# alphacombine

This element can combine a Luma plane from one stream as being the alpha plane of another stream. This element can only work with planar formats that have an equivalent format with an alpha plane. This is notably used to combine VP8/VP9 alpha streams from WebM container.

## Example launch line

     gst-launch-1.0 -v videotestsrc ! c. videotestsrc pattern=ball ! c.
         alphacombine name=c ! compositor ! videoconvert ! autovideosink

This pipeline uses luma of a ball test pattern as alpha, combined with default test pattern and renders the resulting moving ball on a checker board.

## Hierarchy

    GObject
        ╰──GInitiallyUnowned
            ╰──GstObject
                ╰──GstElement
                    ╰──alphacombine

## Factory details

Authors: – Nicolas Dufresne

Classification: – `Codec/Demuxer`

Rank – none

Plugin – codecalpha

Package – GStreamer Bad Plug-ins

## Pad Templates

### `alpha`

    video/x-raw:
             format: { GRAY8, I420, NV12 }
              width: [ 1, 2147483647 ]
             height: [ 1, 2147483647 ]
          framerate: [ 0/1, 2147483647/1 ]

Presence – always

Direction – sink

Object type – GstPad

### `sink`

    video/x-raw:
             format: { I420, NV12 }
              width: [ 1, 2147483647 ]
             height: [ 1, 2147483647 ]
          framerate: [ 0/1, 2147483647/1 ]

Presence – always

Direction – sink

Object type – GstPad

### `src`

    video/x-raw:
             format: { A420, AV12 }
              width: [ 1, 2147483647 ]
             height: [ 1, 2147483647 ]
          framerate: [ 0/1, 2147483647/1 ]

Presence – always

Direction – src

Object type – GstPad

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