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RE: Addressing media files: the SMIL video element

From: <guido.grassel@nokia.com>
Date: Thu, 18 Nov 2004 15:14:50 +0200
Message-ID: <BF61076329C8224A8816F9ABDEBB0190544EC0@esebe053.ntc.nokia.com>
To: <cyril.concolato@enst.fr>, <symm@w3.org>
Cc: <www-tag@w3.org>, <www-international@w3.org>, <w3c-svg-wg@w3.org>

Dear Cyril Concolato,

In SMIL The content author has the choice to use one combined audio visual file or separate audio and video files:

<video src="audio-visual.mpeg" />


  <video src="visual.mpeg" />
  <audio src="audio.mp3" />

Both options have advantage and disadvantages.

Using the latter option and further SMIL interaction functionality the content author can also provide means to the end-user to switch between different language option audio files etc.

For more complex cases of combining vector graphics and audio visual content the content author might want to use SMIL as a container format for SVG and the audio visual content. 

  <video src="visual.mpeg" />
  <audio src="audio.mp3" />
  <image src="graphics.svg" />

Just my three cents ...

- Guido

Guido Grassel, Nokia Research Center
email: guido.grassel@nokia.com
mobile: +358 50 48 37297


> -----Original Message-----
> From: symm-request@w3.org [mailto:symm-request@w3.org]On Behalf Of ext
> Cyril Concolato
> Sent: 17 November, 2004 11:15
> To: symm@w3.org
> Cc: www-tag@w3.org; www-international@w3.org; SVG WG
> Subject: Addressing media files: the SMIL video element
> Dear all,
> I am sending this email to all your groups as requested during an SVG
> meeting by Chris Lilley and Patrick Schmitz. It is believed that the
> problem I will raise is of concern of all your groups.
> The problem concerns the specification of the <video> element 
> as defined
> in the SVG 1.2 LC specification, taken from the SMIL specification. It
> currently reads:
> "The video element specifies a video file which is to be rendered to
> provide synchronized video. The usual SMIL animation features are used
> to start and stop the video at the appropriate times. An xlink:href is
> used to link to the video content. It is assumed that the 
> video content
> also includes an audio stream, since this is the usual way that video
> content is produced, and thus the audio is controlled by the video
> element's media attributes."
> My concern is with the last sentence in this quote. I think the video
> element should only deal with video. It is a wrong to require 
> the video
> element to also render audio data. I believe video streams and audio
> streams should be adressed separately.
> * One argument for this is the following use case:
> If a user does not want to play the audio, it would have to turn the
> audio level to 0. But in this case, the player will have no 
> way to decide:
> - if the audio stream has to be decoded but not rendered. It would be
> rendered only at some point in time during the presentation 
> as a result
> of an interaction, therefore decoding has to be done silently to keep
> sync with the video;
> - or if the audio stream can be ignored because it will never be used.
> * A second argument is the following: what would happen if 
> the the video
> element adressed an AVI file with a video stream and two audio streams
> (one for French, one for English) ? We should let the author decide,
> possibly with feature strings testing the language. I would 
> like to have
> the opinion of the internationalisation group on this point.
> One remark I had already is that the the <video> element does not
> require the video file to also contain an audio track. Indeed, but it
> forces an author to put all its media resources in different files if
> he/she wants to play them separately, which is quite unconvenient.
> My suggestion is to specify that the audio element should handle audio
> streams only, and the video element video streams only. This means
> removing (or deprecating) the audio related attributes from the video
> element. It also means that the xlink:href attribute of those elements
> have to be precise enough to identify one stream (in a container file,
> on a server, ...) maybe using fragment identifiers. The mimeType
> attribute in this case would describe the type of media stream and not
> the type of container.
> I'm looking forward to reading your comments about this 
> problem from all
> your point of views.
> Best regards,
> Cyril Concolato
> Department COMELEC,
> ENST, Paris, France
> http://www.enst.fr
Received on Thursday, 18 November 2004 13:20:20 UTC

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