[CinCV] Difference key + motion tracking

[Nicolas Ecarnot]

Hi there,

It's been a long time I wanted to use both diffkey and tracking to play
with a cute effect :

I was wondering : as transparency exist as alpha channel in static
picture (gif, png...), does the same exist in videos?
I mean, I'm using transparency every time I'm playing with Cinelerra,
but once my video is rendered, I guess the resulting file has lost any
transparency information... (or not? I don't know?)
And if this could exist, can Cinelerra re-import a video with an alpha
channel ?

I'm asking that because the video show here was a mini-struggle, and
could have been much easier to produce step-by-step, with intermediate
transparency-capable files...

[David Armstrong]

Nicolas,

I have created some "motion graphics" with 'PNG Alpha' codec, and then
applied that over another video.
But that was with graphical shapes and text.
But have not done that with a moving life-like image.

cheers
David

Post by Nicolas Ecarnot
Hi there,
It's been a long time I wanted to use both diffkey and tracking to
http://youtu.be/WeQEG_UNnng
I was wondering : as transparency exist as alpha channel in static
picture (gif, png...), does the same exist in videos?
I mean, I'm using transparency every time I'm playing with Cinelerra,
but once my video is rendered, I guess the resulting file has lost any
transparency information... (or not? I don't know?)
And if this could exist, can Cinelerra re-import a video with an alpha
channel ?
I'm asking that because the video show here was a mini-struggle, and
could have been much easier to produce step-by-step, with intermediate
transparency-capable files...

[Burkhard Plaum]

Hi,

Post by Nicolas Ecarnot
Hi there,
http://youtu.be/WeQEG_UNnng
I was wondering : as transparency exist as alpha channel in static picture (gif, png...), does the same exist in videos?
I mean, I'm using transparency every time I'm playing with Cinelerra, but once my video is rendered, I guess the resulting file has lost any transparency information... (or not? I don't know?)

It depends on the codec. Typical (end-user) video codecs have no alpha channel.
But movs with png codec have alpha support.

Burkhard

[Nicolas Ecarnot]

Post by Burkhard Plaum
Hi,

Post by Nicolas Ecarnot
Hi there,
It's been a long time I wanted to use both diffkey and tracking to
http://youtu.be/WeQEG_UNnng
I was wondering : as transparency exist as alpha channel in static
picture (gif, png...), does the same exist in videos?
I mean, I'm using transparency every time I'm playing with Cinelerra,
but once my video is rendered, I guess the resulting file has lost any
transparency information... (or not? I don't know?)

It depends on the codec. Typical (end-user) video codecs have no alpha channel.
But movs with png codec have alpha support.
Burkhard

Hi there,

I've just finished this simple test :

- from a common video, add a mask to dig a transparency hole in the
middle of the area
- export it into mov for linux, with the png+alpha compression (*this*
is the trick)
- the resulting video will be played in vlc with no visible hole

BUT

- loading it in another cinelerra project, and putting it in front of
another video will show the transparency hole !!!!!!!!!!!!

GREAT, a new effect world is opening to me !!!

[Nicolas Ecarnot]

Post by Nicolas Ecarnot

Post by Burkhard Plaum

Post by Nicolas Ecarnot
I was wondering : as transparency exist as alpha channel in static
picture (gif, png...), does the same exist in videos?
I mean, I'm using transparency every time I'm playing with Cinelerra,
but once my video is rendered, I guess the resulting file has lost any
transparency information... (or not? I don't know?)

It depends on the codec. Typical (end-user) video codecs have no alpha channel.
But movs with png codec have alpha support.
Burkhard

Hi there,
- from a common video, add a mask to dig a transparency hole in the
middle of the area
- export it into mov for linux, with the png+alpha compression (*this*
is the trick)
- the resulting video will be played in vlc with no visible hole
BUT
- loading it in another cinelerra project, and putting it in front of
another video will show the transparency hole !!!!!!!!!!!!
GREAT, a new effect world is opening to me !!!

Hi,

Today, i'm trying to play with these transparent movies I'm importing
into Cinelerra, and there's a point I'm missing.

When I create a transparent video from Cinelerra (for example, using a
mask and "transparenting" a part of the picture) and export it, I can
use it in another Cinelerra project and its transparency is respected.

Now I'm creating another transparent video from Cinelerra that is using
a transparent .png image.
When importing this video into another Cinelerra project, the
transparency has gone.


Seems like the only transparency being respected/recorded is the one
coming from the Cinelerra masks, or at least the one that was "produced"
by Cinelerra.


Has anyone ever noticed that?