moq-wg / warp-streaming-format

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How does the client learn about group numbers and their relationship to media time and wallclock time? #22

Open wilaw opened 1 year ago

wilaw commented 1 year ago

The subscription hints allow a client to seek to an absolute group number. How would a WARP player discover absolute group numbers that it had not received?

One suggestion has been the addition of a timeline track. This track would supply an array of offsets of group number to media time and wallclock time. Group boundaries could supply the complete history and delta updates would supply relative changes. Payload would be binary. This schema allows for variable group durations.

// Group number, wall-clock time, media PTS
[
{0,1698351160362,0}
{1,1698353162,2002}
{2,1698355164,4004}
...
{3745,1705848650,7497490}
]

As a refinement we could consider two timeline tracks.

A player could start playback by subscribing to the "live edge" timeline and only subscribe to the complete timeline if it needed to build a scrub bar or seek.