It is currently Tue May 22, 2018 8:46 pm

All times are UTC - 7 hours





Post new topic Reply to topic  [ 78 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6
Author Message
PostPosted: Wed Mar 21, 2018 9:24 pm 
Offline

Joined: Wed May 19, 2010 6:12 pm
Posts: 2647
Is it a coincidence that 1.3Mhz at -3dB is the standard chroma bandwidth for NTSC, and it just so happens that a basic (-1/4, 0, 1/2, 0, -1/4) FIR filter with a sample rate of 14.32 Mhz gives a -3dB level at 3.58 +/- 1.3 Mhz?


Top
 Profile  
 
PostPosted: Thu Mar 22, 2018 7:04 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7123
Location: Seattle
Yes.

You can painstakingly work out the math longform if you'd rather. Nothing magical will show up about a number that works out to very approximately roughly Fs/11.

Is there possibly some special relationship between the sampling rate—4x the colorburst frequency—and 1.3MHz? Yes, that I think might be deliberate. But your choice of discrete-time filter? Absolutely not, discrete-time stuff was basically not a practical option during NTSC's genesis.


Top
 Profile  
 
PostPosted: Wed Mar 28, 2018 1:02 pm 
Offline

Joined: Wed May 19, 2010 6:12 pm
Posts: 2647
This thread has turned into a "ask questions about analog TVs" thread.

Is there any research about the SNES's RF modulator circuit? I know that most composite encoder chips have a max of 133 IRE, and RF has a smaller range of 120 IRE. Does the SNES in RF have a smaller chroma amplitude, or does the SNES clamp yellows and cyans?


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 78 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6

All times are UTC - 7 hours


Who is online

Users browsing this forum: grynold and 10 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group