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Re: Fixing appcache: a proposal to get us started

From: Jonas Sicking <jonas@sicking.cc>
Date: Fri, 29 Mar 2013 13:08:48 -0700
Message-ID: <CA+c2ei8TmPwP94J2KvmFg8yNRpSkQjadDJD0NR0n+=Tr0hLdUQ@mail.gmail.com>
To: Emerson Estrella <emerson.estrella@gmail.com>
Cc: Webapps WG <public-webapps@w3.org>
On Tue, Mar 26, 2013 at 10:03 PM, Emerson Estrella
<emerson.estrella@gmail.com> wrote:
> I'm writing a web application that uses the AppCache API for offline
> browsing. But I'm also using the Audio API to play back-ground music and a
> few audio effects.
>
>
> For audio support in different browsers I'm delivering each sound/music in
> two different file formats: OGG and MP3.
>
>
> The problem is regarding the cache manifest file. If we add all audio files
> (MP3 and OGG) in the cache manifest file, all browsers will cache all files.
> Including the unsupported ones. So, we end up with a huge storage
> requirement. Which is really bad if you are on a 3G connection for example.
>
>
> To prevent browser caching unsupported resources, the best approach I've
> found was to split the manifest file. This way we can tell browsers that
> sopport OGG files to cache only OGG files, and do tha same for other formats
> like MP3.
>
>
> But it is a "ugly solution". Now I have two manifest cache files, one with
> all OGG files listed (ogg.appcache) and the other one with the MP3 files
> (mp3.appcache).

I could see a few ways of handling this:

* Cache both files (poor bandwidth)
* We could enable some way of flagging which context different URLs
are expected to be used in. That way the UA can send the normal
content negotiation headers for images vs media files. I'm not sure
that this is worth it though given how few websites use content
negotiation headers.
* Use script to detect which formats are supported by the UA and then
use cacheURL to add the appropriate URL to the cache.
* Use the NavigationController feature.
* Use UA-string detection. You can either send different manifests
that point to different URLs for the media, or use a single manifest
but do the UA detection and serve different media files from the same
media URL. This is a pretty crappy solution though.

/ Jonas
Received on Friday, 29 March 2013 20:09:45 UTC

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