standards conversion) that causes the long delays that
cause lip-sync problems, rather that is due to more fundamental aspects of
the way flat-screen displays work.

David.

SPDIF delay question.
 

Jim Lesurf wrote:
In article , Don
Pearce
wrote:
Jim Lesurf wrote:
In article , Eiron
wrote:

Most modern amps seem to have lip-sync delay built in. It's just not
something you think about until your CRT TV dies.
For me, it is the other way around. Having thought about the lip synch
problems, I decided to stay with CRT. :-)


Not an answer I'm afraid Jim. I have CRT and lip sync problems. My
answer is to give up and listen to records. TV programmes are a total
disgrace these days.

I occasionally notice lip synch problems on DTTV broadcasts, but it seems
rare in my experience. Mind you, my eyesight isn't marvellous... and when I
use a DTTV box to pick up R3/4 I'm not looking. :-)

Can't comment on satellite TV as I don't have a way to receive it.

What DTTV RX are you using? What stations?

Slainte,

Jim


Two of them - one is a Panasonic TU-CT30 and the other is unaccountably
shy and has no name. The big chip is by Phillips. Ought to be good
though - I think I paid all of £20 in Asda for it.

d

SPDIF delay question.
 

In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...

With a CRT in principle all you have to do is allow the CRT to switch
scan width. No need for any 'pan and scan' or 'letterbox' processing
by either source or display.

In principle yes, I'm talking about what actually happens, not what is
possible. Since the end of 405-line transmissions TV sets (as opposed to
computer monitors) have never had switching for horizontal scan
frequency or width.

Eh? My CRT TV switches both. It switches between 16:9 and 4:3 - by altering
the horizontal scan width. It switches also for PAL/NTSC. No idea where you
got the idea that CRT TV "never had" this after 405 line. Not all do, I
guess, but I doubt my set is unique!

Quite a lot can switch the vertical frequency between 50 and 60Hz and a
few have a vertical scan amplitude switching for letterbox presentation
of widescreen material.

Yes. My TV can also switch scaling for something like 14:9 letterboxed.
Though these days I only notice this on a weirder channel like UKTV History
where they seem unable to bother to transmit 16:9 for some odd reason.


I had thought we had been discussing lip synch delays caused by
*displays*. For fairly obvious reasons, if a source like a DVD player
or tuner has to have a process delay for the image it can easily then
apply a similar delay to the sound. This just requires the designer
to know what they are doing. However when the display has a vision
delay, the designer may have no control over the sound path from an
external source feeding video to the display.


Well we were, I just made the point that just because you are watching
on a CRT that doesn't mean there isn't any "faffing about". Widscreen
CRT TV's all have digital processing to cope with various aspect ratios
etc.

You classify operating two or three analogue switches for the two scan
waveforms as "digital processing" in the same sense as the digital domain
*image* processing that pixel displays carry out? Can't say that treating
those as being the same makes much sense to me. Partilularly as I'm not
clear that much "digital" would be needed to switch aspects and scan rates
on a CRT TV.

But it isn't the faffing about needed to convert the pixel number/layout
(which is in effect standards conversion) that causes the long delays
that cause lip-sync problems, rather that is due to more fundamental
aspects of the way flat-screen displays work.

That may be so, if you mean how the makers have *designed* them to work.
Including the use of numbers of pixel rows/columns that don't match the
image, and the manner in which they address/latch the pixels. Problem here
is that they started off making computer monitors (primarily to USA
expectations) and then have simply applied the same methods to TV. Alas, in
TV the requirements differ from general computer use. But as I said, I
suspect in time the makers will make what they'll announce as "spectacular
breakthoughs" when they get around to making displays actually with the
specific TV systems in mind. :-)

Slainte,

Jim

--
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SPDIF delay question.
 

In article , Jim Lesurf
scribeth thus
In article , Don
Pearce
wrote:
Jim Lesurf wrote:
In article , Eiron
wrote:

Most modern amps seem to have lip-sync delay built in. It's just not
something you think about until your CRT TV dies.

For me, it is the other way around. Having thought about the lip synch
problems, I decided to stay with CRT. :-)


Not an answer I'm afraid Jim. I have CRT and lip sync problems. My
answer is to give up and listen to records. TV programmes are a total
disgrace these days.

I occasionally notice lip synch problems on DTTV broadcasts, but it seems
rare in my experience. Mind you, my eyesight isn't marvellous... and when I
use a DTTV box to pick up R3/4 I'm not looking. :-)

Can't comment on satellite TV as I don't have a way to receive it.

Why not?, some lump of granite in the way...

What DTTV RX are you using? What stations?

Slainte,

Jim


--
Tony Sayer

SPDIF delay question.
 

In article , tony sayer

wrote:
In article , Jim Lesurf
scribeth thus


Can't comment on satellite TV as I don't have a way to receive it.

Why not?, some lump of granite in the way...

I wouldn't call our neighbour's house a "lump of granite". :-) But it may
well be in the way...

That said, I was referring to not having any dish or sat RX. But if you
want to let me have a free dish and freesat RX to give it a try, let me
know. ;-

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

SPDIF delay question.
 

In article , Don
Pearce
wrote:

Not an answer I'm afraid Jim. I have CRT and lip sync problems. My
answer is to give up and listen to records. TV programmes are a total
disgrace these days.

I occasionally notice lip synch problems on DTTV broadcasts, but it
seems rare in my experience. Mind you, my eyesight isn't marvellous...
and when I use a DTTV box to pick up R3/4 I'm not looking. :-)

What DTTV RX are you using? What stations?

Two of them - one is a Panasonic TU-CT30 and the other is unaccountably
shy and has no name. The big chip is by Phillips. Ought to be good
though - I think I paid all of £20 in Asda for it.

I wonder if this depends on the RX. Apart from one or two (i.e. rare)
occasions I haven't noticed lip synch problems using either a Nokia 221T
DTTV box scart-feeding a CRT, or using a Panasonic DVD recorder with
inbuilt DTTV tuner. Alternatively, it may be that I'm just very aware of
the problem due to my lousy eyesight.

Only time I normally notice lip synch offsets is if I'm looking at video
from the Panasonic recorder's tuner to setup a recording, but am still
listening to the Nokia! But hardly surprising that two RXs have different
process delays.

I do also have a Philips DTTV box. But I just use that as a sound tuner
tfor BBC radio to go with the audio system in the dining room (where I also
keep my computer and so type - as now). So lip synch isn't an issue in that
case.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

SPDIF delay question.
 

Jim Lesurf said:


Yes. My TV can also switch scaling for something like 14:9 letterboxed.
Though these days I only notice this on a weirder channel like UKTV History
where they seem unable to bother to transmit 16:9 for some odd reason.

It's the second-hand programmes they buy from boot sales.

The test cards back, yippee
http://www.digitalspy.biz/forums/sho...d.php?t=728920

--
Ken
Contribute to: www.audiophilewiki.org

SPDIF delay question.
 

"Jim Lesurf" wrote in message
...

Eh? My CRT TV switches both. It switches between 16:9 and 4:3 - by
altering
the horizontal scan width. It switches also for PAL/NTSC. No idea where
you
got the idea that CRT TV "never had" this after 405 line. Not all do, I
guess, but I doubt my set is unique!

The widescreen sets that I have experience of switch between 16:9 and 4:3 by
time-compressing 4:3 video in the digital process area rather than altering
the scan width. Once the digital box is present it's cheaper to do
it that way. But if your set does it by altering the scan width then clearly
not *all* do it digitally. OK, I'll rephase my remark as "Since the end of
405-line transmissions 4:3 TV sets (as opposed to computer monitors) have
never had switching for horizontal scan frequency or width".

Switching between PAL & NTSC doesn't require any change to the horizontal
scan, only the switch between 50 & 60 Hz vertical scan.

Quite a lot can switch the vertical frequency between 50 and 60Hz and a
few have a vertical scan amplitude switching for letterbox presentation
of widescreen material.


You classify operating two or three analogue switches for the two scan
waveforms as "digital processing" in the same sense as the digital domain
*image* processing that pixel displays carry out?

I certainly do not! By digital processing I mean that the image shape is
changed by manipulating the image data. The video processing (colour
decoding, Y/C delay equalisation etc.) has been done digitally in all but
the cheapest sets for quite a few years now, so it doesn't add much to the
cost
of that to add image size/shape conversion as well.


Can't say that treating
those as being the same makes much sense to me.

It wouldn't to me either, if that was what I meant.

Partilularly as I'm not
clear that much "digital" would be needed to switch aspects and scan rates
on a CRT TV.

It's not "needed" it's just cheaper, as any switching associated with the
horizontal scan is expensive.

But it isn't the faffing about needed to convert the pixel number/layout
(which is in effect standards conversion) that causes the long delays
that cause lip-sync problems, rather that is due to more fundamental
aspects of the way flat-screen displays work.

That may be so, if you mean how the makers have *designed* them to work.
Including the use of numbers of pixel rows/columns that don't match the
image,

It really doesn't take long to convert from one image dimension to another,
the added delay is measured in hundreds of microseconds, not milliseconds.
You certainly won't notice that delay on lip-sync

David.

SPDIF delay question.
 

In article ,
UnsteadyKen
wrote:
Jim Lesurf said:


Yes. My TV can also switch scaling for something like 14:9
letterboxed. Though these days I only notice this on a weirder channel
like UKTV History where they seem unable to bother to transmit 16:9
for some odd reason.

It's the second-hand programmes they buy from boot sales.

Does the BBC issue letterbox 14:9 into 4:3 versions of 16:9 source
specifically for purchase at lower prices? I'm asking because some of the
programmes I've seen on UKTV History at 14:9 letterbox were, IIRC, ones
I've also seen on the BBC in 16:9... Maybe the price is per pixel. :-)

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
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Audio Misc http://www.audiomisc.co.uk/index.html

SPDIF delay question.
 

In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...

Eh? My CRT TV switches both. It switches between 16:9 and 4:3 - by
altering the horizontal scan width. It switches also for PAL/NTSC. No
idea where you got the idea that CRT TV "never had" this after 405
line. Not all do, I guess, but I doubt my set is unique!

The widescreen sets that I have experience of switch between 16:9 and
4:3 by time-compressing 4:3 video in the digital process area rather
than altering the scan width.

Erm...

For CRT that would make little sense to me. Perhaps you aren't making it
clear, or are confusing different things. Are you saying every 16:9 CRT
you've used displays 4:3 by scanning the entire 16:9 area, but puts the 4:3
image into the central portion? if so, why does it do this when fed with
something like 4:3 via SCART? Seems a weird option to me. Changing
the amplitude of the horizontal scan level seems a trivially easier
way to deal with the matter, and probably gives better results.

Mind you, I never cease to be impressed by the mindless ways some TV
manufacturers invent 'around the barn' ways to make things needlessly
complex so as to sell the result as being 'clever'. Bolony still
baffles brains, I guess, even after all these years... :-)

But so far as I can tell, when my TV CRT sees the input change to 4:3
from 16:9 there is a click as the horizontal scan amplitude alters, and the
picture falls back into the central portion of the screen. No scanning
outwith that area. Since it is a pretty standard Panasonic CRT set bought
just a few years ago I assume this is a fairly standard option. Seems like
sensible engineering to me. But if what you say is right Panasonic seem to
have shown rather more sense than other makers. Are they unique? I'd
be surprised to find they were given the simplicity of the method.

I'd agree that the levels used for the scans are set 'digitally', though,
as the widths, etc, are all accessible via onscreen menus - once you have
found the hidden service menus. :-) I assume this just means the scaling
voltages are held in something like a non-volatile RAM and then used to
reference the sizes of the analogue scan waveforms. But perhaps they do
write waveforms into RAM to get shapes right, then read the RAM series
during each line and frame. Not exactly what I'd call 'digital processing',
though. Just like using look up tables with a cheap sig gen.


Once the digital box is present it's cheaper to do it that way. But if
your set does it by altering the scan width then clearly not *all* do it
digitally.

Depends what you mean. See above. You may be confusing a 'digital box'
(i.e. external tuner) having to do the job with the display coping
with changes in aspect.


OK, I'll rephase my remark as "Since the end of 405-line
transmissions 4:3 TV sets (as opposed to computer monitors) have never
had switching for horizontal scan frequency or width".

Your point being that sets made with no provision for other than 4:3
have no provision for other than 4:3? I can see the logic of that. ;-

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html