[Kdenlive-devel] Slomo test

[Dan Dennedy]

On Wed, Dec 12, 2012 at 9:46 AM, Dan Dennedy <dan at dennedy.org> wrote:
> Hi Evert, I made a change in MLT to fix the frame rate override.
> However, it does not automatically change the duration of the clip
> accordingly and requires a funky MLT XML workaround. It will not be
> possible to make it automatically adjust the duration within the
> framework or plugin due to a design limitation. You see, the duration
> is computed when the ffmpeg object is created, but it does not know
> the new frame rate at that time! The new frame rate is supplied as a
> property after the object is created. Therefore, the app needs to make
> this duration adjustment when the user overrides the frame rate.

JB,
I made a change in the MLT framebuffer producer to do this
automatically if the real producer's fps is greater than the profile's
fps. So, it now comes for free when using the Kdenlive speed effect.
:-) However, if someone overrides the frame rate in the advanced clip
properties, then perhaps consider to adjust the duration. Or not: one
can argue the overrides are to fix mis-detected things, and the
duration just comes from libavformat duration, which may or may not be
computed from the fps.

> In the meantime, here is what you can do (after updating mlt from git master):
>
> 1.) melt gopro.mp4 force_fps=60 -consumer xml | grep length
> 2.) do the math: new_length = length * (native_fps / force_fps).
> For the file you provided, new_length = 925 * (240/60) = 925 * 4 = 3700
> 3.) supply the new value to melt to create a MLT XML wrapper:
> melt gopro.mp4 length=3700 out=3699 -consumer xml:gopro.mlt
> (Out is always one less than duration and must be provided when
> overriding the duration.)
>
> Now you can use gopro.mlt like a clip with either melt or kdenlive.
>
> On Sat, Nov 3, 2012 at 12:09 PM, Evert Vorster <evorster at gmail.com> wrote:
>> Ah, great.
>>
>> I was not aware that you were out of town, and mistakenly assumed that you
>> had forgotten about the footage.
>>
>> Hope you are having a great weekend!
>> -Evert-
>>
>>
>>
>> On 3 November 2012 20:48, Dan Dennedy <dan at dennedy.org> wrote:
>>>
>>> I made some quick tests while I was out-of-town. I am not sure at this
>>> time what the effort it. I will be looking into it over next week.
>>>
>>> On Sat, Nov 3, 2012 at 2:00 AM, Evert Vorster <evorster at gmail.com> wrote:
>>> > Hi there, Dan...
>>> >
>>> > Have you had a look at that 240fps footage I sent to your ftp server?
>>> >
>>> > How much work would it be for kdenlive to be able to support slowing
>>> > down
>>> > such footage natively without me having to mess with ffmpeg?
>>> >
>>> > Kind regards,
>>> > -Evert-
>>> >
>>> > --
>>> > Those who do not understand UNIX are doomed to reinvent it, poorly.



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