Proposal for a subtitle section

[CCMA-Enginyeria]

We have been doing EBU-TT-D subtitles tests in HbbTV using streams from HbbTV Reference Application, ARD, DASH-IF, BBC, CCMA, and others. Some of them VOD, but few for Live. Most streams are not intended specifically for subtitles tests, but for other functionalities: Multiperiod, Advertisings, DRM, multi-Moof, etc.

So different streams , different TV sets and too many different behaviours that leads to a bad interoperability because we

It would be helpfull to create a section with reference streams for testing only subtitles in HbbTV with HTML5 native player. In order to work in the largest number of devices, the streams should be compliant to these profiles, though we understand that there are some devices where subtitles will not work :

• "urn :dvb :dash :profile:dvb-dash:2014 " (HbbTV 2.0 DASH profiles)
• "urn: hbbtv :dash :profile:isoff-live:2012" (HbbTV 1.5 DASH profiles)
• "urn: hbbtv :dash :profile:isoff-live:2011" 

In this subtitles section it would be interesting to have at least the four streams as described below which are focused only on subtitles avoiding other features that could mask the results.

• VOD Stream PROFILE "MP4_AVC_HD_25_HEAAC_EBUTTD"
  • 1 Stream with 1 subtítle "in band"
  • 1 Stream with 2 languages subtitles "in band"
• LIVE Stream PROFILE "MP4_AVC_HD_25_HEAAC_EBUTTD"
  • 1 Stream with 1 subtítle "in band"
  • 1 Stream with 2 languages subtitles "in band"

How these reference streams and reference player could help:

• A group of official reference streams is needed for testing subtitles on VOD and Live. These reference streams, only intended for testing subtitles.
• This would facilitate communication between the different actors, content providers, developers, device manufacturers and streaming services providers, helping to detect and solve interoperability problems.

[Murmur]

>>It would be helpfull to create a section with reference streams for testing only subtitles in HbbTV with HTML5 native player

I link here #79 Subtitles on MSE mode, textTrack.mode="showing" not working on all hbbtv devices ticket. Many SmartTV-Hbbtv apps are relying on MSE based players(dashjs, shaka, videojs, etc..).

DashjS is considering changes of how to handle a ttml text track so that a specific HbbTV device manufacturer's browser is not a problem. Currently need to modify dashjs sources to overcome a bug in HbbTV device videoElement textTrack.mode=hidden never switch to showing state.

[JohnPaulHaroldPlutoTV]

Interesting. I'd very much welcome some good documentation along with example code for how to reliably handle in-manifest captions/subtitles. Both for VOD and Live content and ideally focussing on the "native" DASH players.

[Murmur]

in-manifest subtitles

Just to be on the same page, what do you mean?

• ttml subs in 123.m4s segments (live and vod) "in-band"
• ttml.xml link element in manifest (vod only?) "out-of-band"

Native HbbTV players support ttml.xml link element poorly so fragments in 123.m4s is only safe option.