Tip #701: How to Export an Alpha Channel
… for Codecs & Media
Tip #701: How to Export an Alpha Channel
Larry Jordan – LarryJordan.com
Alpha channels are not supported in H.264 or HEVC media.
The alpha channel determines transparency in a clip. However, no compressed codec supports alpha channels. Why? Because including the alpha channel makes a file really big!
Here, courtesy of RocketStock.com is a list of video codecs and image formats that support alpha channels.
Video Codecs and Image Formats with Alpha Channels
- Apple Animation
- Apple ProRes 4444
- Avid DNxHD
- Avid DNxHR
- Avid Meridien
- Cineon
- DPX
- GoPro Cineform
- Maya IFF
- OpenEXR Sequence With Alpha
- PNG Sequence With Alpha
- Targa
- TIFF
Be sure to test your codec before committing to a project. Not all versions of DNx or GoPro Cineform support alpha channels.
How does compressing the alpha channel affect the image.
and does this mean that even if a project is 422 one should do the master render to prores 444
to retain the alpha?
Mike:
You can’t compress the alpha channel. It is either there, or it isn’t. For example, ProRes 422 does not support (contain) an alpha channel. Only ProRes 4444 supports it (and ProRes 4444 XQ).
Larry