mpeg2 and transparency

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ADBest
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Location: Sunderland

mpeg2 and transparency

Post by ADBest »

Having tried very hard to solve the following problem myself I am hoping that someone will point out where I am going wrong. I am using Adobe Premiere CS5.5.

I wish to create a graphic, (of simulated smoke), by defining the shape of the smoke envelope, copying it and then painting, (in Photoshop), two different pictures of the smoke.

These two versions of the smoke envelope are then played alternately in 5 frame clips on the time line for the time required.

If I now place a colour matte on a time line below the alternating smoke clips to check that the smoke behaves as I wish it to behave; and it does.

I then remove the colour matte because I wish to ‘export the media’, with the smoke on a transparent background, and import it into another project.

I export as an mpeg2 file but when I import it into the other project the transparency is lost and the smoke plays on a black background which, of course, defeats the object of the exercise.

There are other ‘workarounds’, which I have adopted, but I would like to understand why the more elegant approach did not succeed.

Arthur Best

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TimStannard
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Re: mpeg2 and transparency

Post by TimStannard »

ADBest wrote: I export as an mpeg2 file
I think that's your problem, Arthur. MPEG-2 does not support alpha channel (or transparency).
You'll need to export in a format that does (I'm not sure what Premiere offers)

Alternatively, you could make the bits you want transparent all one colour and then chroma key out that colour when editing.
Tim
Proud to be an amateur film maker - I do it for the love of it
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ADBest
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Location: Sunderland

Re: mpeg2 and transparency

Post by ADBest »

Thanks Tim

I have had a similar problem when importing stills with transparency. I know that there are several formats, including .psd, that will retain transparency but I don't know the equivalent video format.

Premiere has 23 different 'export media' options but I don't know which, if any, will retain transparency for a video file.

I suppose, in extremis, I could try them all but if anyone knows the answer it could save me from a long boring exercise.
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ADBest
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Re: mpeg2 and transparency

Post by ADBest »

The Chroma key solution worked fine - but it's a bit of a work-around.
If I stumble on an elegant solution I'll share it.

Thanks for your suggestion.
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TimStannard
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Re: mpeg2 and transparency

Post by TimStannard »

I tend to use uncompressed DV when i need to do it, but this does produce very large files. (Not a problem as they are only ever intermediate)
Tim
Proud to be an amateur film maker - I do it for the love of it
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