Details dictionary parameters description could be more precise

[youennf]

The seekOffset dictionary member is the time in seconds to move the playback time by. If present, it should always be positive.

Should we change should always to MUST?

The fastSeek dictionary member will be true if the seek action is being called multiple times as part of a sequence and this is not the last call in that sequence.

The sentence is not mandating to use false (or undefined?) for the last call in the sequence.
We have true, false and undefined possible values.
Should we only have true and false and make the member required?

[chrisn]

For seekOffset, changing to a MUST sounds reasonable. Why would an implementation provide a zero value?

For fastSeek, in which circumstances might this member not be present? The current spec language suggests it's always present so should indeed be required.