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Maharadja's Avatar
Posts: 92 | Thanked: 57 times | Joined on Aug 2010 @ Netherlands
#1
I was reading on the wiki for video encoding on de N900 and it told me that to encode HD content (Lets say 1280 X 720 16:9) the best resolution is 800 X 448 for 16:9 ratios.

In my opinion, this isn't correct.
The N900 has a max resolution of 800 X 450. This is in the 16:9 ratio, so why encode to 800 X 448? Why not use 800 X 450?

I've tried making a new image in photoshop with 1280 X 720, then i resized it to make the width 800, keeping the original aspact ratio. The height output was 480.

Am I wrong, or is the wiki wrong?

Last edited by Maharadja; 2010-12-15 at 12:43. Reason: Typo in title
 
Posts: 2,829 | Thanked: 1,459 times | Joined on Dec 2009 @ Finland
#2
-add link to wiki
-n900 max resolution is 800x480
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Maharadja's Avatar
Posts: 92 | Thanked: 57 times | Joined on Aug 2010 @ Netherlands
#3
Oh damn, you're right. I made a miscalculation. The resolution from the N900 is indeed 800x480.
Got the wrong info somewhere i think.

But then again, why 800x448? 800x450 is, in my opinion, the better resolution.

Link to wiki: http://wiki.maemo.org/Video_encoding#HD_sources
 
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#4
Iīm not sure but it might have something to do with resolution being multiple of 16. Donīt now remember whole thing but well that wiki article is bit of mess and if you have time then please make fixes.
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Posts: 2,829 | Thanked: 1,459 times | Joined on Dec 2009 @ Finland
#5
Probably something to do with 8x8, 16x16 blocks that encoders use. I have not enough information on how using resolution that are not clean multiples of 16 affect different encoders & decoders. IIRC I have encoded with 800x450 h.264 and didn't notice anything special.

.edit
Some info here:
http://en.wikipedia.org/wiki/JPEG#Block_splitting

..edit
And more
http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC#Features
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Last edited by slender; 2010-12-15 at 13:49.
 
Maharadja's Avatar
Posts: 92 | Thanked: 57 times | Joined on Aug 2010 @ Netherlands
#6
Well im going to convert a lot of mkv's to mp4, so it would be nice to have the optimal resolution.
With 800x448 you are throwing away vertical data; with 800x450 you're not.
But there are no problems with 800x450? the mediaplayer is very picky about it's formats and resolutions...

Then 800x450 = highest resolution for HD content conversion with 16:9 aspect ratio.

Last edited by Maharadja; 2010-12-15 at 13:59. Reason: Extra info
 
Posts: 2,829 | Thanked: 1,459 times | Joined on Dec 2009 @ Finland
#7
I do not know any "perfect" answer for you. Only thing I know is that it seems that encoders use these block while they do their tricks to pack stuff smaller. I donīt know how video resolution that is not multiple of 16 affects the final encoded video quality.

Understandably N900's HW video decoder is limited to screen resolution.
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Maharadja's Avatar
Posts: 92 | Thanked: 57 times | Joined on Aug 2010 @ Netherlands
#8
Well thank you for the help.
I'll encode my movies with H264 or Xvid with a resolution of 800x450 because that, is in my opinion, the ideal resolution.

Note: Divx acts buggy on default player(if player reaches end of movie, it will continue to play but keep the last frame of the movie.)

Last edited by Maharadja; 2010-12-15 at 14:21. Reason: DAMN SMILEY
 
Jack6428's Avatar
Posts: 635 | Thanked: 282 times | Joined on Sep 2009 @ Black Mesa Research Facility
#9
Actaully, the N900 can play videos with a resolution of 848x480 well if you use good settings. I have most of the videos on my N900 in that resolution/quality, though sometimes I also use 700x400.

Someone should try 848x576 widescreen if it works...
 
Posts: 214 | Thanked: 256 times | Joined on May 2010
#10
Originally Posted by Jack6428 View Post
Actaully, the N900 can play videos with a resolution of 848x480 well if you use good settings. I have most of the videos on my N900 in that resolution/quality, though sometimes I also use 700x400.

Someone should try 848x576 widescreen if it works...
How do you record 700x400 videos on the N900? Or did you mean playing?
 
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