[x264-devel] [patch] x264 --sar in mp4 container

[vmrsss]

Hi Loren,

On 11 May 2008, at 17:30, Loren Merritt wrote:
> On Sat, 10 May 2008, vmrsss wrote:
>
>> Inspecting the code shows that in fact the DAR is not computed from  
>> the frame
>> size and the SAR. The patch attached just does this, and then calls a
>> suitable GPAC function to set the "Indicated track size". Can this  
>> please be
>> considered for inclusion in the build tree?
>
> From the <<16, I assume that mp4 supports sub-pixel precision? In that
> case, don't perform intermediate rounding.

Well spotted. Inspecting gpac, I gathered that the code expects u32  
which then interprets as 16.16 fixed point floats, and indeed I am  
using 16.0, as I set the lower 16 bits to zero.

I don't know what the effect of a fractional display size would be on  
players (and I am not able to do any tests for the next couple of  
days), but if you think that's the way to go, I can clearly change the  
code easily.

A related issue is whether or not we want the command lines

> x264 [OPTS] -o test.mp4

and

> x264 [OPTS] -o test.264; MP4Box -add test.264 -new test.mp4

to give the same result, in which case we ought to check whether or  
not MP4Box drops the lower 16 bits when imports h264 raw streams  
(which I think it does).

Let me know. Thanks,
-vmrsss