[pulseaudio-discuss] [PATCH] echo-cancel: Add function pa_echo_canceller_blocksize_power2()

[Peter Meerwald]

From: Peter Meerwald <p.meerwald at bct-electronic.com>

computes EC block size in frames (rounded down to nearest power-of-2) based
on sample rate and milliseconds

move code from speex AEC implementation to module-echo-cancel such that
functionality can be reused by other AEC implementations

Signed-off-by: Peter Meerwald <p.meerwald at bct-electronic.com>
---
 src/modules/echo-cancel/echo-cancel.h        |    4 ++++
 src/modules/echo-cancel/module-echo-cancel.c |   15 +++++++++++++++
 src/modules/echo-cancel/speex.c              |   11 +++--------
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/src/modules/echo-cancel/echo-cancel.h b/src/modules/echo-cancel/echo-cancel.h
index d9929df..7f333b8 100644
--- a/src/modules/echo-cancel/echo-cancel.h
+++ b/src/modules/echo-cancel/echo-cancel.h
@@ -152,6 +152,10 @@ struct pa_echo_canceller {
 void pa_echo_canceller_get_capture_volume(pa_echo_canceller *ec, pa_cvolume *v);
 void pa_echo_canceller_set_capture_volume(pa_echo_canceller *ec, pa_cvolume *v);
 
+/* Computes EC block size in frames (rounded down to nearest power-of-2) based
+ * on sample rate and milliseconds. */
+uint32_t pa_echo_canceller_blocksize_power2(unsigned rate, unsigned ms);
+
 /* Null canceller functions */
 pa_bool_t pa_null_ec_init(pa_core *c, pa_echo_canceller *ec,
                            pa_sample_spec *rec_ss, pa_channel_map *rec_map,
diff --git a/src/modules/echo-cancel/module-echo-cancel.c b/src/modules/echo-cancel/module-echo-cancel.c
index f550245..b0dcbf0 100644
--- a/src/modules/echo-cancel/module-echo-cancel.c
+++ b/src/modules/echo-cancel/module-echo-cancel.c
@@ -1605,6 +1605,21 @@ void pa_echo_canceller_set_capture_volume(pa_echo_canceller *ec, pa_cvolume *v)
     }
 }
 
+uint32_t pa_echo_canceller_blocksize_power2(unsigned rate, unsigned ms) {
+    unsigned nframes = (rate * ms) / 1000;
+    uint32_t y = 1 << ((8 * sizeof(uint32_t)) - 2);
+
+    assert(rate >= 4000);
+    assert(ms >= 1);
+
+    /* nframes should be a power of 2, round down to nearest power of two */
+    while (y > nframes)
+      y >>= 1;
+
+    assert(y >= 1);
+    return y;
+}
+
 static pa_echo_canceller_method_t get_ec_method_from_string(const char *method) {
     if (pa_streq(method, "null"))
         return PA_ECHO_CANCELLER_NULL;
diff --git a/src/modules/echo-cancel/speex.c b/src/modules/echo-cancel/speex.c
index 5bb4a77..dcaf2ad 100644
--- a/src/modules/echo-cancel/speex.c
+++ b/src/modules/echo-cancel/speex.c
@@ -155,7 +155,7 @@ pa_bool_t pa_speex_ec_init(pa_core *c, pa_echo_canceller *ec,
                            uint32_t *nframes, const char *args)
 {
     int rate;
-    uint32_t y, frame_size_ms, filter_size_ms;
+    uint32_t frame_size_ms, filter_size_ms;
     pa_modargs *ma;
 
     if (!(ma = pa_modargs_new(args, valid_modargs))) {
@@ -178,16 +178,11 @@ pa_bool_t pa_speex_ec_init(pa_core *c, pa_echo_canceller *ec,
     pa_speex_ec_fixate_spec(rec_ss, rec_map, play_ss, play_map, out_ss, out_map);
 
     rate = out_ss->rate;
-    *nframes = (rate * frame_size_ms) / 1000;
-    /* nframes should be a power of 2, round down to nearest power of two */
-    y = 1 << ((8 * sizeof (uint32_t)) - 2);
-    while (y > *nframes)
-      y >>= 1;
-    *nframes = y;
+    *nframes = pa_echo_canceller_blocksize_power2(rate, frame_size_ms);
 
     pa_log_debug ("Using nframes %d, channels %d, rate %d", *nframes, out_ss->channels, out_ss->rate);
 
-    ec->params.priv.speex.state = speex_echo_state_init_mc (*nframes, (rate * filter_size_ms) / 1000, out_ss->channels, out_ss->channels);
+    ec->params.priv.speex.state = speex_echo_state_init_mc(*nframes, (rate * filter_size_ms) / 1000, out_ss->channels, out_ss->channels);
 
     if (!ec->params.priv.speex.state)
         goto fail;
-- 
1.7.9.5