Implement tick duration support for TTML subtitles #26

rrooij · 2020-08-27T21:08:46Z

I tested it with some examples and it should work. For instance, you can take the example Netflix subtitles:

<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/ns/ttml" xmlns:tt="http://www.w3.org/ns/ttml" xmlns:ttm="http://www.w3.org/ns/ttml#metadata" xmlns:ttp="http://www.w3.org/ns/ttml#parameter" xmlns:tts="http://www.w3.org/ns/ttml#styling" ttp:tickRate="10000000" ttp:version="2" xml:lang="ja">
 <head>
  <styling>
   <initial tts:backgroundColor="transparent" tts:color="white" tts:fontSize="6.000vh"/>
   <style xml:id="style0" tts:textAlign="center"/>
   <style xml:id="style1" tts:textAlign="start"/>
   <style xml:id="style2" tts:ruby="container" tts:rubyPosition="auto"/>
   <style xml:id="style3" tts:ruby="base"/>
   <style xml:id="style4" tts:ruby="text"/>
   <style xml:id="style5" tts:ruby="text"/>
  </styling>
  <layout>
   <region xml:id="region0" tts:displayAlign="after"/>
  </layout>
  </head>
 <body xml:space="preserve">
  <div>
   <p xml:id="subtitle1" begin="18637368750t" end="18676157500t" region="region0" style="style0"><span style="style1">テソプ<span style="style2"><span style="style3">の所だ</span><span style="style4">カン食ン</span></span>食おう<br/><span style="style2"><span style="style3">江陵</span><span style="style5">カンヌン</span></span>で刺身でも食おう</span></p>
  </div>
 </body>
</tt>

(Found here: https://netflixtechblog.com/implementing-japanese-subtitles-on-netflix-c165fbe61989 )

coveralls · 2020-08-27T21:09:57Z

Coverage increased (+0.2%) to 77.023% when pulling e69b116 on rrooij:ttml_ticks into 88639b8 on asticode:master.

asticode

This is a nice PR.

Few changes needed though.

Also, could you add tests here ?

ttml.go

asticode · 2020-08-28T10:19:10Z

ttml.go

@@ -288,6 +289,10 @@ func (d TTMLInDuration) duration() time.Duration {
 	if d.framerate > 0 {
 		return d.d + time.Duration(float64(d.frames)/float64(d.framerate)*1e9)*time.Nanosecond
 	}
+	if d.tickrate > 0 {


Why not compute the value once and for all here ? Is the tickrate value not populated at that time ?

Unfortunately, it is not populated at that time.

ttml.go

rrooij · 2020-08-28T18:17:59Z

I created the tests and fixed the styling issues (the alphabetical order).

Unfortunately the proper tick duration is still calculated in the duration function. But, I do think this is the only solution. Unmarshalltext only has access to the duration text itself and the tickrate is not known at that time. (I actually wonder if the framerate is accessible as well in that function).

Unmarshalltext should in my opinion only be responsible for extracting the text to a proper representation, not for calculating it correctly already.

Edit:

We need additional work to completely confirm to the TTMLv2 standard though:

If not specified, then if a frame rate is specified, the tick rate must be considered to be the effective frame rate multiplied by the sub-frame rate (i.e., ticks are interpreted as sub-frames); or, if no frame rate is specified, the tick rate must be considered to be one (1) tick per second of media time. If specified, then the tick rate must not be zero (0).

https://w3c.github.io/ttml2/#parameter-attribute-tickRate

asticode · 2020-08-31T09:47:07Z

I do agree with you regarding UnmarshalText. I'll see what I can do.

FYI I've created a v0.5.0 tag.

Cheers

Implement tick duration support for TTML subtitles

717a2da

asticode requested changes Aug 28, 2020

View reviewed changes

rrooij added 2 commits August 28, 2020 17:40

Fix alphabetical ordering in code

2e96648

tests: add tick rate duration test

e69b116

asticode merged commit e7a6a4e into asticode:master Aug 31, 2020

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Implement tick duration support for TTML subtitles #26

Implement tick duration support for TTML subtitles #26

rrooij commented Aug 27, 2020

coveralls commented Aug 27, 2020 •

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rrooij Aug 28, 2020

rrooij commented Aug 28, 2020 •

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asticode commented Aug 31, 2020

Implement tick duration support for TTML subtitles #26

Implement tick duration support for TTML subtitles #26

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