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Can someone please tell me what in the world Uncompressed is?
Hey guys,
The UltraStudio 3D and other cap and play devices transfer uncompressed! Ok — but how can they if the footage is compressed the moment it hits the camera’s storage card?
(I understand that a live output can also be gotten but what about recorded footage)
In my research I’m learning about all types of things — sampling, lossless compression, etc. But I can’t seem to get that “Aha!” moment where everything just falls in place in English?
Anyone willing to take a shot and share? Please? Thanks in advance.
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6 Replies
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The answer is that….it depends. It is ambiguous as hell, and sometimes I think the vendors like that it is ambiguous.
True uncompressed is 1:1 with a full color space of RGB4:4:4:4. These days, it seems vendors are calling RGB422 ‘uncompressed’, even if there is data compression via other methods than color channel compression. They can refer to 8-bit data recording as ‘uncompressed’ even tho’ an 8-bit recording is not a full color space because of how much you can cram in an 8-bit data recording format. Needless to say, caveat emptor. It behooves you, as the prosumer, to understand the specs on color recording space, bit depth, interframe and intraframe compression and codec used. -
[Frank Black] “(I understand that a live output can also be gotten but what about recorded footage)”
Hi Frank,
SDI, HDMI, YUV, Composite, Y/C, can output uncompressed signals only, for this reason, if the compressed footage of the camera needs to be transmitted using one of these connections, it will be decompressed and so be true uncompressed again (with less picture details).
Hope it helps,Paolo.Castellano@ivs.it
http://www.ivsEdits.com
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“Post Fata Resurgo” -
That is not accurate. Uncompressed means just that: no data compression, in other words, no codec pass. 422, YUV, RGB, and 444 have nothing to do with it. All of those formats can be uncompressed, or compressed using various compression codecs such as DNxHD, ProRes, PhotoJPEG, JPEG2000, H.264, and many, many others. Uncompressed simply means that data compression has not been applied. Period.
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In a purely semantics sense, you’re right. In a pragmatic sense, you’re being misleading. 422 is certainly “compressed” compared to 444. Technically, this is called chroma subsampling, however, this is a compression technique. And the color resolution is sacrificed as a result of this compression. This is an intraframe compression, as opposed to the more conventional inter frame compression.
If you don’t beleive what I’m saying, just look at the recorded file sizes for 444, 422 or 420 recordings.
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>In a purely semantics sense, you’re right. In a pragmatic sense, you’re being misleading. 422 is certainly >”compressed” compared to 444. Technically, this is called chroma subsampling, however, this is a >compression technique.
No, it’s not. Compression is a technique that uses a compression codec to reduce the size of data needed to describe an image or series of images that have already been created, usually by eliminating redundancies, but different codecs use different techniques. Chroma subsampling is chroma subsampling, it’s not compression. Subsampling has been around since the beginning of digital video and is very similar in concept to the scheme used for broadcasting color video since the NTSC standard was developed. You can’t redefine terminology just because the result is similar on one level. Most cars run on gasoline, and some run on electricity. That doesn’t mean that electricity and gasoline are the same thing simply because they can both be used to propel cars.
Redefining terminology just because you think it’s convenient is what is misleading. Data compression is data compression. Chroma subsampling is something else, even if one of the end results is similar. And interframe compression is no more or less “conventional” than intraframe compression. There are intraframe codecs (DNxHD and ProRes are just two among many) and there are interframe codecs (MPEG2, MPEG4, and numerous others). Even H.264 has both interframe and intraframe flavors. The primary reason to use intraframe only compression is to allow proper editing, since all frames are self contained, unlike the “predictive” frames in an interframe compression stream.
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whatever you choose to call it, chroma subsampling was “invented” to fit a video data stream into an available data rate requirement. It is, for all intents and purposes, compression. So, whether you, or the industry, decide to call it something else, it is still compression. And to refer to 422 as uncompressed is nothing but misleading and a sales gimick.It is, in fact, destructive compression that is unrecoverable in post production.
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