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.
: The highly efficient open-source audio codec optimized for interactive speech and high-fidelity music.
: Identifies the Main Profile . This configuration supports 8-bit or 10-bit YCbCr 4:2:0 chroma subsampling, covering standard consumer media.
: Supported by all modern browsers and Android. 💡 Why this combination? codecs av01008m08 399 opus 251 new
But what do these technical identifiers actually mean? This article breaks down the video stream and the Opus (251) audio stream to understand why they are the "new" standard for streaming high-quality content efficiently. What is av01.0.08M.08? (The Video Codec)
On older hardware or with outdated drivers, AV1 might not be accelerated by the GPU. This forces the CPU to decode the video, resulting in stuttering, especially on 25fps or 30fps content.
is an open-source, royalty-free video coding format designed specifically for video transmission over the internet. It is developed by the Alliance for Open Media (AOMedia), a consortium including Google, Amazon, Apple, Netflix, and others. Breaking Down the Identifier av01.0.08M.08 av01 : Identifies the codec as AV1. From 2025 onward, expect to see av01
ffprobe -show_streams -select_streams v video.mp4 | grep codec_name
These strings represent the pinnacle of open-source, royalty-free media compression. Together, they enable platforms like YouTube to deliver crisp 4K resolutions and high-fidelity audio while minimizing data usage. Understanding Video Format: av01.0.08M.08.399
When the system selects "399," it is prioritizing efficiency. It is saying, "Give this user the best possible visual fidelity with the least amount of data," saving the server money and saving the user buffering time. : Identifies the Main Profile
: The final two digits specify the bit depth . Here, the 08 means the video uses 8 bits per color channel. An 8-bit video is perfectly standard, capable of displaying over 16 million colors.
The second half of the string, , identifies the audio stream. Opus is widely considered the best lossy audio codec for the modern internet. Difference between 251 Opus and 141 mp4a? : r/YoutubeMusic
bcrescimanno commented. bcrescimanno. on May 3, 2022. Author. Codecs av01.0.08M.08 (399) / opus (251) 👍 1. New high audio quality format for Premium users (774 Opus)
The importance of AV1 was highlighted in a real-world user scenario on a Mozilla support forum. A user reported video decoding issues on Firefox Nightly, tracing the root cause to the av01.0.08M.08 codec. The temporary solution involved forcing the browser to use H.264 instead. This case study demonstrates a crucial point: as modern codecs like AV1 are rolled out, they can sometimes encounter hardware or software compatibility issues on the cutting edge. It's a reminder that the shift to new technology is an ongoing process.