[x264-devel] Preset parameter for x264

[Son Minh Tran]

Loren Merritt a écrit :
> On Wed, 29 Aug 2007, Tran Minh Son wrote:
>
>   
>> I propose reusing the mode of the neighbour blocks to make an "early
>> stop". As you can hint, with that I can save time at the cost of
>> quality. The gain seems to be more than the lost (15-20% in time again
>> 3-8% in PSNR).
>>     
>
> %bitrate at constant PSNR? because %PSNR is meaningless.
> If so, 8% bitrate is a lot, so I hope you were comparing it relative to
> the fastest possible options.
>   
Actually, when applying the fast technique, I gained 15-20% in time with 
an increase in bitrate about 5-8% , the change in quality (measured in 
PSNR) is inconsiderable (I had a mistake here in my previous mail)

>   
>> you improved you code quickly (frame based multithread,
>>     
>
> What does that have to do with anything? Threading doesn't touch the
> macroblock analysis code.
>
>   
Of course, I mentioned it just to say that there are a lot of changes / 
evolutions in the code x264 in the last year. I worked with mode 
decision, multi threading in h264, therefore I noticed these 
modifications immediately.

>> The comparison of MSU is an occasion for me to really verify the
>> performance of the proposed technique. We do not provide the full
>> implementation of h264 (the core is x264) but at least we would like to
>> see if really the fast mode decision bring some benefits in comparison
>> with the core of x264, from where I started. That is why I need the
>> presets of x264 (for the last year version) to provide the High Quality
>> / High speed.
>>     
>
> Wait, you want to submit two versions of x264 to the MSU comparison,
> because you're too lazy to evaluate the patch yourself? In that case,
> find your own presets.
>   

As I wrote before, my implementation is based deeply on the core of 
x264. From the view point of user, she / he will see that I added 2 more 
options (the threshold for inter/ intra selection). I already  point out 
the advisable thresholds (iterative check with large range of these 
parameters probably as you did for other options of x264) . Other 
parameters are those of the original x264. That is why the modified x264 
should inherit all the features of the original version but the way to 
select the intra / inter mode.
Do not think that I just have an idea, implement something, and let 
someone evaluate it . I already made the evaluation myself. And the 
results  as I showed you are encouraging. But MSU tests are more 
complex, concerning not only with bitrate, PSNR and running time.
MSU test is not for a local  evaluation (between the 2 version of x264), 
but for all  models of H264 coder, including the current version of 
x264. Comparing to the version last year, the current x264 runs faster 
from 10 to 20%. That is why I need to exploit  maximum the capacity of  
x264 (old version)  first then activate the option for fast mode selection.
Best regards
Son TRAN

> --Loren Merritt
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