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Video playback not working in Firefox


Go to solution Solved by TVGuy,

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This is the first time it's happened to me, so it doesn't seem like it will be a common issue. I like using Firefox because it is privacy focused and it's the only browser left that isn't based on Chromium. The fact that it is the only browser not based on Chromium is probably the reason for most website bugs. Since web-devlopers mainly test their websites on Chromium browsers and neglect Firefox because it has small market-share.

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I've been investigating, as this issue has been showing up for me in other ways (that have nothing to do with this site) but is getting really annoying.  It isn't just a simple codec issue, but it appears to be a Firefox bug related specifically to a single metadata descriptor, and is present in both h.264 encoded MP4 video files and JPEG images.

The issue only exists if a video or image has a metadata category for "unit" or "scale-unit".  If this category exists in the file header, regardless if it contains any data or not, or what the data is, the bug can be triggered.  The other thing that is necessary for this bug is for the piece of media in question must be displayed inside an HTML parent element that only has a single dimension defined, width or height, not both.  And then, the media itself, must lack width/height information, inheriting only from the parent element.  If you open the video directly in Firefox, where there is no parent element, it will play fine.

Adobe media encoder seems to include this metadata category with an MP4 video if that video is rendered at a different resolution or frame rate from the original time line, or if video is scaled to a different size or resolution on the timeline.  If a video is edited and exported at the same exact resolution and frame rate in which it was shot, Adobe doesn't include this category in the file's metadata. 

Similarly, I'm only seeing this in JPEG images saved directly as JPEGS from photoshop that undergo specific kinds of edits.  Images that are saved via the 'Save as copy' option, don't undergo specific kinds of edits related to resizing and scaling, or that are processed through lightroom, don't contain the problematic metadata category.

This "scale-unit" metadata seems to be something new.  It isn't present in any of my older videos or photos.  I'm only seeing it in media created since January of 2020.

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9 hours ago, TVGuy said:

I've been investigating, as this issue has been showing up for me in other ways (that have nothing to do with this site) but is getting really annoying.  It isn't just a simple codec issue, but it appears to be a Firefox bug related specifically to a single metadata descriptor, and is present in both h.264 encoded MP4 video files and JPEG images.

The issue only exists if a video or image has a metadata category for "unit" or "scale-unit".  If this category exists in the file header, regardless if it contains any data or not, or what the data is, the bug can be triggered.  The other thing that is necessary for this bug is for the piece of media in question must be displayed inside an HTML parent element that only has a single dimension defined, width or height, not both.  And then, the media itself, must lack width/height information, inheriting only from the parent element.  If you open the video directly in Firefox, where there is no parent element, it will play fine.

Adobe media encoder seems to include this metadata category with an MP4 video if that video is rendered at a different resolution or frame rate from the original time line, or if video is scaled to a different size or resolution on the timeline.  If a video is edited and exported at the same exact resolution and frame rate in which it was shot, Adobe doesn't include this category in the file's metadata. 

Similarly, I'm only seeing this in JPEG images saved directly as JPEGS from photoshop that undergo specific kinds of edits.  Images that are saved via the 'Save as copy' option, don't undergo specific kinds of edits related to resizing and scaling, or that are processed through lightroom, don't contain the problematic metadata category.

This "scale-unit" metadata seems to be something new.  It isn't present in any of my older videos or photos.  I'm only seeing it in media created since January of 2020.

So it is indeed a Firefox issue. Perhaps you can submit a bug report in the hopes that it gets fixed? I would submit one myself, but you clearly know the problem better than me.

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