Better video for mobile RTC with AV1 and HD

This post details Meta's adoption and implementation of the AV1 video codec for real-time communication (RTC) across its apps (Messenger, Instagram, WhatsApp). It highlights the challenges of improving video quality for low-bandwidth users and the benefits of AV1 over older codecs like H.264. Key technical contributions include: custom video scalers that improve quality over default WebRTC scalers, region-of-interest encoding to prioritize important visual areas, and the use of AV1's royalty-free nature and software encoding capabilities for RTC scenarios where hardware encoders are not optimized. The post also discusses AV1's specific features beneficial for RTC, such as palette mode and intra-block copy for screen content, and reference picture resampling (RPR) to avoid costly key frames during resolution changes. It addresses the trade-offs of AV1's higher CPU/battery usage and outlines strategies for seamless codec negotiation and switching.