Re: note on problem reports
Re: note on problem reports
- Subject: Re: note on problem reports
- From: Steve Christensen <email@hidden>
- Date: Mon, 21 Jul 2008 07:14:46 -0700
On Jul 21, 2008, at 4:06 AM, Kristian Harms wrote:
I just wanted to give a quick note on some problems that I believe
I've come across in FCP and Motion, and that I reported on
bugreports.apple.com last week. Hopefully this information can help
other developers as well.
The first problem is fairly easy to grasp: If you have an FxPlug
effect (I've only verified it for software generators) which varies
over time and which somehow smoothly animates *proportionally to*
where one is within the effect (e.g., imagine a bar that starts off
as nothing and then grows to reach the full width of the frame at
the instant the effect ends), then FCP won't handle partial re-
renderings correctly. Imagine you have such an effect, and drag the
end point further out to the right, then only the new part of the
effect will be marked as red (needing render), and the rendered
result you then get will have the bar grow to the full width of the
frame at the point where the effect previously ended, then
instantly fall back to a smaller size and once again grow to the
full width of the frame. Similar incorrect results are obtained by
lengthening the effect using the start point, as well as by
shortening the effect. (Apple devs, the problem ID is #6082523.)
What are you doing to determine the length of the clip?
The second problem is probably the most serious: Let's say you have
an FxPlug effect that not only has a custom parameter, but uses its
value to determine how it should render (e.g. the string "red"
would give red frames, the string "blue" would give blue frames).
You're in FCP and send two arbitrary effects to motion using the
right-click menu item, and apply this effect that has the custom
parameter to either Motion project, setting one to blue and the
other to red. After having saved both Motion projects and you get
back into FCP and render, you'll notice that some frames that
belong to one effect show up in the rendered result for the other.
This effectively precludes using effects with custom parameters in
Motion effects in FCP. (Apple guys, the problem ID is #6079258.)
The third problem is only in Motion: If an FxPlug effect generates
pixels that are fully transparent, but have the R, G and B channels
set to some non-zero value (e.g. 127 if we're talking UInt8), then
Motion won't treat these pixels as fully transparent, but will
instead show any underlying layer as "washed out", and the black
default background will shine through as grey. This is with the
normal blending modes. (Apple guys, the problem ID is #6079465.)
FxBitmaps are pre-multiplied so shouldn't ever see an ARGB pixel
value of (0, 127, 127, 127). If you'd started out with a non pre-
multiplied pixel with those component values, then when the pixel was
pre-multiplied you should end up with (0, 127 * 0, 127 * 0, 127 * 0)
== (0, 0, 0, 0).
A few weeks ago I was on the list about effect duration being
reported incorrectly using the information that comes with
renderOutput: requests -- sometimes I was getting 3000 frames. I've
not been able to reproduce this lately, but I will of course report
it if and when I do.
steve
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