The "bento box" graphic during the presentation yesterday said AV1. From the press release:
The Media Engine of M4 is the most advanced to come to iPad. In addition to supporting the most popular video codecs, like H.264, HEVC, and ProRes, it brings hardware acceleration for AV1 to iPad for the first time. This provides more power-efficient playback of high-resolution video experiences from streaming services.
Does M3/M4 support AV1 encoding?
The "bento box" graphic during the presentation yesterday said AV1. From the press release: