CRI Sofdec2  Last Updated: 2022-11-21 16:25 p
Alpha Movies
Sofdec2 data can contain alpha channel information.

You can encode video materials that include an alpha channel to create movies with transparency.
By combining this type of video with a background image and/or model data, you can create complex effects.

Material Files

The specifications for files used as video materials are generally the same as [video material files] .
To create an alpha movie, you need 32-bit video material data that includes 8-bit alpha channel information.


Video Materials Specifications
Item Details
File format AVI format video file
A file containing sequential numbered still images
Still image format BMP (Uncompressed), TGA (Uncompressed / run-length)
Color depth 32-bit color (ARGB8888)


Procedure for Creating Alpha Movie Data

  1. Run the Sofdec2 Encoding Wizard.

  2. Set the platform.

  3. On the [Specify Input Video Materials] page, specify a video file with an alpha channel.
    After specifying the file, select the [Alpha Movie] checkbox.
    Confirm that the color depth of the video material data is 32-bit.


  4. After you set the output destination and other encoding parameters, perform the encoding to create the alpha movie data.

[Remarks]
(a)
  • When creating Alpha Plus Movie, the average bit rate is about twice that of no alpha.
  1. Basically, it will try to encode by assigning 60% of the display bit rate value of user specification or automatic setting to the RGB part and 40% to the alpha part.
  2. In the automatic setting of H.264/VP9, try to encode by allocating the bit rate assuming H.264/VP9 codec for RGB part and Sofdec.Prime codec for alpha part. （The allocation is different from the case specified by the user)
  3. For the final compression ratio of the alpha part, adjust the image quality using "alpha_quality" option of the command line tool.

(b) You can use the Sofdec2 Viewer to preview any alpha movies you have created.


Playback

Refer to the "Alpha Movie" sample program for details on the rendering method required for alpha movie playback. (This sample is not included on some platforms.)