[flac-dev] [PATCH] Improve LPC order guess

[Jan Stary]

On Dec 04 11:05:24, mle+la at mega-nerd.com wrote:
> Martijn van Beurden wrote:
> 
> > This patch improves compression a very tiny bit on average, but 
> > up to 0.1 percentage point for classical music. I haven't found 
> > any tracks that show worsening compression with this patch.
> 
> Applied, thanks.
> 
> I think this points to the need to have a centralised repository
> of of test files for studying and validating compression ratios
> and speed.
> 
> Martjin, are you able to make your test material available? DO
> you have any test scripts your use to run your tests?

Surely Martijn has something more sophisticated,
here is my test script using SoX to generate the audio.

	Jan


#!/bin/sh

# Test FLAC compression on a set of audio files.
# For each of the test files, we measure the time it takes to compress,
# and the compression ratio, for compression levels from -0 to -8.

die()
{
	echo $* >&2
	exit 1
}

FLAC=`which flac`
test -n $FLAC || die flac not found
FLAC="$FLAC --silent -f"

SOX=`which sox`
test -n $SOX || die sox not found
SOX="$SOX -c 1 -b 16 -n"

TIME=`which time`
test -n $TIME || die time not found
TIME="$TIME -p"

_size()
{
	ls -l "$1" | awk '{print$5}'
}

_time()
{
	$TIME $* 2>&1 | grep real | awk '{print$2}'
}

while read wave ; do
	ifile=${wave%%:*}.wav
	synth=${wave##*:}
	SOXCL="$SOX $ifile synth 60 $synth gain -4"
	echo $SOXCL ; $SOXCL || die SoX failed
	isize=`_size $ifile`
	for level in 0 1 2 3 4 5 6 7 8 ; do
		ofile=$ifile.$level.flac
		otime=`_time $FLAC -$level $ifile -o $ofile`
		osize=`_size $ofile`
		ratio=`echo "scale = 10 ; $osize / $isize" | bc`
		printf "%16s -%d %d/%d bytes (%f) in %f seconds\n" \
			$ifile $level $osize $isize $ratio $otime
		rm -f $ofile
	done
	rm -f $ifile
done << EOF
sine:		sine       440
square:		square     440
triangle:	triangle   440
sawtooth:	sawtooth   440
trapeze: 	trapez     440 
exp:     	exp        440
whitenoise:   	whitenoise
tpdfnoise:    	tpdfnoise
pinknoise:    	pinknoise
brownnoise:  	brownnoise
EOF