Is it just me, or does Clive Myrie's forehead do weird things on the
broadcast from Israel? It'd think it was lack of bandwidth - except all
the white people come over OK.

I suspect the CODEC regards dark areas as less important so not needing
as many updates.

Andy

On 19/10/2023 16:48, Vir Campestris wrote:
>
> Is it just me, or does Clive Myrie's forehead do weird things on the
> broadcast from Israel? It'd think it was lack of bandwidth - except all
> the white people come over OK.
>
> I suspect the CODEC regards dark areas as less important so not needing
> as many updates.

I've not seen this, but I wonder if it could be related to a similar
problem with AI facial recognition, which recognises black faces far
less well than white. Perhaps similarly to AI the codecs are troubled
by the relative lack of contrast in black faces, and so treats a black
face as one area of predominant colour with consequent loss of detail?

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

Obviously I am not qualified to say much. What I do notice on a freeview set
with an internet connection is a whole lot of Arabic news channels, but I've
yet to see a Jewish one. There is even a Japanese news station and an Indian
one.
Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Vir Campestris" <vir.campestris@invalid.invalid> wrote in message
news:ugrj3t$e237$2@dont-email.me...
> Is it just me, or does Clive Myrie's forehead do weird things on the
> broadcast from Israel? It'd think it was lack of bandwidth - except all
> the white people come over OK.
>
> I suspect the CODEC regards dark areas as less important so not needing as
> many updates.
>
> Andy

On Thu, 19 Oct 2023 16:48:13 +0100, Vir Campestris
<vir.campestris@invalid.invalid> wrote:

>Is it just me, or does Clive Myrie's forehead do weird things on the
>broadcast from Israel? It'd think it was lack of bandwidth - except all
>the white people come over OK.
>
>I suspect the CODEC regards dark areas as less important so not needing
>as many updates.
>
>Andy

Dark surfaces reflect less light than light ones (which is why they
appear dark) so any system working on that part of the video signal
will inevitably have less information to work with. We shouldn't be
surprised that it doesn't cope so well.

Rod.

On 20/10/2023 10:05, Roderick Stewart wrote:
> Dark surfaces reflect less light than light ones (which is why they
> appear dark) so any system working on that part of the video signal will
> inevitably have less information to work with. We shouldn't be surprised
> that it doesn't cope so well.

Why don't they use a negative image, I do that quite often when
transcribing a dark document.

Would have thought the software analysing the facial image could try
both and select which gives the best results.

On Fri, 20 Oct 2023 10:57:46 +0100, JMB99 <mb@nospam.net> wrote:

>On 20/10/2023 10:05, Roderick Stewart wrote:
>> Dark surfaces reflect less light than light ones (which is why they
>> appear dark) so any system working on that part of the video signal will
>> inevitably have less information to work with. We shouldn't be surprised
>> that it doesn't cope so well.
>
>
>Why don't they use a negative image, I do that quite often when
>transcribing a dark document.
>
>Would have thought the software analysing the facial image could try
>both and select which gives the best results.
>

It doesn't matter what you do with the signal if the fundamental
problem is that it contains less information. Making it negative is
just turning it upside down, but it's still based on the amount of
light that entered the lens from the subject, and you won't get any
more of it by messing about with the signal after the event.

You can improve matters by shining more light on the subject, or using
a bigger lens (lower f stop) or a more sensitive pickup device, or
designing less noisy video amplifiers, but there will always be less
original information available from darker surfaces.

Rod.

On Fri, 20 Oct 2023 12:22:28 +0100, Roderick Stewart wrote:

> On Fri, 20 Oct 2023 10:57:46 +0100, JMB99 <mb@nospam.net> wrote:
>
>>On 20/10/2023 10:05, Roderick Stewart wrote:
>>> Dark surfaces reflect less light than light ones (which is why they
>>> appear dark) so any system working on that part of the video signal
>>> will inevitably have less information to work with. We shouldn't be
>>> surprised that it doesn't cope so well.
>>
>>
>>Why don't they use a negative image, I do that quite often when
>>transcribing a dark document.
>>
>>Would have thought the software analysing the facial image could try
>>both and select which gives the best results.
>>
>>
> It doesn't matter what you do with the signal if the fundamental problem
> is that it contains less information. Making it negative is just turning
> it upside down, but it's still based on the amount of light that entered
> the lens from the subject, and you won't get any more of it by messing
> about with the signal after the event.
>
> You can improve matters by shining more light on the subject, or using a
> bigger lens (lower f stop) or a more sensitive pickup device, or
> designing less noisy video amplifiers, but there will always be less
> original information available from darker surfaces.
>
> Rod.

Or scanning the spectrum.

On Fri, 20 Oct 2023 17:33:22 -0000 (UTC), jon <jon@nospam.cn> wrote:

>On Fri, 20 Oct 2023 12:22:28 +0100, Roderick Stewart wrote:
>
>> On Fri, 20 Oct 2023 10:57:46 +0100, JMB99 <mb@nospam.net> wrote:
>>
>>>On 20/10/2023 10:05, Roderick Stewart wrote:
>>>> Dark surfaces reflect less light than light ones (which is why they
>>>> appear dark) so any system working on that part of the video signal
>>>> will inevitably have less information to work with. We shouldn't be
>>>> surprised that it doesn't cope so well.
>>>
>>>
>>>Why don't they use a negative image, I do that quite often when
>>>transcribing a dark document.
>>>
>>>Would have thought the software analysing the facial image could try
>>>both and select which gives the best results.
>>>
>>>
>> It doesn't matter what you do with the signal if the fundamental problem
>> is that it contains less information. Making it negative is just turning
>> it upside down, but it's still based on the amount of light that entered
>> the lens from the subject, and you won't get any more of it by messing
>> about with the signal after the event.
>>
>> You can improve matters by shining more light on the subject, or using a
>> bigger lens (lower f stop) or a more sensitive pickup device, or
>> designing less noisy video amplifiers, but there will always be less
>> original information available from darker surfaces.
>>
>> Rod.
>
>Or scanning the spectrum.

I'm not sure what you mean by that. A visual image intended for human
eyes is normally derived only from the part of the spectrum that is
visible to us. There would be plenty more available without that
restriction, but normally what you can see is all you can get.

Rod.

There is I'm afraid a lot of shallow bandwagon jumping people around today,
who have never thought things through. In most wars, in the end people will
have to completely annihilate the opposition, or learn to agree to differ.
Brian

--

--:
This newsgroup posting comes to you directly from...
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Blind user, so no pictures please
Note this Signature is meaningless.!
"Roderick Stewart" <rjfs@escapetime.myzen.co.uk> wrote in message
news:otu6ji5hl872l5u8vvuvfa1p41u9vud44e@4ax.com...
> On Fri, 20 Oct 2023 17:33:22 -0000 (UTC), jon <jon@nospam.cn> wrote:
>
>>On Fri, 20 Oct 2023 12:22:28 +0100, Roderick Stewart wrote:
>>
>>> On Fri, 20 Oct 2023 10:57:46 +0100, JMB99 <mb@nospam.net> wrote:
>>>
>>>>On 20/10/2023 10:05, Roderick Stewart wrote:
>>>>> Dark surfaces reflect less light than light ones (which is why they
>>>>> appear dark) so any system working on that part of the video signal
>>>>> will inevitably have less information to work with. We shouldn't be
>>>>> surprised that it doesn't cope so well.
>>>>
>>>>
>>>>Why don't they use a negative image, I do that quite often when
>>>>transcribing a dark document.
>>>>
>>>>Would have thought the software analysing the facial image could try
>>>>both and select which gives the best results.
>>>>
>>>>
>>> It doesn't matter what you do with the signal if the fundamental problem
>>> is that it contains less information. Making it negative is just turning
>>> it upside down, but it's still based on the amount of light that entered
>>> the lens from the subject, and you won't get any more of it by messing
>>> about with the signal after the event.
>>>
>>> You can improve matters by shining more light on the subject, or using a
>>> bigger lens (lower f stop) or a more sensitive pickup device, or
>>> designing less noisy video amplifiers, but there will always be less
>>> original information available from darker surfaces.
>>>
>>> Rod.
>>
>>Or scanning the spectrum.
>
> I'm not sure what you mean by that. A visual image intended for human
> eyes is normally derived only from the part of the spectrum that is
> visible to us. There would be plenty more available without that
> restriction, but normally what you can see is all you can get.
>
> Rod.

On 20/10/2023 12:22, Roderick Stewart wrote:
> It doesn't matter what you do with the signal if the fundamental problem
> is that it contains less information. Making it negative is just turning
> it upside down, but it's still based on the amount of light that entered
> the lens from the subject, and you won't get any more of it by messing
> about with the signal after the event. You can improve matters by
> shining more light on the subject, or using a bigger lens (lower f stop)
> or a more sensitive pickup device, or designing less noisy video
> amplifiers, but there will always be less original information available
> from darker surfaces.

That's not the problem.

When he holds still I can see him perfectly well. But when he nods his
head the CODEC only updates the edges of his forehead, while moving
everything from the eyes down and the outline of his head correctly.
After a while (next I frame?) his forehead catches up.

My guess is is that the authors have chosen to reduce the update
frequency on dark surfaces - as you say they aren't as easily seen.

At least I think that's what is going on. I'd like confirmation that
other people are seeing the same phenomenon.

Note to all TV lovers: never ever EVER get a job developing TVs. You
will be taught how to see all the picture defects, and it will interfere
with your viewing. DAMHIK...

Andy

On Sat, 21 Oct 2023 16:51:49 +0100, Vir Campestris
<vir.campestris@invalid.invalid> wrote:

>On 20/10/2023 12:22, Roderick Stewart wrote:
>> It doesn't matter what you do with the signal if the fundamental problem
>> is that it contains less information. Making it negative is just turning
>> it upside down, but it's still based on the amount of light that entered
>> the lens from the subject, and you won't get any more of it by messing
>> about with the signal after the event. You can improve matters by
>> shining more light on the subject, or using a bigger lens (lower f stop)
>> or a more sensitive pickup device, or designing less noisy video
>> amplifiers, but there will always be less original information available
>> from darker surfaces.
>
>That's not the problem.
>
>When he holds still I can see him perfectly well. But when he nods his
>head the CODEC only updates the edges of his forehead, while moving
>everything from the eyes down and the outline of his head correctly.
>After a while (next I frame?) his forehead catches up.
>
>My guess is is that the authors have chosen to reduce the update
>frequency on dark surfaces - as you say they aren't as easily seen.

In order for the system to update something that has changed between
frames, it has to detect that something has in fact changed. It can
only do that by comparing information between frames. This will
inevitably be more difficult to do in parts of the frame that contain
less information, so that changes are less apparent.

For me, the type of shot that shows up low bit rates most readily is
in a low key scene where an actor is lit from the side and they nod
their head, whereupon their face almost seems to split into two parts
that move independently. The two sides of the face are at different
brightness levels and so the system treats them differently, the
brighter side presumably receiving more frequent and/or more accurate
updates because there is more information to work on.

Rod.

Vir Campestris wrote:

> On 20/10/2023 12:22, Roderick Stewart wrote:
> > It doesn't matter what you do with the signal if the fundamental
> > problem is that it contains less information. Making it negative
> > is just turning it upside down, but it's still based on the amount
> > of light that entered the lens from the subject, and you won't get
> > any more of it by messing about with the signal after the event.
> > You can improve matters by shining more light on the subject, or
> > using a bigger lens (lower f stop) or a more sensitive pickup
> > device, or designing less noisy video amplifiers, but there will
> > always be less original information available from darker surfaces.
>
> That's not the problem.
>
> When he holds still I can see him perfectly well. But when he nods
> his head the CODEC only updates the edges of his forehead, while
> moving everything from the eyes down and the outline of his head
> correctly. After a while (next I frame?) his forehead catches up.
>
> My guess is is that the authors have chosen to reduce the update
> frequency on dark surfaces - as you say they aren't as easily seen.
>
> At least I think that's what is going on. I'd like confirmation that
> other people are seeing the same phenomenon.
>
> Note to all TV lovers: never ever EVER get a job developing TVs. You
> will be taught how to see all the picture defects, and it will
> interfere with your viewing. DAMHIK...
>
> Andy

I used to align a telicine. (Rank Cintel MkIII).
When watching a film on tv I kept on spotting registration etc errors
and was shouting out 'tweek r17!' or whatever it was.

--

On 21/10/2023 16:51, Vir Campestris wrote:
>
> When he holds still I can see him perfectly well. But when he nods his
> head the CODEC only updates the edges of his forehead, while moving
> everything from the eyes down and the outline of his head correctly.
> After a while (next I frame?) his forehead catches up.

He's gone home, and Rita Chakrabarti has taken over.

She's not bald, but she has black hair. Which looks just as bad :(

Andy

On Friday, 20 October 2023 at 09:52:53 UTC+1, Brian Gaff wrote:
> Obviously I am not qualified to say much.

That never stops you!

Bill

On Saturday, 21 October 2023 at 16:51:53 UTC+1, Vir Campestris wrote:
> On 20/10/2023 12:22, Roderick Stewart wrote:

> Note to all TV lovers: never ever EVER get a job developing TVs. You
> will be taught how to see all the picture defects, and it will interfere
> with your viewing. DAMHIK...

I still look for ghosting!

Bill

In article <05215226-a421-477f-a25e-d8802730199en@googlegroups.com>,
wrightsaerials@aol.com <wrightsaerials@f2s.com> wrote:
> On Saturday, 21 October 2023 at 16:51:53 UTC+1, Vir Campestris wrote:
> > On 20/10/2023 12:22, Roderick Stewart wrote:

> > Note to all TV lovers: never ever EVER get a job developing TVs. You
> > will be taught how to see all the picture defects, and it will
> > interfere with your viewing. DAMHIK...

> I still look for ghosting!

> Bill

I watch very little. Having to watch all 24 episodes of War & Peace over a
weekend was enough tv for life.

--
from KT24 in Surrey, England - sent from my RISC OS 4té²
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 25/10/2023 20:17, wrightsaerials@aol.com wrote:
> On Saturday, 21 October 2023 at 16:51:53 UTC+1, Vir Campestris wrote:
>> On 20/10/2023 12:22, Roderick Stewart wrote:
>
>> Note to all TV lovers: never ever EVER get a job developing TVs. You
>> will be taught how to see all the picture defects, and it will interfere
>> with your viewing. DAMHIK...
>
> I still look for ghosting!
>
> Bill

I still look for moire!