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#!/usr/bin/env bash
## bash script to generate file magic support for flac.
## https://github.com/file/file/blob/master/magic/Magdir/audio
## below "#some common sample rates" (line 471), ie:
## >>17 belong&0xfffff0 0x2ee000 \b, 192 kHz
LANG=C
target=magic/Magdir/audio
## construct static list of sample rates based on standard crystal
## oscillator frequencies.
## 16.384 MHz Unknown audio application
## (16384 kHz = 32 kHz * 512 = 32 * 2^9)
## 22.5792 MHz Redbook/CD
## (22579.2 kHz = 44.1kHz * 512 = 44.1 * 2^9)
## also used: 11.2896, 16.9344, 33.8688 and 45.1584
## 24.576 MHz DAT/Video
## (24576 kHz = 48 kHz * 512 = 48 * 2^9)
## also used: 49.1520
## 33.8688 > 16.9344
## 36.864 > 18.432000
declare -a a_ground_fs=(16384000 22579200 24576000)
## multiply ground clock frequencies by 1953 to get usable base
## frequencies, for instance:
## DAT/video: 24.576 MHz * 1000000 / 512 = 48000Hz
## Redbook/CD: 22.5792 MHz * 1000000 / 512 = 44100Hz
## use base rates for calculating derived rates
declare -a samplerates
## min divider: fs/n
def_fs_n=512
min_fs_n=4
## start at base_fs/(def_fs*min_fs)
## add each derived sample rate to the array
for base_fs in "${a_ground_fs[@]}"; do
min_fs=$( echo "${base_fs} / ( ${def_fs_n} * ${min_fs_n} )" | bc)
## max multiplier: fs*n*min_fs
max_fs_n=$(( 8 * min_fs_n ))
n=${max_fs_n}
while [[ ${n} -ge 1 ]]; do
sample_rate=$(( min_fs * n ))
samplerates+=(${sample_rate})
n=$(( n / 2 ))
done
done
declare -a stripped_rates
declare -a lines
for samplerate in "${samplerates[@]}"; do
## use bc with sed to convert and format Hz to kHz
stripped_rate="$(LANG=C bc <<< "scale=5; ${samplerate} / 1000" | \
sed 's#[0\.]*$##g')"
## only add uniq sample rates (should be necessary
if [[ ! "${stripped_rates[@]}" =~ ${stripped_rate} ]]; then
printf -v line ">>17\tbelong&%#-15x\t%#08x\t%s, %s kHz\n" \
"16777200" \
"$(( samplerate * 16 ))" \
"\b" \
"${stripped_rate}"
stripped_rates+=("${stripped_rate}")
lines+=("${line}")
fi
done
printf "## start cutting >>> \n"
## print out the formatted lines
printf "%s" "${lines[@]}" | sort -k5 -n
printf "## <<< stop cutting\n"
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