[Flac] flac -- exhaustive model search vs. -A <*>?

[Linda A. Walsh]

Brian Willoughby wrote:
> On Jun 10, 2012, at 21:32, Linda A. Walsh wrote:
>   
>> what does the exhaustive model search do?
>>
>> Does it try all of the functions listed under "-A" to find the 'best',
>> i.e. bartlett, bartlett_hann, blackman, blackman_har-
>>      ris_4term_92db, connes, flattop, gauss(STDDEV),  hamming,  hann,
>>      kaiser_bessel, nuttall, rectangle, triangle, tukey(P), welch.
>>
>> Or is that something else?
>>
>> I've been using the -e option for a while in my flac encoding,
>> but for something that sounds like it should be slow I wonder
>> if it is testing all the models or if it might not be
>> working correctly?
>>
>>  Thanks...
>>     
>
>
> A better question might be: "What do the -A options do?"
>
> All of those windowing functions are lossy, and are used for  
> frequency domain transforms.  I'm not sure how they would be used in  
> a lossless encoder.  Then again, I have not yet studied the entire  
> mathematics behind FLAC.
>
>
> As for your question, I've never used the exhaustive model search  
> option, but I had originally assumed that it meant a search among the  
> various compression level options.  For example, -l -b -r -M and -m  
> all are preset when using -0 through -9 and --fast and --best as if  
> they were macros, but you can also manually set those options in  
> different combinations.  I initially thought that the exhaustive  
> search went through the -l -b -r -M/-m options to find an adaptive  
> "best" compression rather than a preset one.
>
> However, now that you've made me think about this in more detail, I  
> tend to assume that the exhaustive model search has more to do with  
> the LPC (linear predictive coding).  The key to lossless compression  
> is to find a model that predicts each sample from the previous  
> samples, and the better the model the smaller the file.  An  
> exhaustive model search must go through all possible LPC models  
> rather than the quicker default list.
>
>
> Anyway, my apologies for responding without an actual answer, but a  
> conversation might be slightly more interesting than a quick answer  
> (I hope).
>
> Brian Willoughby
> Sound Consulting
>
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