add recommendation to use the 1+9 pattern

AOMediaCodec / av1-isobmff

Official specification of the AOM group for the carriage of AV1 in ISOBMFF

https://AOMediaCodec.github.io/av1-isobmff

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add recommendation to use the 1+9 pattern #110

Closed cconcolato closed 5 years ago

cconcolato commented 5 years ago

This PR addresses a comment made in #109. This is an initial proposal to recommend the use of 1+9 over other patterns.

agrange commented 5 years ago

Would this reduce validation tests at all? If all other patterns are optional (MAY) then presumably they still have to be tested?

alexismt73 commented 5 years ago

We would recommend the following text:

"When the protected scheme cbcs is used, samples SHALL be protected using subsample encryption and SHALL use pattern encryption. [CENC] recommends that the Pattern Block length be 10, i.e. crypt_byte_block + skip_byte_block = 10. The combination [crypt_byte_block:skip_byte_block] SHALL be from the set {[1:9], [5:5], [10:0]}. The combination [1:9] SHOULD be used."