Electronics > Beginners
Why does the average digital TV set take so long to "come on"?
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paulca:
Switching channel delay is due to buffering.  The TV wants to get WELL ahead in the stream, like several seconds ahead so it can drop corrupt packets.  If it cannot decode an audio or video packet it has to drop the correct length of both audio and video streams to keep the audio in sync.  Even with a perfect signal all it takes is someone to switch on the oven or hoover and it will glitch.  There is error correction built into the DVB stream but it has it's limits.

Trust me, you want this.  If you ever get a raw DVB card when it plays a corrupt audio packet it "chirps" really loudly, when it plays a corrupt video packet the screen goes nuts, when it doesn't resync the A and V streams the lip sync gets out of phase.  When it runs out of buffer (or has none) then it freezes and stutters from time to time.

If the later happens anyway, and it does, use "Live pause" if you have it available to create a new buffer of a few seconds.

As to it taking ages to come on, probably because most of the TVs are just a custom built computer with a CPU and DSP which has a boot up time, possibly a warm up time on the analogue receiver and then buffering time for the selected channel.
bson:

--- Quote from: coppice on April 13, 2018, 11:48:56 pm ---A modern TV is not just like a computer. It is a computer, and a perfectly good development system for its own code. In the TV development labs I've been to, people just connect a USB keyboard and mouse to a TV, and sit in from of its 65" panel developing the TV's code.

--- End quote ---
I've never seen that, but I have worked many times with Broadcom's reference boxes to create firmware for TVs, Blu-Ray players, and whatnot.  (And grown to completely hate MIPS in the process.)  Since these run Linux (usually very much the BCM stock BSP system and toolchains) it's convenient to tftpboot them from a cross build on the computer you work on when doing anything kernel or system related.  For app development they all these days have environments like Air/Flash Lite with tricks like running off a USB stick or a CIFS mount.
bson:
Audio always leads video, so in an MTS stream the audio you receive right now correlates with future video.  This is to maintain lip sync; it's much cheaper and easier buffer and delay audio than video, then sync it to the video playback.  This means when you first start demuxing MTS you get video for which you don't yet have audio.  This delay also permits all kinds of audio processing, like surround sound and room equalization.  This means if the video lags the audio in the muxed MTS stream by 1 second there's at least a 1 second playback delay, plus whatever lag the video decode and playback pipeline introduces.  Obviously you also might suffer from large GOP sizes.

Video processors also add lag when doing cadence corrections, cadence changes, and hide bad splices that introduce cadence errors.  (This also ties into quality deinterlacing since apart from a slight stutter a cadence error can introduce field flips, where you get two odd/even fields in a row, which need to be detected and avoided as it causes horrible artifacting.)
ez24:
I have a Hisense and the problem is it takes too long to turn off.  I have to turn it off two times and there is about a 15 second delay between each turn off.  It comes back on when I turn it off the first time.

Chris Wilson:
I never though my post would creates as many replies, seems I am expecting too much and the old analogue sets, once warmed up were superior in instant channel locking ;) I still run two proper CRT analogue sets with digital converters, much to my wife's disgust who gets sniffy about having "ancient old tat" about the place. She won't want to her watch her soaps on one of mine then, when her SMPS caps in her mega screen beast let go.... :)

Thanks for all the fascinating info!
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