During March 2026, Guangyu Sun focused on stabilizing VP9 encoding colorspace handling in the ossrs/ffmpeg-webrtc repository, addressing a nuanced edge case involving non-RGB pixel formats. Working in C, he implemented a targeted bug fix that ensures decodable output when AVCOL_SPC_RGB is present with YUV formats, aligning 4:4:4 RGB data handling with existing GBRP logic. His approach introduced explicit error signaling to prevent silent mis-encodes, improving both reliability and developer feedback. This work demonstrated a deep understanding of codec development and video encoding, enhancing FFmpeg’s internal color management and maintainability without introducing new features during the period.