This post contains the presentation made at the MPEG meeting in Shanghai, China, in October 2012, related to the input contribution M26906. The presentation gives the details about the demonstration made during the meeting. This demonstration showed the use of the Google Chrome browser to display synchronized video and subtitles, using the Media Source Extension draft specification and the WebVTT subtitle format. The video and DASH content was prepared using GPAC MP4Box tool.
WebVTT is a new subtilting format that is becoming popular amongst browser implementors. Chrome (v23), Opera (v12.5), IE 10 already support it and soon Firefox will too. As opposed to previous formats for subtitles such as DVB subtitles or 3GPP Timed Text, it is being defined by the WHATWG/W3C primarily for the Web. However, the Web being almost ubiquitous, Web technologies now have to be usable in different delivery environment, not only in download and play mode. In particular, just like all the previous subtitle formats, WebVTT has to be also streamable, and for instance usable the context of Dynamic Streaming over HTTP (DASH). This post is about my experiments on this topic. For those who don’t want to read the whole post, in summary, it seems possible to generate WebVTT streams, with good random access properties, that can be delivered in chunks and be processed by standard browsers. Continue reading WebVTT streaming
My experience with multimedia standards, such as MPEG-4 BIFS, made me used to very good synchronization between video streams and graphics. So I wanted to check that the same was possible with web technologies, in particular with the plugin-less HTML5. To be more precise, I would like to display graphics on top of a video in a synchronized manner, with frame accuracy. The synchronization should be preserved when: playing, at different speed; paused; seeked; when the video stalls, …. I investigated several options and present some of the results. Continue reading HTML 5 Video and SVG Graphics Synchronization