mimetypes does not support webm type

[giampaolo]

BPO	16329
Nosy	@terryjreedy, @jcea, @giampaolo, @ezio-melotti, @bitdancer, @berkerpeksag, @JimJJewett
Files	webm.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2016-04-09.05:19:25.201>
created_at = <Date 2012-10-26.13:34:58.461>
labels = ['type-feature', 'library']
title = 'mimetypes does not support webm type'
updated_at = <Date 2016-04-09.05:19:25.198>
user = 'https://github.com/giampaolo'

bugs.python.org fields:

activity = <Date 2016-04-09.05:19:25.198>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2016-04-09.05:19:25.201>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2012-10-26.13:34:58.461>
creator = 'giampaolo.rodola'
dependencies = []
files = ['27728']
hgrepos = []
issue_num = 16329
keywords = ['patch']
message_count = 17.0
messages = ['173843', '173844', '173845', '173846', '173847', '173997', '174055', '213990', '232088', '232090', '232095', '232096', '232097', '232098', '263064', '263065', '263068']
nosy_count = 9.0
nosy_names = ['terry.reedy', 'jcea', 'giampaolo.rodola', 'ezio.melotti', 'r.david.murray', 'cvrebert', 'python-dev', 'berker.peksag', 'Jim.Jewett']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue16329'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6']

[giampaolo]

http://www.webmproject.org/docs/container/#naming

[giampaolo]

(patch in attachment)

[jcea]

How do we know if the "webm" file is video+audio or audio only?. Mimetypes are different. :-?

[giampaolo]

I'd say we can't but I suppose the same problem might exist for other mime types as well.
Given that we can't inspect file content the only choice we have is either decide to not support a certain mime type or assume the most common scenario, which in case of webm is "video".

[bitdancer]

I suppose this is a flaw in the mimetype API. At some point perhaps we should fix it, but in the meantime....does anyone have a pointer to an actual IANA submission for this mime type? I think we can probably no longer wait for official IANA approval, but it would be nice to have some sort of documentation that a given type is more than just in de-facto existence.

[cvrebert]

AFAICT, there is currently no entry for WebM in IANA's registry (http://www.iana.org/assignments/media-types/index.html ).
A bug in WebM's tracker regarding its MIME type(s) was closed over a year ago as WONTFIX (http://code.google.com/p/webm/issues/detail?id=15 ).

Giampaolo has already pointed out the relevant part of the WebM spec. WebM itself has no RFCs (there are 2 relating to VP8, its video codec, but they don't have anything that's relevant here).

To independently corroborate the existence of the MIME type, we have the following:

Mozilla, Microsoft, and Opera all acknowledge the MIME type in question:
https://developer.mozilla.org/en-US/docs/Media_formats_supported_by_the_audio_and_video_elements
http://msdn.microsoft.com/en-us/library/ff975073%28v=VS.85%29.aspx
http://dev.opera.com/articles/view/opera-supports-webm-video/

The de-facto *nix MIME type database/package maintained by freedesktop.org includes it:
http://cgit.freedesktop.org/xdg/shared-mime-info/tree/NEWS?id=391ae76f6a2f3af93406ac31bc8735695f41d07d#n92

[bitdancer]

Interesting. So we have two choices: leave it to the platform mime types file to define because it is not even on track to be an official IANA standard, or include it with a comment that it is a de-facto standard.

The question, I guess, is how fluid the definition is likely to be. It doesn't seem like the filetype mapping for the existing definitions is going to change, and since we don't (currently) have content-detection of any sort, the impact of a change in the definitions to users of our code seems minimal. So I guess I'd be OK with adding it as a de-facto standard, though I'm not entirely comfortable with it. But that would represent a change in policy, so others may want to weigh in.

[cvrebert]

So, nobody seems to have cared enough about the policy change to weigh in during the intervening year and ~3mos...

[jimjjewett]

I interpreted Issue 15's closure as being about the distinction between Application/webm vs Video/webm, etc.

As far as I understand it, the python stdlib doesn't actually care what the major Mime type is, or, frankly, even whether the definition makes sense. We just want Video/webm to be registered.

I have created issue 886 on the webm site at
https://code.google.com/p/webm/issues/detail?id=886&can=4&colspec=ID%20Pri%20mstone%20ReleaseBlock%20Type%20Component%20Status%20Owner%20Summary

Anyone with more detail (e.g., do we need to define Application/webm as well as Video/webm ... do we care what the definition is ... etc ...) is encouraged to chime in.

[cvrebert]

WebM's docs use "video/webm" and never use an "application/*" type.
See http://www.webmproject.org/docs/container/

They also specify "audio/webm" for audio-only content, but both use the same file extension, so associating ".webm" with "video/webm" seems quite reasonable since it's more general (an audio-only file is just a degenerate case of an audiovideo file).

[terryjreedy]

Antoine Pitrou and Ethan Furman agreed on pydev that this should be applied. Chris, is the existing patch exactly what you think is needed?

[terryjreedy]

Does test_mimetypes (assuming it exists), have a test for the mapping, are is something needed?

[cvrebert]

Yes, the existing patch looks fine.