[Flac] Questions: FLAC performance, compression ratio and extra documentation

[Fernando Alberto Marengo Rodriguez]

Dear list,

I' m studying FLAC performance, and I'd like to know how much
compression can be achieved for different audio files. 


1) It seems that
for nontonal sound (wideband noise), the compression factor is better
than for compound sound (tones + nontonal components),
which is typically 2. The reason for this result could be the following: the
LPC filter is more suitable for estimating the amplitude spectrum
of non tonal information, and do not take into account the phase contribution for each spectral component. Do you agree with me, or do you suggest other reasons for this?


2) As
far as I know, the compression ratio is defined as 

output file size / input
file size, 

where the output file size includes frame header and other information which do not represent the input samples. 

My questions are:

a) What percentage of the output sile size is exclusively representing the input data? As this performance may depend on how many tones are present in the input, I'd like to know some average results if possible.

b) Is redundancy added to the compressed data in order to make FLAC more robust? If this is the case, what's the percentage of these data in the output file?


3) Where can I find more documentation about FLAC format and design? Are there any more documents than those in the FLAC web page? It' d be extremely useful not only for me, but also for many people investigating about this interesting open-source format.


Thanks in advance.

Best regards,

Dr. Fernando A. Marengo
 Rodriguez
Acoustics and Electroacoustics Laboratory
School of Electronics Engineering
Faculty of Sciencies, Engineering and Surveying
National University of Rosario
Rosario, Argentina


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