From cddfc3d1dbcf2214393b800a59ad0a9edf7ec6f8 Mon Sep 17 00:00:00 2001
From: Christopher Snowhill <kode54@gmail.com>
Date: Tue, 11 Feb 2025 18:09:04 -0800
Subject: [PATCH] Rubber Band: Handle end of stream flushing better

The end of stream flushing should only request remaining samples once,
as should the rest of the process. The problem with the Rubber Band code
in this case is that it will wrap the remaining samples pointer after it
has been flushed, and emit a really huge number.

Also, add code to try to equalize the samples output with the samples
input, relative to the tempo stretching, as Rubber Band seems to flush
entirely too much data at end of stream, which can create noticeable
gaps in the output. This solves that as well.

Signed-off-by: Christopher Snowhill <kode54@gmail.com>
---
 Audio/Chain/DSPRubberbandNode.m | 66 +++++++++++++++++++++------------
 1 file changed, 42 insertions(+), 24 deletions(-)

diff --git a/Audio/Chain/DSPRubberbandNode.m b/Audio/Chain/DSPRubberbandNode.m
index e4ed12206..e1d8eba6a 100644
--- a/Audio/Chain/DSPRubberbandNode.m
+++ b/Audio/Chain/DSPRubberbandNode.m
@@ -23,6 +23,7 @@ static void * kDSPRubberbandNodeContext = &kDSPRubberbandNodeContext;
 	BOOL tsrestartengine;
 	double tempo, pitch;
 	double lastTempo, lastPitch;
+	double stretchIn, stretchOut;
 
 	BOOL stopping, paused;
 	BOOL processEntered;
@@ -246,6 +247,9 @@ static void * kDSPRubberbandNodeContext = &kDSPRubberbandNodeContext;
 	tsapplynewoptions = NO;
 	tsrestartengine = NO;
 
+	stretchIn = 0.0;
+	stretchOut = 0.0;
+
 	return YES;
 }
 
@@ -390,6 +394,8 @@ static void * kDSPRubberbandNodeContext = &kDSPRubberbandNodeContext;
 		return nil;
 	}
 
+	stretchIn += [chunk duration] / tempo;
+
 	bool endOfStream = [[previousNode buffer] isEmpty] && [previousNode endOfStream] == YES;
 
 	size_t frameCount = [chunk frameCount];
@@ -406,32 +412,43 @@ static void * kDSPRubberbandNodeContext = &kDSPRubberbandNodeContext;
 	rubberband_process(ts, (const float * const *)rsPtrs, len, endOfStream);
 
 	size_t samplesAvailable;
-	while(!stopping && (samplesAvailable = rubberband_available(ts)) > 0) {
-		if(toDrop > 0) {
-			size_t blockDrop = toDrop;
-			if(blockDrop > samplesAvailable) blockDrop = samplesAvailable;
-			if(blockDrop > blockSize) blockDrop = blockSize;
-			rubberband_retrieve(ts, (float * const *)rsPtrs, (int)blockDrop);
-			toDrop -= blockDrop;
-			continue;
-		}
-		size_t maxAvailable = 65536 - samplesBuffered;
-		if(samplesAvailable > maxAvailable) {
-			samplesAvailable = maxAvailable;
-			if(!samplesAvailable) {
-				break;
+	if(!stopping && (samplesAvailable = rubberband_available(ts)) > 0) {
+		while(!stopping && samplesAvailable > 0) {
+			if(toDrop > 0) {
+				size_t blockDrop = toDrop;
+				if(blockDrop > samplesAvailable) blockDrop = samplesAvailable;
+				if(blockDrop > blockSize) blockDrop = blockSize;
+				rubberband_retrieve(ts, (float * const *)rsPtrs, (int)blockDrop);
+				toDrop -= blockDrop;
+				samplesAvailable -= blockDrop;
+				continue;
 			}
+			size_t maxAvailable = 65536 - samplesBuffered;
+			size_t samplesOut = samplesAvailable;
+			if(samplesOut > maxAvailable) {
+				samplesOut = maxAvailable;
+				if(!samplesOut) {
+					break;
+				}
+			}
+			if(samplesOut > blockSize) samplesOut = blockSize;
+			rubberband_retrieve(ts, (float * const *)rsPtrs, (int)samplesOut);
+			for(size_t i = 0; i < channels; ++i) {
+				cblas_scopy((int)samplesOut, rsPtrs[i], 1, &rsOutBuffer[samplesBuffered * channels + i], channels);
+			}
+			samplesBuffered += samplesOut;
+			samplesAvailable -= samplesOut;
 		}
-		size_t samplesOut = samplesAvailable;
-		if(samplesOut > blockSize) samplesOut = blockSize;
-		rubberband_retrieve(ts, (float * const *)rsPtrs, (int)samplesOut);
-		for(size_t i = 0; i < channels; ++i) {
-			cblas_scopy((int)samplesOut, rsPtrs[i], 1, &rsOutBuffer[samplesBuffered * channels + i], channels);
-		}
-		samplesBuffered += samplesOut;
-		if(endOfStream && samplesOut < 4096) {
-			self->endOfStream = YES;
-			break;
+	}
+
+	if(endOfStream) {
+		self->endOfStream = YES;
+		if(samplesBuffered) {
+			double outputDuration = (double)(samplesBuffered) / inputFormat.mSampleRate;
+			if(outputDuration + stretchOut > stretchIn) {
+				// Seems that Rubber Band over-flushes when it hits end of stream
+				samplesBuffered = (size_t)((stretchIn - stretchOut) * inputFormat.mSampleRate);
+			}
 		}
 	}
 
@@ -444,6 +461,7 @@ static void * kDSPRubberbandNodeContext = &kDSPRubberbandNodeContext;
 		}
 		[outputChunk assignSamples:rsOutBuffer frameCount:samplesBuffered];
 		samplesBuffered = 0;
+		stretchOut += [outputChunk duration];
 	}
 
 	processEntered = NO;