Recognize ISO 13818-7 MPEG-2 object types for AAC.

[kinetiknz]

Object types sourced from https://mp4ra.org/#/object_types.

This addresses BMO 1722497. I included 0x66 as well, since that's listed in the above reference as another (uncommon) AAC object type.

Curiously, the 0x41 object type we've accepted since this code was first added isn't listed. I'm not sure where that value came from.

[baumanj]

Apologies for the very delayed review. The added code all looks good.

Curiously, the 0x41 object type we've accepted since this code was first added isn't listed. I'm not sure where that value came from.

Having looked through #38, I think it may be an oversight. Per the MPEG-4 spec (ISO/IEC 14496-1:2010) § 7.2.6.6.2:

0x40: Audio ISO/IEC 14496-3
0x41-0x5F: reserved for ISO use

I've also checked the 2 published amendments and they don't revise this range at all.

I tried changing the 0x40 to a 0x41 in this sample file, and that still works in Firefox, but it's rejected by Chrome, Safari and QuickTime Player, so I'm fairly confident that's an error on our part to accept it. I think we should probably remove the 0x41, but it might make sense to bring that change in at the beginning of the next nightly cycle (Nov 1) so we have ample time for it to show up if that code is being used in the wild.

Would you rather do that as a separate change?

[kinetiknz]

Thanks for looking into 0x41 further - I wasn't able to find any reference (including in the old stagefright code) suggesting it should be treated as anything but a reserved OTI. I've added a second commit to this PR to remove it. Merging after the next nightly cycle sounds like a great plan.