Issue 266 in webp: File read correctly by Chrome (and WebPDemux) but fails with webpmux (and WebPMux)

[we...@googlecode.com]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 266 by tal.lev...@gmail.com: File read correctly by Chrome (and
WebPDemux) but fails with webpmux (and WebPMux)
https://code.google.com/p/webp/issues/detail?id=266

What steps will reproduce the problem?
1. Open attached file with webpmux -info

What is the expected output? What do you see instead?
Error message "Failed to create mux object from file"

What version of the product are you using? On what operating system?
0.4.3 on Linux/OS-X

Please provide any additional information below.
The file was created via ffmpeg. Chrome plays correctly and WebPDemux is
able to traverse frames correctly, but
WebPDemux fails.



Attachments:
animated.webp 28.2 KB

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Updates:
Status: Invalid

Comment #1 on issue 266 by urv...@google.com: File read correctly by Chrome

(and WebPDemux) but fails with webpmux (and WebPMux)
https://code.google.com/p/webp/issues/detail?id=266

This is, in fact, and invalid file.
The VP8X chunk in the file has 'Alpha bit' set, but none of the frames
contain transparency information.

If you look at the spec
(https://developers.google.com/speed/webp/docs/riff_container?hl=en#extended_file_format):

<Quote>
Alpha (L): 1 bit
Set if any of the frames of the image contain transparency information
("alpha").
<Unquote>

The WebPDemux library is just being tolerant about it, but WebPMux library
is strict and rejects the file as invalid.

This is actually a problem with ffmpeg's WebP muxer code: it always sets
alpha bit to be true (regardless of whether any frames contain
transparency), which is wrong.
Please file a bug on ffmpeg.

[we...@googlecode.com]

Comment #2 on issue 266 by urv...@google.com: File read correctly by Chrome

(and WebPDemux) but fails with webpmux (and WebPMux)
https://code.google.com/p/webp/issues/detail?id=266

Reported the issue on ffmpeg mailing list:
http://ffmpeg.org/pipermail/ffmpeg-devel/2015-October/179955.html