Home | History | Annotate | Line # | Download | only in scripts 
      1 #!/usr/bin/env bash
      2 
      3 ## bash script to generate file magic support for flac.
      4 ## https://github.com/file/file/blob/master/magic/Magdir/audio
      5 ## below "#some common sample rates" (line 471), ie:
      6 ## >>17	belong&0xfffff0		0x2ee000	\b, 192 kHz
      7 
      8 LANG=C
      9 
     10 target=magic/Magdir/audio
     11 
     12 ## construct static list of sample rates based on standard crystal
     13 ## oscillator frequencies.
     14 ## 16.384  MHz Unknown audio application
     15 ##             (16384 kHz  = 32 kHz * 512 = 32 * 2^9)
     16 ## 22.5792 MHz Redbook/CD
     17 ##             (22579.2 kHz = 44.1kHz * 512 = 44.1 * 2^9)
     18 ##             also used: 11.2896, 16.9344, 33.8688 and 45.1584
     19 ## 24.576  MHz DAT/Video
     20 ##             (24576 kHz = 48 kHz * 512 = 48 * 2^9)
     21 ##             also used: 49.1520
     22 
     23 ## 33.8688 > 16.9344
     24 ## 36.864  > 18.432000
     25 declare -a a_ground_fs=(16384000 22579200 24576000)
     26 
     27 ## multiply ground clock frequencies by 1953 to get usable base
     28 ## frequencies, for instance:
     29 ##  DAT/video:  24.576  MHz * 1000000 / 512 = 48000Hz
     30 ##  Redbook/CD: 22.5792 MHz * 1000000 / 512 = 44100Hz
     31 ## use base rates for calculating derived rates
     32 declare -a samplerates
     33 ## min divider: fs/n
     34 def_fs_n=512
     35 min_fs_n=4
     36 ## start at base_fs/(def_fs*min_fs)
     37 ## add each derived sample rate to the array
     38 for base_fs in "${a_ground_fs[@]}"; do 
     39     min_fs=$( echo "${base_fs} / ( ${def_fs_n} * ${min_fs_n} )" | bc)
     40     ## max multiplier: fs*n*min_fs
     41     max_fs_n=$(( 8 * min_fs_n ))
     42     n=${max_fs_n}
     43     while [[ ${n} -ge 1 ]]; do
     44 	sample_rate=$(( min_fs * n ))
     45 	samplerates+=(${sample_rate})
     46 	n=$(( n / 2 ))
     47     done
     48 done
     49 
     50 declare -a stripped_rates
     51 declare -a lines
     52 for samplerate in "${samplerates[@]}"; do
     53     ## use bc with sed to convert and format Hz to kHz
     54     stripped_rate="$(LANG=C bc <<< "scale=5; ${samplerate} / 1000" | \
     55 			      sed 's#[0\.]*$##g')"
     56     ## only add uniq sample rates (should be necessary
     57     if [[ ! "${stripped_rates[@]}" =~ ${stripped_rate} ]]; then
     58 	printf -v line ">>17\tbelong&%#-15x\t%#08x\t%s, %s kHz\n" \
     59 	       "16777200" \
     60 	       "$(( samplerate * 16 ))" \
     61 	       "\b" \
     62 	       "${stripped_rate}"
     63 	stripped_rates+=("${stripped_rate}")
     64 	lines+=("${line}")
     65     fi
     66 
     67 done
     68 printf "## start cutting >>> \n"
     69 ## print out the formatted lines
     70 printf "%s" "${lines[@]}" | sort -k5 -n
     71 printf "## <<< stop cutting\n"
     72