Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Clarify leb128 padding limit #817

Closed
jwcullen opened this issue May 16, 2024 · 1 comment
Closed

Clarify leb128 padding limit #817

jwcullen opened this issue May 16, 2024 · 1 comment

Comments

@jwcullen
Copy link
Collaborator

In a draft version of the spec we used normatively reference AV1 to define leb128.

This was changed in https://github.com/AOMediaCodec/iamf/pull/558/files to bring in an explicit definition. Later a NOTE was added to clarify that "leading zero bytes" are allowed.

It seems like an oversight that we are missing a limit on the amount of zero-padded bytes.

It is a requirement of bitstream conformance that the most significant bit of leb128_byte is equal to 0 if i is equal to 7. (This ensures that this syntax descriptor never uses more than 8 bytes.)

The benefit of allowing zero-padded bytes is to allow certain use-cases to leave leb128s blank, but fill them in arbitrarily later. But it seems prudent to limit the amount of zero-padded bytes. I think we intended this, but it was just missed in review.

I suggest adding language similar to the AV1 quote above to the IAMF definition of leb128().

@shawnisingh
Copy link

+1 that we need to clarify the limit to be 8 bytes or similar limit

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

No branches or pull requests

2 participants