libobs: Add OBS_ENCODER_CAP_SCALING cap
#10951
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WizardCM
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Aug 11, 2024
This logic would previously have written any changed scale resolution set by the encoder in the `.get_video_info` callback back to the encoder, however this functionality was "broken" by 20d8779. In reality, this would have never worked with texture encoders or with GPU rescaling enabled, and probably would have had odd side effects for CPU rescaling, too. It's best just to remove this functionality.
Adds a new encoder cap which tells libobs that rather than scaling video frames in software, the encoder is capable of scaling them via its own (presumably more efficient) means. An encoder may implement this cap by comparing the VOI of its assigned `video_t` and the results of `obs_encoder_get_width/height()`. If the width/height values differ, then the encoder is being asked by libobs to self-scale, and the resolution in VOI will be the raw frame size, with the `...get_width/height()` being the intended output resolution of the encoder. It is important to note that GPU rescaling mode will take priority over self-scaling. If GPU rescaling is enabled, the encoder will never be asked to self-scale. This is useful for discrete hardware encoders, where they might have fixed-function video scaling logic that is highly efficient and fast. Additionally, this feature allows a hardware device which is encoding a full ABR ladder of tracks to be smart and only copy a video frame from GPU -> Host -> Device once for the entire ladder, rather than once for every track.
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OBS_ENCODER_CAP_SELF_SCALE capOBS_ENCODER_CAP_SCALING cap
WizardCM
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Description
Adds a new encoder cap which tells libobs that rather than scaling video frames in software, the encoder is capable of scaling them via its own (presumably more efficient) means.
An encoder may implement this cap by comparing the VOI of its assigned
video_tand the results ofobs_encoder_get_width/height(). If the width/height values differ, then the encoder is being asked by libobs to self-scale, and the resolution in VOI will be the raw frame size, with the...get_width/height()being the intended output resolution of the encoder.It is important to note that GPU rescaling mode will take priority over self-scaling. If GPU rescaling is enabled, the encoder will never be asked to self-scale.
Motivation and Context
This is useful for discrete hardware encoders, where they might have fixed-function video scaling logic that is highly efficient and fast. Additionally, this feature allows a hardware device which is encoding a full ABR ladder of tracks to be smart and only copy a video frame from GPU -> Host -> Device once for the entire ladder, rather than once for every track.
How Has This Been Tested?
Tested with a plugin of mine for the MA35D card. Frames received by the encoder are the normal output resolution of OBS, regardless of what the "scaled" size is (this change does not make the UI aware of self-scaling, so this requires custom encoder management).
Ubuntu 22.04
Types of changes
Checklist: