Add multitrack video dynamic bitrate support #12097
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Also reconfigure all grouped encoders on the same frame.
The bitrate interpolation points are sent in JSON configuration and need to be forwarded to `create_video_encoders()`. Also remove the `HandleIncompatibleSettings()` handler because there are no longer any incompatible settings.
The `amf_xxx_update()` functions for AVC, HEVC, and AV1 are unconditionally invoking Flush() and ReInit() even though this is not required in all situations. Changing the bitrate at least in CBR mode does not require the flush operation and can result in unaligned IDR frames across members of an encoder group. Do not flush the pipeline for CBR bitrate changes; instead, force an IDR to occur with the bitrate change.
Remove the locale strings that are no longer needed now that `HandleIncompatibleSettings()` is removed.
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Description
Dynamic bitrate (or DBR to keep it short), is a beta feature enabled via Settings -> Advanced -> Network -> "Dynamically change bitrate to manage congestion (Beta)" in the OBS GUI. This feature automatically modulates the video bitrate based on network bandwidth to avoid dropping frames. Support for DBR with multitrack video had been disabled in OBS while it was being tested in the TEB (Twitch Enhanced Broadcasting) beta program. This PR adds support for multitrack video dynamic bitrate.
Note that this PR depends on 2 previous PRs, due to a shared common function
HandleIncompatibleSettings()that requires changes in all 3 PRs:The dependent PRs were merged as of 2025.04.30 and this PR has been rebased against
master.Motivation and Context
Multitrack video sends several video streams in parallel hence uses more overall bandwidth than sending a single stream. In some cases the streamers' available uplink bandwidth is not adequate for multitrack video, so modulating the bitrate on each stream is needed.
How Has This Been Tested?
Testing of multitrack DBR has been occurring for several months in the TEB beta program. In addition, it has been locally tested with NVIDIA GPUs, AMD GPUs (9070XT and 7800XT), and Intel Arc A770.
NVIDIA GPUs work well with multitrack DBR.
AMD GPUs also showed issues with DBR, however this PR introduces changes that forces IDRs on the appropriate frame without needing to flush or reinitialize the AMF pipeline to solve the issues.
The Intel Arc A770 test revealed an issue:
The failure to reconfigure resulted in all streams ceasing to transmit data and an eventual hang of OBS which needed to be terminated with Task Manager. The multitrack DBR feature checks if the encoder supports reconfiguration (it looks for
OBS_ENCODER_CAP_DYN_BITRATE. It is possible that Intel Arc GPUs do not support reconfiguration but have the bit set. This requires further investigation and testing.Types of changes
Checklist: