Hi quality frame grabs

[John Carey]

I am having an application created which allows users to view a sports video and capture frames. I would like to have the frame grabs as high resolution as possible for printing 5x7's and possibly 8x10's.

My question is, what format would be best? The application has been started and is being developed in flash. I heard that with Hi Def we should be able to get almost a 2MB file? but the samples I have seen (using .flv video files) are all smaller sizes.

Can, and does it make sense to use flv files for this?or does it make sense to use 2 files per video, low res for viewing and hi res for frame grab?

What formats would have the best quality in a frame grab?

What would the recommendations be to grab hi res frames/photo files?

thanks

John

[Bill Davis]

This is actually a bit complex to properly understand.

Modern digital video encompasses a pretty wide array of raster resolution standards (think sensor megapixels), a wide variety of compressions schemes, (some more "lossy" than others) and various color encoding processes which can hurt the actual dot resolution of the color layer of composited video scenes.

So the game starts with obtaining the highest raster you can. Next, you'd hope for a camera source that's recording progressive rather than interlaced EXCEPT if your scenes are in fast motion. If that's the case, objects moving across the screen rapidly can distort since the raster is captured over time and an object may well move between the beginning and the end of a scan.

Honestly, pulling stills from video is always a compromise compared to taking stills from a still camera - since still cameras are generally built to exposes the whole sensor at once, and video cameras are built to record scan lines that are captured over relatively slower time frames.

If you have a lower raster source that records interlace - then you have to "de-interlace" and there are other motion anomalies such as diagonal edge stair stepping that can be introduced when you're pulling stills.

So the bottom line is that a truly useful app would need to have the capabilities to deal with these and other issues that are a typical part of grabbing stills from video.

This kinda just scratches the surface - but it's at least a start in understanding the overall issues.

FWIW.