// title: Sound file chunks: Workaround for single-precision buffer indexing
// author: jamshark70
// description:
// One of the common questions on the list is about handling very large sound files with BufRd. BufRd indexes into the buffer using a single-precision float, which supports buffers only up to 2**24 frames (a bit more than six minutes at 44.1 kHz).
// 
// This approach loads sequential chunks of a sound file into buffers that are within reach of BufRd. Then, the SynthDef can advance from one buffer to the next during playback.
// 
// Each buffer holds one extra sample, to try to give BufRd's linear interpolation enough information to work with. There may or may not be an off-by-one bug here. If you find a problem, let me know.
// code:
(
~loadChunks = { |server, path, startFrame = 0, numFrames = -1, action, chunkSize = 1048576|
	var sf, numCh, bufs, incr = 0;
	sf = SoundFile.openRead(path);
	if(sf.isOpen) {
		numCh = sf.numChannels;
		if(numFrames < 0) {
			numFrames = sf.numFrames - startFrame;
		} {
			numFrames = min(numFrames, sf.numFrames - startFrame);
		};
		sf.close;
		bufs = Buffer.allocConsecutive((numFrames / (chunkSize - 1)).roundUp, server, chunkSize, numCh);
		{
			server.sync;
			bufs.do { |buf, i|
				buf.read(path, startFrame + incr, chunkSize, 0);
				server.sync;
				incr = incr + chunkSize - 1;  // overlap 1 sample for interpolation
			};
			action.value(bufs);
		}.fork(AppClock);
		bufs
	} {
		"% could not be opened.".format(path).warn;
	};
};
)

b = ~loadChunks.value(s, "your-file.aiff", action: { "done".postln });

(
SynthDef(\playchunks, { |out = 0, bufnum, numbufs = 1, rate = 1, amp = 0.1|
	var phaseTrigFb = LocalIn.ar(1),
	frames = BufFrames.kr(bufnum),
	phase = Phasor.ar(phaseTrigFb, rate, 1, frames + 1000, 1),
	phaseTrig = phase >= (frames - 1),
	bufOffset = PulseCount.ar(phaseTrig),
	sig = BufRd.ar(2, bufnum + bufOffset, phase, loop: 0);
	FreeSelf.kr(bufOffset >= numbufs);
	LocalOut.ar(phaseTrig);
	Out.ar(out, sig * amp);
}).add;
)

a = Synth(\playchunks, [bufnum: b.first, numbufs: b.size, amp: 1]);

a.free;

b.do(_.free);