Unity’s Video Clip and Video Player components support alpha in video files, which is the standard term used for transparency.
Alpha transparency creates the appearance of semi-transparent or fully transparent areas in a video, which is important for visual effects and layering content over other elements. Alpha values are continuous: the lowest alpha value means an image is fully transparent, while the highest alpha value means the image is fully opaque. Intermediate values make the image partially transparent, which means you can view both the image and the background behind it simultaneously.
The Video Player component supports a global alpha value when playing its content in a cameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
See in Glossary’s near or far planes. However, videos can have per-pixel alpha values, which means that transparency can vary across the video image. This per-pixel transparency is not controlled in the Unity Editor, but in applications that produce images and videos such as NUKE or After Effects.
Unity supports only two codecs that have per-pixel alpha: Apple ProRes 4444 and WebM with VP8.
The Apple ProRes 4444 codec is a high-quality version of Apple ProRes for 4:4:4:4 image sources, including alpha channels. It provides the same level of visual fidelity as the source video. This codec typically produces large files, which increases storage and bandwidth requirements.
When importing a video that uses this codec, enable both the Transcode and Keep Alpha options by selecting the relevant checkboxes in the Video Clip Importer. Omitting the transcode operation leaves the ProRes representation in the Asset, meaning the target platform has to support this codec. Your operating system’s video playback software might have the functionality to identify which codecs your video uses.
During transcoding, Unity inserts the alpha into the color stream so it can be used with both H.264 or VP8.
Note: Apple ProRes 4444 is only supported on macOS. It typically appears in .mov files.
The WebM file format has a specification refinement that allows it to carry alpha information natively when combined with the VP8 video codec. This means that any Editor platform can read videos with transparency with this format.
Note: Most of Unity’s supported platforms use a software implementation for decoding these files, so they don’t need to be transcoded for these platforms. However, Android’s native VP8 support doesn’t include transparency support, so you must enable transcoding so Unity uses its internal alpha representation.