#yet another PAR question
26 messages in this thread
Hi Greg,
Just a simple question for you, Can the PAR be set to output at 24 fps,
and can it capture at the same rate?
Inquiring minds want to know…
David
David:
There is a slider for output speed on the PAR application that is adjustable in
frames per second for slow motion, so that part is easy.
I'll have to check on the input side, though.
Greg Pyros
Greg: I noticed from your DPS PAR ZIP file that the PAR runs in 752 X
480 (fixed) resolution. I'm used to using my Targa+ at 512 X 486 and
storing the individual frames on my optical drive.
How would I set up my system with the PAR? I can render to .TGA files
at any resolution, I think and it sounds like I can also render
directly to the PAR's disk drive.
Also, I read a review of the DPS PAR (I don't remember where – Maybe
in 3D Artist, or maybe New Media…) and they said something about
the 500 Mb drive holding 3 to 5 minutes of video but being limited to
about 2 minutes of video because of some kind of recalibration done
to or by the drive every 2 minutes. Does this match your experience?
Chris
All disk drives which use thin film heads need to periodically run a
degauss and recal cycle. It is possible to make these less visible
for video use by modifying the drive's firmware. Both Seagate and
Micropolis have done this on certain drives.
Ok, thanks. Do all drives do the degauss and recal cycle in one shot, or is
this something that they can distribute over time?
Chris
Chris:
Most drives need to do a seek to initiate a degauss cycle, and the
process can take over 100 ms. It needs to be repeated every 500
seconds or so on a standard Seagate ST-12550N drive, and every 250
seconds or so on a Maxtor MXT-540S drive.
Thermal recal is worse, and can take over a second.
I don't have details on how Seagate has optimized their drives for PAR
use – I imagine they start a degauss cycle at the begining of a large
block transfer command, giving 500 seconds of uninterrupted data.
Micropolis has developed an embedded degauss and thermal recal cycle
which take 11 ms and 30 ms respectively. The drive can maintain a
2.9 MB/s *worst case* data transfer all day long – with no
interruptions. That is enough for good video quality. Unfortunately,
the feature is is only available on their 2210AV and 2217AV Fast
SCSI-2 drives – not on IDE drives.
Because of this, the Seagate IDE units (with special firmware) are
probably the best bet for PARs.
Evan,
>> Because of this, the Seagate IDE units (with special firmware) are probably
the best bet for PARs.<<
DPS is now recommending the Micropolis 2205A ~500mb IDE drive. I'm not sure why
but they say it's better than the Seagates.
Martin:
I haven't kept up, but if Micropolis has incorporated the AV features on an
IDE/ATA drive, it is an excellent choice.
Evan
Evan,
>> I haven't kept up, but if Micropolis has incorporated the AV features on an
IDE/ATA drive, it is an excellent choice. <<
I'm not sure why it's such a good choice, but Dave White said it's their
recommended best choice for the PAR now.
So it sounds like the drive does the recal whenever it thinks that it
needs it or when it gets a command to move a lot of data. Is that
standard procedure for the Seagate drive that is used with the PAR,
or do you need a version with special firmware?
Chris:
The main problem is not the thermal recalibration, it is the head
degauss.
Most drives have a degauss track. So they need to seek to it periodically to
degauss. The Micropolis AV drives have a dedicated degauss sector on each
track, so they don't have to seek to degauss.
Evan
Do most drives recalibrate on their own whenever they think that it is a good
idea, or do they recalibrate before a read or write?
Chris
Chris:
This is all getting to the level of asking how many pixels can sit on the head
of a pin.
The characteristic throughput curves of drives vary based on model and
manufacturer. It's hard to say exactly how each manufacturer does their recal
and degauss.
Evan
Evan: It probably isn't important at all, but I was interested in how they do
their recalibration strategy. It says something about what the designers had
in mind for the drive.
Chris
P.S. How many pixels will fit on the end of the pin? Is there a standard pin
for this test? An ASTM standard?? <g>
Chris:
Evan answered that perfectly. The thermal recalibration was a problem
in earlier drives/firmware, but we are getting 5 minutes on the 500
meg that the mag tested! The newer drives, as Evan mentioned, have
no problem.
The 752×480 is full screen, we regularly render tests at half of this
and Gus's driver just centers it on the screen perfectly! Or render
at 90% to save a little time on the portion that would be overscanned
anyway!
Greg: Ok. The magazine article was in DTVW (Desk Top Video World?, Devils,
Trolls, Vampires and Werewolves?? I'm not sure – all my copy has on the bottom
where most magazines identify themselves is DTVW) and it said: "The specified
540MB hard disk holds from five to seven minutes of compressed video; however,
the disk automatically recalibrates every two minutes, so you can play only up
to two minutes at a time."
It sounds from what you say that the recal period isn't fixed at two minutes.
It sounds like rendering my existing 512 X486 TGA files shouldn't be a problem
with centering, etc. I wonder why they went with a vertical resolution of 480
pixels – I thought that video resolution was 486…
Chris
Chris:
I think that the 480 vertical is a leftover from the Amiga version…
Greg Pyros
Greg: Since I have not seen the question, at least lately, WHEN will the DPS
PC PAR be venturing forth from DPS?
Also, do they know the amount of discussion that has centered around them
here, and possibly other areas also? Have you suggested to them that they
might join in? Not having seen anything, I have assumed that they are not on
Compuserve now.
Albert:
Actually, they are! Dave White just posted a message here within the last few
days asking for sample animations for the NAB show!
The latest I heard was the first part of February, and we are there!!! Won't
be long now!
Greg Pyros
I spoke to the shipping dept in Canada Monday to find out status.
They said the weather put a delay on some parts of the package but
the first batch should be ready to ship by Friday to the DPS branch
in Ky.
I received the HD Micropolis 2210A today. There was a price
adjustment 2-1 so I'm glad I waited. I also learned that the 2205A
is being discontinued. That's what my distributor said but he has
been known to be less accurate than the weatherman.
The TBC IV is quite the TBC. It has facilities to upgrade to full CAV
with an option card. Were you aware of this? I spoke to Dave White
on Monday and he said the option card won't be out for awhile yet but
recommended that the best way to use it is the Y/C for betacam but
use the option card for output to a component switcher. From my
first experience with DPS two years ago they have become quite the
capable video hardware company. They need a pattern generator card
for their line next.
I try to take the Yost motto of "we will not discuss new features
until their time", especially when under non-disclosure. DPS is a
company to watch!
OK. Does that say that the Amiga version does not run at full
vertical resolution?
Chris:
No, it just says that the resolution if 752×480! <g>
Greg Pyros
Greg: Ok, Ok! <g> Do my Targa files with 486 vertical resolution get centered
or do I just lose the last 6 lines?
Chris
Chris:
You just lose 6 lines. You'll never even miss them!
Greg Pyros
But Greg! My animations are so carefully crafted that I really need those 6
lines <G!>…..
Chris