How important is Blu-ray bitrate to image quality? - AVS Forum | Home Theater Discussions And Reviews
Baselworld is only a few weeks away. Getting the latest news is easy, Click Here for info on how to join the Watchuseek.com newsletter list. Follow our team for updates featuring event coverage, new product unveilings, watch industry news & more!



Forum Jump: 
 1Likes
  • 1 Post By John Mason
 
Thread Tools
post #1 of 5 Old 08-27-2015, 05:38 AM - Thread Starter
Member
 
marko7's Avatar
 
Join Date: Sep 2011
Location: Europe
Posts: 46
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 10
How important is Blu-ray bitrate to image quality?

Just how important is the video bitrate of a Blu-ray disc to image quality? While doing some research recently, I found something that intrigued me. for example, the film Avatar came to Blu-ray in its original, single-disc version and, shortly thereafter, as 3-disc Extended Collector's edition set. Now, here's what intrigued me: the original release has an average video bitrate of around 28 Mbps, while the 3-disc version, where they had to fit 16 additional minutes on a single disc, has a video bitrate of around 22-23 Mbps. Likewise, I found similar differences with Django Unchained. The US Blu-ray release of that film has a bitrate of 28 Mbps, compared to the European version's 23 Mbps. And I'm sure these are not the only 2 such cases.

But my question is: does this necessarily mean that those lower-bitrate versions have slightly worse image quality? What can technically be done to keep image quality the same, while reducing the bitrate by 5 Mbps (when, as far as I know, Blu-ray already pushes codecs to their limits)?

P.S.: I don't have both versions of the above mentioned films to do a comparison myself.

Last edited by marko7; 08-27-2015 at 05:41 AM.
marko7 is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 08-27-2015, 12:32 PM
Advanced Member
 
Speed Daemon's Avatar
 
Join Date: Jan 2010
Location: Location, Location
Posts: 618
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 91 Post(s)
Liked: 46
Quote:
Originally Posted by marko7 View Post
But my question is: does this necessarily mean that those lower-bitrate versions have slightly worse image quality? What can technically be done to keep image quality the same, while reducing the bitrate by 5 Mbps (when, as far as I know, Blu-ray already pushes codecs to their limits)?
It's possible that whomever mastered the first edition learned from the experience and found a way to reduce the average bit rate without reducing the amount of data in critical scenes. Progress is made by people who push the boundaries beyond what was previously thought possible.

OTOH the vendor may have made a conscious decision to let quality suffer to make room for all the extra fan content. Perhaps the people who buy these versions aren't as picky about getting top bit rates...

You get what you pay for.  For professional advice, pay the professional rate.
Speed Daemon is offline  
post #3 of 5 Old 08-29-2015, 12:29 PM
AVS Special Member
 
John Mason's Avatar
 
Join Date: Jul 2000
Location: New York, NY
Posts: 11,099
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 76 Post(s)
Liked: 83
If there's a visible PQ difference between the two versions perhaps, if it's subtle, it could be measured on screen by comparing specific image details to multiburst patterns. This 2014 post shows measurement results from a filmed, 4k-DI movie, with a sublink to one multiburst Blu-ray source test pattern. -- John


Edit: Just watched "The Theory of Everything" (TOE) on a FIOS premium channel and briefly measured a hair of Hawking's wife in bright sunlight, a similar scene to the 4k-DI movie above. In that film recall the wife's hair was ~2mm wide, while it measured ~3mm from the TOE production. The table in the linked post has a rez conversion--and of course more than bit rates factor in. Maybe Wheaties vs a UK breakfast. ;-)

Last edited by John Mason; 01-19-2016 at 08:58 AM. Reason: add on
John Mason is offline  
post #4 of 5 Old 08-30-2015, 01:59 PM
Member
 
Join Date: Oct 2014
Posts: 19
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 0
Interesting to know, I always go for blu ray over rips/streams whenever possible because whilst the general public are basically sheep and go for resolution over bitrate and such I can tell a difference.
dekaman is offline  
post #5 of 5 Old 12-13-2015, 08:52 AM
AVS Special Member
 
John Mason's Avatar
 
Join Date: Jul 2000
Location: New York, NY
Posts: 11,099
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 76 Post(s)
Liked: 83
Here's an interesting avsforum thread discussing Blu-ray (AVC) bitrates and rates that will be used in upcoming 4k Blu-rays (HEVC). The thread includes graphs and photos from a presentation at last year's NAB show. Came across a tech paper, from a 2014 conference, by the same author (John Pallett) covering similar material in the Oct. 2015 SMPTE "Motion Imaging Jounal." -- John


EDIT: Notice the Motion Imaging article contains graphs comparing PQ besides those comparing signal-to-noise ratios (avs thread).
Joe Bloggs likes this.

Last edited by John Mason; 12-13-2015 at 09:06 AM. Reason: add-on
John Mason is offline  
Sponsored Links
Advertisement
 
Reply HDTV Software Media Discussion

Tags
blu-ray bitrate image quality

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