[FFmpeg-devel] [PATCH] MMX VP3 Loop Filter

[David Conrad]

On Oct 6, 2008, at 6:23 AM, Michael Niedermayer wrote:

> On Mon, Oct 06, 2008 at 01:15:54AM -0700, Jason Garrett-Glaser wrote:
>> On Mon, Oct 6, 2008 at 1:03 AM, David Conrad <lessen42 at gmail.com>  
>> wrote:
>>> On Oct 6, 2008, at 3:42 AM, Jason Garrett-Glaser wrote:
>>>
>>>> On Mon, Oct 6, 2008 at 12:35 AM, David Conrad <lessen42 at gmail.com>
>>>> wrote:
>>>>> On Oct 4, 2008, at 2:18 PM, Michael Niedermayer wrote:
>>>>>> I'm not sure if this can be done with only 8-bit math;
>>>>>> filter_limit can
>>>>> theoretically be 127 which pushes CONST0/1 to +- 254, and mm2/mm3
>>>>> can range
>>>>> from -127 to 128.
>>>>
>>>> Are you sure filter_limit can be that large?  I know of no sane
>>>> deblocker that allows such high limit values.
>>>
>>> Quoting the Theora spec,
>>>
>>> LFLIMS - Integer array - 7 bits - Not signed
>>>
>>> This procedure decodes the table of loop ?lter limit values used  
>>> to
>>> drive the
>>> loop ?lter, which is described in Section 6.4.1. It is decoded as
>>> follows:
>>>
>>> 1. Read a 3-bit unsigned integer as NBITS.
>>> 2. For each consecutive value of qi from 0 to 63, inclusive:
>>> (a) Read an NBITS-bit unsigned integer as LFLIMS[qi ].
>>>
>>> I can't find anything in the spec that limits it any further.
>>
>
>> Then just fall back to the C code for such utterly absurd bitstreams.
>
> I too think this is the most reasonable solution ...

Here's an 8-bit version. However, checking for the C fallback negates  
the small speedup on my Penryn compared to the 16-bit version.

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