Black line when zooming on alpha image

lighthope wrote on 6/1/2012, 4:36 PM

Movie Edit Pro MX

I have inserted a bmp image. Name is in multi-colour blue. Background is green.

I have set the Chroma Key to green.

I have the image zooming in from 100 to 400 percent over a couple seconds.

As the image begins to move, a black line appears around the edge of the chroma'ed image. It only appears when the image is near to its original size.

I have uploaded the test file here so you can see what the problem is: www.dwad.net/test.wmv

Comments

johnebaker wrote on 6/2/2012, 7:41 AM

I presume you created the bitmap in image editing software - it looks like when the text was created it had a black border set - check that the text does not have a black border set as shown in this image

John

lighthope wrote on 6/2/2012, 12:58 PM

Hi

I presume you created the bitmap in image editing software - it looks like when the text was created it had a black border set - check that the text does not have a black border set as shown in this image

John

There was no black border in the original bmp file. As you saw in the video, the black border only appears for a short time. If the border was part of the image, it would appear all the time.

Also note that the sequece renders correctly in Movie Magic Pro 17. It is only in 18 where the problem surfaces.

terrypin wrote on 6/3/2012, 2:03 AM

Hi,

Is your MEP MX updated to the latest version, 11.0.5.0?

I'd been struggling with a rendering quirk (not present in MEP 17) until John asked me that same question. I was on 11.0.1.4, which I'd assumed was the latest, as I expected to get automatic notifications of updates. I installed 11.0.5.0 and my problem disappeared.

Otherwise, perhaps it's an aspect ratio issue. Backup your project with its media using File > Backup copy > Copy project and media into folder, and upload it as a ZIP so that we can study the detail. (Ideally just the fragment displaying the black line, to keep it small.)

--
Terry, East Grinstead, UK

johnebaker wrote on 6/3/2012, 3:04 AM

Anti-aliasing of the original text can also cause this problem with chroma key. The reason I asked about a border is because a 1 pixel wide border would only appear when the image approaches its original size as you said in the original post.

If the update as Terry has suggested does not make any difference, try this alternative

Rereate the text image at least double ( or 4x ) the resolution of your movie settings you originally used with a transparent background.

Add the text as large as possible.

Save the image as a png file - this will preserve the transparency of the background.

Import the png file into MEP - you do not need to use any chroma key as MEP recognises the image transparancy.

John