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Old March 5th, 2009, 05:19 PM   #1
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Low quality when encoding to WMV.

I'm running Vegas 7 and I'm wondering why I'm getting a lower quality video when I render to WMV as opposed to Mpeg. I've been playing with the encoding settings and no matter what I do WMV looks worse than Mpeg. Am I missing something here?
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Old March 5th, 2009, 06:00 PM   #2
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Possibly, you are missing something.

In general, for a given bitrate, wmv looks better than mpeg2 by far.

If you're looking for similar results, you should have them for standard definition about 1800Kbps for WMV to about 6000Kbps for MPEG2.

What wmv settings have given you the best results? What MPEG settings are you using as a reference?
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Old March 6th, 2009, 10:13 AM   #3
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Ok, I went back and tried things again. These are the settings I used. This time the videos look about the same, but the wmv ends up being a bigger file than the mpeg. I must be doing something wrong.
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Low quality when encoding to WMV.-mpeg-settings.jpg   Low quality when encoding to WMV.-wmv-settings.jpg  

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Old March 6th, 2009, 11:34 AM   #4
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I've not had any experience with 24fps in WMV and MPEG2 - don't know if that could be contributing to the problems you're seeing.

And, what are those problems, btw?

One thing I do notice that would explain the file size differences and possibly contribute to perceived quality differences - You're encoding your MPEG2 at a variable bitrate (VBR), and WMV at constant bitrate (CBR). VBR allows bursts of bits in high motion frames. CBR doesn't. VBR will throttle down the bps in scenes that contain less motion.

So, an apples-to-apples comparison would be VBR to VBR, or CBR to CBR.

One setting in the WMV that is kinda' subtle but can have a big effect is the Seconds per keyframe setting. Right now it is at 5, which is very high, way too high for anything with much motion, and kind of high even for footage without much motion - I'd say no more than 3 for smooth footage, and experiment with less for motion. This setting controls the length of the GOP.

My working figure for standard def WMV is 1800Kbps (1.8M). Of course I'm not jumping out of airplanes with my camera, or holding up my cellphone at a concert - what I'm compressing tends to be professionally lit and shot on a tripod, ie., it's not really high-motion, and it's not noisy, both of which can give a compressor fits.

All the above is assuming that for the WMV encode you used the bitrates on the 6.4Mbps wmv template, perhaps you should confirm that the bitrate tab says 6.4M, and that there are no other boxes filled in (meaning that it isn't a multibitrate encode, which would skew everything).

So, it looks like we have to go a little deeper to understand these differences between expectations and results. What does your source footage look like, HD, SD, jerky, smooth, motion, video noise, lighting? What playback device and display are you using to evaluate the MPEG2 and the WMV? Are we on PC, Mac, DVD player?
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Old March 6th, 2009, 11:57 AM   #5
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Well,

On the surface, I have to ask what kind of file you're outputting? The Mpeg2 settings are set up for an SD output, and the WMV settings indicate a non-square pixel HD output.

So let's start with that...
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Old March 7th, 2009, 11:31 AM   #6
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Quote:
Originally Posted by Perrone Ford View Post
Well,

On the surface, I have to ask what kind of file you're outputting? The Mpeg2 settings are set up for an SD output, and the WMV settings indicate a non-square pixel HD output.

So let's start with that...
I wanted to output to SD, but the source video was HD 24p so I wasn’t sure if I needed to keep the non-square pixel setting or not.

Last edited by Stephen Boss; March 7th, 2009 at 12:46 PM.
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Old March 7th, 2009, 11:39 AM   #7
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Seth-
The video does have a goof bit of motion. My problem was that I was getting some motion blur (that was evident in both the mpeg & wmv), and my colors were much more vibrant on the mpeg. The mpeg also seemed to be a bit sharper that the wmv.

I went back and changed the wmv to CBR at 3M, dropped the seconds per keyframe to 3, and dropped the smoothness to 90%. That helped tremendously. I also had the override compression buffer unchecked this time (donít know how much of a factor that has on things). Iím still not sure what frame rate and pixel ratio I should be using to get the best output though.
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Old March 9th, 2009, 05:09 PM   #8
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Bump for more advice...
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Old March 9th, 2009, 05:42 PM   #9
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Frame Rate should be the same as the source. Pixels should be 720x480 for NTSC with a pixel aspect ration of .9091, or square with 655x480 dimensions. Also, go to 1 keyframe per second, and smoothness to 94 or 95.

That ought to get you where you need to be.

-P
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