[mythtv-users] new PC build that's MythTV compatible

[R. G. Newbury]

On 2020-12-01 6:45 a.m., James Linder wrote:

>> I can only suggest that you must need a new Telly, or new eyes. ;-)
>> There's a massive difference between HD/SD channels when I look at them - even live - I don't need to pause it to see the difference, it's extremely noticeable.
> 
> Owen thanks very much.
> These are two screen shots on a macbook retina display (2650x1650) ish
> They look similar on intel-1080 monitor. I'll examin a real TV now.
> They are ABC SD and HD. My critical look is at the text, but scene changes do not make much difference.
> http://tigger.ws/downloads/twoSD.png
> http://tigger.ws/downloads/twoHD.png
> Cheers
> James

That second shot is NOT HD. It never was HD. It is a shot from the TV 
show 'Doc Martin'. A quick look at IMDB shows that the show is now 10 
seasons old and for at least the first 8 years filming was done with 
*16mm film* (Arriflex cameras). The show would then have been scanned to 
European standard broadcast (PAL / SECAM) and quite likely *from that* 
to any other standard (NTSC). And your broadcast (originally in PAL) 
would have then been further transcribed to DVB-T for broadcast.
So too many steps in that chain.

And that explains to me, why Doc Martin is always letterboxed when I see 
it broadcast OTA *or* via cable from PBS Buffalo, New York: they cannot 
do anything to change how it displays. Without looking I suspect that 
OTA, on a 720i tv screen, I am seeing the original 576 line PAL scan image!

You need to find some real HD content. I suggest that you dial up some 
on air sports, such as AFL and take a close look at panning scenes such 
as where the camera follows a kick. (You may find it hard to record such 
shows in SD, as nowadays, they are almost always in HD.)

Broadcasters can (and do) change the transmission rate for certain 
shows. Each radio spectrum 'channel' has a limited amount of bandwidth: 
about 20GB per hour total. So one digital stream within the 'channel' 
can be given more of the bandwidth than normal and the subsidiary 
'channels'/ digital streams are decreased.

For US broadcast, NBC increases the transmission rate for sports to 
10-11 Gb per hour. This is especially visible when 'signature' sports 
programs are being transmitted. Olympic hockey as a high motion sport 
may get even more than 12GB. CBC does the same thing with sports. I 
would bet that ABC (Oz) does the same.

Regular programs are 6-7 GB per hour while news and other 'static' 
programs are even less than 5Gb. (Just look at the recorded program 
size).  The visual differences are notable and the exact decoding method 
used (nvidia slim, high, opengl etc) make a visible difference for 
tracking shots.

Geoff


              R. Geoffrey Newbury