OBS Studio is dropping support for Nvidia's first generation of GPUs, which featured hardware GPU encoding support. The latest version of the streaming and recording software, 31.0.0 Beta 1, no longer works with GTX 600 and 700 series Kepler GPUs.
The developers behind OBS did not give a reason for dropping Kepler GPU support, but it was inevitable that this would happen at some point. Three years ago, Nvidia dropped driver support for the Kepler-powered GTX 700 series lineup, making software compatibility with the ancient GPU architecture rather pointless for modern-day applications.
The Kepler GPU architecture was Nvidia's first-ever GPU design to integrate an NVENC encoder engine, and it was equipped with a hardware accelerator. Kepler featured Nvidia's first-generation NVENC engine, capable of only encoding in H.264. It wasn't known for being a super high-quality encoder and was often outperformed by software-based encoders that operated on the CPU. It was also very limited in features, only supporting Chroma 4:2:0 and lacking a lossless encoding option. Regardless, it laid the groundwork for future NVENC encoders to compete with software encoders in terms of quality and features.
If you are one of the few people still operating a GTX 600 or 700 series card for encoding purposes, prior versions of OBS Studio still support the NVENC encoder on Kepler-based GPUs.
OBS Studio 31.0.0 Beta 1 adds many new features and changes to the streaming/recording application, including new Nvidia blur, background filters, and first-party YouTube chat features. Nvidia-specific changes include a refactored NVENC implementation with various improvements. SDK 12.2 features such as split encoding, B-Frames references, and Target Quality VBR mode from old SDKs are now supported. This NVENC refactoring could be why Kepler support was stripped, but we can't be sure.