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[Offline Storage] IndexedDB as alternative to File* APIs

From: SULLIVAN, BRYAN L <bs3131@att.com>
Date: Tue, 30 Oct 2012 01:43:53 +0000
To: "public-web-and-tv@w3.org" <public-web-and-tv@w3.org>
CC: Giuseppe Pascale <giuseppep@opera.com>
Message-ID: <685E16AE-EE22-4FA4-8C18-11129A455047@att.com>
An update to my agenda item discussed today. In the Webapps meeting, feasibility of IndexedDB for this purpose (virtual Filesystem API) was discussed and it was claimed (at least for Firefox) that it addresses all the needs (even storage volume and native performance) that offline media storage would need. I did some checking and found [1], and will create some performance tests based upon that to see how verifiable the claims are, in the latest browser versions.

But the known gaps in the IndexedDB approach, which IMO are still substantial are:

1) mutability of large blobs stored in IndexedDB. Performance will not support video editing for example. But maybe not a key initial use case for Web&TV.

2) inability to access the sandboxed FS data from outside the browser. I think there may be efforts in Webapps to close this gap, with spec updates.

3) same-origin restrictions: having a large media store that is accessible to a single Webapp is pretty limiting IMO. Users will likely want to use different player apps and will not like having to rebuild their entire library to change apps. Web Intents may provide an option to address this gap. I will bring that up in DAP, where a media picker intent is drafted (we would also need media storage support in an intent).

[1] http://ericbidelman.tumblr.com/post/21649963613/idb-filesystem-js-bringing-the-html5-filesystem-api

Thanks,
Bryan Sullivan

On Oct 29, 2012, at 9:56 AM, "Bryan Sullivan" <blsaws@gmail.com> wrote:


Re my proposed agenda topic for File* and Indexed DB use for offline
content storage: There is a proposal in Webapps to take the FileSystem API
[1] off REC track. But there is no alternate proposal or effort to develop
an explicit Gallery API (this was dropped from DAP earlier when the
FileSystem API was handed to Webapps, and gallery use cases expected to be
implemented on top of them, e.g. with metadata extensions etc). The
ability to manage and access large amounts of locally stored content
(local meaning on the device or in the local network) is key to enabling
offline use cases. IMO this is one of the top 3 gaps in the current Web
platform support for Web & TV (the other two are adaptive streaming and
content protection). We either need to ensure that the File*/FileSystem
APIs support these use cases, or that we have feasible support for
network-local storage management/access from Web apps. Network-local in
this case means something accessible via HTTP (even device-locally served)
or abstracted e.g. through a Gallery Intent [2] which allows the storage
of media as well as "picking" something to play. But for local storage
accessed directly through JavaScript APIs exposed by the Web
browser/runtime (the preferred capability), we need either the
earlier-envisioned functionality of the DAP FileSystem API, or Indexed DB
APIs and storage support that supports in essence a
high-performance/volume virtual filesystem managed by the browser.

[1] http://dev.w3.org/2009/dap/file-system/file-dir-sys.html

[2] http://www.w3.org/TR/2012/WD-gallery-20120712/

Thanks, Bryan

On 10/26/12 6:08 AM, "Giuseppe Pascale" <giuseppep@opera.com> wrote:

> Hi all,
> based on the input I've received so far (offline), I've done a tentative
> allocation of topic/presenters for our F2F.
> 
> 
> (9.30-10.30) Testing
> * Testing requirements originating TV community - Mark Vickers (Comcast)
> * W3C testing work: Overview and how to integrate TV community
> requirements - Philip Hoscha (W3C)
> (10.30-11 break)
> (11-11.30) API to access low level functionality on TV devices
> * TV Channel API - Geunhyung Kim (member of mobile web forum in Korea)
> (11.30-12.00) Relationship between MPEG MMT-CI and HTML5
> * Youngsun Ryu (Samsung) on behalf of MPEG.
> (12-14 lunch)
> (14.00-14.30) Exposing Broadcast metadata to the Web
> * synchronisation, hybrid services, query, control - Olivier Thereaux, BBC
> (14.30-15) TV Profiling
> * Olivier (BBC), Giuseppe
> (15.0015.30) HNTF followup
> * Jean-Claude Dufourd, Telecom Paris Tech
> (15.30-16 break)
> (16-17) Joint with Broadcasters BG
> * Various topics, Yosuke
> 
> 
> -- 
> Giuseppe Pascale
> TV & Connected Devices
> Opera Software
> 
Received on Tuesday, 30 October 2012 01:45:29 GMT

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