My, my...there certainly are a lot of misconceptions floating around in this thread regarding HD. Let's see if I can set a few things straight:
Originally Posted by beauchamp
... the 720p on the site also says 24fps (and that's not HDTV rate - 60fps at 720p is HD)
Wrong. 24p is fully embraced by the HDTV standard for cinematic sources, as are 25p, 50p, 50i (PAL) and 30p, 60p and 60i (NTSC). See http://en.wikipedia.org/wiki/High-definition_television
Originally Posted by vinea
Yes because 720p describes resolution and that its progressive not interlaced. 720p/24 is for film sources to save bandwidth. 720p/60 is 55Mpixels/sec. 720p/24 is 22Mpixels/sec. Yes Virginia it is 720p and it is even HDTV. Total is 8-10 Mbps in MPEG-2. Don't know for H.264...around half?
Anyway from film material this avoids needing to do 3-2 pulldown out of 720p/60 and you get to conserve 60% of the bandwidth.
Mostly wrong. 720p24 (and 1080p24) are used for film sources because motion pictures are shot at 24fps, it has nothing to do with "conserving bandwidth." Presently, Hollywood DVDs are encoded at 480i24 (for NTSC). Blue Ray movies will most likely be stored as 1080p24. Star Wars II, one of the first major motion pictures shot on HD cameras, was shot at 1080p24 to preserve the "film look." The reason 24fps will persist for many years to come is that people are used to the "look" of it for cinema. Converting a 24fps film to 60fps video DOES NOT make the picture better, in fact it makes things worse.
However, few if any current displays are capable of accepting a 24fps signal, so 2:3 reverse pulldown MUST be performed to generate a 30p or 60i/p NTSC signal. This is done in the DVD player, when the player sees certain "flags" in the MPEG stream indicating that the material was telecined at 24fps. Once again, this frame rate conversion ALWAYS makes things worse, but if DVDs were encoded at 60i, pulldown would still
be needed (during telecining). For a good explanation of the workings and pitfalls of pulldown, see http://www.dvdfile.com/news/special_...2_pulldown.htm
As an aside, the "holy grail" for cinematic picture quality with emerging technologies would be a 1080p24 source (think Blue Ray or HD-DVD) passing a signal purely in the digital domain (think HDMI) to a 24p capable, 1920x1080 display. This would avoid all picture degradation due to:
* deinterlacing and scaling effects
* motion artifacts (judder) introduced by pulldown
* needless digital to analog conversions
and would provide the best possible picture with the least possible image processing. The display would need to run at a 72Hz vertical refresh rate, of course, to avoid flicker. Each film frame would thus be displayed for 3 consecutive refresh cycles. This is similar to theatrical projection today--movie projectors actually run at 48fps and display each film frame twice.
All of this says...24fps is nothing to fear, and is in fact the appropriate frame rate for movies.