Fix an audio resampling problem which was causing regular clicking.

The cause was that the resampling code was using only the samples in the buffer
but not really handling the transition between two buffers (which it would
handle completely independently). The new code remembers the last sample from
the previous buffer and uses it in the resampling. We therefore end up one
sample behind and without the clicks.

1 files changed, 74 insertions, 41 deletions

diff --git a/src/xine-engine/resample.c b/src/xine-engine/resample.c
index a7b16917c..1bc9dfaf9 100644
--- a/src/xine-engine/resample.c
+++ b/src/xine-engine/resample.c
@@ -24,26 +24,34 @@
 #include "config.h"
 #endif
 
+#include <string.h>
 #include <inttypes.h>
 #include "attributes.h"
 #include "resample.h"
 
 /* contributed by paul flinders */
 
-void _x_audio_out_resample_mono(int16_t* input_samples, uint32_t in_samples, 
+void _x_audio_out_resample_mono(int16_t *last_sample,
+				int16_t* input_samples, uint32_t in_samples, 
 				int16_t* output_samples, uint32_t out_samples)
 {
   unsigned int osample;
   /* 16+16 fixed point math */
-  uint32_t isample = 0;
-  uint32_t istep = ((in_samples-2) << 16)/(out_samples-2);
+  uint32_t isample = 0xFFFF0000U;
+  uint32_t istep = (in_samples << 16) / out_samples + 1;
 
 #ifdef VERBOSE
   printf ("Audio : resample %d samples to %d\n",
           in_samples, out_samples);
 #endif
 
-  for (osample = 0; osample < out_samples - 1; osample++) {
+  for (osample = 0; osample < out_samples && isample >= 0xFFFF0000U; osample++) {
+    uint32_t t = isample&0xffff;
+    output_samples[osample] = (last_sample[0] * (0x10000-t) + input_samples[0] * t) >> 16;
+    isample += istep;
+  }
+
+  for (; osample < out_samples; osample++) {
     int  s1;
     int  s2;
     int16_t  os;
@@ -58,23 +66,31 @@ void _x_audio_out_resample_mono(int16_t* input_samples, uint32_t in_samples,
 
     isample += istep;
   }
-  output_samples[out_samples-1] = input_samples[in_samples-1];
+  last_sample[0] = input_samples[in_samples - 1];
 }
 
-void _x_audio_out_resample_stereo(int16_t* input_samples, uint32_t in_samples, 
+void _x_audio_out_resample_stereo(int16_t *last_sample,
+				  int16_t* input_samples, uint32_t in_samples, 
 				  int16_t* output_samples, uint32_t out_samples)
 {
   unsigned int osample;
   /* 16+16 fixed point math */
-  uint32_t isample = 0;
-  uint32_t istep = ((in_samples-2) << 16)/(out_samples-2);
+  uint32_t isample = 0xFFFF0000U;
+  uint32_t istep = (in_samples << 16) / out_samples + 1;
 
 #ifdef VERBOSE
   printf ("Audio : resample %d samples to %d\n",
           in_samples, out_samples);
 #endif
 
-  for (osample = 0; osample < out_samples - 1; osample++) {
+  for (osample = 0; osample < out_samples && isample >= 0xFFFF0000U; osample++) {
+    uint32_t t = isample&0xffff;
+    output_samples[osample*2  ] = (last_sample[0] * (0x10000-t) + input_samples[0] * t) >> 16;
+    output_samples[osample*2+1] = (last_sample[1] * (0x10000-t) + input_samples[1] * t) >> 16;
+    isample += istep;
+  }
+
+  for (; osample < out_samples; osample++) {
     int  s1;
     int  s2;
     int16_t  os;
@@ -94,25 +110,34 @@ void _x_audio_out_resample_stereo(int16_t* input_samples, uint32_t in_samples,
     output_samples[(osample * 2 )+1] = os;
     isample += istep;
   }
-  output_samples[out_samples*2-2] = input_samples[in_samples*2-2];
-  output_samples[out_samples*2-1] = input_samples[in_samples*2-1];
+  memcpy (last_sample, &input_samples[in_samples*2-2], 2 * sizeof (last_sample[0]));
 }
 
 
-void _x_audio_out_resample_4channel(int16_t* input_samples, uint32_t in_samples, 
+void _x_audio_out_resample_4channel(int16_t *last_sample,
+				    int16_t* input_samples, uint32_t in_samples, 
 				    int16_t* output_samples, uint32_t out_samples)
 {
   unsigned int osample;
   /* 16+16 fixed point math */
-  uint32_t isample = 0;
-  uint32_t istep = ((in_samples-2) << 16)/(out_samples-2);
+  uint32_t isample = 0xFFFF0000U;
+  uint32_t istep = (in_samples << 16) / out_samples + 1;
 
 #ifdef VERBOSE
   printf ("Audio : resample %d samples to %d\n",
           in_samples, out_samples);
 #endif
 
-  for (osample = 0; osample < out_samples - 1; osample++) {
+  for (osample = 0; osample < out_samples && isample >= 0xFFFF0000U; osample++) {
+    uint32_t t = isample&0xffff;
+    output_samples[osample*4  ] = (last_sample[0] * (0x10000-t) + input_samples[0] * t) >> 16;
+    output_samples[osample*4+1] = (last_sample[1] * (0x10000-t) + input_samples[1] * t) >> 16;
+    output_samples[osample*4+2] = (last_sample[2] * (0x10000-t) + input_samples[2] * t) >> 16;
+    output_samples[osample*4+3] = (last_sample[3] * (0x10000-t) + input_samples[3] * t) >> 16;
+    isample += istep;
+  }
+
+  for (; osample < out_samples; osample++) {
     int  s1;
     int  s2;
     int16_t  os;
@@ -145,28 +170,35 @@ void _x_audio_out_resample_4channel(int16_t* input_samples, uint32_t in_samples,
 
     isample += istep;
   }
-  output_samples[out_samples*4-4] = input_samples[in_samples*4-4];
-  output_samples[out_samples*4-3] = input_samples[in_samples*4-3];
-  output_samples[out_samples*4-2] = input_samples[in_samples*4-2];
-  output_samples[out_samples*4-1] = input_samples[in_samples*4-1];
-
+  memcpy (last_sample, &input_samples[in_samples*4-4], 4 * sizeof (last_sample[0]));
 }
 
 
-void _x_audio_out_resample_5channel(int16_t* input_samples, uint32_t in_samples, 
+void _x_audio_out_resample_5channel(int16_t *last_sample,
+				    int16_t* input_samples, uint32_t in_samples, 
 				    int16_t* output_samples, uint32_t out_samples)
 {
   unsigned int osample;
   /* 16+16 fixed point math */
-  uint32_t isample = 0;
-  uint32_t istep = ((in_samples-2) << 16)/(out_samples-2);
+  uint32_t isample = 0xFFFF0000U;
+  uint32_t istep = (in_samples << 16) / out_samples + 1;
 
 #ifdef VERBOSE
   printf ("Audio : resample %d samples to %d\n",
           in_samples, out_samples);
 #endif
 
-  for (osample = 0; osample < out_samples - 1; osample++) {
+  for (osample = 0; osample < out_samples && isample >= 0xFFFF0000U; osample++) {
+    uint32_t t = isample&0xffff;
+    output_samples[osample*5  ] = (last_sample[0] * (0x10000-t) + input_samples[0] * t) >> 16;
+    output_samples[osample*5+1] = (last_sample[1] * (0x10000-t) + input_samples[1] * t) >> 16;
+    output_samples[osample*5+2] = (last_sample[2] * (0x10000-t) + input_samples[2] * t) >> 16;
+    output_samples[osample*5+3] = (last_sample[3] * (0x10000-t) + input_samples[3] * t) >> 16;
+    output_samples[osample*5+4] = (last_sample[4] * (0x10000-t) + input_samples[4] * t) >> 16;
+    isample += istep;
+  }
+
+  for (; osample < out_samples; osample++) {
     int  s1;
     int  s2;
     int16_t  os;
@@ -205,29 +237,36 @@ void _x_audio_out_resample_5channel(int16_t* input_samples, uint32_t in_samples,
 
     isample += istep;
   }
-
-  output_samples[out_samples*5-5] = input_samples[in_samples*5-5];
-  output_samples[out_samples*5-4] = input_samples[in_samples*5-4];
-  output_samples[out_samples*5-3] = input_samples[in_samples*5-3];
-  output_samples[out_samples*5-2] = input_samples[in_samples*5-2];
-  output_samples[out_samples*5-1] = input_samples[in_samples*5-1];
+  memcpy (last_sample, &input_samples[in_samples*5-5], 5 * sizeof (last_sample[0]));
 }
 
 
-void _x_audio_out_resample_6channel(int16_t* input_samples, uint32_t in_samples, 
+void _x_audio_out_resample_6channel(int16_t *last_sample,
+				    int16_t* input_samples, uint32_t in_samples, 
 				    int16_t* output_samples, uint32_t out_samples)
 {
   unsigned int osample;
   /* 16+16 fixed point math */
-  uint32_t isample = 0;
-  uint32_t istep = ((in_samples-2) << 16)/(out_samples-2);
+  uint32_t isample = 0xFFFF0000U;
+  uint32_t istep = (in_samples << 16) / out_samples + 1;
 
 #ifdef VERBOSE
   printf ("Audio : resample %d samples to %d\n",
           in_samples, out_samples);
 #endif
 
-  for (osample = 0; osample < out_samples - 1; osample++) {
+  for (osample = 0; osample < out_samples && isample >= 0xFFFF0000U; osample++) {
+    uint32_t t = isample&0xffff;
+    output_samples[osample*6  ] = (last_sample[0] * (0x10000-t) + input_samples[0] * t) >> 16;
+    output_samples[osample*6+1] = (last_sample[1] * (0x10000-t) + input_samples[1] * t) >> 16;
+    output_samples[osample*6+2] = (last_sample[2] * (0x10000-t) + input_samples[2] * t) >> 16;
+    output_samples[osample*6+3] = (last_sample[3] * (0x10000-t) + input_samples[3] * t) >> 16;
+    output_samples[osample*6+4] = (last_sample[4] * (0x10000-t) + input_samples[4] * t) >> 16;
+    output_samples[osample*6+5] = (last_sample[5] * (0x10000-t) + input_samples[5] * t) >> 16;
+    isample += istep;
+  }
+
+  for (; osample < out_samples; osample++) {
     int  s1;
     int  s2;
     int16_t  os;
@@ -272,13 +311,7 @@ void _x_audio_out_resample_6channel(int16_t* input_samples, uint32_t in_samples,
 
     isample += istep;
   }
-
-  output_samples[out_samples*6-6] = input_samples[in_samples*6-6];
-  output_samples[out_samples*6-5] = input_samples[in_samples*6-5];
-  output_samples[out_samples*6-4] = input_samples[in_samples*6-4];
-  output_samples[out_samples*6-3] = input_samples[in_samples*6-3];
-  output_samples[out_samples*6-2] = input_samples[in_samples*6-2];
-  output_samples[out_samples*6-1] = input_samples[in_samples*6-1];
+  memcpy (last_sample, &input_samples[in_samples*6-6], 6 * sizeof (last_sample[0]));
 }
 
 void _x_audio_out_resample_8to16(int8_t* input_samples,