An objection I have: metadata tags. Let me start with it. The Vorbis Comment structure has a framing bit. This is only used for the comment packet on Vorbis

An objection I have: metadata tags. Let me start with it. The Vorbis Comment structure has a framing bit. This is only used for the comment packet on Vorbis streams. Theora, Flac (and Flac native), and Speex do not use it. I'm not sure about Opus. The good point is that the rest is simple and relatively flexible. 4 bytes as a number of tags each with a 4 byte length. Definitely excessive and perhaps should have some flag for different versions. 1, 2, 3, and 4 byte lengths and count. Keys being limited in the spec to ASCII printable is a downside but since it's utf8, 0x3d (the equals sign =) would still work as the key-value separator. The spec also says that they should be case insensitive which would make the utf8 comparisons harder.