Media Types

2013-04-14T16:57:25Z

Dthompson: Fix typo.

Media types are plugin-like

== File structure ==

<pre>
mediagoblin/media_types/video
├── __init__.py # Contains the MEDIA_MANAGER
├── migrations.py # DB migrations
├── models.py # DB models
├── processing.py # De-facto standard main file
├── .... # Additional files
└── .... #
</pre>

== MEDIA_MANAGER ==

The media manager contains metadata about the media type,
along with a reference to the method used to process the media.

<pre>
MEDIA_MANAGER = {
"human_readable": "Video",
"processor": process_video,
"sniff_handler": sniff_handler,
"display_template": "mediagoblin/media_displays/video.html",
"default_thumb": "images/media_thumbs/video.jpg",
"accepted_extensions": [
"mp4", "mov", "webm", "avi", "3gp", "3gpp", "mkv", "ogv", "m4v"]}
</pre>

==== human_readable ====

A human-readable name for the media type.

==== processor ====

A reference to the media processing method for the media type.

==== sniff_handler ====

A reference to the sniffing handler for the media type.

==== display_template ====

A path to the [[Media Types/Display|display template]], relative to <code>mediagoblin/templates</code>.

==== default_thumb ====

No current use.

==== accepted_extensions ====

A list containing file extensions that should be associated to this media type. This is used as a fast way to get the media type based on an uploaded file before MediaGoblin falls back to sniffing.

== Negotiating media type based on a file upload ==

To decide which of the available media types that should handle a file upload, we first match the file extension to extensions in the available [[Media Types#MEDIA_MANAGER|MEDIA_MANAGERS]], then we resort to sniffing.

=== Sniffing ===

As a second step in media type negotiation, if the file-extension based lookup fails, <code>mediagoblin.media_types.get_media_type_and_manager</code> will call <code>mediagoblin.media_types.sniff_media</code>, which will iterate and run all the enabled media types's sniffing handlers.

The sniffing handlers can respond with either true or false, responding with true indicates that the media type believes it can parse the file.

This is mediagoblin.media_types.video.processing.sniff_handler.

<pre>
def sniff_handler(media_file, **kw):
transcoder = transcoders.VideoTranscoder()
data = transcoder.discover(media_file.name)

_log.debug('Discovered: {0}'.format(data))

if not data:
_log.error('Could not discover {0}'.format(
kw.get('media')))
return False

if data['is_video'] == True:
return True

return False
</pre>

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Media Types