Speex echo cancellation configuration

Question

I am making an Android-to-Android VoIP (loudspeaker) app using its AudioRecord and AudioTrack class, along with Speex via NDK to do echo cancellation. I was able to successf

Answer 1

Your code is right but missing something in native codes, I modified init method and added speex preprocess after echo cancellation, then your code worked well (I tried in windows) Here is Native Code

#include <jni.h>
#include "speex/speex_echo.h"
#include "speex/speex_preprocess.h"
#include "EchoCanceller_jniHeader.h"
SpeexEchoState *st;
SpeexPreprocessState *den;

JNIEXPORT void JNICALL Java_speex_EchoCanceller_open
  (JNIEnv *env, jobject jObj, jint jSampleRate, jint jBufSize, jint jTotalSize)
{
     //init
     int sampleRate=jSampleRate;
     st = speex_echo_state_init(jBufSize, jTotalSize);
     den = speex_preprocess_state_init(jBufSize, sampleRate);
     speex_echo_ctl(st, SPEEX_ECHO_SET_SAMPLING_RATE, &sampleRate);
     speex_preprocess_ctl(den, SPEEX_PREPROCESS_SET_ECHO_STATE, st);
}

JNIEXPORT jshortArray JNICALL Java_speex_EchoCanceller_process
  (JNIEnv * env, jobject jObj, jshortArray input_frame, jshortArray echo_frame)
{
  //create native shorts from java shorts
  jshort *native_input_frame = (*env)->GetShortArrayElements(env, input_frame, NULL);
  jshort *native_echo_frame = (*env)->GetShortArrayElements(env, echo_frame, NULL);

  //allocate memory for output data
  jint length = (*env)->GetArrayLength(env, input_frame);
  jshortArray temp = (*env)->NewShortArray(env, length);
  jshort *native_output_frame = (*env)->GetShortArrayElements(env, temp, 0);

  //call echo cancellation
  speex_echo_cancellation(st, native_input_frame, native_echo_frame, native_output_frame);
  //preprocess output frame
  speex_preprocess_run(den, native_output_frame);

  //convert native output to java layer output
  jshortArray output_shorts = (*env)->NewShortArray(env, length);
  (*env)->SetShortArrayRegion(env, output_shorts, 0, length, native_output_frame);

  //cleanup and return
  (*env)->ReleaseShortArrayElements(env, input_frame, native_input_frame, 0);
  (*env)->ReleaseShortArrayElements(env, echo_frame, native_echo_frame, 0);
  (*env)->ReleaseShortArrayElements(env, temp, native_output_frame, 0);

  return output_shorts;   
}

JNIEXPORT void JNICALL Java_speex_EchoCanceller_close
  (JNIEnv *env, jobject jObj)
{
     //close
     speex_echo_state_destroy(st);
     speex_preprocess_state_destroy(den);
}

You can find useful samples such as Encoding, Decoding, Echo Cancellation in speex library's source (http://www.speex.org/downloads/)

Answer 2

Are you properly aligning the far-end signal (what you call recv) and near end signal (what you call record)? There is always some playback/record latency which needs to be accounted for. This generally requires buffering of the far-end signal in a ring buffer for some specified period of time. On PCs this is usually about 50 - 120ms. On Android I suspect it's much higher. Probably in the range of 150 - 400ms. I would recommend using a 100ms taillength with speex and adjusting the size of your far-end buffer until the AEC converges. These changes should allow the AEC to converge, independently of the inclusion of the preprocessor, which is not required here.