1054970 - Seeking fails to complete on MSE videos since landing of bug 1050652

Status: RESOLVED FIXED

(Core :: Audio/Video, defect)

Description

[cajbir (:cajbir)]

Since the landing of Bug 1050652 seeking on MSE videos no longer completes. Reverting the patch in that bug allows seeking to work again.

Steps to reproduce:

1) Make sure MSE is enabled
2) Visit URL http://cd.pn/mse/ytdemo/dash-player.html?url=http://cd.pn/mse/ytdemo/feelings2.mpd
3) When video starts playing, seek somewhere

Expected result:

4) Seek completes and playback continues

Actual result

5) Seek does not complete, but data shows as being buffered. Playback does not continue.

Comment 1

[bull500]

aren't bug id 1040552 and this similar cases?

Comment 2

[Matthew Gregan [:kinetik]]

Changing http://dxr.mozilla.org/mozilla-central/source/content/media/webm/WebMReader.cpp#1014 from CLUSTER_START to BLOCK_START will give you back the old behaviour (which is also broken, no idea how it ever worked, but...)

Comment 3

[Matthew Gregan [:kinetik]]

It looks like it was working before out of luck, mostly.  A block offset was passed to nestegg_seek_offset (which expects a cluster offset), and the parser would recover by skipping unexpected elements until it arrived at the next cluster.

With my changes from bug 1050652, nestegg_seek_offset is passed a cluster offset.  Unfortunately, the calculation of this offset was slightly off and resulted in the seek landing in the wrong position, from which the parser could not recover.  Fix coming up.

Comment 4

[Matthew Gregan [:kinetik]]

Attachment: WebM cluster offset calculation accounted for size of ID incorrectly.

The old implementation copied the block offset calculation, which adjusted
the offset by 1 byte (the length of the block element ID).  The cluster
element ID is 4 bytes, so the offset must be adjusted by that amount.

Comment 5

[Matthew Gregan [:kinetik]]

Oops, the landed got attributed to bug 1050652.

https://hg.mozilla.org/integration/mozilla-inbound/rev/59cc2ccbdd64
https://hg.mozilla.org/mozilla-central/rev/59cc2ccbdd64