y0017566 schrieb:
> It would be great to use the 50 frame advantage of interlaced source instead
> of the progressive 25 fps which results in stuttering.

> During my learning process I've alwas tried to raise the qualitiy of the 
> source material (camera handling, in the past A/D, now easy with DV, no 
> transcoding/damaging of the original source material). Therefore I am 
> surprised of your suggestion.

Hello Chris,

certainly my goal wasn't to convince you that "progressive is better";
my intention was to set you on a route which is much more smooth and painless
especially for a beginner.

In an ideal world, it would be possible to shoot 4k 70 fps progressive
and the software would just handle it in a breeze. Well, dreaming ;-)

Working in interlaced and retaining the additional temporal information
only makes sense, if you have a suitable playback solution. Like, for example,
watching on a TV set or similar. If you have a suitable fast running LCD
computer monitor (or an CRT with 120Hz), and your X server is also running
with a suitable high frame rate, you can use Vlc to playback interlaced
footage with this higher framerate. To achieve that, use the deinterlace
methods "linear" or "bob" (are there any others which retain the higher
framerate?). Of course, there will be always a slight loss in sharpness
(because somehow we have to interpolate the missing lines to get the
progressive frames with the higher framerate for the display).
But -- at least for me -- the difference in terms of smooth movements
can be striking. Especially when the camera is moving laterally.


But the bad news is: cinelerra has not built-in specific support for
handling interlaced footage. As long as you just feed the material through
without applying effects, you can get along with cinelerra. But everything
which changes the position of the scan lines is apt to mess up interlaced
footage. This includes zooming and vertical panning, masks, any blurs,
moving titles, motion tracking and a lot more.

The only possibility to get past those problems (and retaining the additional
50i temporal information) is to use an intermediary project which runs with
the higher framerate (50fps in this case) and to use cinelerra's "frames to
fields" and "fields to frames" effects for conversion. The details of this
procedure are described in the online manual of the CV version. The catch
is, that you inevitably get one additional intermediary render step, you
need additional time and storage, and -- overall -- it can get quite an
organisational nightmare.

> And no, I doubt I don't understand the relationschip between interlacing and
>  concrete advantages in ReframeRT yet

if you use the ReframeRT in such a setup, i.e. in an project running with
50fps, and chained up *after* an "frames to fields" effect, then cinelerra
can make more smooth slow motion, because you have gotten 50 halfframes
of temporal information to work with, as opposed to just 25 full frames.

Cheers,
Hermann V

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