[Ffmpeg-devel] FLAC encoder

[Benjamin Larsson]

Justin Ruggles wrote:

>Hello,
>
>I wrote:
>  
>
>>Well, the FLAC encoder is getting better by the day.  I'll post some
>>results some time soon of my most recent version, which has marked
>>improvement in compression.
>>    
>>
>
>Here are some current results.  The latest version is here:
>
>http://home.earthlink.net/~jruggle/flake/flake-02.tar.bz2
>
>I still haven't integrated with FFmpeg...that's coming soon though.  The
>biggest improvement I have made is the application of a window function
>before calculating the LPC coefficients.  After testing several
>different window types, I found that for most audio clips, either the
>Hamming window or the Bartlett window was the best choice.  So I changed
>the encoder to calculate LPC coefficients using each of these windows.
>  
>
Regaring the choise of window, read this thread:
http://www.hydrogenaudio.org/forums/index.php?showtopic=44229
Hope it helps.

>Optimal LPC order estimation is done for each set, and the smaller order
>of the 2 is used along with the corresponding coeffs.  It's amazing how
>such a simple thing can increase compression so much!  I got the idea
>from a general description of MPEG-4 ALS.  It could be patented for all
>I know...
>
>If anyone wants to do tests with the clip I used for the test below:
>http://home.earthlink.net/~jruggle/flake/answering_bell.flac
>
>-Justin
>  
>
MvH
Benjamin Larsson

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