Issue 1785 in webm: dash/vp9/isobmff spec does specify what compatible brands to put in the ftyp box (if any)

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ystre… via monorail

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Nov 4, 2022, 3:23:01 AM11/4/22
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Status: Unconfirmed
Owner: louqu...@google.com
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New issue 1785 by ystre...@gmail.com: dash/vp9/isobmff spec does specify what compatible brands to put in the ftyp box (if any)
https://bugs.chromium.org/p/webm/issues/detail?id=1785

Hi,

Is there a requirement to put any kind of brand in the ftyp box when packaging vp9 in isobmff? e.g. CMAF may require something like this and if we take AV1 as an example, this would be defined in https://aomediacodec.github.io/av1-isobmff/#brands.

I notice that https://source.chromium.org/chromium/chromium/src/+/main:media/test/data/bear-320x240-v_frag-vp9.mp4 contains the 'vp09' brand however this is not registered at http://mp4ra.org/#/brands.

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jz… via monorail

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Nov 7, 2022, 9:01:50 PM11/7/22
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Cc: fgal...@google.com tomfi...@google.com kqy...@chromium.org

Comment #1 on issue 1785 by jz...@google.com: dash/vp9/isobmff spec does specify what compatible brands to put in the ftyp box (if any)
https://bugs.chromium.org/p/webm/issues/detail?id=1785#c1

As it stands now the spec [1], and the dash-if guidelines [2] which reference it, don't mention any and tools like ffmpeg don't write the fourccs as compatible brands.

The inclusion of it in the test file may have been an oversight, but I think registering the brands is in the spirit of what is suggested in 14496-12 [3].

[1] https://www.webmproject.org/vp9/mp4/
[2] https://dashif.org/docs/DASH-IF-IOP-v4.3.pdf
[3]
C.3.2 Usage of the Brand
In order to identify the specifications to which the file complies, brands are used as identifiers in the file format.
These brands are set in the File Type Box. In the File Type Box, two kinds of brands can be indicated. One is
the major_brand that identifies the specification of the best use for the file. Second is the compatible_brands,
which can identify multiple specifications to which the file complies.
For example, a brand might indicate:
(1) the codecs that may be present in the file,
(2) how the data of each codec is stored,
(3) constraints and extensions that are applied to the file.
New brands may be registered if it is necessary to make a new specification that is not fully conformant to the
existing standards. For example, 3GPP allows using AMR and H.263 in the file format. Since these codecs
were not supported in any standards at that time, 3GPP specified the usage of the SampleEntry and template
fields in the ISO Base Media Format as well as defining new boxes to which these codecs refer. Considering
that the file format is used more widely in the future, it is expected that more brands will be needed.

jz… via monorail

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Jun 10, 2024, 2:41:14 PMJun 10
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Owner: fgal...@google.com

Comment #2 on issue 1785 by jz...@google.com: dash/vp9/isobmff spec does specify what compatible brands to put in the ftyp box (if any)
https://bugs.chromium.org/p/webm/issues/detail?id=1785#c2

(No comment was entered for this change.)

fgall… via monorail

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Jun 20, 2024, 3:33:17 PMJun 20
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Status: WontFix

Comment #3 on issue 1785 by fgal...@google.com: dash/vp9/isobmff spec does specify what compatible brands to put in the ftyp box (if any)
https://bugs.chromium.org/p/webm/issues/detail?id=1785#c3

I'm going to close this bug as Won'tFix. I agree that this was an oversight and we should have defined a brand/s for VP9 in ISOBMFF, but defining it now 7+ years later without an explicit need, I worry we would cause more issues for current tools than what we would get out of defining a brand.

If an explicit need arises please create a new issue and you can reference this issue.
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