[GEM-dev] gem framerate acuracy

[chris clepper]

On 5/15/07, marius schebella <marius.schebella at gmail.com> wrote:
>
>
> I was thinking Gem does not support all codecs.


GEM supports all Quicktime codecs on OSX, Directshow and Quicktime codecs on
Windows and quite a few on Linux (depending on what libs you build).

with "faster" do you mean less cpu consuming? I thought the fastest/less
> cpu consuming is a frame by frame codec like photo-jpeg because the gfx
> card can just take the jpegs and texture them onto a geo???


All codecs have to be decompressed into RAM and then uploaded to the
graphics card.

maybe I was thinking of the isight, which uses uyvy, and a conversion
> slows the process down.


The iSight might use 'Component' video UYVY but the conversion is pretty
simple and fast.  Often the device will do the conversion in hardware or the
driver does it automatically.  '2vuy' is probably the most universal format
for YUV video.

since you are probably the only one who knows that, can you explain how
> gem deals with the codecs? only if you have time... I do not understand
> why the apple intermediate should be faster for example when using the
> movie as a texture for a rectangle than the frame by frame jpeg
> compression?


Apple Intermediate Codec uses different code than Photo-JPEG for compression
and decompression.  In particular, Apple Intermediate is multi-threaded
internally and it avoids some slow code that the JPEG codec uses.

I have started using AIC for work since it takes any video dimensions unlike
HDV, DV or DVCPro.  Those codecs are all faster than AIC at their native
resolutions but are not flexible enough for some uses.  Also, the DVCPro
codecs only come with Final Cut and are not part of the standard Quicktime
install.  If you don't have Apple Intermediate then copy the codec from a
mahcine that has it in /Library/Quicktime/ or install iMovie.
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