mirror of
https://github.com/oxen-io/session-android.git
synced 2024-11-24 02:25:19 +00:00
73 lines
2.0 KiB
Mathematica
73 lines
2.0 KiB
Mathematica
|
% Attempts to diagnose AEC problems from recorded samples
|
||
|
|
%
|
||
|
|
% out = echo_diagnostic(rec_file, play_file, out_file, tail_length)
|
||
|
|
%
|
||
|
|
% Computes the full matrix inversion to cancel echo from the
|
||
|
|
% recording 'rec_file' using the far end signal 'play_file' using
|
||
|
|
% a filter length of 'tail_length'. The output is saved to 'out_file'.
|
||
|
|
function out = echo_diagnostic(rec_file, play_file, out_file, tail_length)
|
||
|
|
|
||
|
|
F=fopen(rec_file,'rb');
|
||
|
|
rec=fread(F,Inf,'short');
|
||
|
|
fclose (F);
|
||
|
|
F=fopen(play_file,'rb');
|
||
|
|
play=fread(F,Inf,'short');
|
||
|
|
fclose (F);
|
||
|
|
|
||
|
|
rec = [rec; zeros(1024,1)];
|
||
|
|
play = [play; zeros(1024,1)];
|
||
|
|
|
||
|
|
N = length(rec);
|
||
|
|
corr = real(ifft(fft(rec).*conj(fft(play))));
|
||
|
|
acorr = real(ifft(fft(play).*conj(fft(play))));
|
||
|
|
|
||
|
|
[a,b] = max(corr);
|
||
|
|
|
||
|
|
if b > N/2
|
||
|
|
b = b-N;
|
||
|
|
end
|
||
|
|
printf ("Far end to near end delay is %d samples\n", b);
|
||
|
|
if (b > .3*tail_length)
|
||
|
|
printf ('This is too much delay, try delaying the far-end signal a bit\n');
|
||
|
|
else if (b < 0)
|
||
|
|
printf ('You have a negative delay, the echo canceller has no chance to cancel anything!\n');
|
||
|
|
else
|
||
|
|
printf ('Delay looks OK.\n');
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
N2 = round(N/2);
|
||
|
|
corr1 = real(ifft(fft(rec(1:N2)).*conj(fft(play(1:N2)))));
|
||
|
|
corr2 = real(ifft(fft(rec(N2+1:end)).*conj(fft(play(N2+1:end)))));
|
||
|
|
|
||
|
|
[a,b1] = max(corr1);
|
||
|
|
if b1 > N2/2
|
||
|
|
b1 = b1-N2;
|
||
|
|
end
|
||
|
|
[a,b2] = max(corr2);
|
||
|
|
if b2 > N2/2
|
||
|
|
b2 = b2-N2;
|
||
|
|
end
|
||
|
|
drift = (b1-b2)/N2;
|
||
|
|
printf ('Drift estimate is %f%% (%d samples)\n', 100*drift, b1-b2);
|
||
|
|
if abs(b1-b2) < 10
|
||
|
|
printf ('A drift of a few (+-10) samples is normal.\n');
|
||
|
|
else
|
||
|
|
if abs(b1-b2) < 30
|
||
|
|
printf ('There may be (not sure) excessive clock drift. Is the capture and playback done on the same soundcard?\n');
|
||
|
|
else
|
||
|
|
printf ('Your clock is drifting! No way the AEC will be able to do anything with that. Most likely, you''re doing capture and playback from two different cards.\n');
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
acorr(1) = .001+1.00001*acorr(1);
|
||
|
|
AtA = toeplitz(acorr(1:tail_length));
|
||
|
|
bb = corr(1:tail_length);
|
||
|
|
h = AtA\bb;
|
||
|
|
|
||
|
|
out = (rec - filter(h, 1, play));
|
||
|
|
|
||
|
|
F=fopen(out_file,'w');
|
||
|
|
fwrite(F,out,'short');
|
||
|
|
fclose (F);
|