PHP - Map a 16 digit number pattern to binary chunks - php

Question

I am working on a step sequencer program for drum sounds. It takes a 16 bit binary pattern example: '1010010100101001' and then it breaks the binary pattern into chunks like so: 10, 100, 10, 100, 10, 100, 1. It then assigns each chunk a time value based on how many digits. Reason why, is some drum sample sounds ring out longer than the length of 1 beat, so the chunking solves this part. (for example if the beat was 60bpm 1 digit = 1 second) '10' = 2 seconds, '100' = 3 seconds, '1' = seconds. (allowing me to trim the sounds to the proper length in the pattern and concat it into a final wav using ffmpeg) Also 1 = drum hit / 0 = silent hit..... This method works great for my needs.
Now I can make perfect beat loops.... and I want to add a velocity pattern layer on top of this to allow ghost notes / add human feel / dynamics to my drum patterns. I have decided to use a 0,1,2,3,4 value system for the velocity patterns. '0' = 0% volume, '1' = 25% volume, '2' = 50% volume, '3' = 75% volume, and '4' = %100 volume. (0 volume so I can add open hi hat / cymbal crash hard stops that a 0 in binary pattern wouldn't do) So along with the '1111111111111111' pattern you would see a velocity pattern layer, say '4242424242424242' (That velocity pattern alternates 100% hit and 50% hit and sounds good with hi hats / like a real drummer)
Using PHP I am breaking 16 bit binary patterns into an array of chunks. '1001110011110010' would be
['100','1','1','100','1','1','1','100','10']
Now via a loop, I need to map another 16 digit number layer pattern of 0,1,2,3,4 digits to first digit of each chunk.
Example 1:
Velocity Pattern: '4242424242424242'
Binary Pattern: '1001110011110010'
Array = ['100','1','1','100','1','1','1','100','10']
'100' = 4 (1st digit in 4242424242424242 pattern)
'1' = 2 (4th digit in 4242424242424242 pattern)
'1' = 4 (5th digit in 4242424242424242 pattern)
'100' = 2 (6th digit in the 4242424242424242 pattern)
'1' = 4 (9th digit in the 4242424242424242 pattern)
'1' = 2 (10th digit in the 4242424242424242 pattern)
'1' = 4 (11th digit in the 4242424242424242 pattern)
'100' = 2 (12th digit in the 4242424242424242 pattern)
'10' = 4 (15th digit in the 4242424242424242 pattern)
Example 2:
Velocity Pattern: '4242424242424242'
Binary Pattern: '1111111111111111'
Array = ['1','1','1','1','1','1','1','1','1','1','1','1','1','1','1','1']
'1' = 4 (n1 digit in 4242424242424242 pattern)
'1' = 2 (n2 digit in 4242424242424242 pattern)
'1' = 4 (n3 digit in 4242424242424242 pattern)
'1' = 2 (n4 digit in 4242424242424242 pattern)
'1' = 4 (n5 digit in 4242424242424242 pattern)
'1' = 2 (n6 digit in 4242424242424242 pattern)
'1' = 4 (n7 digit in 4242424242424242 pattern)
'1' = 2 (n8 digit in 4242424242424242 pattern)
'1' = 4 (n9 digit in 4242424242424242 pattern)
'1' = 2 (n10 digit in 4242424242424242 pattern)
'1' = 4 (n11 digit in 4242424242424242 pattern)
'1' = 2 (n12 digit in 4242424242424242 pattern)
'1' = 4 (n13 digit in 4242424242424242 pattern)
'1' = 2 (n14 digit in 4242424242424242 pattern)
'1' = 4 (n15 digit in 4242424242424242 pattern)
'1' = 2 (n16 digit in 4242424242424242 pattern)
Example 3:
Velocity Pattern: '4231423142314231'
Binary Pattern: '0001000100010001'
Array = ['0','0','0','1000','1000','1000','1']
'0' = 4 (1st digit in 4231423142314231 pattern)
'0' = 2 (2nd digit in 4231423142314231 pattern)
'0' = 3 (3rd digit in 4231423142314231 pattern)
'1000' = 1 (4th digit in 4231423142314231 pattern)
'1000' = 1 (8th digit in 4231423142314231 pattern)
'1000' = 1 (12th digit in 4231423142314231 pattern)
'1' = 1 (16th digit in 4231423142314231 pattern)
The patterns will vary, so I need a method that works even if the pattern starts with 0, ect.
a pattern of 111111111111111 would be easy since each 1 is already split into a group by itself.
I tried using a counter called "$v_count" to map find the position in the pattern but its not working like expected.
$v_count = 0;
$beat_pattern = '1001110011110010';
$velocity_pattern = '4242424242424242';
preg_match_all('/10*|0/', $beat_pattern, $m);
$c_count = count($m, COUNT_RECURSIVE) - 1;
for ($z = 0; $z < $c_count; $z++) {
$z2 = $z;
${"c" . $z} = $m[0][$z];
${"cl" . $z} = strlen($m[0][$z]);
if (${"cl" . $z} == 1 & $m[0][$z] == "0") {
$v_count = $v_count + 1;
echo 'the position of this chunk is: '.$v_count.' in the velocity_pattern<br>';
};
if (${"cl" . $z} == 1 & $m[0][$z] == "1") {
$v_count = $v_count + 1;
echo 'the position of this chunk is: '.$v_count.' in the velocity_pattern<br>';
};
if (${"cl" . $z} > 1) {
if ($z == 1)
{
$v_count = 1;
}
if ($z > 1)
{
$v_count = $v_count + 1;
}
echo ' - the velocity position of this chunk is: '.$v_count.' in the pattern<br>';
$v_count = $v_count + ${"cl" . $z} + 1;
};
}

Answer 1

From the example you've given, it seems that you need the corresponding value from the velocity array and the duration between the 1's in the beat array.
This code first extracts the 1's by splitting it into an array and then filtering out the 0's. So
$beat_pattern = '1001110011110010';
$velocity_pattern = '4242424242424242';
$beat = array_filter(str_split($beat_pattern));
would give in $beat...
Array
(
[0] => 1
[3] => 1
[4] => 1
[5] => 1
[8] => 1
[9] => 1
[10] => 1
[11] => 1
[14] => 1
)
it then takes each entry in turn, works out the length by looking at the next key and subtract the two, also using the index to get the corresponding velocity.
To account for the starting with 0, you can loop up to the first instance of 1 and output the velocity pattern for the same element...
$beat_pattern = '1001110011110010';
$velocity_pattern = '4242424242424242';
$beat = array_filter(str_split($beat_pattern));
$beatKeys = array_keys($beat);
// For the leading 0's
for( $i = 0; $i < $beatKeys[0]; $i++ ) {
echo "1-". $velocity_pattern[$i] . PHP_EOL;
}
for ( $i = 0; $i < count($beatKeys); $i++ ) {
echo ($beatKeys[$i+1] ?? strlen($beat_pattern)) - $beatKeys[$i] . "-".
$velocity_pattern[$beatKeys[$i]] . PHP_EOL;
}
gives (length-velocity)...
3-4
1-2
1-4
3-2
1-4
1-2
1-4
3-2
2-4

Answer 2

Assuming your two input strings:
$binary = '0001000110101001';
$velocity = '4231423142314231';
If you analyse the pattern with a regex, you can obtain all the component parts in one operation, including pauses at the start of the pattern (which are essentially 0% volume beats).
$index = 0;
preg_match_all('/^0+|10*/', $binary, $parts);
foreach ($parts[0] as $part) {
$duration = strlen($part); // How many beats
$volume = $part[0] ? $velocity[$index] : 0; // The corresponding volume number
$index += $duration;
}
To develop this further, it seems to me that it would be practical to produce a proper array of data for the pattern, and you could package up this functionality if you so wanted:
function drumPattern($binary, $velocity) {
$output = [];
$index = 0;
preg_match_all('/^0+|10*/', $binary, $parts);
foreach ($parts[0] as $part) {
$duration = strlen($part);
$output[] = [
'duration' => $duration,
'volume' => $part[0] ? $velocity[$index] : 0
];
$index += $duration;
}
return $output;
}
Example
drumPattern($binary, $velocity);
Produces the following output
Array
(
[0] => Array
(
[duration] => 3
[volume] => 0
)
[1] => Array
(
[duration] => 4
[volume] => 1
)
[2] => Array
(
[duration] => 1
[volume] => 1
)
[3] => Array
(
[duration] => 2
[volume] => 4
)
[4] => Array
(
[duration] => 2
[volume] => 3
)
[5] => Array
(
[duration] => 3
[volume] => 4
)
[6] => Array
(
[duration] => 1
[volume] => 1
)
)