Fails to parse matroska file with projection metadata

[wader]

System info

Operating System: Alpine linux 3.12.1
Shaka Packager Version: 2.4.3 (5bf8ad5-release)

Issue and steps to reproduce the problem

Packager Command:

Matroska file with projection metadata:

$ packager 'input=test_projection.mkv,stream=video,format=webm,init_segment=init.webm,segment_template=$Number$.webm'
[0416/114025:INFO:demuxer.cc(88)] Demuxer::Run() on file 'test_projection.mkv'.
[0416/114025:INFO:demuxer.cc(160)] Initialize Demuxer for file 'test_projection.mkv'.
[0416/114025:ERROR:packager_main.cc(523)] Packaging Error: 8 (PARSER_FAILURE): Cannot parse media file test_projection.mkv

Matroska file without projection metadata:

$ packager 'input=test_no_projection.mkv,stream=video,format=webm,init_segment=init.webm,segment_template=$Number$.webm'
[0416/114136:INFO:demuxer.cc(88)] Demuxer::Run() on file 'test_no_projection.mkv'.
[0416/114136:INFO:demuxer.cc(160)] Initialize Demuxer for file 'test_no_projection.mkv'.
[0416/114136:WARNING:vp_codec_configuration_record.cc(45)] VPx video full range flag is inconsistent, 1 vs 0
[0416/114136:INFO:webm_muxer.cc(57)] WEBM file 'init.webm' finalized.
Packaging completed successfully.

What is the expected result?

Clearer error messge? Maybe possibility to filter out/ignore projection metadata? Maybe automatically ignore if projection metdata is a "identity" projection. In the original file with this metadata the video is just a flat video not meant to be projected on a non-flat surface which makes me think that StereoMode: top - bottom (left eye is first) and
ProjectionType: equirectangular means identify projection and could probably be ignored, but i'm not 3d video expert.

What happens instead?

[0416/114025:ERROR:packager_main.cc(523)] Packaging Error: 8 (PARSER_FAILURE): Cannot parse media file test_projection.mkv

The parse error i suspect is due to that matroska EBML tags Projection/ProjectionType and StereoMode are not defined in https://github.com/google/shaka-packager/blob/master/packager/media/formats/webm/webm_parser.cc

test_no_projection.mkv.zip
test_projection.mkv.zip

[kqyang]

Yes, you are right. @wader Will you be interested in helping us adding support for it? Alternatively, we can ignore all the unknown tags.

[wader]

Im interested, do you have any ideas how it could work? Im thinking something like this: If there is projection metadata automatically ignore "identity" projections if it is possible detect. Otherwise fail with error unless some explicit argument to ignore has been given?

Another option i think is to just make the error message clearer and not support it. Then it would at least make it clear to a user what they needs to filter out.

[kqyang]

@wader Thanks for your interest in helping us!

Your proposal SGTM.

• To do that, we'll first need to add support for Projection and its children tags. You can find the definition of these tags in Matroska specification: https://www.matroska.org/technical/elements.html, and look for Projection.
• Then add the Ids to https://github.com/google/shaka-packager/blob/master/packager/media/formats/webm/webm_constants.h.
• Add a kWebMProjection with type LIST to kVideoIds: https://github.com/google/shaka-packager/blob/master/packager/media/formats/webm/webm_parser.cc#L184.
• Add a kProjectionIds just like kColorIds: https://github.com/google/shaka-packager/blob/master/packager/media/formats/webm/webm_parser.cc#L203
• Add an entry in kListElementInfo for projection: https://github.com/google/shaka-packager/blob/master/packager/media/formats/webm/webm_parser.cc#L403.
• The values can be handled appropriately in webm_video_client.cc: https://github.com/google/shaka-packager/blob/master/packager/media/formats/webm/webm_video_client.cc#L255.