Add VideoFrame.rotation

[lgeiger]

This adds a VideoFrame.rotation property which uses av_display_rotation_get to read the rotation value from DISPLAYMATRIX.

This exposes a wrapper around av_display_rotation_get allowing users to read the rotation value from the DISPLAYMATRIX.

Not sure if this is the most usable API but at least this brings back the ability to read display rotation information.

Fixes #1047
Closes #1629

[lgeiger]

Not sure if this is the most usable API but at least this brings back the ability to read display rotation information.

A more user friendly API would be #1676 but will be a breaking/behaviour change for some users.

[WyattBlue]

This API seems weird to me
Would frame.rotation be better?

[hmaarrfk]

This API seems weird to me
Would frame.rotation be better?

My understanding is that the rotation is now part of sidechannel data in MP4 streams.

[lgeiger]

My understanding is that the rotation is now part of sidechannel data in MP4 streams.

If I understand the FFmpeg documentation correctly, the rotation information is only part of the AVPacket side data (which PyAV doesn't expose yet) or part of the AVFrame side data.

I think frame.rotation would make sense not sure if there is a performance impact to reading the rotation for every frame. Maybe it would be more performant to have packet.rotation instead or in addition? Not sure whether this data can actually change from frame to frame or packet to packet in which case one could do some caching.

[lgeiger]

Would frame.rotation be better?

Done in 17b0b96

The mypy failure in tests/test_audioframe.py seems unrelated.