Hi there,
Apple devices have issues on showing HLS top-positioning IMSC1 subtitles:
Once top-positioning subtitles are shown, the succeeding subtitles will not be shown any more after the position is changed.
e.g.
expected: bottom->top->top->bottom->bottom->top->...
but: bottom->top->top->nothing till the end.
Some test results are as follows quickTime : issues as above -- no subs shown after an entry is shown with the top position
safari: all entries are displayed at the bottom. But at least it continues to show subtitles after that.
tvOS: same as QuickTime
iOS: same as safari
Based on
https://developer.apple.com/documentation/http_live_streaming/hls_authoring_specification_for_apple_devices
IMSC1 subtitles (text profile only) It looks like HLS does not support IMSC1 styling.
Could anyone tell me whether Apple supports such a styling e.g. subtitles positioning?
If not, would Apple support it later?
IMSC1 is a W3C recommendation and the only TTML profile that is part of the CMAF specification. I would like to see that support.
The following is the sample subtitle:
<?xml version="1.0" encoding="utf-8"?>
<tt xml:lang="de" xmlns="http://www.w3.org/ns/ttml"
xmlns:tts="http://www.w3.org/ns/ttml#styling">
<head>
<styling>
<style xml:id="s1" tts:color="white"/>
</styling>
<layout>
<region xml:id="r1"
tts:extent="80% 20%"
tts:origin="10% 70%"
tts:textAlign="center"
tts:wrapOption="noWrap"/>
<region xml:id="r2"
tts:extent="80% 20%"
tts:origin="10% 10%"
tts:textAlign="center"
tts:wrapOption="noWrap"/>
</layout>
</head>
<body>
<div region="r1">
</div>
<div region="r2">
<p xml:id="sub48000" begin="00:00:48.000" end="00:00:49.769">
<span style="s1">26 Angestellte<br/>kamen bei dem Giftmüll-Skandal</span>
</p>
<p xml:id="sub48001" begin="00:00:49.929" end="00:00:52.000">
<span style="s1">in Washington Township ums Leben,<br/>über den ausgiebig berichtet wurde.</span>
</p>
</div>
</body>
</tt>
I appreciate for replies.
syt
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