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Re: WM9 720p export from After Effects.....Ben ?

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Jason Howard
Re: WM9 720p export from After Effects.....Ben ?
on Jan 22, 2004 at 1:04:54 am

Hey Kino!

I thought I might step in a clarify a few things.

The PNG file format is actually very similar to TIFF, in that it encapsulated multiple formats (Now not nearly as many as TIFF). A PNG deals with most any color bit depth, has support for alpha channels, and even uses a lossless compression (zlib) similar to that used in some TIFF formats. It was really created as a better GIF, but with way more functionality than that of the aging GIF. (There is even a animated version called MNG). Compression can be scanline, interlaced, or full frame based.

The JPEG format actually works in YUV space as it's lossy compression scheme is meant to throw away as much data as possible while having minimal impact on the visual domain (So, for instance we can subsample the chroma by half and no one notices, well most of the time). There is actually support in the JPEG spec for lossless compression, but nobody ever implements it because it just isn't that useful.

The mighty TIFF format is probably _the_ most advanced image format. It is very much like the quicktime of the still image formats. It allows for a real codec like framework. I don't know how many times I have gotten a TIFF format I can't read because it is some in-house floating point proprietary TIFF :)

That brings me to formats like Targa and SGI. These formats are especially useful because the require no packing or unpacking. The data exists in the file in exactly the same way it will exist in our framebuffer rasters. So, yes, while reading this data may take more time (because it is uncompressed) it, the time that it saves in unpacking and decompression make up for that several times over. Now as CPU speeds increase the line is skewing towards lossless compression and things are getting more interesting.

We are, in fact, playing with lossless compression in our DDR that both save disk space and overall system bandwidth. Also, because of the time required to read the file is less, we are actually reading and decoding the frame in the same amount of time it takes for us to read an uncompressed frame. Talk about getting more for the same price!! The future is going to be interesting.

Just a couple more $0.02.

Jason Howard
Linux & Media COW Leader

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