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TTML PNG image captions scaled differently due to regions straddling segment boundaries #4839

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david-hm-morgan opened this issue Dec 14, 2022 · 2 comments · Fixed by #4841
Closed

TTML PNG image captions scaled differently due to regions straddling segment boundaries #4839

david-hm-morgan opened this issue Dec 14, 2022 · 2 comments · Fixed by #4841
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@david-hm-morgan
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component: captions/subtitles The issue involves captions or subtitles component: TTML The issue involves TTML subtitles specifically component: UI The issue involves the Shaka Player UI priority: P2 Smaller impact or easy workaround status: archived Archived and locked; will not be updated type: bug Something isn't working correctly
Milestone
v4.4

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@david-hm-morgan
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Have you read the FAQ and checked for duplicate open issues?
Yes

What link can we use to reproduce this?
https://v4-3-1-dot-shaka-player-demo.appspot.com/demo/#audiolang=en;textlang=sv;uilang=en;asset=https://otvplayer.nagra.com/demo/content/shakaPlayer/otvpl-3672/otvpl-3672-shorter.mpd;panel=CUSTOM%20CONTENT;build=uncompiled

What version of Shaka Player are you using?
v4.3.1-uncompiled

What browser and OS are you using?
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

What did you do?

Play the stream
Enable captions.
If necessary scrub back and forth between 00:00:06:26 & 00:00:07:29
Pay attention to the size of the PNG subtitles.

What did you expect to happen?
Consistent size and no gap (absence) between the cues showing the same PNG for time range.

What actually happened?

Image shown scaled at different sizes during its time span.

Analysis so far:
Images that appear in more than one consecutive segment are defined in equivalent but differently labelled regions.
As time progresses the earlier version of the label will be replaced but may linger around in the DOM and hence affect scaling of images.

image

image

History: works well in 4.1.2 but has regressed since, 4.3.1 worsens as we seem gaps of no captions in the timeline.
@david-hm-morgan
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I now understand the problem and why it regressed when it did.

Captions straddle the fixed segment boundary
one caption therefore has to be repeated in two boundaries
regions with size are allocated according to the number of lines of text in the image
6% for 1 line, 13% for two
in each segment the regions are defined freshly
but the ids of the regions are reused!
when segment 2's region 0 comes up to be rendered the code has assumed region 0 is the one it knows about already
image can appear wrongly sized
Before v4.1.3 the code separated regions uniquely and they were new every time and therefore correctly as requested.

In v4.1.3 a code change for dealing with regions regressed by letting what it believed were uniquely named regions linger for re-use.

image

@david-hm-morgan
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I am working on a fix

@avelad avelad added type: bug Something isn't working correctly component: TTML The issue involves TTML subtitles specifically component: UI The issue involves the Shaka Player UI component: captions/subtitles The issue involves captions or subtitles priority: P2 Smaller impact or easy workaround labels Dec 15, 2022
@avelad avelad added this to the v4.4 milestone Dec 15, 2022
@avelad avelad mentioned this issue Dec 15, 2022
Merged
avelad pushed a commit that referenced this issue Dec 15, 2022
@david-hm-morgan
fix: Treat regions uniquely (#4841)
5681efe 
Captions split over stream segment boundaries are repeated over more
than one segment.
Regions in which they sit maybe described the same but allocated
different ids and vice versa.
Proposal to treat internal region ids uniqely by encoding the dimensions
in the id.

fixes #4839
@github-actions github-actions bot mentioned this issue Dec 15, 2022
Merged
joeyparrish pushed a commit that referenced this issue Jan 13, 2023
@david-hm-morgan @joeyparrish
fix: Treat regions uniquely (#4841)
36a3a44 
Captions split over stream segment boundaries are repeated over more
than one segment.
Regions in which they sit maybe described the same but allocated
different ids and vice versa.
Proposal to treat internal region ids uniqely by encoding the dimensions
in the id.

fixes #4839
@github-actions github-actions bot mentioned this issue Jan 13, 2023
Merged
joeyparrish pushed a commit that referenced this issue Jan 13, 2023
@david-hm-morgan @joeyparrish
fix: Treat regions uniquely (#4841)
7952af9 
Captions split over stream segment boundaries are repeated over more
than one segment.
Regions in which they sit maybe described the same but allocated
different ids and vice versa.
Proposal to treat internal region ids uniqely by encoding the dimensions
in the id.

fixes #4839
@github-actions github-actions bot mentioned this issue Jan 13, 2023
Merged
joeyparrish pushed a commit that referenced this issue Jan 13, 2023
@david-hm-morgan @joeyparrish
fix: Treat regions uniquely (#4841)
1c63ab0 
Captions split over stream segment boundaries are repeated over more
than one segment.
Regions in which they sit maybe described the same but allocated
different ids and vice versa.
Proposal to treat internal region ids uniqely by encoding the dimensions
in the id.

fixes #4839
@github-actions github-actions bot mentioned this issue Jan 13, 2023
Merged
joeyparrish pushed a commit that referenced this issue Jan 13, 2023
@david-hm-morgan @joeyparrish
fix: Treat regions uniquely (#4841)
f893e78 
Captions split over stream segment boundaries are repeated over more
than one segment.
Regions in which they sit maybe described the same but allocated
different ids and vice versa.
Proposal to treat internal region ids uniqely by encoding the dimensions
in the id.

fixes #4839
@github-actions github-actions bot mentioned this issue Jan 13, 2023
Merged
Robloche pushed a commit to Robloche/shaka-player that referenced this issue Feb 8, 2023
@david-hm-morgan
fix: Treat regions uniquely (shaka-project#4841)
c737006 
Captions split over stream segment boundaries are repeated over more
than one segment.
Regions in which they sit maybe described the same but allocated
different ids and vice versa.
Proposal to treat internal region ids uniqely by encoding the dimensions
in the id.

fixes shaka-project#4839
@github-actions github-actions bot added the status: archived Archived and locked; will not be updated label Feb 13, 2023
@github-actions github-actions bot locked as resolved and limited conversation to collaborators Feb 13, 2023
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Assignees

@david-hm-morgan david-hm-morgan

Labels
component: captions/subtitles The issue involves captions or subtitles component: TTML The issue involves TTML subtitles specifically component: UI The issue involves the Shaka Player UI priority: P2 Smaller impact or easy workaround status: archived Archived and locked; will not be updated type: bug Something isn't working correctly
Projects
None yet
Milestone
v4.4
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fix: Treat regions uniquely david-hm-morgan/shaka-player
2 participants
@avelad @david-hm-morgan