[x265] patch for faster intra

[chen]

Hi Dave,
 
I haven't find any mistake between table and Predict::filteringIntraReferenceSamples.
Here is my verify code.
 
Best,
Min

At 2014-08-04 23:45:08,dave <dtyx265 at gmail.com> wrote:
>On 08/03/2014 07:52 PM, Steve Borho wrote:
>> On 08/02, dave wrote:
>>> A few other things...
>>>
>>> In my testing of encoding a single frame where I only examined processing of
>>> the first few CUs this search method always found the lowest cost but cost
>>> values never followed a consistent curve with a single low point.  Without
>>> further testing or deeper knowledge of the angle intra modes I wouldn't
>>> guarantee the lowest cost will always be found.
>> It's understood there will be a trade-off between compression and
>> performance; so this is ok.  It would be interesting to measure the
>> average "error" or difference in cost between the lowest cost found by
>> the fast-scan and the lowest cost found by the exhaustive scan. If
>> nothing else we can advertise this number in the documentation for the
>> option.
>>
>>> Also, unfortunately my system is old and doesn't support sse4 and that is
>>> the only level of assembler supported for intra mode predictions so I was
>>> only able to develop and test for the c primitives.  I need to upgrade...
>> that's unfortunate; x265 really prefers SSE4.
>>
>>> Yes, there was a small performance increase that seemed larger when encoding
>>> a single frame than a short video.  Neither produced consistent results on
>>> my system but the new search method was slightly faster most of the time
>>> when encoding a single frame and always faster when encoding a short video.
>> Looking at the code, I had forgotten about the details of picking
>> filtered or unfiltered sources based on the size and angle. This is
>> something else that the 'all-angs' function does for you implicitly.
>all-angs uses a lookup table in intrapred.cpp to determine filtering.  
>If the table were more publicly available that would help speed things 
>up.  Also, the table and Predict::filteringIntraReferenceSamples don't 
>return the same results for all possible values.
>> I'm pretty sure the fast scan would be faster if it ran the 'all-angs'
>> function and then only measured satd/sa8d in the same pattern you have
>> now.  The only gotchya will be to make sure you compare with transposed
>> source pixels for those modes that require it.
>>
>>> On 08/01/2014 09:50 PM, Steve Borho wrote:
>>>> On 08/01, dave wrote:
>>>>> I am submitting a patch to implement the faster intra search suggested by
>>>>> Steve Borho here:
>>>>>
>>>>> https://mailman.videolan.org/pipermail/x265-devel/2014-July/004873.html
>>>> nice!
>>>>
>>>>> The patch is implements the faster search in slicetype.cpp.  The same
>>>>> approach can also be used in analysis.cpp but it's a little more than a
>>>>> simple cut and paste though it shouldn't take long.
>>>> yep
>>>>
>>>>> TEncSearch.cpp also calls intra_pred_allangs for which this is the faster
>>>>> alternative but at first look, TEncSearch.cpp is more complex.  Depending on
>>>>> what is desired, either this search could greatly simplify this part of
>>>>> TEncSearch.cpp or it might not be applicable to what TEncSearch.cpp is
>>>>> doing.  I will be looking into it.
>>>> it should also apply here; this function is a little more complicated
>>>> because it keeps a "best N" list of modes, and then performs
>>>> rate-distortion measurements (encodes each option and records the actual
>>>> distortion and bit cost) to select the final intra mode.  The same 'fast
>>>> scan' mode could be used to build the 'best N' list. But I imagine most
>>>> presets that use this RDO version of intra will not want a fast scan.
>>>>
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>
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