[pulseaudio-discuss] [PATCH 1/2] Rework the peaks resampler

[Maarten Bosmans]

The algorithm had been implemented the same way as the trivial resampler.  But
an important difference between the two is that the trivial resampler can write
an output as soon as the first corresponding input sample is seen, whereas the
peaks resampler must have read all input samples before writing an output
sample.

With this rework, the peaks resampler now outputs samples correctly when the
input data is spanning multiple memblocks.
---
 src/pulsecore/resampler.c |   67 +++++++++++++++++++--------------------------
 1 files changed, 28 insertions(+), 39 deletions(-)

diff --git a/src/pulsecore/resampler.c b/src/pulsecore/resampler.c
index d4a7204..cbf5782 100644
--- a/src/pulsecore/resampler.c
+++ b/src/pulsecore/resampler.c
@@ -1435,40 +1435,33 @@ static int trivial_init(pa_resampler*r) {
 /* Peak finder implementation */
 
 static void peaks_resample(pa_resampler *r, const pa_memchunk *input, unsigned in_n_frames, pa_memchunk *output, unsigned *out_n_frames) {
-    size_t fz;
-    unsigned o_index;
-    void *src, *dst;
-    unsigned start = 0;
+    unsigned c, o_index = 0;
+    unsigned i, i_end = 0;
+    uint8_t *src, *dst;
 
     pa_assert(r);
     pa_assert(input);
     pa_assert(output);
     pa_assert(out_n_frames);
-
-    fz = r->w_sz * r->o_ss.channels;
+    pa_assert(r->i_ss.channels == r->o_ss.channels);
 
     src = (uint8_t*) pa_memblock_acquire(input->memblock) + input->index;
     dst = (uint8_t*) pa_memblock_acquire(output->memblock) + output->index;
 
-    for (o_index = 0;; o_index++, r->peaks.o_counter++) {
-        unsigned j;
-
-        j = ((r->peaks.o_counter * r->i_ss.rate) / r->o_ss.rate);
+    i = (r->peaks.o_counter * r->i_ss.rate) / r->o_ss.rate;
+    i = i > r->peaks.i_counter ? i - r->peaks.i_counter : 0;
 
-        if (j > r->peaks.i_counter)
-            j -= r->peaks.i_counter;
-        else
-            j = 0;
+    while (i_end < in_n_frames) {
+        i_end = ((r->peaks.o_counter+1) * r->i_ss.rate) / r->o_ss.rate;
+        i_end = i_end > r->peaks.i_counter ? i_end - r->peaks.i_counter : 0;
 
-        pa_assert(o_index * fz < pa_memblock_get_length(output->memblock));
+        pa_assert(o_index * r->w_sz * r->o_ss.channels < pa_memblock_get_length(output->memblock));
 
         if (r->work_format == PA_SAMPLE_S16NE) {
-            unsigned i, c;
-            int16_t *s = (int16_t*) ((uint8_t*) src + fz * start);
-            int16_t *d = (int16_t*) ((uint8_t*) dst + fz * o_index);
-
-            for (i = start; i <= j && i < in_n_frames; i++)
+            int16_t *s = (int16_t*) src + r->i_ss.channels * i;
+            int16_t *d = (int16_t*) dst + r->o_ss.channels * o_index;
 
+            for (; i < i_end && i < in_n_frames; i++)
                 for (c = 0; c < r->o_ss.channels; c++, s++) {
                     int16_t n;
 
@@ -1478,22 +1471,20 @@ static void peaks_resample(pa_resampler *r, const pa_memchunk *input, unsigned i
                         r->peaks.max_i[c] = n;
                 }
 
-            if (i >= in_n_frames)
-                break;
-
-            for (c = 0; c < r->o_ss.channels; c++, d++) {
-                *d = r->peaks.max_i[c];
-                r->peaks.max_i[c] = 0;
+            if (i == i_end) {
+                for (c = 0; c < r->o_ss.channels; c++, d++) {
+                    *d = r->peaks.max_i[c];
+                    r->peaks.max_i[c] = 0;
+                }
+                o_index++, r->peaks.o_counter++;
             }
-
         } else {
-            unsigned i, c;
-            float *s = (float*) ((uint8_t*) src + fz * start);
-            float *d = (float*) ((uint8_t*) dst + fz * o_index);
+            float *s = (float*) src + r->i_ss.channels * i;
+            float *d = (float*) dst + r->o_ss.channels * o_index;
 
             pa_assert(r->work_format == PA_SAMPLE_FLOAT32NE);
 
-            for (i = start; i <= j && i < in_n_frames; i++)
+            for (; i < i_end && i < in_n_frames; i++)
                 for (c = 0; c < r->o_ss.channels; c++, s++) {
                     float n = fabsf(*s);
 
@@ -1501,16 +1492,14 @@ static void peaks_resample(pa_resampler *r, const pa_memchunk *input, unsigned i
                         r->peaks.max_f[c] = n;
                 }
 
-            if (i >= in_n_frames)
-                break;
-
-            for (c = 0; c < r->o_ss.channels; c++, d++) {
-                *d = r->peaks.max_f[c];
-                r->peaks.max_f[c] = 0;
+            if (i == i_end) {
+                for (c = 0; c < r->o_ss.channels; c++, d++) {
+                    *d = r->peaks.max_f[c];
+                    r->peaks.max_f[c] = 0;
+                }
+                o_index++, r->peaks.o_counter++;
             }
         }
-
-        start = j;
     }
 
     pa_memblock_release(input->memblock);
-- 
1.7.4.1