Set HDR_SPEED

[walmik]

• Added set Ticks (HDR_SPEED) functionality on File object
• Added tests for valid & invalid input

To use this function:

file = new Midi.File({
    ticks: 1000
});
file
    .addTrack()
        ...

fs.writeFileSync('test.mid', file.toBytes(), 'binary');

[walmik]

I have 2 implementations for this which I ve put in a jsbin (in case you wanna take a look) http://jsbin.com/wiwuhayuze/1/edit?js,console

[walmik]

We can also use buffers and do the same as follows:

var speed = new Buffer(2);
speed.writeInt16BE(num);
this.HDR_SPEED = String.fromCharCode(speed[0], speed[1]);

I did not use this Buffer based approach directly as we are exporting the module for the browser as well. But this seems like the least hacky way so far.

[walmik]

Hi @dingram Did you need some more changes to this PR?

[walmik]

I ve made the change and moved the input validation but I m not sure what is the range for the valid input. Is it 1 to 65536?

[walmik]

I need it for the specific error message.

[dingram]

I'd probably do:

if (c.ticks) {
  if (typeof c.ticks !== 'number') {
    throw new Error('Ticks per beat must be a number');
  }
  if (c.ticks <=0 || c.ticks >= (1 << 15)) {
    throw new Error('Ticks per beat must be between 1 and 32767');
  }
  this.ticks = Math.floor(c.ticks);
} else {
  this.ticks = 128;
}

in order to have clear error messages for different types of errors... and also to ensure that the number of ticks is an integer.

[walmik]

Not sure about nesting ifs but I guess it s fine in this scenario.

[walmik]

Hi Dave, do you have any further requirements in this PR?

Apart from that, I had a question. I have a node module that depends on jsdmidgen for converting notes to pitches and rendering to MIDI. Whenever I render, I get a lowered octave from what I set. I am aware that there s some confusion regarding the middle C when it comes to MIDI devices. I d like to know what do you consider as middle C? I m trying to see if there is an issue in my module or is there a difference of opinion when it comes to middle C :)

Thanks!

[dingram]

Middle C is C4 in this library.