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phil · 12-04-2008, 05:36 AM

I'd like to discuss two things

a) what is the best resolution for encoding to wmv9; for targeting approx 500kbit/s full bitrate inclusively Audio? 16:9 Material PAL. Is it 426 x 240, or 536x302 or 640x302 - and why?

b) what is the ideal bandwith around 500kbit/s. 512kbit/s, 540kbit/s and why?

its for a internet vod-streaming page.
best regards!

Dave · (This post was last modified: 12-05-2008 05:18 PM by Dave.)

(12-04-2008 05:36 AM)phil Wrote: a) what is the best resolution for encoding to wmv9; for targeting approx 500kbit/s full bitrate inclusively Audio? 16:9 Material PAL. Is it 426 x 240, or 536x302 or 640x302 - and why?

Sounds like it could be a trick question ?

On face value, if displaying on a square pixel aspect ratio device I'd probably go for 512x288 maintaining the 16:9 ratio as well as being divisible by 16 to keep the macroblocks happy, whilst probably still being doable at 500kbps.

However, most 16x9 PAL content isn't 16x9 when you trim off the letterboxing so those dimensions would probably need some adjustment. I believe that keeping the letterboxing can result in CODEC issues with vertical motion estimation algorithms, as the motion moves into the letterbox area as opposed to off the top of the frame. Also streaming
the black letterbox seems a bit of a waste.

Also depending upon the subject material being encoded, 500kbps may not be enough to maintain perceived quality at that size, or alternatively it may be overkill, so some scaling may be considered.

(12-04-2008 05:36 AM)phil Wrote: b) what is the ideal bandwith around 500kbit/s. 512kbit/s, 540kbit/s and why?

Another trick question ?

Depends on the context. An extra 28kbps could improve perceived quality, on the other hand 28kbps less will probably mean that more people can recieve it.

Dave

benwaggoner · 02-07-2009, 01:46 AM

Also, for maximum efficiency, you want to encode with width and height both divisible by 16. 432x240 or 416x240 is better than 426.

512x288 sounds like a fine starting point, but as always, it'll need to be further tweaked based on content and delivery mechanism (live streaming needs more bits/pixel than offline 2-pass VBR encoding for progressive download).