Codecs Av01008m08 399 Opus 251 New Exclusive
av01.0.08M.08 / opus (251)
If you have ever enabled "Stats for Nerds" on a YouTube video, you may have noticed a cryptic string like . This sequence represents the cutting-edge technology YouTube uses to deliver high-quality video and audio while consuming as little data as possible.
Hardware
: Requires modern GPUs (RTX 30-series, RDNA 2) for smooth playback. Video Codec: 399 (AV1 1080p) codecs av01008m08 399 opus 251 new
hybrid of AV1 encoding parameters, YouTube itag numbers, and user annotation
codecs av01008m08 399 opus 251 new is not a valid codec – it’s a . Video Codec: 399 (AV1 1080p) hybrid of AV1
"The file uses AV1 (profile 0, level 8, main tier, 8-bit) at 399 kbps video, and Opus audio track 251. It’s newly encoded." From 2025 onward, expect to see av01
Hypothesis:
This string selects or describes an Opus audio stream (ID 251, codec opus) combined with an experimental video track av01008m08 , track ID 399, marked as new .
From 2025 onward, expect to see av01.0.12M.10 opus 251 (10-bit, level 12) as the new high-end standard. The string 399 will disappear, replaced by av1 + average bitrate in separate JSON metadata.