Media Signing SEIs and MP4 BMFF format

[bjornvolcker]

There has been discussions and concerns about Media Signing and how to store the SEIs in an MP4 file. Since it is crucial that the SEIs are kept in order, could it jeopardize the feature?

It is described in the ISO/IEC 14496-15 specification that (some) SEIs shall not be part of the AVC video elementary stream. This only applies to some types of SEIs, namely sub-sequence, layering and filling data SEIs. The SEI type Media Signing uses is not part of these types.
Note that there are 53 different types of SEIs.

The order of SEIs is that they should be right before video coding units (slices). This is fulfilled if following the guide in the open-source repository.

Comment: I added this issue to track the discussions and document my answers in case it is brought up again. I read the 2017 version and I can of course have misunderstood things, but from what I understand there is no issue with adding the Media Signing SEIs in-band as is.

[bjornvolcker]

Note that SEIs are allowed to be placed in various ways.

[bjornvolcker]

I've also talked to an expert group at Canon and they confirmed that SEIs (part from the explicit types) are allowed in the bitstream. Both PREFIX and SUFFIX SEIs.

[sujithhanwha]

Agree with @bjornvolcker, since the media signing SEI type does not fall into the restricted types (Sub-Sequence, Layering and Filler data), I don't see any issue with storing it in-band with video.