Re: Low precision on time remap
Re: Low precision on time remap
- Subject: Re: Low precision on time remap
- From: Bruce Sharpe <email@hidden>
- Date: Mon, 16 Feb 2009 11:10:50 -0800
[Re-sent to the whole list.]
Comments below.
On Mon, Feb 16, 2009 at 9:52 AM, Ky Hopwood <email@hidden> wrote:
> You have audio that is not in sync with video and are trying to adjust the
> speed the video to match the audio?
That's about right, but more often I want to adjust the speed of the
audio rather than the video.
> Is you audio fine at the start, and then drifts linearly , or is completely
> ok and then at some point goes off?
It has a linear drift that I know to a high degree of precision.
> In addition, I gather from what you are saying that you are not really using
> xml is this workflow, but rather you are using that simply to display the
> values of the speed keyframes. Is that correct?
XML is in the workflow. I am writing a plugin that helps with
synchronization. It retrieves the project XML, analyzes the clips to
determine the drift and writes back XML with a time remap speed
parameter to compensate. My concerns are that (1) FCP may not respect
the full precision of the speed parameter in the XML, (2) even if it
does, it may not persist when the project is saved, and (3) if the
user looks at the speed in the UI, its value will be corrupted.
I'm pretty sure about #2 and #3, but I'm doing an experiment to assess
#1 right now and will let you know shortly.
Bruce
On Mon, Feb 16, 2009 at 9:52 AM, Ky Hopwood <email@hidden> wrote:
> I am not certain I have your scenario correct, so a few questions to verify.
>
> You have audio that is not in sync with video and are trying to adjust the
> speed the video to match the audio?
> Is you audio fine at the start, and then drifts linearly , or is completely
> ok and then at some point goes off?
>
> In addition, I gather from what you are saying that you are not really using
> xml is this workflow, but rather you are using that simply to display the
> values of the speed keyframes. Is that correct?
>
> ky
>
>
>> I want to overlay clips from recording devices that are free-running
>> (not jam-synched). Even though most of the clocks are pretty
>> accurate, these are clips of live events that last a long time and
>> over the course of many minutes it is not unusual for them to drift
>> apart from one another by an amount that needs to be corrected. Time
>> remap seems like a good mechanism to adjust things back into sync.
>> But the speed value only seems to be able to retain numbers up to a
>> precision of two decimal places. For example, enter 100.12345 in the
>> user interface and 100.133 is what gets stored in the XML, which is
>> not even rounded properly. The residual error over the length of an
>> hour can be hundreds of milliseconds, which is not acceptable for many
>> synchronization purposes.
>>
>> I can't figure out if this is an artifact of the user interface or
>> some fundamental limitation. Is there a sneaky way to specify a remap
>> speed with greater precision?
>>
>> Bruce
>
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