[x264-devel] Re: [PATCH] set constraint_set[01]_flag when possible

[Loren Merritt]

On Thu, 11 May 2006, Loïc Le Loarer wrote:

> Here is a patch which set the flags constraint_set0_flag and
> constraint_set1_flag when possible. This has the advandage of giving
> more information on the stream which may help decoders.
>
> I have included the text from the H.264 norm so that in case of
> improvement in x264 supported feature, the flags can be corrected
> accordingly easily.
>
>+ Set constraint_set0_flag if the BASELINE constraint are fulfilled
>+ even if the profile is not BASELINE, this allows a BASELINE only 
>+ decoder to decode the stream

Why? x264 selects profile based on which features are enabled. It will 
never generate a Baseline-compatible stream that isn't actually marked as 
Baseline.
I suppose you could argue that there is some value in setting 
constraint_set1_flag for Baseline files, because there are decoders that 
support Main but not all of Baseline.
If you still think constraint_set[01]_flag should be set, then I'll set 
them based on the value of sps->i_profile, not duplicate all the 
parameter checks.

--Loren Merritt