Issue 1775 in webm: How to play transparent webm video?

teemo… via monorail

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Aug 15, 2022, 10:06:19 PM8/15/22

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Status: Untriaged
Owner: ----
Labels: Pri-2 Type-Enhancement
Components: libvpx

New issue 1775 by teemo...@gmail.com: How to play transparent webm video?
https://bugs.chromium.org/p/webm/issues/detail?id=1775

Using vpxplayer to play transparent webm video, the background is black, how can I play transparent webm video correctly?

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teemo… via monorail

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Aug 15, 2022, 11:03:52 PM8/15/22

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Comment #1 on issue 1775 by teemo...@gmail.com: How to play transparent webm video?
https://bugs.chromium.org/p/webm/issues/detail?id=1775#c1

iOS platform

Using vpxplayer to play transparent webm video on iOS platform, the background is black, how to play transparent webm video correctly?

jz… via monorail

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Aug 16, 2022, 4:22:06 PM8/16/22

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Updates:
	Cc: tomfi...@google.com

Comment #2 on issue 1775 by jz...@google.com: How to play transparent webm video?
https://bugs.chromium.org/p/webm/issues/detail?id=1775#c2

Do you mean https://chromium.googlesource.com/webm/webm-tools/+/refs/heads/main/vpx_ios/ or another player?

In the VPXExample player in vpx_ios some additional code would be needed to decode the alpha plane. It's stored separately to the main video [1].

[1] http://wiki.webmproject.org/alpha-channel

teemo… via monorail

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Aug 16, 2022, 10:29:38 PM8/16/22

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Comment #3 on issue 1775 by teemo...@gmail.com: How to play transparent webm video?
https://bugs.chromium.org/p/webm/issues/detail?id=1775#c3

Yes, in the VPXExample player of vpx_ios.
These additional decoding alpha plane codes, do I need to implement the code by myself? Or is it already in the webm project? If it is open source, can you provide the url?

jz… via monorail

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Aug 17, 2022, 4:55:44 PM8/17/22

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Comment #4 on issue 1775 by jz...@google.com: How to play transparent webm video?
https://bugs.chromium.org/p/webm/issues/detail?id=1775#c4

There's no implementation for this in this player. You can see an example of decoding both streams in ffmpeg [1]. The side data referenced there is the block additional data from the webm file.

[1] https://git.ffmpeg.org/gitweb/ffmpeg.git/blob/refs/heads/release/5.1:/libavcodec/libvpxdec.c#l218

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