Video Overlays with Transparency

PAW wrote on 7/3/2003, 1:01 PM

Yow,

Just creating a video overlay with transparency, is the only option the render as uncompressed to keep the transparancy channel.

I have tried a couple of codecs but they seem to have a 32bit option but when I put the output on the Vegas timeline the background is black.

Any suggestions, I don't want to keep a load of huge uncompressed AVi's

Cheers, PAW

Comments

SonyEPM wrote on 7/3/2003, 2:30 PM
Enable the alpha channel in media properties- if the alpha channel is present, we should be able to use it. DV .avi does not support alpha fyi.
sdmoore wrote on 7/3/2003, 2:37 PM
Hi SonicEPM,

This sort of support request seems to come up fairly often and I've always wondered why, if Vegas detects the media has 32bit colour depth, does Vegas not activate the alpha channel by default?

Scott
PAW wrote on 7/3/2003, 3:16 PM
I have tried a number of ways to retain the alpha channel from a video composite without success

I have no problem using the alpha channel with stills .png etc

Perhaps my understanding is wrong

I create a piece of text in Boris/3D Studio

The display shows the background as transparent

I render the file and the only format to retain the alpha channel is 32bit uncompressed - big files and I want to do a lot of them :-[

Any of the codecs I choose seem to loose the alpha channel even though they appear to support alpha channels i.e the Intel Video 4.5 Codec has alpha channel options. Others refuse to encode the output.

Is it possible to encode/compress with an alpha channel or do you always have to use uncompressed?

If you can encode 32bit/alpha channel which is the codec to use and the options?

Thanks for the replies

PAW
sdmoore wrote on 7/3/2003, 4:14 PM
There is a compression setting on the Quicktime encoder which allows alpha - I think it's called something like 'Animation'

Scott
VIDEOGRAM wrote on 7/3/2003, 4:18 PM
Hi,

I often produce .mov files in 32 bits in AE with the animation codec.
Works fine when imported in V4. But it is done in AE and the resulting file is quite big.

Gilles
JohnnyRoy wrote on 7/3/2003, 4:20 PM
I have only been able to get a 32bit alpha channel to work with uncompressed video.

~jr
PAW wrote on 7/4/2003, 6:21 AM

Thanks for the input I have gone through the options and thought I would post it - it may help someone who does a search

Transparency in AVI - it has to be 32bit uncompressed to retain the alpha channel. A couple of the codecs give options for transparency but the encoded file ends up 24bit with no transparency channel. Not sure what the transparency options refer to in these codecs.

Boris Red - Using the Quicktime encoder and setting colours to millions+ retains an alpha channel and you get some compression. Vegas did not automatically pick up the quicktime alpha channel I had to right click the event and specify the alpha channel.

Cool 3D Production Studio can produce the uncompressed AVI and has the ability to use the quicktime encoder with the same results.

Serif ImpactPlus only has the uncompressed AVI option. There is a .stv format within Serif to create video transparencies but Vegas could not read this format.

Conclusion - quicktime is the best option for retaining alpha channels and give some compression to avoid huge AVI files.

Thanks, PAW
kalony wrote on 7/5/2003, 4:39 AM
hi...,

does someone know, how does it works with cinema 4d? i can choose the intel video 4.5 codec with alpha chanel, but if i render, there is no transparency in the avi.....what is wrong?
and the quicktime codec does not produce any video-files.
PAW wrote on 7/5/2003, 5:01 AM

I will make a wild guess here.

If your standard DVD stuff needs 16bits per sample it needs another 16bits for the alpha channel, the intel video can't encode 32bit - perhaps it can include an alpha channel if the video is 8bits per sample making 16 bits with the alpha channel - it definately can't make an AVI with transparency

The quicktime codec lets me choose animation type with millions of colours+ which generates an AVI with transparency, you do have to switch on the alpha channel within Vegas though

PAW
kalony wrote on 7/5/2003, 7:18 AM
thanxxx...this i understand....but my cinema 4d does not have this quicktime-codec...it just can render pics.....so i had try it with an imagesequenz, and render out from cinema 4d some targa-files, but by trying to import them into vegas i got en error-message cause of a wrong file-format....but vegas supports targa....hmmm...i dont know....i will try it later with an image sequenz built with psd-files....

kalony
PAW wrote on 7/5/2003, 7:38 AM

I was guessing with the bit stuff so I could be a mile off

You have to have the full version of quicktime installed to encode with it I think?

I would be suprised if a package like Cinema 4D did not support quicktime, don't know though

PAW
kalony wrote on 7/5/2003, 9:58 AM
ohh...sorry....i don`t have installed the full version of quicktime...this will be the mistake....so that in cinema is just a standard or a small version codec....i will look for this...thanxxx

kalony
PAW wrote on 7/5/2003, 10:47 AM

Quicktime does not usualy appear as a codec in the normal list in most apps, not sure about Cinema4D

Usually they have a specific quicktime option.

Have Fun, PAW
sbloombaum wrote on 7/5/2003, 7:25 PM
If your video is all nicely legal at black = 7.5 ire you can use "superblack" 0 ire as a matte color.

you can choose some heinous green color and stick that in your transparent areas and cut a matte with chroma. Of course there's some risk of the color shifting around with any compression.

BTW, I believe that the indeo codec only supports 1 bitdepth of transparency, not 8 bits of transparency like you'd expect.
JohnnyRoy wrote on 7/5/2003, 9:58 PM
> If your standard DVD stuff needs 16bits per sample it needs another 16bits for the alpha channel

Just to clarify any confusion here. Each channel is 8 bits. That’s 8 for Red, 8 for Green, 8 for Blue (making a normal AVI file 24bits) and 8 for alpha, which gives you 32 bits. So its 24bit RGB or 32 bit RGB+Alpha, and not 16 + 16. You did say it was a wild guess ...and it was. ;-)

~jr
PAW wrote on 7/6/2003, 3:12 PM

JohnyRoy thanks for the correction, you are right except for one thing.

According to documentation I have the Intel Indeo 5 codecs need 1 bit for alpha channel.

The thing I am struggling to get my head around is the codec offering the option of transparency but it not being available in Vegas.

I dont think it is an issue with either piece of software just my understanding

if it is 8 bits each for RGB plus one for Alpha thats 25?

Do these codecs only support 24bit encoding so you will never be able to encode truecolour with an alpha channel.

I am curious now to understand why it does not stack up.

Cheers, PAW
PAW wrote on 7/6/2003, 3:33 PM

Seth, just picked up your post about 1bit depth - thanks

Cinema4D does have qucktime option in render settings you can choose quicktime movie, type animation with millions of colours + which should retain the alpha channel.

PAW
JohnnyRoy wrote on 7/6/2003, 6:04 PM
Hmmm... I’ve never heard of just 1 bit depth for alpha but I guess that would be on or off (i.e., either something is background or not). The full 8 bits are needed to represent 256 shades of transparency (0 – 255).

~jr
mark30 wrote on 7/7/2003, 6:19 AM
I hope this might help..

I imported a .tif - file, with transparent background. Once it was in the mediapool it had a black background..
You can change this by changing the alpha-channel properties in th properties-tab under -> file. I think it was 'straight/unmatted' or something. Then the transparent background was back again..

Dunno if I understand your problem correctly, but hey.. hope it helps

gr
Mark