From 7cc89c9f92d890dd1cbb5da46fab16219bcdf854 Mon Sep 17 00:00:00 2001
From: Christopher Snowhill <kode54@gmail.com>
Date: Thu, 13 Jan 2022 23:03:53 -0800
Subject: [PATCH] Cog Audio: Enhance track end extrapolator so it will always
 have a reasonable amount of buffered data for extrapolation

---
 Audio/Chain/ConverterNode.h |  3 +++
 Audio/Chain/ConverterNode.m | 38 ++++++++++++++++++++++++++++++++++---
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/Audio/Chain/ConverterNode.h b/Audio/Chain/ConverterNode.h
index 8d5ab1bc5..f7bcd5992 100644
--- a/Audio/Chain/ConverterNode.h
+++ b/Audio/Chain/ConverterNode.h
@@ -45,6 +45,9 @@
     void *floatBuffer;
     size_t floatBufferSize;
     size_t floatSize, floatOffset;
+    
+    size_t floatConvertedSize;
+    float floatConvertedLast[CHUNK_SIZE];
 	
 	AudioStreamBasicDescription inputFormat;
     AudioStreamBasicDescription floatFormat;
diff --git a/Audio/Chain/ConverterNode.m b/Audio/Chain/ConverterNode.m
index 5f76af1d1..5190e1fb5 100644
--- a/Audio/Chain/ConverterNode.m
+++ b/Audio/Chain/ConverterNode.m
@@ -485,12 +485,35 @@ tryagain:
                 extrapolateEnd = ioNumberPackets;
                 
                 // Extrapolate end samples
-                if (inpSize)
+                if ( inpSize < sizeof(floatConvertedLast))
                 {
-                    extrapolate( inputBuffer, floatFormat.mChannelsPerFrame, inpSize / floatFormat.mBytesPerPacket, extrapolateEnd, NO);
+                    size_t inpTotal = newSize + floatConvertedSize;
+                    if (inpTotal > sizeof(floatConvertedLast))
+                        inpTotal = sizeof(floatConvertedLast);
+                    
+                    if (inpTotal - newSize < floatConvertedSize)
+                    {
+                        memmove(floatConvertedLast, ((uint8_t*)floatConvertedLast) + newSize, inpTotal - newSize);
+                        floatConvertedSize = inpTotal - newSize;
+                    }
+                    
+                    memcpy(((uint8_t*)floatConvertedLast) + floatConvertedSize, inputBuffer, inpSize);
+                    
+                    extrapolate( floatConvertedLast, floatFormat.mChannelsPerFrame, inpTotal / floatFormat.mBytesPerPacket, extrapolateEnd, NO );
+                    
+                    newSize = ioNumberPackets * floatFormat.mBytesPerPacket;
+                    
+                    memcpy( inputBuffer, ((uint8_t*)floatConvertedLast) + inpTotal - newSize, newSize );
+                    
+                    inpSize = newSize;
+                    inpOffset = 0;
+                }
+                else
+                {
+                    extrapolate( inputBuffer, floatFormat.mChannelsPerFrame, newSize / floatFormat.mBytesPerPacket, extrapolateEnd, NO );
                 
                     inpOffset = inpSize;
-                    inpSize += extrapolateEnd * floatFormat.mBytesPerPacket;
+                    inpSize = newSize;
                 }
                 latencyPostfill = YES;
                 break;
@@ -628,6 +651,13 @@ tryagain:
         // Input now contains bytesReadFromInput worth of floats, in the input sample rate
         inpSize = bytesReadFromInput;
         inpOffset = 0;
+        
+        // Preserve last samples, for end extrapolator, if needed
+        size_t preserved = inpSize;
+        if (preserved > sizeof(floatConvertedLast))
+            preserved = sizeof(floatConvertedLast);
+        memcpy(floatConvertedLast, inputBuffer + inpSize - preserved, preserved);
+        floatConvertedSize = preserved;
     }
     
     if (inpOffset != inpSize && floatOffset == floatSize)
@@ -823,6 +853,8 @@ static float db_to_scale(float db)
     floatOffset = 0;
     floatSize = 0;
     
+    floatConvertedSize = 0;
+    
     // This is a post resampler, post-down/upmix format
     
     dmFloatFormat = floatFormat;