mac-videotoolbox: Add service-requested low latency rate control - #2
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ghbogarin wants to merge 1 commit into
Open
mac-videotoolbox: Add service-requested low latency rate control#2ghbogarin wants to merge 1 commit into
ghbogarin wants to merge 1 commit into
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Description
Adds support for VideoToolbox's low latency rate control (
kVTVideoEncoderSpecification_EnableLowLatencyRateControl) to the Apple H.264 and HEVC hardware encoders.The mode is not exposed in the UI. It is requested programmatically through a hidden
low_latencyboolean registered on the encoder's property list, so a service can opt its encoder into it fromapply_encoder_settings.When it is requested,
create_encoderasks VideoToolbox for the low latency counterpart of the selected encoder withVTCopySupportedPropertyDictionaryForEncoder(the.rtvcvariant) and builds the session against that encoder ID rather than overriding the user's encoder selection.Motivation and Context
The Apple encoders currently target throughput and quality. Low latency rate control disables the encoder-side buffering and frame reordering that the default configuration relies on, which is what real-time delivery needs, at the cost of some compression efficiency, which is why it should not be turned on globally by default.
This change is