- From: Timed Text Working Group Issue Tracker <sysbot+tracker@w3.org>
- Date: Thu, 07 Aug 2014 12:22:00 +0000
- To: public-tt@w3.org
ISSUE-332 (-): #cellResolution support [TTML IMSC 1.0] http://www.w3.org/AudioVideo/TT/tracker/issues/332 Raised by: Frans de Jong On product: TTML IMSC 1.0 ------------------ Request ------------------ Chapter 4.8 (Common Constraints -> Features) The part: "#cellResolution SHALL NOT be used." should be deleted. ------------------ Reasoning ------------------ IMSC currently does not allow the use of the feature #cellResolution https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml-ww-profiles/ttml-ww-profiles.html#features It is not sufficient that an IMSC processor processes the EBU-TT-D document but ignores cellResolution values. Indirectly the cellResolution defines the fontSize. IMSC calculates the fontSize in percentages with an implicit cellResolution (with the TTML initial value, "32 15"). EBU-TT-D documents (example here: http://tech.ebu.ch/docs/ebu-tt/ebu-tt-d-imsc-compliance-example.xml ) will renderin a different font-size and therefore intended line breaks cannot be guaranteed. In this use case this is not acceptable for the broadcaster. -------------------------- General use case ------------------------- A german broadcaster uses an EBU-TT-D document (https://tech.ebu.ch/docs/ebu-tt/ebu-tt-d-imsc-compliance-example.xml) for HbbTV subtitles and for their catch up tv - portal for PC. Both the HbbTV application (or in the future the HbbTV 2.0 compliant device) and the player of the EBU-TT-D portal support EBU-TT-D. Now the broadcaster licences the same AV content together with the subtitles to a commercial on-demand Internet streaming media provider. The provider distributes its content to a client which is conformant to IMSC 1.0 (IMSC 1.0 Text - http://www.w3.org/ns/ttml/profile/imsc1/text). Conformance to EBU-TT-D of this player is not documented. ------------------- Requirement ------------------- The broadcaster demands from the provider that the subtitles will be displayed as specified in the EBU-TT-D file. The provider will distribute the EBU-TT-D file as it is provided and will not convert the EBU-TT-D file.
Received on Thursday, 7 August 2014 12:22:02 UTC