Electronics > Beginners
Why does the average digital TV set take so long to "come on"?
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james_s:

--- Quote from: Teledog on April 13, 2018, 01:54:26 am ---The TVs for the last X years have been "Green" & energy efficient, etc. etc.
Mandated by the government (along with RoHS built in obsolescence, but that's another topic)
The old "instant on" were always drawing power, which the powers that be do not care for.
My opinion?
If I'm paying $$ for my power/water/resources, then the decision should be left up to me?
But again, 98% of people have no clue as to how their appliances/automobiles/toilet/etc. operate..so, ..legislation is typically mandated down to the least common denominator
/end politico rant

--- End quote ---

The "Instant On" you refer to kept the filaments in the vacuum tubes heated all the time, obviously consuming quite a bit of power. On the plus side they were great for cats, which had a tendency to sleep on the always warm TV console. I don't know how much energy regulations affect TV boot times now, I suspect if the CPU kept running all the time it would get in a bad state and need rebooting eventually anyway.
HT1950:
The TV warming up so slowly is one (very annoying) thing, but why the screen goes off and on while the soundbar starts working? I have a soundbar connected to the TV, bothswitch on at the same tim, but soundbar needs even more time and because of it it looks like the TV needs to warm up two times... So the whole operation takes at least 15 seconds. Do you know why?
KD4PBS:
The CPU/controller and firmware in the TV for sure take quite some time to initialize, depending on the TV.
And the channel change?  Yes, the I-frame is part of the equation, but there are other things that affect this.  We run all of our broadcast OTA channels with a variable GOP schema.  For us, it might take as many as 45 frames until an I frame is sent, or it might happen every frame, all depending on how much motion exists in the video.  I don't know how other broadcasters have their encoders configured, and there really is no "standard" on how many P and B frames before an I frame.
The other factors are the PSIP table repeat rates.  There are several that are sent, at different rates, and a few of them are essential to being able to put a picture on your screen, while the rest are not needed to display the picture.  The most important table is the MGT (Master Guide Table).  It's the table that describes all of the separate PIDs being sent in the program stream, including all of the other PSIP data.  Without it, your TV doesn't know what to display.  That's why we have ours set to repeat at 90 millisecond intervals.  Next up would be the VCT (Virtual Channel Table).  Again, the TV will likely not be able to display pictures until this table is received and processed.  I've set ours to repeat every 395 milliseconds.  These two tables are essential to displaying the pictures.  As such, your TV has to wait until both have been received before making those pictures visible.  I think the "standard" allows for slightly longer intervals for the MGT and VCT (I think 150ms and 400ms, respectively) So, a "channel flicker" will have to wait at least 400ms with most terrestrial broadcast stations before it's displayed.
grifftech:
CCFL backlight warmup?
james_s:

--- Quote from: HT1950 on April 13, 2018, 08:28:57 am ---The TV warming up so slowly is one (very annoying) thing, but why the screen goes off and on while the soundbar starts working? I have a soundbar connected to the TV, bothswitch on at the same tim, but soundbar needs even more time and because of it it looks like the TV needs to warm up two times... So the whole operation takes at least 15 seconds. Do you know why?

--- End quote ---

That's largely down to the HDCP (useless copy protection) the sound bar picks the audio off the HDMI I'm guessing so it has to negotiate with the source and provide the decryption keys, then the TV has to negotiate with it and provide its decryption keys, then if you get lucky everything actually works and you get video and audio.

Of course HDCP was cracked years ago so it's completely worthless as copy protection but that doesn't stop it from being mandatory.
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