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RE: Definition for ma:compressions and ma:format

From: Bailer, Werner <werner.bailer@joanneum.at>
Date: Mon, 29 Nov 2010 11:58:31 +0100
To: Joakim Söderberg <joakim.soderberg@ericsson.com>, "public-media-annotation@w3.org" <public-media-annotation@w3.org>
CC: Robin Berjon <robin@berjon.com>, Torbjörn Einarsson <torbjorn.einarsson@ericsson.com>, David Singer <singer@apple.com>
Message-ID: <CD9846F872C7874BB4E0FDF2A61EF09F965B783DE0@RZJC1EX.jr1.local>
Dear Joakim,

The proposed approach works, if there is a single compressed stream inside a file, i.e. the extended MIME type could be used to specify an AVI file with MPEG-2 inside.

However, in many cases, there are differently compressed streams (typically video and one or more audio streams) in the container, in which case ma:compression is needed for the track fragments.

It seems that, when using extended MIME types (although I'm not sure if they cover all cases), that ma:format is only needed for media resources while ma:compression is only needed for tracks.

Best regards,
Werner

> -----Original Message-----
> From: public-media-annotation-request@w3.org [mailto:public-media-
> annotation-request@w3.org] On Behalf Of Joakim Söderberg
> Sent: Montag, 29. November 2010 11:48
> To: public-media-annotation@w3.org
> Cc: Robin Berjon; Torbjörn Einarsson; David Singer
> Subject: Definition for ma:compressions and ma:format
> 
> Regarding the definition for ma:compressions and ma:format.
> 
> The response I got from my colleague, Torbjörn Einarsson, is that he
> agrees with LC comment (LC-2418, Robin Berjon), in that's unclear what
> to return for "ma:compression" as it is defined now.
> 
> "- even something as simple as JPEG can be coded in different ways. The
> file format was called "jfif", but as we know "jpeg" became de facto."
> 
> He suggest that the mime-type (which is well defined) should be in
> ma:format (as it is) but also include rfc4281 extensions (that
> describes what's in the file).
> Then consequently ma:compression becomes somewhat obsolete, but it
> could be used in for the case there are no codec parameters, and then
> perhaps rename it to "ma:codecs".
> 
> 
> /Joakim
> 
> substantial: It's unclear what to return for Compression. Is JPEG a
> compression? Something more specific? Is it case sensitive? Partially
> controlled?
> 
> substantial: Does ma:format include media type parameters?
> 
> 
Received on Monday, 29 November 2010 10:59:07 UTC

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