[mythtv-users] HD3000 and Myth. Please help me understand

[Michael T. Dean]

Steve Adeff wrote:

>you must be doing something wrong if you can't get an SD 1hr show into 700mb 
>with such a loss in quality. A clean SD source is easy to fit 1hr onto 700mb 
>with no discernable quality loss using XviD. I don't know what the space 
>savings are though, I haven't played around enough in this area to check.
>
>As for HD:
>use IVTC to cut the frame rate to 24000/1001, then scale the resolution to 
>960x544. Using the high quality settings and 2-pass for XviD you'll get a 
>great encode that can fit onto a 700mb CD with the original AC3 track. 
>Noticable issues arise around network logos and for shows with lots of high 
>movement scenes you'll lose some background information in slower areas. BUT 
>you can burn a 1hr show to a CD.
>
>Another option is to just use IVTC keep the resolution and convert to XviD 
>using high quality settings and use constant Q set to 4 or below (2 being the 
>best choice). this will cut the size down by roughly 1/2. IVTC is a huge 
>space savigs as it basically gets rid of 6fps (30000/10001 -> 24000/1001).
>
>Note with IVTC though, WB uses a weird patterning and normal IVTC methods 
>won't work. ABC, NBC, CBS, FOX and UPN all seem to stick with proper IVTC 
>patterns and shouldn't be a problem.
>  
>
This would seem to imply that all high-def content is filmed at 24fps 
and then converted to 30/60fps using telecine.  (Otherwise, how could 
you do an inverse telecine?)  Is that right?  If so, then what's the 
point of 720p60 and 1080i60?  Why not just transmit everything at 720p24 
or 1080p24?  This would mean that the whole benefit of 720p60 
(additional frame rate) is lost because there are only 24 real frames...

I could see that being true for movies, but what about normal TV dramas, 
etc.?  I would think that since CBS standardized on 1080i, they would 
shoot at 1080i60/1080p30/1080p24.  (Do they actually switch frame 
rates?  I know they stick with either 1080i or 720p, but each includes 3 
different frame rates.)  Similarly, ABC should shoot at 720p60.  (And, 
if networks do switch frame rates, they could just transmit 
720p24/1080p24 for the movies that are shot at 24fps.)

Or, when you're talking about IVTC, are you just saying that you're 
telling it to throw away some frames or completely re-sample or something?

Mike