gmane.comp.systems.sam-coupe

Dave Laundon | 22 May 14:45

Interlaced video

2008/5/21 Thomas Harte <tomh.retrospec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:

Also, one further question: am I right to think that the Sam has no
means of producing interlaced video?

It's funny you should mention that... I recently got a new LCD TV (a nice Samsung 32", unfortunately not "Full HD" though...) and just the other day I thought I would dig Sam out and see how it looks on it. It's been a while since I've used my real Sam and it seems my floppy has finally died (an original Citizen; it sounds like the usual stretched drive belt problem, but that's another story), so I was restricted to playing about in BASIC for a bit. Anyway, it seems my TV doesn't realise the signal is not interlaced!

With a static display there is nothing to show it, but with fast movement (I did a ROLL of a small area in a loop with PAUSE 1) it is clear that the TV is interpreting pairs of Sam frames as the two fields of a single interlaced frame. In an extreme example I had a pair of ROLLs shifting an area left then right and the TV shows a static image with a nice comb effect.

Makes me want to dig out those Fred issues with "interlaced" images on them to see how they look. If only my drive worked... (Colin, do you still have spare belts? :-)

Dave (de-lurking after aaaages).

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Colin Piggot | 22 May 15:13

Re: Interlaced video

Dave wrote:
> Anyway, it seems my TV doesn't realise the signal is not interlaced!

Hmmm... sounds an interesting telly! The "comb effect" definitely shows it's
interlacing. I've not come across a telly that will automatically interlace
non-interlaced video before - although I have seen one that refuses to sync
to the SAM - a bit of a dodgy widescreen 26" CRT!

Now the question is, depending how the TV is interlacing the frames, and how
many frames there's been since the SAM was powered up - when the 'Interlaced
Pictures' from FRED are loaded the frames might show with the intended
'interlacing', or be reversed - if 'A' is the frame with the top row, 'B' is
the frame with the row to be shown below, your telly could interlace
correctly so the TV displays with the lines ordered ABABAB, or could be out
of order and display BABABA....  (hope that makes sense!)

> Makes me want to dig out those Fred issues with "interlaced" images on
them
> to see how they look.  If only my drive worked...  (Colin, do you still
have
> spare belts? 

Should do, I'll drop you an email in a bit once i've checked :)

Colin
=====
Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
1995-2008 - Celebrating 14 Years of developing for the SAM Coupe
Website: http://www.samcoupe.com/

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Dave Laundon | 22 May 21:55

Re: Interlaced video

2008/5/22 Colin Piggot <quazar@...>:
> Now the question is, depending how the TV is interlacing the frames, and how
> many frames there's been since the SAM was powered up - when the 'Interlaced
> Pictures' from FRED are loaded the frames might show with the intended
> 'interlacing', or be reversed - if 'A' is the frame with the top row, 'B' is
> the frame with the row to be shown below, your telly could interlace
> correctly so the TV displays with the lines ordered ABABAB, or could be out
> of order and display BABABA....  (hope that makes sense!)

Hmm, I hadn't thought of that.  I guess it's going to be pretty
random.  I'll type that ROLL test in again and keep running it and see
if the orientation changes.  Kind of makes any applications difficult
without a calibration option!

I seem to remember there was a cover tape on one of the magazines that
had a "new display mode" that swapped between two screens at 50Hz or
something.  Can't remember if it was "interlacing" or some method of
increasing colours.  My memory is vague...

> > Makes me want to dig out those Fred issues with "interlaced" images on
> them
> > to see how they look.  If only my drive worked...  (Colin, do you still
> have
> > spare belts? 
>
> Should do, I'll drop you an email in a bit once i've checked :)

Thanks.  Must get him up and running again 

Dave.

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Colin Piggot | 22 May 22:15

Re: Interlaced video

Dave wrote:
> I seem to remember there was a cover tape on one of the magazines that
> had a "new display mode" that swapped between two screens at 50Hz or
> something.  Can't remember if it was "interlacing" or some method of
> increasing colours.  My memory is vague...

Yes, it was Simon Goodwin's routine on a Crash cover tape in 1990 or so. On
the frame interrupt it toggled between two screens with different palettes,
which looked absolutely horrid though on the TV's I'd tried it on. Other
routines in the issue did MODE 3 interlacing - flicking between MODE3
screens saying it would give a screen resolution of 512x384, but it's not as
the SAM only outputs non-interlaced video so again, it just appears as a bit
of a flickery mess!

Out of curiosity, what model of TV is it you have?

Colin
=====
Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
1995-2008 - Celebrating 14 Years of developing for the SAM Coupe
Website: http://www.samcoupe.com/

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Dave Laundon | 23 May 00:43

Re: Interlaced video

2008/5/22 Colin Piggot <quazar@...>:
> Yes, it was Simon Goodwin's routine on a Crash cover tape in 1990 or so. On
> the frame interrupt it toggled between two screens with different palettes,
> which looked absolutely horrid though on the TV's I'd tried it on. Other
> routines in the issue did MODE 3 interlacing - flicking between MODE3
> screens saying it would give a screen resolution of 512x384, but it's not as
> the SAM only outputs non-interlaced video so again, it just appears as a bit
> of a flickery mess!

Ah right, another one for me to track down and try then!

> Out of curiosity, what model of TV is it you have?

It's a Samsung LE32R88

> Colin
> =====
> Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
> 1995-2008 - Celebrating 14 Years of developing for the SAM Coupe
> Website: http://www.samcoupe.com/
>
>

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Andy Chandler | 23 May 00:55

Re[2]: Interlaced video

Funny that about your TV.....
I had a TV that wouldn't display a picture from the SAM correctly way
back when I first bought it (I had one out of the first batch of 100
made). I told them and was invited down for the day while we tried
different things and I met Alan Miles etc. which was pretty cool.

In the end we had to admit defeat and gave up. They gave me a free
256KB RAM expansion as a consolation so not all bad 

(Weeks later, the problem was fixed by adjusting frequencies on the
PCB inside the TV so may not have been the SAM at all though it never
had problems with any of my Speccys etc.)

Thursday, May 22, 2008, 11:43:19 PM, you wrote:

Dave> 2008/5/22 Colin Piggot <quazar@...>:
>> Yes, it was Simon Goodwin's routine on a Crash cover tape in 1990 or so. On
>> the frame interrupt it toggled between two screens with different palettes,
>> which looked absolutely horrid though on the TV's I'd tried it on. Other
>> routines in the issue did MODE 3 interlacing - flicking between MODE3
>> screens saying it would give a screen resolution of 512x384, but it's not as
>> the SAM only outputs non-interlaced video so again, it just appears as a bit
>> of a flickery mess!

Dave> Ah right, another one for me to track down and try then!

>> Out of curiosity, what model of TV is it you have?

Dave> It's a Samsung LE32R88

>> Colin
>> =====
>> Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
>> 1995-2008 - Celebrating 14 Years of developing for the SAM Coupe
>> Website: http://www.samcoupe.com/
>>
>>

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Frode Tenneboe | 23 May 09:59

Re: Interlaced video


On Thu, 2008-05-22 at 23:43 +0100, Dave Laundon wrote:
> 2008/5/22 Colin Piggot <quazar@...>:
> > Yes, it was Simon Goodwin's routine on a Crash cover tape in 1990 or so. On
> > the frame interrupt it toggled between two screens with different palettes,
> > which looked absolutely horrid though on the TV's I'd tried it on. Other
> > routines in the issue did MODE 3 interlacing - flicking between MODE3
> > screens saying it would give a screen resolution of 512x384, but it's not as
> > the SAM only outputs non-interlaced video so again, it just appears as a bit
> > of a flickery mess!
> 
> Ah right, another one for me to track down and try then!

ftp://ftp.worldofspectrum.org/pub/sinclair/magazines/SinclairUser/Issue099/Tape/SUIssue99-Megatape27.tzx.zip

..or more easily accessible:

ftp://ftp.nvg.ntnu.no/pub/sam-coupe/disks/demos/SimonGoodwin-512x384Interlace.zip

 -Frode
--

-- 
^ Frode Tennebø             | email: Frode.Tennebo@... ^
| SAAB Microwave Systems AS | Isebakkeveien 49                   |
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Dave Laundon | 26 May 01:39

Re: Interlaced video

2008/5/23 Frode Tenneboe <frode.tennebo@...>:
> ftp://ftp.worldofspectrum.org/pub/sinclair/magazines/SinclairUser/Issue099/Tape/SUIssue99-Megatape27.tzx.zip
>
> ..or more easily accessible:
>
> ftp://ftp.nvg.ntnu.no/pub/sam-coupe/disks/demos/SimonGoodwin-512x384Interlace.zip

Thanks Frode.  Brings back memories loading a program on SAM from
"tape" (my laptop playing back the converted tzx file)  

Here's Simon's vision finally realised 18 years on 
http://myweb.tiscali.co.uk/dlaundon/mode3+3a.jpg

and when the TV gets the fields the wrong way around...
http://myweb.tiscali.co.uk/dlaundon/mode3+3b.jpg

Unfortunately today the TV seems to be having trouble locking on to
SAM's signal.  It will periodically show a blank screen for half a
second or so, annoyingly frequently at times.  Also the picture seems
quite noisy (the photos don't really show it though).  On a previous
TV (years ago) it seemed like the composite signal and RGB signals
were interfering with each other (and one seemed to be offset from the
other by a few lines).  I wonder if something similar is happening
here (anyone know if it's possible to wire a scart lead without the
composite signal?  I had an idea it was still needed for some reason).

Dave.

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Colin Piggot | 26 May 02:15

Re: Interlaced video

Dave wrote:
> Here's Simon's vision finally realised 18 years on 
> http://myweb.tiscali.co.uk/dlaundon/mode3+3a.jpg

Oooh, nice!

> On a previous
> TV (years ago) it seemed like the composite signal and RGB signals
> were interfering with each other (and one seemed to be offset from the
> other by a few lines).  I wonder if something similar is happening
> here (anyone know if it's possible to wire a scart lead without the
> composite signal?  I had an idea it was still needed for some reason).

On a SAM RGB Scart cable the composite video output from the SAM (pin 19) is
not connected. At the TV end, Pin 19 connects to Pin 16 via a 470ohm
resistor - the diagram in the SAM manual of a RGB Scart lead just has a wire
link between 16 and 19 but the pop a resistor in instead. If you don't have
a suitable cable to canabalise I do have RGB Scart leads made up.

Colin
=====
Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
1995-2008 - Celebrating 14 Years of developing for the SAM Coupe
Website: http://www.samcoupe.com/

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Dave Laundon | 26 May 03:03

Re: Interlaced video

2008/5/26 Colin Piggot <quazar@...>:
> On a SAM RGB Scart cable the composite video output from the SAM (pin 19) is
> not connected. At the TV end, Pin 19 connects to Pin 16 via a 470ohm
> resistor - the diagram in the SAM manual of a RGB Scart lead just has a wire
> link between 16 and 19 but the pop a resistor in instead. If you don't have
> a suitable cable to canabalise I do have RGB Scart leads made up.

Hmm, I'll have to have a look at what mine is doing then.  I'm pretty
certain it has been used on a non-RGB TV in the past, so it looks like
there is a difference to the ones you provide.  I think it is an
original MGT/Samco one, with the "T.V./MONITOR" white label on one
end, but no label on the other end (didn't they have a similar label
on the other end?) - so maybe it has been messed about with at some
point!

Dave.

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Tobermory | 24 May 12:20

RE: Interlaced video

>I guess it's going to be pretty random.  
Hmm interesting.  If its interlace mode for normal broadcast telly works,
(ie you always get ABABAB not BABABA) then it must be receiving some other
signal to identify the A frames from the Bs.  Does turning off the screen
with an OUT 252,0 reset it?

Howard

-----Original Message-----
From: owner-sam-users@...
[mailto:owner-sam-users@...] On
Behalf Of Dave Laundon
Sent: 22 May 2008 20:56
To: sam-users@...
Subject: Re: Interlaced video

2008/5/22 Colin Piggot <quazar@...>:
> Now the question is, depending how the TV is interlacing the frames, and
how
> many frames there's been since the SAM was powered up - when the
'Interlaced
> Pictures' from FRED are loaded the frames might show with the intended
> 'interlacing', or be reversed - if 'A' is the frame with the top row, 'B'
is
> the frame with the row to be shown below, your telly could interlace
> correctly so the TV displays with the lines ordered ABABAB, or could be
out
> of order and display BABABA....  (hope that makes sense!)

Hmm, I hadn't thought of that.  I guess it's going to be pretty
random.  I'll type that ROLL test in again and keep running it and see
if the orientation changes.  Kind of makes any applications difficult
without a calibration option!

I seem to remember there was a cover tape on one of the magazines that
had a "new display mode" that swapped between two screens at 50Hz or
something.  Can't remember if it was "interlacing" or some method of
increasing colours.  My memory is vague...

> > Makes me want to dig out those Fred issues with "interlaced" images on
> them
> > to see how they look.  If only my drive worked...  (Colin, do you still
> have
> > spare belts? 
>
> Should do, I'll drop you an email in a bit once i've checked :)

Thanks.  Must get him up and running again 

Dave.

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Thomas Harte | 24 May 14:20

Re: Interlaced video

There's a timing difference between even frames and odd fields in the  
syncs generated at the field end. Non-interlaced video essentially  
sends only even fields.

That said, I'm not sure if non-interlaced video was ever an official  
part of the PAL spec, so perhaps this TV is justified in its  
implementation. Though it seems odd, as even technology as recent as  
the Playstation 2 uses non-interlaced video modes for some games.

On 24 May 2008, at 11:20, Tobermory wrote:

>> I guess it's going to be pretty random.
> Hmm interesting.  If its interlace mode for normal broadcast telly  
> works,
> (ie you always get ABABAB not BABABA) then it must be receiving some  
> other
> signal to identify the A frames from the Bs.  Does turning off the  
> screen
> with an OUT 252,0 reset it?
>
> Howard
>
> -----Original Message-----
> From: owner-sam-users@... [mailto:owner-sam- 
> users@...] On
> Behalf Of Dave Laundon
> Sent: 22 May 2008 20:56
> To: sam-users@...
> Subject: Re: Interlaced video
>
> 2008/5/22 Colin Piggot <quazar@...>:
>> Now the question is, depending how the TV is interlacing the  
>> frames, and
> how
>> many frames there's been since the SAM was powered up - when the
> 'Interlaced
>> Pictures' from FRED are loaded the frames might show with the  
>> intended
>> 'interlacing', or be reversed - if 'A' is the frame with the top  
>> row, 'B'
> is
>> the frame with the row to be shown below, your telly could interlace
>> correctly so the TV displays with the lines ordered ABABAB, or  
>> could be
> out
>> of order and display BABABA....  (hope that makes sense!)
>
> Hmm, I hadn't thought of that.  I guess it's going to be pretty
> random.  I'll type that ROLL test in again and keep running it and see
> if the orientation changes.  Kind of makes any applications difficult
> without a calibration option!
>
> I seem to remember there was a cover tape on one of the magazines that
> had a "new display mode" that swapped between two screens at 50Hz or
> something.  Can't remember if it was "interlacing" or some method of
> increasing colours.  My memory is vague...
>
>>> Makes me want to dig out those Fred issues with "interlaced"  
>>> images on
>> them
>>> to see how they look.  If only my drive worked...  (Colin, do you  
>>> still
>> have
>>> spare belts? 
>>
>> Should do, I'll drop you an email in a bit once i've checked :)
>
> Thanks.  Must get him up and running again 
>
> Dave.
>
> No virus found in this incoming message.
> Checked by AVG.
> Version: 7.5.524 / Virus Database: 269.24.1/1463 - Release Date:  
> 23/05/2008
> 15:36
>
> No virus found in this outgoing message.
> Checked by AVG.
> Version: 7.5.524 / Virus Database: 269.24.1/1463 - Release Date:  
> 23/05/2008
> 15:36
>
>

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Colin Piggot | 24 May 14:49

Re: Interlaced video

Thomas wrote:
> There's a timing difference between even frames and odd fields in the
> syncs generated at the field end. Non-interlaced video essentially
> sends only even fields.

Was about to say the same thing. The standard 625 line frame (consisting of
one odd and one even field) has several sync pulse bursts (taking up 15 of
the 625 lines) to mark the start of the odd and even fields within.

Non interlaced PAL is only sending single 312 line fields which always have
the same sync pulses so there is no way a TV would be able to know which is
meant to be an odd or even field because they aren't marked differently.
Dave's TV must just be alternating between displaying it as an odd or even
field itself.

Colin
=====
Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
1995-2008 - Celebrating 14 Years of developing for the SAM Coupe
Website: http://www.samcoupe.com/

headers

James R Curry | 23 May 01:13

Re: Interlaced video


>  > Yes, it was Simon Goodwin's routine on a Crash cover tape in 1990 or so. On
>  > the frame interrupt it toggled between two screens with different palettes,
>  > which looked absolutely horrid though on the TV's I'd tried it on. Other
>  > routines in the issue did MODE 3 interlacing - flicking between MODE3
>  > screens saying it would give a screen resolution of 512x384, but it's not as
>  > the SAM only outputs non-interlaced video so again, it just appears as a bit
>  > of a flickery mess!

Wasn't it Sinclair User?

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Colin Piggot | 23 May 08:48

Re: Interlaced video

James wrote:
> Wasn't it Sinclair User?

Oops! Yes, you're quite right. It was Sinclair User - issue 99.

Colin
=====
Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
1995-2008 - Celebrating 14 Years of developing for the SAM Coupe
Website: http://www.samcoupe.com/