We recently onlined a show on the DS that was different for us in two ways:
we used DNxHD for the first time, and it was very graphics-heavy compared
to what we usually do. We had about 10-11 minutes of stills and animation
for the hour-long sequence, which is high for us. We ran into major problems
with the DS crashing, not playing down, and eventually failing to render
properly. We'd like to know how to avoid these problems in the future, because I had to
work a lot of extra agonizing hours trying to get this show out the door. Any
hunches or advice would be greatly appreciated.
So here's the setup: We have an hour-long 1080i/DNxHD 220 sequence with
a lot of stills and animations. The effects in our sequence are not
particularly difficult, just basic stills with alphas in up to four of
five layers.
To conform the stills, I opened a graphics effect and imported the
stills, fitting them to the size of the HD frame. Some of the stills
were a couple times the size of the HD frame, but I scaled them to fit.
One short sequence contained 30 or so stills, each a single frame. (I called
this the "seizure clip".)
After we started color correction, we noticed that it was taking a long
time to save the sequence, about 2 or 3 minutes. I did some digging,
and discovered that the sequence had grown to 400 megabytes, whereas the
conformed sequence had started at 4 megs before I started placing
stills.
Soon after that we started having playback errors. I could only play
back a few seconds of footage before I got an error message saying that
the nitris had a CRC decoding error, or "the video hardware is having
difficulty reading images" / "waiting time to get image expired." We
also got a lot of out-of-memory errors when trying to work with the
effects. Just clicking locations in the timeline would generate memory
errors.
Since the sequence was so huge, I thought that perhaps the problem was
that the stills were being stored in the sequence (which seems daft),
and that they were consuming too much memory. I proceeded to replace
stills wherever I could with quicktime outputs of the effects. For
instance, the seizure clip became a single small quicktime that I
dropped in to replace the graphics effect.
I also deleted all the media from a previous show and defraged with O&O
using the "space" method.
Unfortunately this didn't solve the problems. The sequence was still
400 megs and I was still having problems playing the sequence. At this
point it also started crashing, and sometimes upon recovery it said it
had trouble with some of the effects. It claimed some of the effects
were not installed correctly. At this point I was afraid the sequence
was getting corrupt. We seeked out all the places where effects trees
had nodes that said "effect not installed" and fixed them.
I then tried pasting the entire sequence into a new, blank sequence, and
that reduced the sequence size to 100 megs, which is big but manageable.
It has since grown back to 200 megs, even though we didn't any more
stills.
As the online progressed, the playback problems nearly disappeared, but
soon we had a lot of trouble processing frames. Usually the render
would hang, saying "waiting for rendered image...". When I get that
message I exit out of DS and reboot the Nitris hardware, but this time
that didn't fix the problem. A few times it would say "can't write
image to disk through node based graph". I don't know what that means.
Basically it became impossible to render most effects, even simple
things like a software-realtime DVE and color correction.
I figured out that we could get it to render most things if we had our
RP box render them. Using that method we got all but three small
sections rendered. From there we had to rearrange effets or tweak them
slightly before they would render. Again this suggests to me a corrupt
sequence, but why on earth would the RP be able to cope with the problems?
We were able to output the show, but we still can't render effects reliably
unless we send them to the RP, and that takes a long time, even with 220 media.
Here are my questions:
* should the nitris be able to store a large number of high-quality
stills and perform effects on them?
* If so, why did our sequence get so huge, and why did I keep running out of
memory operating on stills?
* did our sequence get corrupt, and is there a way to repair that
corruption?
* why did remote processing work, but not local processing?
* why does remote processing process realtime (green) sections even when I don't
want it to?
* why does the RP reload the entire sequence for every single process operation, instead of
caching the last copy or just copying the relevant section of timeline?
thanks,
Owen Williams
Online Editor
Powderhouse Productions
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