"CPH" (constant pixel height) video formats? - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 3 Old 03-29-2014, 04:28 PM - Thread Starter
ADU
AVS Special Member
 
ADU's Avatar
 
Join Date: Apr 2003
Posts: 6,554
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 146 Post(s)
Liked: 197

Video/Film Format:

Image Aspect:

Approx. HD CPH Resolution:

Approx. UHD CPH Resolution:
Silent films & traditional SD TV (4:3 ratio) 1.33... 1440x1080 2880x2160
Academy film ratio 1.375 1488x1080 2970x2160
European widescreen film (5:3 ratio) 1.66... 1800x1080 3600x2160
Normal HD/UHDTV (16:9 ratio) 1.77... 1920x1080 3840x2160
US flat theatrical ratio

1.85

2000x1080

(2 pixels wider than DCI spec)

4000x2160

(4 pixels wider than DCI spec)

70mm & various other large film formats 2.21 2384x1080 4776x2160
US anamorphic film ratio from 1957-1970

2.35

2536x1080 5072x2160
Widescreen "21:9" HD/UHDTV (64:27 ratio) 2.37 2560x1080 5120x2160
US anamorphic theatrical ratio from 1971-present

2.39

2584x1080 5160x2160
Early Cinemascope from 1953-1957 2.55 2752x1080 5504x2160
Cinerama 2.59 2800x1080 5592x2160
Ultra Panavision (e.g. Ben Hur, 1959) 2.76 2984x1080 5960x2160

 

Is this where we're headed?


HD displays seem to be settling in at two basic resolutions: 1920x1080 pixels for standard 16:9 ratio HDTVs, and 2560x1080 pixels for newer 64:27 (~21:9) ratio computer monitors, and projectors (from Digital Projection, Projection Design and Avielo according to Wikipedia).


UHD also seems to be following the same path with 3840x2160 pixels (4x HDTV resolution) for 16:9 displays, and 5120x2160 pixels for ~21:9 displays like the new 105" curved models from LG and Samsung, planned for release later this year.


With proper video format support, the ~21:9 ratio displays have the potential to maintain a constant pixel height of either 1080 or 2160 pixels on all video content up to a ratio of 2.37:1. And on 16:9 displays, the wider than 16:9 ratio CPH content could either be cropped on the sides (to maintain 1:1 pixel mapping) or scaled/letterboxed to fit the horizontal resolution of the TV.

 

I'm not particularly crazy about the idea of cropping scoped content on 16:9 TVs. But the more I think about it, the more the idea of maintaining consistent pixel height in video content seems to make sense,... and I don't currently own a 21:9 display.


Pixel ratios could be either square or anamorphic, as long as a CPH of either 1080p or 2160p is maintained (though my personal preference would be square pixels). And some cropping or scaling would also be necessary on 2.39 ratio and wider content to maintain CPH on ~21:9 ratio displays. Or the content could be scaled/letterboxed to fit the screen.


Anyone else have thoughts on this?


Recent discussions which prompted this post:

http://www.avsforum.com/t/1046679/why-so-few-anamorphic-blu-ray-discs

http://www.avsforum.com/t/1513517/dr-no-blu-ray-impressions-and-aspect-ratio-question

 

Request to Forum Mods: Please do not move this to the 2.35 CIH forum, since the HD/UHD video formats above may relate to either 16:9 or 21:9 displays.


ADU
ADU is offline  
Sponsored Links
Advertisement
 
post #2 of 3 Old 03-30-2014, 03:20 PM
AVS Special Member
 
Joe Bloggs's Avatar
 
Join Date: Apr 2007
Location: UK
Posts: 2,673
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 213 Post(s)
Liked: 75
I think ideally the best would be the square pixel formats at 2160p (for UHDTV1 type res). Though I think for the UHDTV "4K" Blu-ray format extension, even though I think they should add ~"21:9" format at 2160p to the spec (eg. 5120x2160 - even though that's 2.37:1), I think the studios might be against giving the consumer higher res cinema content than the current DCI specs (max 4096). For recent films, if they'll be putting them on a Blu-ray 4K format, they'll likely want to create a master from the DCI/DI format (so max 4096?). Also, I think any potential video format would probably need to be divisible by 8. They might have to change the HEVC codec for it if they wanted >4096 across? So perhaps they might just go with encoding it anamorphically at 3840 or 4096 wide (unless they go with that MFE - multi-format encoding method - but I don't really think that's the best way to go as well as it not being the most efficient).

From the broadcast companies I don't think I've heard them saying anything really about storing it in anything other than a 1.78:1 format (eg. 3840x2160 or 7680x4320), so they may use black bars as they do now. Perhaps it could be the "digital" formats that could be the first to encode at something like 5120x2160. They already have YouTube 4096 wide video, and any UHD Blu-ray format will want to show that they are better quality than the other consumer formats (so I wonder if they will include 4096 wide as well as 3840), but like I said they might not want to go higher than that yet as it would be higher than the DCI 4K spec. Though it won't be that long before Japan will be broadcasting 7680x4320@120 fps (they may choose a different fps in other countries) so as well as a video standard for that, they might have a disc standard for it.
ADU likes this.
Joe Bloggs is offline  
post #3 of 3 Old 04-01-2014, 12:42 AM - Thread Starter
ADU
AVS Special Member
 
ADU's Avatar
 
Join Date: Apr 2003
Posts: 6,554
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 146 Post(s)
Liked: 197

Some interesting thoughts, Joe. Thanks.


Per your comments, I've revised some of the resolutions on the table above so they're all multiples of 8. I'm not as up on the requirements and limitations of different video codecs as you seem to be. I guess the resolutions need to be divisible by 8 though for chroma sub-sampling? I've also added several other film ratios, and put the current 16:9 and ~21:9 HD/UHD TV ratios in boldface to make it easier to see where those fit in the scheme of things.


The UHD resolutions are not all 2x the horizontal resolution of the HD resolutions btw. Instead of carrying the rounding errors up, I simply choose the horizontal resolutions that were closest to the intended ratio, and multiples of 8. I also had to deviate slightly from the DCI spec on 1.85 ratio content, because the DCI horizontal resolutions are not all multiples of 8...

 

DCI Resolution Standards:

2048x1080 (2K) at 24 frame/s or 48 frame/s, or 4096x2160 (4K) at 24 frame/s

  • In 2K, for Scope (2.39:1) presentation 2048x858 pixels of the imager is used
  • In 2K, for Flat (1.85:1) presentation 1998x1080 pixels of the imager is used
  • In 4K, for Scope (2.39:1) presentation 4096x1716 pixels of the imager is used
  • In 4K, for Flat (1.85:1) presentation 3996x2160 pixels of the imager is used

 

I'll be curious to try some of the 1080p resolutions on my Blu-ray player to see how they work. I've tried 1920x1080p MP4s at various frame rates (up to 60fps), but nothing with a horizontal resolution higher or lower than that so far. So not really sure what the player will do. I'd like to see if it's possible though to encode and display content at a variety of different ratios and pixels widths, without having to encode any black bars in the content.


Maybe, at some point, I can upload some tests for others to try as well (including possibly some anamorphic 1080p files). Might take awhile though.


ADU
ADU is offline  
Reply HDTV Software Media Discussion

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off