[FFmpeg-devel] Why is writing the colr atom not the default in the mov muxer?

Dave Rice dave at dericed.com
Sat Feb 21 02:34:21 CET 2015

Hi Robert, Kevin,

> On Feb 20, 2015, at 9:56 AM, Robert Krüger <krueger at lesspain.de> wrote:
> Am Freitag, 20. Februar 2015 schrieb Kevin Wheatley :
>> On Fri, Feb 20, 2015 at 1:30 PM, Robert Krüger <krueger at lesspain.de
>> <javascript:;>> wrote:
>>> if I read the code correctly, the colr atom is only written in the mov
>>> muxer if the flag write_colr is specified. Was that behaviour chosen to
>>> have better backward compatibility or is there another reason not to
>> write
>>> this standard atom by default?
>> I chose that way to preserve the older behaviour, as it can change how
>> files will be interpreted.
>> I assumed that but isn't the change then a change for the better (then
> maybe requiring a version bump and an entry in the release notes)? After
> all Apple muxers write it by default as well and not trusting the input
> metadata seems to me like something that should be opt-out rather than
> opt-in but that's just my 2c.

That's also my two cents and I also wondered why users have to opt-in to a correctly written file. The QuickTime spec says that colr is required with some streams (such as raw uyvy422 and v210), see: https://developer.apple.com/library/mac/technotes/tn2162/_index.html#//apple_ref/doc/uid/DTS40013070-CH1-TNTAG9.

I'd propose that colr be written by default. The interpretation may be different but, since a file with a colr atom is more self-descriptive, the interpretation is more likely to be correct.
Dave Rice

> Just as another data point, I think ffmbc writes it by default. If it helps,
> I can go through a few samples created by well-known tools (e.g. Adobe
> Media Encoder) and post, if they write it by default.
> Best regards,
> Robert
> Kevin
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> -- 
> Robert Krüger
> Managing Partner
> Lesspain GmbH & Co. KG
> www.lesspain-software.com
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