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imscJS 1.0.x only implements IMSC 1.0.1, and is no longer being actively developed.
A sample web app that uses imscJS is available at http://sandflow.com/imsc1_1/index.html.
Documentation is available on MDN.
imscJS is primarily developed on Firefox. Latest versions of Chrome, Safari, and Microsoft Edge are intended to be supported nevertheless, albeit with potentially reduced capabilities. In particular, advanced ruby layout is currently only supported by Firefox.
imscJS is intended to reflect the most recent published versions of IMSC 1.0.1 and IMSC 1.1. These publications are routinely clarified by proposed resolutions to issues captured in their respective bug trackers.
imscJS bugs are tracked at https://github.com/sandflow/imscJS/issues.
(required) sax-js 1.2.1
Rendering to HTML5 requires a browser environment, but parsing an IMSC document and transforming it into ISDs does not.
(required) node.js (see package.json for a complete list of dependencies)
sax.js files at
build/public_html/libs are, respectively, the imscJS library and its sax-js dependency. For example, both libraries can be included in a web page as follows:
<script src="libs/sax.js"></script> <script src="libs/imsc.js"></script>
See BUILD ARTIFACTS for a full list of build artifacts, and TESTS AND SAMPLES for a list of samples and tests available.
imscJS renders an IMSC document in three distinct steps:
fromXML(xmlstring, errorHandler, metadataHandler) parses the document and returns a TT object. The latter contains opaque representation of the document and exposes the method
getMediaTimeEvents() that returns a list of time offsets (in seconds) of the ISD, i.e. the points in time where the visual representation of the document change.
generateISD(tt, offset, errorHandler) creates a canonical representation of the document (provided as a TT object generated by
fromXML()) at a point in time (
offset parameter). This point in time does not have to be one of the values returned by
getMediaTimeEvents(). For example, given an ISOBMFF sample covering the interval
generateISD(tt, offset, errorHandler) would be called first with
offset = a, then in turn with offset set to each value of
getMediaTimeEvents() that fall in the interval
renderHTML(isd, element, imgResolver, eheight, ewidth, displayForcedOnlyMode, errorHandler, previousISDState, enableRollUp) renders an
isd object returned by
generateISD() into a newly-created
div element that is appended to the
element must be attached to the DOM. The height and width of the child
div element are equal to
ewidth if not null, or
clientHeight of the parent
element otherwise. Images URIs specified in
smpte:background attributes are mapped to image resource URLs by the
imgResolver function. The latter takes the value of the
smpte:background attribute URI and an
img DOM element as input and is expected to set the
src attribute of the
img DOM element to the absolute URI of the image.
displayForcedOnlyMode sets the (boolean) value of the IMSC displayForcedOnlyMode parameter.
enableRollUp enables roll-up as specified in CEA 708.
previousISDState maintains states across calls, e.g. for roll-up processing.
In each step, the caller can provide an
errorHandler to be notified of events during processing. The
errorHandler may define four methods:
fatal. Each is called with a string argument describing the event, and will cause processing to terminate if it returns
Inline documentation provides additional information.
imscJS consists of the following modules, which can be used in a node
environment using the
require functionality, or standalone, in which case each module hosts its
definitions under a global name (the token between parantheses):
imscDoc): parses an IMSC document into an in-memory TT object
imscISD): generates an ISD object from a TT object
imscHTML): generates an HTML fragment from an ISD object
imscNames): common constants
imscStyles): defines TTML styling attributes processing
imscUtils): common utility functions
imscJS is built using the
build:debug Grunt tasks -- the
build task is an alias of
dist directory contains the following build artifacts:
imsc.all.debug.js: Non-minified build that includes the sax-js dependency.
imsc.all.min.js: Minified build that includes the sax-js dependency.
imsc.debug.js: Non-minified build that does not include the sax-js dependency.
imsc.min.js: Minified build that does not include the sax-js dependency.
build/public_html/libs/imsc.js files is identical to:
imsc.debug.js, if the
build:debugtask is executed.
imsc.min.js, if the
build:releasetask is executed.
imscJS is released as an NPM package under imsc. The
dev distribution tag indicates pre-releases.
All builds are available on the unpkg CDN under the
imscJS imports the IMSC test suite as a submodule at
src/test/resources/imsc-tests. The gen-renders.html web app can be used to generate PNG renderings as as well intermediary files from these tests.
Unit tests run using QUnit are split between: