1. Tolerance margin for the sum of MO durations? (issue epub-specs#2093)

See github issue epub-specs#2093.

See github pull request epub-specs#2106.

Dave Cramer: we say the sum of the duration for each MO document should equal the total duration, but we've never specified a margin or tolerance for this.
… suggestion was that perhaps we should do so?.
… the suggestion was to allow 1 sec of tolerance before epubcheck would complain, to account for rounding errors.

Avneesh Singh: I think this is not controversial.

Ivan Herman: what I learned when I made tests, is that this value which is in the manifest is there to check the data.
… marissa has even suggested that this is unnecessary.

Ivan Herman: I can't say whether or not that is so, but if it is just for checking purposes, then allowing some rounding error is fine.
… not sure what the actual threshold should be, so for now I think 1 second is fine.

Zheng Xu (徐征): from what i've implemented, the duration is variable for different players on different platforms.
… so i wonder if this is even useful.

Avneesh Singh: regarding 1 second, i feel this is more than enough. Maximum 50 ms is what i've used in the past.
… for large audios (120 hours), a tolerance of 150 ms was enough.
… per my understanding, the purpose of stating this metadata is to allow RS to pull a "total duration" value into features like "you are 5 minutes into 12 total hours".

Brady Duga: can epubcheck just tell you the total duration value that should be in the manifest?.
… epubcheck can give you the right value, right?.

Matt Garrish: epubcheck is checking the total time, yes. I guess it could output that value..

GeorgeK: my recollection is that its difficult to calculate some of these things precisely, depending upon the compression that is being used, resulting in it being off by a smidgen in each file.
… so this type of tolerance seems absolutely fine, 1 second seems fine.

Ivan Herman: +1 to George.

Zheng Xu (徐征): as a RS I appreciate having the duration values for the whole book, and for each file.
… we use it as an indication of approximately where the user is, but it doesn't have to be that accurate.

Dave Cramer: i'm not hearing an argument against the 1 sec tolerance.
… it's obviously a useful piece of metadata for people reading the book.
… and having epubcheck able to tell if the sum = total is useful authoring tool, with 1 second tolerance.

Zheng Xu (徐征): +1.

Ivan Herman: +1.

Proposed resolution: Merge PR 2106, close issue 2093. (Wendy Reid)

Dave Cramer: +1.

Matt Garrish: +1.

Matthew Chan: +1.

Brady Duga: +1.

Masakazu Kitahara: +1.

Wendy Reid: +1.

Laura Brady: +1.

Avneesh Singh: +1.

Bill Kasdorf: +1.

Ivan Herman: +1.

GeorgeK: +1.

Zheng Xu (徐征): +1.

Ben Schroeter: +1.

Resolution #1: Merge PR 2106, close issue 2093.

Rick Johnson: +1.