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Pi power

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  Pi power Tim Streater <timstreater@greenbee.net> - 2021-01-05 22:54 +0000
    Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-05 23:16 +0000
      Re: Pi power "Mayayana" <mayayana@invalid.nospam> - 2021-01-05 19:59 -0500
        Re: Pi power A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-06 07:31 +0000
          Re: Pi power "Mayayana" <mayayana@invalid.nospam> - 2021-01-06 08:18 -0500
          Re: Pi power jornws200602@xs4all.nl (Oscar) - 2021-01-06 14:02 +0000
      Re: Pi power mjb@signal11.invalid (Mike) - 2021-01-06 09:44 +0000
        Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-06 10:31 +0000
          Re: Pi power Tim Streater <timstreater@greenbee.net> - 2021-01-06 10:44 +0000
            Re: Pi power Joe <joe@jretrading.com> - 2021-01-06 11:03 +0000
        Re: Pi power Tim Streater <timstreater@greenbee.net> - 2021-01-06 10:32 +0000
          Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-06 10:57 +0000
            Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 11:44 +0000
              Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-06 12:10 +0000
                Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 13:25 +0000
                  Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-06 14:41 +0000
                    Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 15:17 +0000
                      Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-06 16:05 +0000
                        Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 16:14 +0000
          Re: Pi power A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-06 12:02 +0000
        Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-06 10:55 +0000
          Re: Pi power Chris Green <cl@isbd.net> - 2021-01-06 11:19 +0000
            Re: Pi power Axel Berger <Spam@Berger-Odenthal.De> - 2021-01-06 13:13 +0100
              Re: Pi power Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-06 12:47 +0000
                Re: Pi power Joe <joe@jretrading.com> - 2021-01-06 20:20 +0000
                  Re: Pi power druck <news@druck.org.uk> - 2021-01-06 20:43 +0000
                Re: Pi power Eli the Bearded <*@eli.users.panix.com> - 2021-01-06 23:08 +0000
                  Re: Pi power Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-07 07:40 +0000
                    Re: Pi power Axel Berger <Spam@Berger-Odenthal.De> - 2021-01-07 09:08 +0100
                      Re: Pi power John Aldridge <jpsa@cantab.net> - 2021-01-07 09:20 +0000
                    Re: Pi power The Natural Philosopher <tnp@invalid.invalid> - 2021-01-07 08:16 +0000
                    Re: Pi power druck <news@druck.org.uk> - 2021-01-07 09:53 +0000
                      Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-07 12:40 +0000
                    Re: Pi power Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2021-01-07 19:29 +0000
                    Re: Pi power David Higton <dave@davehigton.me.uk> - 2021-01-07 21:05 +0000
            Re: Pi power Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-06 12:39 +0000
              Re: Pi power Chris Green <cl@isbd.net> - 2021-01-06 17:04 +0000
                Re: Pi power Theo <theom+news@chiark.greenend.org.uk> - 2021-01-06 18:02 +0000
            Re: Pi power Theo <theom+news@chiark.greenend.org.uk> - 2021-01-06 16:41 +0000
              Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-06 17:04 +0000
                Re: Pi power druck <news@druck.org.uk> - 2021-01-06 18:50 +0000
                  Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-06 20:39 +0000
              Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 18:58 +0000
    Re: Pi power Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2021-01-08 22:33 -0500
      Re: Pi power Anssi Saari <as@sci.fi> - 2021-01-09 12:03 +0200

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#25529

Mike wrote:

> Andy Burns wrote:
>
>> Tim Streater wrote:
>> 
>>> The Pi carried on being powered.
>> 
>> Unless a 4B is different to any other rPi, they never turn off, they
>> just halt.
> 
> But, from the original post, which you snipped :-
> 
>> A bit later I shut it down, **and then turned off the Pi power supply.**
>> The Pi carried on being powered.
> 
> Are you saying the Pi 4B is a stealth free-energy device? ;)

The Pi is the HDMI source, and the monitor is the HDMI sink, per the 
spec the 5V power should be supplied from the Pi to the monitor, not the 
reverse ...

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#25532

Andy Burns <usenet@andyburns.uk> wrote:
> Mike wrote:
> 
> > Andy Burns wrote:
> >
> >> Tim Streater wrote:
> >> 
> >>> The Pi carried on being powered.
> >> 
> >> Unless a 4B is different to any other rPi, they never turn off, they
> >> just halt.
> > 
> > But, from the original post, which you snipped :-
> > 
> >> A bit later I shut it down, **and then turned off the Pi power supply.**
> >> The Pi carried on being powered.
> > 
> > Are you saying the Pi 4B is a stealth free-energy device? ;)
> 
> The Pi is the HDMI source, and the monitor is the HDMI sink, per the 
> spec the 5V power should be supplied from the Pi to the monitor, not the 
> reverse ...
> 
I've heard it said that the HDMI spec is a real can of worms.

This thread is just another thing that increases my dislike of HDMI.

It's a real pity that there isn't really a modern video/display cable
that isn't beset by the software and 'anti pirating' stuff that's in
HDMI.

-- 
Chris Green
·

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#25536

Chris Green wrote:
> that isn't beset by the software and 'anti pirating' stuff that's in
> HDMI.

Exactly. And there is another thing. Originally video had to be fast,
for the eye needed at least 70 Hz not to see annnoying flicker. Those
days are long gone. Current dispays are static or buffered. Not all
computing is video or games (though admittedly those are the uses that
bring the revenue in), so cables, buffers and a lot of critical stuff
could be made much easier by reducing to 10 frames per socond or even
less. One frame per second is plenty for many use cases, at least all
those requiring long cables and long distances.


-- 
/¯\   No  |    Dipl.-Ing. F. Axel Berger    Tel: +49/ 221/ 7771 8067
\ /  HTML |    Roald-Amundsen-Straße 2a     Fax: +49/ 221/ 7771 8069
 X    in  |    D-50829 Köln-Ossendorf      http://berger-odenthal.de
/ \  Mail | -- No unannounced, large, binary attachments, please! --

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#25539

On Wed, 06 Jan 2021 13:13:42 +0100
Axel Berger <Spam@Berger-Odenthal.De> wrote:

> Chris Green wrote:
> > that isn't beset by the software and 'anti pirating' stuff that's in
> > HDMI.
> 
> Exactly. And there is another thing. Originally video had to be fast,
> for the eye needed at least 70 Hz not to see annnoying flicker. Those

	That number seems to have been creeping up all my life - 24FPS was
once considered good enough for movie cameras.

> days are long gone. Current dispays are static or buffered. Not all
> computing is video or games (though admittedly those are the uses that

	It is rare that any system has no video or similar high update
speed requirement at all, not counting headless machines that have no
monitor.

> bring the revenue in), so cables, buffers and a lot of critical stuff
> could be made much easier by reducing to 10 frames per socond or even
> less. One frame per second is plenty for many use cases, at least all
> those requiring long cables and long distances.

	However if you need *any* video or similar then you need better
frame rates unless you can build a cable that supports high burst rates but
not high continuous rates which seems unlikely without a lot of circuitry
and latency.

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

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#25568

On Wed, 6 Jan 2021 12:47:44 +0000
Ahem A Rivet's Shot <steveo@eircom.net> wrote:

> On Wed, 06 Jan 2021 13:13:42 +0100
> Axel Berger <Spam@Berger-Odenthal.De> wrote:

> > 
> > Exactly. And there is another thing. Originally video had to be
> > fast, for the eye needed at least 70 Hz not to see annnoying
> > flicker. Those  
> 
> 	That number seems to have been creeping up all my life -
> 24FPS was once considered good enough for movie cameras.
> 

For filming, but it was never displayed at that rate. In 50Hz countries,
telecines and cinema projectors had a double shutter to display each
frame twice (though no interpolation) and NTSC telecines repeated
alternately 2/3 times to get it up to 60. Not sure if US cinemas did
that, or put up with 48Hz. Modern telecines can interpolate for
smoother motion, and play at any film speed.

-- 
Joe

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#25570

On 06/01/2021 20:20, Joe wrote:
> For filming, but it was never displayed at that rate. In 50Hz countries,
> telecines and cinema projectors had a double shutter to display each
> frame twice (though no interpolation) 

They actually played it 4% faster at 25fps and then doubled it to 50fps.

> and NTSC telecines repeated alternately 2/3 times to get it up to 60. 

Which gives the correct speed, but terrible tearing of movement when 
different film frames are used for each field of an interlaced TV frame.
Luckily not something you see any more with progressive formats.

---druck

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#25573

In comp.sys.raspberry-pi, Ahem A Rivet's Shot  <steveo@eircom.net> wrote:
> Axel Berger <Spam@Berger-Odenthal.De> wrote:
>> Exactly. And there is another thing. Originally video had to be fast,
>> for the eye needed at least 70 Hz not to see annnoying flicker. Those
> 	That number seems to have been creeping up all my life - 24FPS was
> once considered good enough for movie cameras.

Possibly, but probably not. Thomas Edison believed 48 FPS was minimum
quality projection. Is that during your life? Film was recorded at 24
FPS, yes, but projected so that each frame was shown two or three
times, 48 to 72 FPS.

At around 16 FPS the motion stops looking jerky, but there's still a
visible flicker and some eyestrain. Faster playback rates (with
duplicated frames) removes the flicker, but depending on the duplication
method can introduce other artifacts. 24FPS source shown on a
television, for example.

Televisions used AC frequency as a reference, so preferred 50 FPS in
50Hz parts of the world and 60 FPS in 60 Hz areas for projection and
half that for recording. Stuff recorded at other frame rates get extra
frame duplication to keep pace.

25FPS source     ABCDEFGHIJKLMNOPQRSTUVWXY
yeilds by simple doubling:
50FPS display    AABBCCDDEEFFGGHHIIJJKKLLMMNNOOPPQQRRSSTTUUVVWWXXYY

24FPS source     ABCDEFGHIJKLMNOPQRSTUVWX
yeilds by mostly doubling but also padding:
50FPS display    AAAABBCCDDEEFFGGHHIIJJKKLLMMNNOOPPQQRRSSTTUUVVWWXX

Theoretically you could do something like:
                 AAABBCCDDEEFFGGHHIIJJKKLLMMMNNOOPPQQRRSSTTUUVVWWXX
but I think TV signal pipeline is designed around 25 FPS input.

24FPS to 60FPS works similarly, but has more doubled doubles.

As technology has improved, so have standards, though. Artifacts of
a slower displays were previously tolerated, but now a effort is made
to avoid those problems. Now you can more easily accomodate that
AAABBCCDDEEFFGGHHIIJJKKLLMMMNNOOPPQQRRSSTTUUVVWWXX version, for example.

Totally as an aside:

One interesting trick I've seen done is mixing "frame" rates to make
things look jerky. In the _Lego Movie_ the camera and backgrounds
update at 24FPS, but the characters in the foreground update at 12FPS.
It gives the film a much more hand animated look.

I've got a slowed down sample from a since removed Youtube clip that I
made in 2014:

https://qaz.wtf/C/lego-sample.gif

Note that the character spinning in the background on the left animates
every frame, while the walking hero front and center animates every
other frame.

Elijah
------
severely compressed the colors in the gif to get the file size down

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#25575

On Wed, 6 Jan 2021 23:08:51 +0000 (UTC)
Eli the Bearded <*@eli.users.panix.com> wrote:

> In comp.sys.raspberry-pi, Ahem A Rivet's Shot  <steveo@eircom.net> wrote:
> > Axel Berger <Spam@Berger-Odenthal.De> wrote:
> >> Exactly. And there is another thing. Originally video had to be fast,
> >> for the eye needed at least 70 Hz not to see annnoying flicker. Those
> > 	That number seems to have been creeping up all my life - 24FPS
> > was once considered good enough for movie cameras.
> 
> Possibly, but probably not. Thomas Edison believed 48 FPS was minimum
> quality projection. Is that during your life?

	No, but 50Hz interlaced monitors (stripped TVs really) are and
removing the interlace was considered enough to make it flicker free and
"professional" circa 1980 - I sometimes turned the interlace back on and
pushed the resolution up. In more recent times 60Hz was said to be needed
for flicker free and now it's 70Hz I'm seeing and high end TVs are currently
advertising 120Hz.

> Film was recorded at 24
> FPS, yes, but projected so that each frame was shown two or three
> times, 48 to 72 FPS.

	Weren't domestic cine projectors 24 fps and considered good enough
for the use ?

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

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#25576

Ahem A Rivet's Shot wrote:
> In more recent times 60Hz was said to be needed
> for flicker free and now it's 70Hz I'm seeing and high end TVs are currently
> advertising 120Hz.

The way I remember it is, that one of the reason for white on black was
the lower sensitivity of the eye for flicker. The first monitors with a
white background were hailed as a huge improvement but they all -- both
highly expesive ISA card monitor combos and the Atari -- needed 70 Hz to
be acceptable. 60 Hz was considered borderline for colour when white
backgrounds were avoided.


-- 
/¯\   No  |    Dipl.-Ing. F. Axel Berger    Tel: +49/ 221/ 7771 8067
\ /  HTML |    Roald-Amundsen-Straße 2a     Fax: +49/ 221/ 7771 8069
 X    in  |    D-50829 Köln-Ossendorf      http://berger-odenthal.de
/ \  Mail | -- No unannounced, large, binary attachments, please! --

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#25578

In article <5FF6C171.23E2CA59@Berger-Odenthal.De>, Spam@Berger-
Odenthal.De says...
> 
> Ahem A Rivet's Shot wrote:
> > In more recent times 60Hz was said to be needed
> > for flicker free and now it's 70Hz I'm seeing and high end TVs are currently
> > advertising 120Hz.
> 
> The way I remember it is, that one of the reason for white on black was
> the lower sensitivity of the eye for flicker. The first monitors with a
> white background were hailed as a huge improvement but they all -- both
> highly expesive ISA card monitor combos and the Atari -- needed 70 Hz to
> be acceptable. 60 Hz was considered borderline for colour when white
> backgrounds were avoided.

It was interestingly variable from person to person. Some of my 
colleagues worked happily on monitors set at 60 Hz, but anything less 
than 70, preferably 75 Hz, made me feel sick.

John

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#25577

On 07/01/2021 07:40, Ahem A Rivet's Shot wrote:
> On Wed, 6 Jan 2021 23:08:51 +0000 (UTC)
> Eli the Bearded <*@eli.users.panix.com> wrote:
> 
>> In comp.sys.raspberry-pi, Ahem A Rivet's Shot  <steveo@eircom.net> wrote:
>>> Axel Berger <Spam@Berger-Odenthal.De> wrote:
>>>> Exactly. And there is another thing. Originally video had to be fast,
>>>> for the eye needed at least 70 Hz not to see annnoying flicker. Those
>>> 	That number seems to have been creeping up all my life - 24FPS
>>> was once considered good enough for movie cameras.
>>
>> Possibly, but probably not. Thomas Edison believed 48 FPS was minimum
>> quality projection. Is that during your life?
> 
> 	No, but 50Hz interlaced monitors (stripped TVs really) are and
> removing the interlace was considered enough to make it flicker free and
> "professional" circa 1980 - I sometimes turned the interlace back on and
> pushed the resolution up. In more recent times 60Hz was said to be needed
> for flicker free and now it's 70Hz I'm seeing and high end TVs are currently
> advertising 120Hz.
> 
>> Film was recorded at 24
>> FPS, yes, but projected so that each frame was shown two or three
>> times, 48 to 72 FPS.
> 
> 	Weren't domestic cine projectors 24 fps and considered good enough
> for the use ?
> 
16fps IIRC?


-- 
Ideas are more powerful than guns. We would not let our enemies have 
guns, why should we let them have ideas?

Josef Stalin

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#25579

On 07/01/2021 07:40, Ahem A Rivet's Shot wrote:
> 	No, but 50Hz interlaced monitors (stripped TVs really) are and
> removing the interlace was considered enough to make it flicker free and
> "professional" circa 1980 - I sometimes turned the interlace back on and
> pushed the resolution up. In more recent times 60Hz was said to be needed
> for flicker free and now it's 70Hz I'm seeing and high end TVs are currently
> advertising 120Hz.

Several different issues there.

Old CRT TVs worked with an interlaced signal so needed long persistence 
phosphors so the each field of alternating scan lines would still be 
visible when the next field was displayed. UK PAL TVs were set up for 
50Hz fields so had a longer persistence than US NTSC at 60Hz.

CRT monitors (generally) worked with non interlaced signals, so had low 
persistence phosphors as all the scan lines would be updated every 
frame. Monitors were invariably designed for the US market so had 
phosphor persistence for a minimum of 60Hz frame rate, and would look 
terrible if driven at 50Hz.

As monitor resolutions and sizes increased the frame rates also 
increased to 70Hz or 75Hz, to reduce flicker and smearing of screen updates.

Now with LCD, LCD/LED and OLED technologies the screen does not flicker 
at the update rate. Panels used to have a 60Hz update rate to match US 
content (but would be fine for 50Hz), but active 3D drove the adoption 
of 120Hz or greater panels, so alternate views could be shown at 60Hz. 
3D has largely been dropped now, but 120Hz or greater panels still 
exist, so they can either be driven at a higher frame rate by games 
consoles, or additional intermediate frames are generated for lower 
refresh rate content, in both cases to make animation smoother.

---druck

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#25581

On Thu, 07 Jan 2021 09:53:53 +0000, druck wrote:

> Now with LCD, LCD/LED and OLED technologies the screen does not flicker
> at the update rate. Panels used to have a 60Hz update rate to match US
> content (but would be fine for 50Hz), but active 3D drove the adoption
> of 120Hz or greater panels, so alternate views could be shown at 60Hz.
> 3D has largely been dropped now, but 120Hz or greater panels still
> exist, so they can either be driven at a higher frame rate by games
> consoles, or additional intermediate frames are generated for lower
> refresh rate content, in both cases to make animation smoother.
> 
Modern phones seem to have refresh rates of anywhere between 60Hz and 
120Hz - apparently the gaming crowd want it.


-- 
--  
Martin    | martin at
Gregorie  | gregorie dot org

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#25588

On 2021-01-07, Ahem A Rivet's Shot <steveo@eircom.net> wrote:

> 	Weren't domestic cine projectors 24 fps and considered good enough
> for the use ?

Yes, but panning across a scene could be a bit jarring
when viewed on the big screen.

-- 
/~\  Charlie Gibbs                  |  "Some of you may die,
\ /  <cgibbs@kltpzyxm.invalid>      |  but it's a sacrifice
 X   I'm really at ac.dekanfrus     |  I'm willing to make."
/ \  if you read it the right way.  |    -- Lord Farquaad (Shrek)

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#25592

In message <20210107074042.df7dcb8f3d2a551a78cf1a64@eircom.net>
          Ahem A Rivet's Shot <steveo@eircom.net> wrote:

> Weren't domestic cine projectors 24 fps and considered good enough
> for the use ?

I remembered 18 fps, with a 3-bladed shutter in the projector, giving
54 flashes per second.

I see someone else said 16 fps, so I turned to good old Wikipedia, which
suggests that Super 8 was 18 fps and Standard 8 was 16 fps.  So we
were both right!

David

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#25538

On Wed, 6 Jan 2021 11:19:51 +0000
Chris Green <cl@isbd.net> wrote:

> It's a real pity that there isn't really a modern video/display cable
> that isn't beset by the software and 'anti pirating' stuff that's in
> HDMI.

	The software and anti-pirating stuff is HDCP not HDMI. HDCP runs
over HDMI, DVI and DisplayPort as well as USB-3 and will probably be
required in anything new that comes up even though it is essentially
useless. HDMI itself doesn't seem worse than any of the others, better than
DVI in that it carries audio as well as video.

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

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#25554

Ahem A Rivet's Shot <steveo@eircom.net> wrote:
> On Wed, 6 Jan 2021 11:19:51 +0000
> Chris Green <cl@isbd.net> wrote:
> 
> > It's a real pity that there isn't really a modern video/display cable
> > that isn't beset by the software and 'anti pirating' stuff that's in
> > HDMI.
> 
>         The software and anti-pirating stuff is HDCP not HDMI. HDCP runs
> over HDMI, DVI and DisplayPort as well as USB-3 and will probably be
> required in anything new that comes up even though it is essentially
> useless. HDMI itself doesn't seem worse than any of the others, better than
> DVI in that it carries audio as well as video.
> 
Yes, but you can't get an HDMI interface that doesn't implement HDCP
can you?  That's the whole point, it prevents (supposedly) you viewing
things you shouldn't with your TV (or whatever) that has an HDMI
connector.

-- 
Chris Green
·

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#25556

Chris Green <cl@isbd.net> wrote:
> Yes, but you can't get an HDMI interface that doesn't implement HDCP
> can you?  That's the whole point, it prevents (supposedly) you viewing
> things you shouldn't with your TV (or whatever) that has an HDMI
> connector.

HDCP is optional - both sources and sinks can elect not to have it (the Pi
has HDCP support in hardware but doesn't enable it, for example).  Obviously
if you're a monitor and don't implement it, you won't work with HDCP
sources.

Many cheap HDMI splitters strip off HDCP (there's no way to pass through
HDCP communication with 3 concurrent sinks and it's cheaper just to strip
it) so it can easily be bypassed.

Theo

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#25551

Chris Green <cl@isbd.net> wrote:
> Andy Burns <usenet@andyburns.uk> wrote:
> > The Pi is the HDMI source, and the monitor is the HDMI sink, per the 
> > spec the 5V power should be supplied from the Pi to the monitor, not the 
> > reverse ...
> > 
> I've heard it said that the HDMI spec is a real can of worms.
> 
> This thread is just another thing that increases my dislike of HDMI.

It's exactly the same with VGA.

The purpose of this is for the computer to read the EDID ROM from the
monitor.  It supplies 5V to allow detection of the connected monitor even if
it's turned off.

The monitor/KVM should not be emitting power on this rail.

Although it wouldn't have taken much for the Pi to incorporate a diode to
prevent back-powered.  Maybe there are use cases where people want to power
their Pis from HDMI, I don't know.

Theo

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#25552

On Wed, 06 Jan 2021 16:41:25 +0000, Theo wrote:


> Maybe there are use cases where people want to
> power their Pis from HDMI, I don't know.
>
Doing that would make the installation tidier if I wanted to glue the Pi 
enclosure to the back of the screen - provided that the screen
can provide the wattage needed. Is that likely, bearing in mind that, if 
I did that, I'd also want it to power a keyboard and mouse via the USB 
sockets on the Pi.
 

-- 
--  
Martin    | martin at
Gregorie  | gregorie dot org

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