Decoding the Inner Workings of Television Encoding Schemes

[mearvk]

Hi guys/gals.

Enjoying the Superbowl here on the east coast. Hope you guys are having a good evening too.

My question is how is the encoding for TVs done? I've read the NTSC link below. I didn't see how exactly the signal is created but rather more about where the different data are stored in the encoding. Does anyone on this forum have this knowledge?

http://en.wikipedia.org/wiki/NTSC

Thanks.

 

[jim hardy]

i don't have the knowledge. But i once looked for it.

Since TV went digital it changed a LOT from NTSC.

I think you want to look into ATSC standards
http://www.atsc.org/cms/index.php/standards/standards/50-atsc-a53-standard

google on "digital tv standards"
you will be amazed at what is possible. Your TV can be controlled from the broadcast station; commands exist to change channel..
I'm surprised there's not hackers yet.

my intent when looking was to decode the frame information and make a gizmo to turn way down both the volume and brightness during viagra commercials.
There are law aginst blocking them, but knocking them both down about 20db might be legal.
If so, can you imagine how that device would sell?

But it's too complex for this old analog guy.

Good luck !

 

[dlgoff]

...my intent when looking was to decode the frame information and make a gizmo to turn way down both the volume and brightness during viagra commercials.

BTW IIRC there was a FCC law to keep the dB level within some range years ago. This one, ‘‘Commercial Advertisement Loudness
Mitigation Act’’ or the ‘‘CALM Act’’, is probably new due to the change to digital.

And from their Guid "Loud Commercials and the CALM Act"...

Effective December 13, 2012, the FCC's rules require television commercial advertisements to have the same average volume as the programs that they accompany.

 

[mearvk]

Interesting notion. Are commercials framed in somehow so they can be detected? In other words how would your device know when to start working and when to stop?

 

[jim hardy]

Interesting notion. Are commercials framed in somehow so they can be detected? In other words how would your device know when to start working and when to stop?

The standards are absolutely amazing to read.
Everything is preceded by a frame saying what is its content. I think once every seven seconds the program's name, episode number, etc is sent, and immediately prior to a change eg from program to commercial A to commercial B...

Your TV is now a computer. It could easily be made to do anything by somebody with intimate knowledge of how today's TV's work.

I too thought they still used the old NTSC intervals of flyback and vertical blanking for such information. But your TV signal is a cacophonous bitstream now.
This new digital world has left me in the dust. I had to get one of these handsets in order to use the wife's cellphone.
http://www.bedbathandbeyond.com/assets/product_images/230/21442140088358p.jpg


I would love to crack the TV computers, and am still competent with logic analyser and oscilloscope. But i just didnt keep up with the software world. All i can fix in today's TV's is power supply problems.

old jim