[x264-devel] Max number of motion vectors

[Li, Stephen]

Do you have an idea what is the impact of the video quality when p4x4 is disabled? 

Thanks
Steve

-----Original Message-----
From: x264-devel [mailto:x264-devel-bounces at videolan.org] On Behalf Of BugMaster
Sent: May-12-16 6:44 PM
To: Mailing list for x264 developers
Subject: Re: [x264-devel] Max number of motion vectors

On Thu, 12 May 2016 22:19:24 +0000, Li, Stephen wrote:
> Thanks for your response. Removing p4x4 fixes the problem. Is it a 
> known issue with x264? What is the effect of removing p4x4?

> Thanks
> Steve

It is known that with p4x4 we can in theory violate this level constraint. But imho it is really stupid constraint of higher levels
(3.1+) while lower levels allow up to 64 MVs per 2 consecutive MBs i.e. hardware still need to support this number of MVs and this constraint is only stupid performance micro optimization at higher bitrates (levels) for very slow decoders (1-gen H.264 devices?). There is no known issue with it at any real device. But if you stream analyzer so picky and you need to conform to it you can disable p4x4.
It will disable use of partitions with 4x4, 4x8 and 8x4 sizes.

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