[Unichrome-devel] Re: [mythtv] [PATCH] xvmcvld picture quality

[Terry Barnaby]

Hi Ivor and Thomas,

I have had a quick look at the MythTv QMatrix code.

Some points from what I can see:
1. The Default QMatrix is setup using:
	s->intra_matrix[s->dsp.idct_permutation[i]] = default_matrix[i];
2. The QMatrix is setup from MPEG using:
	s->intra_matrix[s->dsp.idct_permutation[ff_zigzag_direct[i]]] = default_matrix[i];
	I assume the MPEG data streams QMATRIX is sent in a zigzag pattern ?

It appears that MythTv sets separate scan tables (inter_scantable ?) for alternate
scan's for the various IDCT algorithems and that intra_matrix is unchanged.

So I would have assumed we can set the viaXvMC using:
	qmatrix.intra_quantiser_matrix[i] = s->intra_matrix[s->dsp.idct_permutation[i]];
This seems to match Ivors last patch.
Does this make sense ?

Also I note that MythTv can and does set separate chroma qmatrixes if present
int the MPEG stream. If they are not present it appears to use
the standard qmatrix's in the MPEG stream for them.
I also note that the Via hardware decoder, from the datasheet has the ability
to set these Matrixes. Should we be doing this ??

Terry

Ivor Hewitt wrote:
> Terry Barnaby wrote:
> 
>> Hi Ivor,
>>
>> I will have a go. I was not sure about the Qmatrix stuff in the
>> ViaXvMC patch.
>> One other aspect I have noticed is that sometimes there seems
>> to be an issue with motion. This may be the source material (DVB-T).
>> I have yet to check the same scene with software decode so this
>> may be a red herring.
>>
> Yeah I'm getting jumpy motion at the moment now too, which wasn't there 
> with the ddmpeg code. So I don't think its a source material issue.... 
> although a lot of changes were made to the myth vsync logic recently 
> which may be causing this.
> 
> Ivor.
> 
> 
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