Render a 50fps project at 25fps

Tue Oct 24 11:47:57 UTC 2017

Hi,

Thanks again for these detailed information!
Evert, I have not received the mail mentioned by Harald (that's why you
may thing I am ignoring it), it is not in the archive of the list
neither, can you resend it?

Can't we render directly at 25fps from kdenlive (and from a 50fps
project)? It uses to be possible (from the link of my first post),
generating bug as well?

Regards,
Cyril

Le mardi 24 octobre 2017 à 13:06 +0200, Evert Vorster a écrit :
> Hi there, Cyril. 
> 
> I can describe the bug to you, and then you can decide whether you
> want to take your chances with it. 
> Kdenlive uses frames to refer to certain points in the video, as well
> as the associated clips. 
> 
> Say you have a clip of you playing fetch with a dog that is 2000
> frames long, and encoded at 50fps. 
> 
> If you read that clip into a project that is only 25fps, kdenlive
> would then do some behind the scenes math and present the clip to you
> as only 1000 frames, with every second frame dropped. 
> This is to preserve the original length of the clip, and make editing
> easier. It's all good and well, and the right thing to do. 
> 
> The problem comes in when you start your project with one framerate,
> and loaded your clips, and then change to another framerate. 
> The clips in the project are re-read and updated to have the right
> amount of frames for the new framerate, but the starting end ending
> points of the clips on the timeline are not. 
> 
> To put this into the example of the clip with the dog playing
> fetch.... Let's assume that at 50fps from frame 1500 to 1800 the dog
> is catching the ball. You select this range, and put it on the
> timeline.
> At the lower framerate, the catching of the ball should happen at
> frame 750 to 900, right? The timeline never updates that start and
> end frame are never updated. 
> In this case it would refer to frames that does not even exist in the
> clip at the new framerate. In all cases it changes the _content_ of
> the clips, so at best you will be looking at another part of the clip
> in the final render than the part you selected.
> 
> I highly recommend against changing a project's frame rate at this
> point in time. 
> 
> Here is the latest bug in the bug reporter:
> https://bugs.kde.org/show_bug.cgi?id=368962
> 
> Kind regards,
> -Evert-
> 
> 
> On 24 October 2017 at 12:37, harald.albrecht <harald.albrecht at gmx.net
> > wrote:
> > Yes, and no. As Evert pointed out, there's currently a bug in the
> > timeline handling that sometimes causes issues (but not always as
> > far as I understand, but I may be wrong here). The safest approach
> > is as Evert suggested to render at 50fps and then use ffmpeg for
> > post-processing to drop every second frame.
> > 
> > Best regards,
> > Harald
> > 
> > 
> > -------- Ursprüngliche Nachricht --------
> > Von: Cyril Duveau <linux4cyril at free.fr>
> > Datum: 24.10.17 10:12 (GMT+01:00)
> > An: kdenlive at kde.org
> > Betreff: Re: Render a 50fps project at 25fps
> > 
> > Hello Harald,
> > 
> > Thank you for your detailed response.
> > Just to be sure, I can do that change while all my files are loaded
> > and
> > I am ready to render?
> > Once I have the settings at 25fps, could I go back to 50fps the
> > same
> > way (HD 1080p 50 fps)?
> > 
> > I want to perform tests to see if it is really worth rendering at
> > 50fps
> > or if 25 is enough...
> > 
> > Thanks & Regards,
> > Cyril
> > 
> > Le lundi 23 octobre 2017 à 21:08 +0200, Harald Albrecht a écrit :
> > > Cyril,
> > > you don't mention the other project settings, so I need to guess
> > to
> > > some extend; I'm assuming FullHD for the moment. In the Project >
> > > Project Settings... dialog, set the "Fps" drop down to 25 so you
> > > don't need to sift through all the many profiles. In the list,
> > open
> > > the "Full HD 1080", so you see (assuming that no filter is set
> > for
> > > scanning) two entries: HD 1080i 25 fps, as well as HD 1080p 25
> > fps.
> > > Select the second one (HD 1080p 25 fps), click "Ok". Done.
> > > 
> > > Best regards,
> > > Harald
> > > 
> > > Am 23.10.2017 um 12:38 schrieb Cyril Duveau:
> > > > Hi,
> > > > 
> > > > I would like to produce a video at 25fps from footage at 50fps.
> > > > The project settings are for 50fps, that's the rendering
> > profile
> > > > for
> > > > exporting that I don't know where/how to specify the fps.
> > > > 
> > > > I found this but I can't find how to adapt it to the new
> > system:
> > > > https://forum.kde.org/viewtopic.php?f=272&t=124869#p329129
> > > > Can you help?
> > > > 
> > > > Thanks,
> > > > Cyril
> > >  
> 
> 
> 