Don't return a zero delay with insufficient data.

For estimating a delay over a long segment (e.g. a file) this can
throw off the estimate. Better not to add values to the AEC's histogram
until they're reliable.

BUG=
TEST=audiproc, audioproc_unittest

Review URL: http://webrtc-codereview.appspot.com/292004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@1035 4adac7df-926f-26a2-2b94-8c16560cd09d

src/modules/audio_processing/aec/echo_cancellation.c

@@ -367,6 +367,7 @@ WebRtc_Word32 WebRtcAec_Process(void *aecInst, const WebRtc_Word16 *nearend,
         aecpc->lastError = AEC_BAD_PARAMETER_WARNING;
         retVal = -1;
     }
+    // TODO(andrew): we need to investigate if this +10 is really wanted.
     msInSndCardBuf += 10;
     aecpc->msInSndCardBuf = msInSndCardBuf;
 
@@ -752,7 +753,9 @@ int WebRtcAec_GetDelayMetrics(void* handle, int* median, int* std) {
     num_delay_values += self->aec->delay_histogram[i];
   }
   if (num_delay_values == 0) {
-    // We have no new delay value data
+    // We have no new delay value data. Even though -1 is a valid estimate, it
+    // will practically never be used since multiples of |kMsPerBlock| will
+    // always be returned.
     *median = -1;
     *std = -1;
     return 0;

src/modules/audio_processing/aecm/aecm_core.c

@@ -144,6 +144,7 @@ static void UpdateFarHistory(AecmCore_t* self,
 //
 // Inputs:
 //      - self              : Pointer to the AECM instance.
+//      - delay             : Current delay estimate.
 //
 // Output:
 //      - far_q             : The Q-domain of the aligned far end spectrum
@@ -152,11 +153,10 @@ static void UpdateFarHistory(AecmCore_t* self,
 //      - far_spectrum      : Pointer to the aligned far end spectrum
 //                            NULL - Error
 //
-static const uint16_t* AlignedFarend(AecmCore_t* self, int* far_q) {
+static const uint16_t* AlignedFarend(AecmCore_t* self, int* far_q, int delay) {
   int buffer_position = 0;
   assert(self != NULL);
-  buffer_position = self->far_history_pos -
-      WebRtc_last_delay(self->delay_estimator);
+  buffer_position = self->far_history_pos - delay;
 
   // Check buffer position
   if (buffer_position < 0) {
@@ -308,9 +308,6 @@ int WebRtcAecm_InitCore(AecmCore_t * const aecm, int samplingFreq)
     memset(aecm->far_q_domains, 0, sizeof(int) * MAX_DELAY);
     aecm->far_history_pos = MAX_DELAY;
 
-    // Initialize to reasonable values
-    aecm->currentDelay = 8;
-
     aecm->nlpFlag = 1;
     aecm->fixedDelay = -1;
 
@@ -1215,7 +1212,7 @@ int WebRtcAecm_ProcessBlock(AecmCore_t * aecm,
     WebRtc_Word16 hnl[PART_LEN1];
     WebRtc_Word16 numPosCoef = 0;
     WebRtc_Word16 nlpGain = ONE_Q14;
-    WebRtc_Word16 delay;
+    int delay;
     WebRtc_Word16 tmp16no1;
     WebRtc_Word16 tmp16no2;
     WebRtc_Word16 mu;
@@ -1312,21 +1309,23 @@ int WebRtcAecm_ProcessBlock(AecmCore_t * aecm,
                                             PART_LEN1,
                                             far_q,
                                             aecm->currentVADValue);
-    if (delay < 0)
+    if (delay == -1)
     {
         return -1;
     }
+    else if (delay == -2)
+    {
+        // If the delay is unknown, we assume zero.
+        // NOTE: this will have to be adjusted if we ever add lookahead.
+        delay = 0;
+    }
 
     if (aecm->fixedDelay >= 0)
     {
-        // TODO(bjornv): Make this work in practice, that is, get proper
-        //               aligned farend.
         // Use fixed delay
         delay = aecm->fixedDelay;
     }
 
-    aecm->currentDelay = delay;
-
 #ifdef ARM_WINM_LOG_
     // measure tick end
     QueryPerformanceCounter((LARGE_INTEGER*)&end);
@@ -1337,7 +1336,7 @@ int WebRtcAecm_ProcessBlock(AecmCore_t * aecm,
     QueryPerformanceCounter((LARGE_INTEGER*)&start);
 #endif
     // Get aligned far end spectrum
-    far_spectrum_ptr = AlignedFarend(aecm, &far_q);
+    far_spectrum_ptr = AlignedFarend(aecm, &far_q, delay);
     zerosXBuf = (WebRtc_Word16) far_q;
     if (far_spectrum_ptr == NULL)
     {

src/modules/audio_processing/utility/delay_estimator.c

@@ -163,8 +163,9 @@ int WebRtc_InitBinaryDelayEstimator(BinaryDelayEstimator_t* handle) {
 
   handle->vad_counter = 0;
 
-  // Set to zero delay after compensating for lookahead.
-  handle->last_delay = handle->near_history_size - 1;
+  // Default value to return if we're unable to estimate. -1 is used for
+  // errors.
+  handle->last_delay = -2;
 
   return 0;
 }

src/modules/audio_processing/utility/delay_estimator.h

@@ -79,6 +79,7 @@ int WebRtc_InitBinaryDelayEstimator(BinaryDelayEstimator_t* handle);
 // Return value:
 //    - delay                 :  >= 0 - Calculated delay value
 //                              -1    - Error
+//                              -2    - Insufficient data for estimation.
 //
 int WebRtc_ProcessBinarySpectrum(BinaryDelayEstimator_t* handle,
                                  uint32_t binary_far_spectrum,
@@ -94,6 +95,7 @@ int WebRtc_ProcessBinarySpectrum(BinaryDelayEstimator_t* handle,
 // Return value:
 //    - delay                 :  >= 0 - Last calculated delay value
 //                              -1    - Error
+//                              -2    - Insufficient data for estimation.
 //
 int WebRtc_binary_last_delay(BinaryDelayEstimator_t* handle);
 

src/modules/audio_processing/utility/delay_estimator_wrapper.h

@@ -79,6 +79,7 @@ int WebRtc_InitDelayEstimator(void* handle);
 // Return value:
 //      - delay         :  >= 0 - Calculated delay value
 //                        -1    - Error
+//                        -2    - Insufficient data for estimation.
 //
 int WebRtc_DelayEstimatorProcessFix(void* handle,
                                     uint16_t* far_spectrum,
@@ -103,6 +104,7 @@ int WebRtc_DelayEstimatorProcessFloat(void* handle,
 // Return value:
 //      - delay         :  >= 0 - Last calculated delay value
 //                        -1    - Error
+//                        -2    - Insufficient data for estimation.
 //
 int WebRtc_last_delay(void* handle);