revid-cli: combine intra refresh period and PSI interval into one parameter

[Saxon Milton]

This could be named RefreshPeriod and it's units will be seconds. If we insert PSI before each I-frame then RefreshPeriod will control both I-frame frequency and also PSI frequency.

[Alan Noble]

And to clarify, a ClipDuration can contain multiple RefreshPeriods.

[Saxon Milton]

So you would like to allow for multiple PSI in clips ? or are you saying we can have some SPS, PPS, IDR without PSI before hand, and PSI only denotes the start of a clip ?

[Alan Noble]

Yes, if ClipDuration > RefreshPeriod, it makes sense to allow multiple PSIs per clip.

[Alan Noble]

In particular, each PSI within clips containing multiple ones must contain an accurate timestamp (i.e., not just the timestamp at the start up the clip.) This is important because VidGrind will most likely continue to write MTS to the datastore at per-second granularity regardless of the duration of the received clips.

[Saxon Milton]

So vidgrind will still write to 1-second granularity even if the IDR period (and hence also the PSI period) is > 1 second ?

[Alan Noble]

Yes, I would like to reserve the option of decoupling the datastore clip duration from the received clip duration. In practice, they may be identical most of the time. I’m still not sure what the right refresh period should be.

[Saxon Milton]

Addressed in PR #240