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The second elephant in the room
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What is my mistake here?
When you are reading/writing 25Mbps signal at quadruple speed you are reading/writing 100Mbps.
Are you using QSDI with two of those decks or Sony’s editstation? -
1) the DSR 80/85 deck is huge. HUGE! I’ve carried them up and down many flights of stairs, and it’s not pleasant. The tape mechanism required top speed up a mini dv tape reliably is enormous and heavy.
2) only a 25 mb/sec signal is being written to mini dv tape. Forget what QDSI can move. I don’t know about the chemicals and tape stock on DvCam, but DVCPRO tape is different. It can be sped up to have DVCPRO50 or DVCPRO HD recorded on it. This is why the SDX-900 and varicam take DVCPRO tapes, and not mini dv tapes.
3) mini dv tape can’t be sped up 4 times to record HD. That’s why the varicam takes DVCPRO tapes. DVCPRO tapes can be sped up because they’re heavier and thicker tape and have different chemicals. But that tape won’t fit in a small casette enclosure.
4) tape heads to record HD are expensive. Wildly expensive. They cost more to buy than than the P2 even sells for.
These are the main reasons why the HVX will shoot to P2 and not speed up DVCPRO tape. And why no one will probably make a camera that tries to speed up tape 4 times to get an HD signal. as you’re suggesting, there might be a way to work it out, so that it’s possible, but no one is going to do it, as it’s not a camera that would be (1) small (2) cheap (3) light (4) profitable.
you wrote: “Are you using QSDI with two of those decks or Sony’s editstation?”
Neither, right now. I loaned the deck to friend of mine, and sold my QSDI board a few months back. You can buy it, if you want. It weighs about a million pounds.
jeremiah black
dual 2 gig G5
2.5 gigs of RAM
Decklink Extreme capture card -
[toke lahti] “What is my mistake here?
When you are reading/writing 25Mbps signal at quadruple speed you are reading/writing 100Mbps. “While that may be true I think Jeremiah’s point is that the signal you are writing in that case is still a DV25 signal. So, while that may be interesting it would not really be a solution for the HVX200 for numerous reasons.
First off DVCPro is a different animal.
DVCPro uses Metal Particle tape, not the sam metal evaporated tape that DV and DVCam use.DVCPro uses a wider track pitch than both DV and DVCam (18microns vs. 15 & 10 respectively).
DVCPro runs faster than both DV and DVCam (almost twice as fast as DV in fact), so to quadruple the speed of DVCPro (as is done on the VariCam) would mean an equivalent of about 7 times faster than DV, not 4times.
DV runs at 18.81mm/s
DVCPro runs at 33.82mm/s
DVCProHD runs at 135.28mm/sAs has been said here before, DV tape DOES NOT have the strength to run fast enough to record a DVCProHD signal. Again, maybe you’re right about being able to record 100mb/s to DV tape, but there is more to a codec than the datarate (i.e. track pitch, tape speed, etc). Just because you can push 100mb/s through, doesn’t mean you can record a DVCProHD signal.
Secondly, and much more importantly, while all the tech details I just listed may be true… it’s all a moot point. As has been mentioned several times, a DVCProHD tape transport would cost much more than the $6000 the HVX200 will sell for.
As I have mentioned before, the only reason low cost DVCProHD will be possible is because tape has been taken out of the equation. As cheap as tape may seem, you pay for it up front both in the tape transport on the camera, and in the deck you have to buy to digitize your footage.
Luis Caffesse
Studio 3 Productions, Inc.
Austin, Texas -
[Luis Caffesse] “Again, maybe you’re right about being able to record 100mb/s to DV tape, but there is more to a codec than the datarate (i.e. track pitch, tape speed, etc). Just because you can push 100mb/s through, doesn’t mean you can record a DVCProHD signal.”
If you can record 100Mbps, then you can.
There no magic here and no codecs to record.
Tape does not not with what codec its data will be used.But you guys seem to totally miss my point.
I took DSR-85 just for an example.
You take for granted that HD camera can cost $6k now, when 5 years ago it was $100k.
And camera can be 5 times smaller.
But somehow you can’t believe that tape mechanism that has costed $20k for the last
5 years can cost only $1k. It’s all about manufacturing volumes of mass market.Why aren’t you screaming that HD ccd’s cost $20k per set and that’s why it’s totally
impossible that hvx has HD ccd’s?Ok, I’ve tried to made my point.
If you don’t get it, I give up. ‘Nuff said about this subject. -
[toke lahti] “If you can record 100Mbps, then you can.
There no magic here and no codecs to record.
Tape does not not with what codec its data will be used.Tape may not, but the record heads do, which is where track pitch comes into play.
The codec does matter, each codec has it’s own specification for how it is written to tape. If you want to change the specs, then you are changing the codec.
So again, you may be right about recording 100mb/s to dv tape, it may be possible, but now you have to write a codec that can support that (because DVCProHD cannot do it).No one is implying that this is “magic.”
But the tape and datarate is only part of the equation.
Codec specifications do matter, and you can’t just ignore them.But you guys seem to totally miss my point.
I think this topic has been gone over in minute detail.
Please don’t mistake disagreement with misunderstanding.
I understand what you are saying, and I concede that you may be right about the ability to write 100mb/s to DV tape. It’s the conclusions you seem to be drawing from that that I disagree with.You take for granted that HD camera can cost $6k now, when 5 years ago it was $100k. And camera can be 5 times smaller. But somehow you can’t believe that tape mechanism that has costed $20k for the last 5 years can cost only $1k. It’s all about manufacturing volumes of mass market.
It’s not all about manufacturing volumes of mass market, it’s about new technologies which allow for the removal of expensive components. The only reason an HD camera can cost $6K now instead of $100K is due to the fact that the tape transport is removed from the equation and replaced with inexpensive solid state card slots. The camera is 5 times smaller because once the large tape transport is out of the design, the electronics can be put into a unibody fixed lens camera design (which has already been used for a previous model, and can simply be modified to fit the new camera’s electronics).
There has been no ‘breakthrough’ in tape mechanisms akin to the move to solid state recording. There is no cheaper way to manufacture record heads, or the mechanisms of the transport itself. You could manufacture all the tape transports you want, but the price will only go down to a certain point. Unless there is some advancement in the recording technology used in tape transports, the price will not drop significantly.
Why aren’t you screaming that HD ccd’s cost $20k per set and that’s why it’s totally impossible that hvx has HD ccd’s?
Probably because that isn’t true.
Obviously the CCDs in the HVX don’t cost $20K per set.
You comparisson doesn’t hold because it’s not based on anything factual.
CCD technology has advanced by leaps and bounds over the past 10 years, aided also by the digital still camera advancements. Again, I would ask that you point out the major advancements in tape transport technology, or in record head technology.If you don’t get it, I give up.
Again, I ‘get it,’ I just simply don’t agree with your position.
That’s all.‘Nuff said about this subject.”
That’s something we can both agree on.
Luis Caffesse
Studio 3 Productions, Inc.
Austin, Texas -
Just one last time for this subject:
[Luis Caffesse] “The codec does matter, each codec has it’s own specification for how it is written to tape.”
Nope, tape recording standard and codec are different things.
Codec defines how video data is handled (compression, etc.) to a datastream.
Tape format defines how datastream is recorded in tape.
Just like you can have video with dvcpro codec in hdd and it has nothing to do with tape.[Luis Caffesse] “You could manufacture all the tape transports you want, but the price will only go down to a certain point.”
And you seem to suggest that video tape mechanism can’t get cheaper than they are.
Like the lowest point is somehow reached.
How do you explain that data tape mechanisms have developed in a few years to have ten times faster and cheaper?
Because there is enough competition in that area.
So back to the analogy with ccd chips and tape drives:
Hd ccd’s are now ten times cheaper than five years ago, because there is competition in that area,
and so there is development.
Video tape drives haven’t had enough competition and that’s why price hasn’t dropped.
This speculation about possible video tape drive development is of course purely speculation,
because it never happend. I think now time has gone past it. Disk based recording is today and
solid state maybe tomorrow.One reason for this is that this “prosumer” phenomena is still a quite new and small thing.
Manufacturers have long been making products for two targets that are as far from each other as they can be: consumers and broadcasters.
Other reason is that formats and standards in AV tech has been traditionally designed to be constant for at least for decade. This is because small volumes (to make r&d affordable) and because everything has been “hardwired” hardware that you can’t upgrade easily.Situation is totally changing now when ICT tech and AV tech is converging.
ICT tech development has long been reaying to 3 things:
1)mass volume: everybody’s using (more and more) same tech from supercomputers to child’s home computer
2)software based: products can be upgraded easily
3)modularity: combination of 1 & 2Hdd’s are cheap, because millions of them are sold every year, dvcpro drives are not.
Ccd/cmos chips are getting cheap, because millions of them are sold in digital still cameras.
Cf and sd are cheap, p2 is not.
I believe that in very near future there will also be manufacturers that start to make Hd cameras out
of cheap standard bulk parts, not making new proprietary formats, and that will explode markets.What if somebody had started making cameras based on DLT tape format year ago?
Or if all manufacturers would use it now?
Newest SDLT tape has a capasity of 300GB and transfer rate of 36MBps (=288 Mbps).
So you could record 1080p24 dvcproHD for 400 mins to one tape.
Last year specs were half and three years ago 1/4, but they are all downward compatible.
Sure it’s a $50 per tape, but if whole world’s video would be recorded to them it would be just
a fraction of that and even now it would be less than $10 per hour.
Also cost of a drive is half of what dvcproHD deck, but if the volume would be same as miniDV mechanisms
sold every year, that would also be a fraction of what it is.[Luis Caffesse] “‘Nuff said about this subject.”
That’s something we can both agree on. “Sorry, this got out of the hand once again.
Thank you everybody for interesting conversation! -
Ofcourse it has been developed – it’s called DVCpro50!
Graeme
– http://www.nattress.com – Film Effects for FCP
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My only point is that DVCPRO50 tape records to DVCPRO tape- not mini DV. But, I will concede the possibility that a similar process is maybe possible with regular mini dv tape.
jeremiah black
dual 2 gig G5
2.5 gigs of RAM
Decklink Extreme capture card
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