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between 150 and 300kb? What is the difference between 150 and 75kb? What is the difference between 300kb and uncompressed? The only thing that can be said is that it IS a difference - how visible it is depends on your material...."small" difference on a talking head, "big" difference on, say, a tree full of leaves. If you have the storage and your system can handle it, it´s always better with higher datarates. If you choose a lower datarate, it is always to SAVE something (money, space), NEVER for reasons of quality.
The variables are these: compression scheme, implementation of it and data rate. In some cases the implementation of the compression scheme might vary, so that a data rate from one company might give better results than the same (or higher) data rate from another company even when using the same compression scheme (this have been claimed at a number of occasions for the Media100 implementation of M-JPEG,like it - before quicktime 5 - was claimed that Promax DV codec was much better than the Apple DV codec).
While remembering this, the rule of thumb is: Higher data rates are always better than lower ones within the same compression scheme, but you can´t compare data rates between different compression schemes. For example, MPEG is a much more efficient compression scheme than M-JPEG, and so is even DV (on this one I guess a lot of people would like to chop my head off). At the same data rate MPEG will give results far superior to M-JPEG, and it will give the "same" result on a much lower data rate. Even DV will give better results than M-JPEG at the same data rate, but DVs fixed data rate (5:1 compression) can´t compete with M-JPEG at highest data rates.
As for "broadcast quality"....this doesn´t make much sense any more: No more strict definitions, big difference between various broadcasters, very much dependent on what part of the programming you are producing for. So, again, rules of thumb (at least as I see them in Europe): "Broadcast" is anything which doesn´t LOOK significantly worse than Beta SP. Here, again, we have (at least) three "variables", quality of recording equipment, quality of editing equipment and master format.
"DV" is clearly "broadcast" if recorded with, say, a DSR-500, edited on DV or M-JPEG at high data rates and mastered to Beta SP. If the shooting is done with a PD-150 it will be accepted as "good enough" by a number of broadcasters, but if they still stick to a sort of "broadcast quality" concept, they will most definitely NOT accept it as falling within THAT definition. So...it´s "good enough" for news and documentaries (where the choice of equipment makes sense).
What goes for "DV"(DVCam) goes for DVC-Pro25 - it´s "broadcast" for all purposes other than the "high(-er) quality" part of the programming, which would demand DigiBeta, DVC-Pro50 or Beta SP/SX (well...not for "drama"). But, of course, all this only goes if they KNOW, and broadcasters have always been easy to fool with masters on Beta SP...
As for M-JPEG editing at 150kb, I wouldn´t know....it´s SO dependent on what you´ve had in front of the camera. But, this is for sure: I wouldn´t BRAG about having used a M-JPEG data rate of 150kb. That said, I wouldn´t brag about a data rate of 300kb either...(why should I talk about data rates at all!?). But if they asked, I would feel MUCH more comfortable answering 300 (360) than 150 - and I´m sure they would treat me much better upon THAT answer.
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