Add SEI with resolution payloadType 5 based on H264 specification (Us…

[bruce1i]

This PR will parse SEI with resolution payloadType 5 based on H264 specification. Now you can write custom data to H264 and get it from 'Hls.Events.FRAG_PARSING_USERDATA' event.

Why is this Pull Request needed?

A: User can get custom data from SEI. It's especially useful in live streaming.

Are there any points in the code the reviewer needs to double check?

A: No.

Resolves issues:

A: Just add a SEI parsing rule.

Checklist

• changes have been done against master branch, and PR does not conflict

[michaelcunningham19]

Hey @bruce1i !
Thanks for the contribution, this looks like it could be very useful!

Would you be able to provide either a test stream containing custom data, or some code snippets of how you're inserting data into a stream?

As an aside, I'd like to hear from other collaborators on their thoughts of incorporating additions like this to the core library. Thinking about bundle size and modularity, it may be beneficial to explore emitting helpers alongside with the main code bundle

[bruce1i]

Hey @michaelcunningham19 !
Thanks for the reply.

1. Test stream containing custom data.
A: "https://devstreaming-cdn.apple.com/videos/tutorials/App_Store_Connect_Basics/hls_vod_mvp.m3u8" is I found from the apple website and it contains custom data. The screenshot is below.

2. Some code snippets of how you're inserting data into a stream.
A: I can't. It's difficult for me to insert custom into a stream. The back-end colleague does this in the server according to the H264 specification. I just parse this according to the rule from H264 specification. It's work well for me and also works well for all that insert sei according to the rule of H264 specification.

My purpose

1. Why I commit this PR.
A: The first one is my encounter and the user data unregistered SEI message is a high frequency of use.
I have a requirement to get SEI from a live stream, then I found hls.js that has 'Hls.Events.FRAG_PARSING_USERDATA' event which can parse SEI. I'm so glad, but happiness is short. Because the event cannot be triggered. I googled for what I miss, I can't find the answer. Then I saw the source code, I found the TODO comment, so I fork the code and add the parse rule. I thought it's useful for other people who have the same requirement.

2. The bundle size.
A: SEI has a lot of rules. If we add it all, the size will become bigger and bigger. I don't think we will add all rules to the core library. But some high-frequency rule maybe can add it. Or is there a place that people can find how to get SEI and people can reuse the code.

[bruce1i]

Hi @michaelcunningham19 @johnBartos , Is there any new progress or conclusion?

[iamzhouyi]

Any further progress for this PR? I encountered same issue with hls.js as well.
Be happy to see it's merged

[johnBartos]

@bruce1i @iamzhouyi Sorry for the delay - LGTM