frame_rate support for ASF/WMV formats

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mjs
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frame_rate support for ASF/WMV formats

Post by mjs » Thu Nov 30, 2006 9:50 am

So looking throug the structure.txt file, it appears ASF doesn't have frame_rate support. Am I wrong in my assesment? QuickTime files are returning FPS with no problem, but obviously frame_rate doesn't work with WMV files I'm throwing at it. Anyone guess why Microsoft wouldn't have a frame_rate header in their files??? After all, FPS is one of the basic foundations of video.

Maybe I'm just missing something??? Working with 1.7.7

James Heinrich
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Post by James Heinrich » Thu Nov 30, 2006 10:27 am

If I remember correctly, ASF/WMV has what is essentially a variable frame rate, where it's low-FPS in low-motion scenes and higher-framerate in higher-motion scenes.

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Post by mjs » Thu Nov 30, 2006 11:38 am

Bummer.

What's intersting is that Windows Media Player doesn't even show the current frame-rate in its extra info section. However, play a WMV file in QuickTime Player and it shows the file's stamped FPS as well as current FPS (and it does fluctuate).

Hmmmm... is there a way to get the total number of frames in the video? Then it could simply be devided by playtime_seconds for an average FPS. Surely not acurate on videos that do incorporate variable frame rates, but better than nothing for what I'd like it for.

Thanks for the very speedy reply.

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Post by James Heinrich » Thu Nov 30, 2006 12:11 pm

It is possible for ASF/WMV files to contain an optional header structure that includes data on average time per frame (hence framerate), but none of my sample files include that structure so it's obviously not that commonly used, and therefore not very useful most of the time.

My QuickTime player refused to play my WMV files, so I can't replicate your claim in that regard.

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Post by mjs » Fri Dec 01, 2006 1:03 pm

Hi James,

I failed to mention that I played the WMV files in QuickTime Player on OSX. They don't play on Windows Media Player for me either. Even more interesting that a Mac can display the WMV FPS information that a Windows computer can't. Somehow QuickTime Player is tapping that FPS information out of the WMV file. I'm surprised this topic hasn't come up before.

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Post by mjs » Fri Dec 01, 2006 7:52 pm

Edit: I meant to say, "The WMV files don't play on QuickTime Player for Windows for me either."

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