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How to make wmv into flv without artifacts?

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David Donnenfield
How to make wmv into flv without artifacts?
on Jun 12, 2008 at 5:52:43 am

I took on a job to convert several wmv movie files into Flash files for playback on computer via a thumb drive. The client couldn't provide the source material of master, so got the compressed wmv files instead. Since I needed to shorten some of the movies, I exported the wmv files first as QT files using the Animation codec. I also was able to crop one of the 16:9 movies so they all could be 4:3, as the client desired.

So, I brought these big QT files into FCP to edit and then exported out to Compressor using the FlixExporter Flash encoder. Three out of the five short movies are reasonably acceptable, but two have nasty artifacting, especially with motion and dissovles (where you'd expect it). I have changed the data rate and pushed it up to 4,000 kbps, but that doesn't help. I'm experimenting now with changing the fps to 15 from 30.

Am I nuts for trying to recompress an already compressed movie in going from wmv to flv? Or, is there some trick I can employ to improve picture quality that I haven't thought of yet? My deadline looms. Thanks,
David


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Daniel Low
Re: How to make wmv into flv without artifacts?
on Jun 12, 2008 at 9:24:22 am

If you're getting bad artefacts at 4Mb/s then there's probably not much you can do to improve, but:

What frame size are the source WMVs?

What datarate are the source WMVs?

What method did you use to go from 16:9 to 4:3

What frame size are your output FLVs

What keyframe settings are you using for the FLV?



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David Donnenfield
Re: How to make wmv into flv without artifacts?
on Jun 12, 2008 at 4:00:00 pm

Daniel,
Before I reply to your specific settings request, let me say that after hours and hours of angst and trying different combinations, I got the dang thing to come our decently by re-exporting via QT Pro using the DV/DVPro setting. I also checked "Progressive", dialed the quality setting to "Best" and formatted as a 4:3 VGA output (it's ultimately going to computer display). The outcome lopped 50MB off the file size from the Animation codec QTs that I was making. But, what's more important is that the sucker played without nasty pixelation and motion stutters.

This begs the next question: Was the animation codec just too high a data interpolation for the Flash encoder to handle? Or was it that the DV setting more closely matched the source material from which the wmv file was made? Maybe there are other possibilities, but these are the questions that come to mind for me in getting to the bottom of this particular compression conundrum.

Settings:

What frame size are the source WMVs? 640x480

What datarate are the source WMVs? 2600kbps

What method did you use to go from 16:9 to 4:3 This particular movie was already 4:3, so I didn't have to change the aspect. But the next one I will, it's already exported "squished" (from the sides) using the Animation codec so I've got a problem looming.

What frame size are your output FLVs 640x480

What keyframe settings are you using for the FLV? 60 keyframes


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Daniel Low
Re: How to make wmv into flv without artifacts?
on Jun 12, 2008 at 4:28:24 pm


Typically the animation codec produces huge files as it's a lossless 4:4:4 codec (when the quality is set to 'best' or 100%). The DV codec on the other hand is a lossy codec with a datarate of 25Mb/s

It's likely that by using the DV codec that you have softened/blurred the picture making it a lot easier to compress. The Animation Codec is probably retaining any artefacts present in the WMVs, rather than it it giving the Flix encoder 'too much' data. That said the Animation codec is slow to decode, as well as encode.

I generally use a keyframe setting of 1 forced keyframe every 3 to 8 seconds, depending on the content and how much accuracy is needed while scrubbing through the clip. For example with a keyframe setting of 1 every 3 seconds will give the clip with much better 'scrubability' but will result in a larger file that should be of higher quality.

You might want to try encoding to a smaller frame size - give 576x432 (4:3) or 512x288 (16:9) a try

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Please post back saying what solved your problem. It could help others, and saying 'thanks' is free!


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David Donnenfield
Re: How to make wmv into flv without artifacts?
on Jun 12, 2008 at 4:50:04 pm

Daniel,
This is great information and adds to my understanding. I have already standardized to 640x480 and have gotten several of the wmv files to convert now. But, I am left with one last nagging wmv movie that was shot 16:9 (640x360). so it needs to be cropped as well as converted to flv. The flv conversion I think I'm getting a handle on with my DV settings, but it's the aspect change that has got me wondering. I tried it once, when I was using the Animation codec and the image came out 640x480, but squished in from the sides. So, clearly, I must change some settings governing the image size when I re-export out of QT Pro. But, it's confusing.

Within QT Pro, I'm presented with the choice of Preserving the aspect ratio or Not Preserving it. I would have thought that I don't want to preserve the aspect ratio since I've already selected the image dimension as 640x480.
But if I do select Preserve aspect ratio, I'm given the alluring options of:
Letter box
Crop
Fit within dimension

Do I want to "Crop" and preserve the 16:9 (640x360) aspect ratio? I tried it once, and got the "squished" image --- 4:3, but pushed in from the sides. Will changing to the DV/DVPro VGA settings with square pixels solve the problem automatically? Just one too many variables to know how to proceed.
Thanks,
David


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David Donnenfield
Re: How to make wmv into flv without artifacts?
on Jun 12, 2008 at 5:44:52 pm

Well, I went ahead and exported the 16:9 "cropped" movie in DV codec, put it in a FCP sequence that I had to render, exported to Compressor with the FixExporter Flash Encoder, and got an Error #60003 message: Couldn't get string from resource. Rather cryptic, and disappointing. Besides contacting On2 Technologies, any idea on what to try next?
David



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Daniel Low
Re: How to make wmv into flv without artifacts?
on Jun 13, 2008 at 9:29:38 am

If you don't what to crop away any of the picture then you need to preserve aspect ratio by letterbox.



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Please post back saying what solved your problem. It could help others, and saying 'thanks' is free!


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