View Full Version : SXGA+ mpeg2 encoding
10th April 2005, 12:03 PM
I am trying to find a good Mpeg2 encoder to compress footage in SXGA+ format, which is 1400x1050.
Most encoders, like the Mainconcept codec I use most of the time, do not support non PAL/NTSC formats.
Other encoders, like Tmpeg Encoder Plus v2.5, let you use custom resolutions but these resolution must be multiplies of 8, and neither 1400 nor 1050 are divisible by 8 :(
I am begining to wonder if the "multiply of 8" rule is required to encode in MPEG2 by definition (because of the matrices).
The codec can be commercial, even expensive, as long as it can get the task done professionally. Thanks for your help :)
10th April 2005, 12:27 PM
Well, I just checked my commercial mpeg2 encoder and it maxes out at 720*576, but I did notice something: almost all the encriments are in 6s...
verticle: 64, 80, 96, 112 ... 528, 544, 560, then it jumps right to 576.
horizontal is similar: 96, 112,128,144,160,176,192 ... 672,688,704,720.
Again mostly 6s, but occaisional jumps of 16.
Some google research suggests MPEG2 might be best as a multiple of 4 AND a multiple of 6 both. (does that optimize it as a multiple of 12?)
stumped. Are their no HD mpeg2 solutions yet?
10th April 2005, 12:51 PM
whats the purpose?
why SXGA+? can't you use 720p instead? (1280x720 60fps)
a quick google for hdtv mpeg encoders brings up a few options - they are aimed at hdtv mainly but you might have to put up with that and letterbox your SXGA+ in a 1080p HDTV stream.
at lease HDTV is square pixels!
also have a look at sonicfoundry.com - there mediasite system is designed for utilising computer screen inputs so they may well have solutions to the odd pixel dimentions
10th April 2005, 02:37 PM
I can encode MPEG2 in HD formats (1080 and 720) easily using Tmpgenc 2.5+, but that's not what I want. This is exactly what HDV is all about : 1080 or 720 HD signals compressed in Mpeg2 on a DV tape. That's not what I want.
I want SXGA+ : 1400x1050 square pixels.
Why SXGA+ ? Because it's my projectors native resolution.
The sonicfoundry mediasite isn't a solution at all : all it can do with a VGA signal is capture stills in jpeg format...
Letterboxing into a higher resolution format is the solution I had already found ( 1408x1056 works well : its a multiply of 8 and is 4:3 ), but I was wondering if there was a better solution.
I've read some more theory about mpeg-2 and it looks like it splits the video in 8x8 pixels by definition for some of its compression algorythms - I would really like to be proven wrong on this ...
10th April 2005, 02:50 PM
why mpeg2? - can't you use an MJPEG format or something? - these non mpeg based systems are a lot more flexable when in comes to input / output resolutions.
or get a diferent projector! - i've not come across sxga+ native projectors - everything i've seen has been normal 4:3 aspect ratios at 800x600, 1024x768 and 1280x1024 unlesss its specifically an hdtv projector in which case its 1280x720 or 1920x1080
or get a different software - anything recent and based on gl will be able to scale your source footage at virtually no quality loss with zero impact on framerates.
10th April 2005, 03:26 PM
mpeg is based on 8x8 groups of pixels.
Watch your digital tv signal break up and you'll see it very clearly!
I'm not sure how anyone would go about doing a non multiple of 8... you'd probably have to use something other than mpeg1 or mpeg 2.
10th April 2005, 04:12 PM
thanks for all the information Alan, Tom and Holly.
info for Tom about the resolution : SXGA+ 1400x1050 is a common native resolution in recent high-end DLP projectors, I am surprised you haven't worked with some. Check Barco, Digital Projection and Christie for examples.
10th April 2005, 04:32 PM
maybe i have - i dunno i just plug video into them!
let us know what you end up doing - i guess the barco aproved route will involve hardware scalers that cost more than a car!
i think i'd go for 720p hdtv as a format to make clips in - as an hdtv standard this is inherently more future proof for video work that a wierd 16:10 sxga+ file.
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