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1 /***************************************************************
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2 A.5 Test source code
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3 ***************************************************************/
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4
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5 The microphone and loudspeaker signals have to be synchronized on a
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6 sample-to-sample basis to make acoustic echo cancellation working.
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7 An AC97 conformal on-board soundcard in a Personal Computer can be set
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8 in a special stereo mode: The left channnel records microphone signal
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9 and the right channel records loudspeaker signal.
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10
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11 To set-up a Linux PC with ALSA sound system, electret microphone like
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12 Labtec Verse 333 connected to Mic in and loudspeaker connected to right
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13 Line out enter:
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14
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15 amixer -q set 'Master',0 70% unmute
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16 amixer -q set 'PCM',0 70% unmute
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17 amixer -q set 'Line',0 0% mute
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18 amixer -q set 'CD',0 0% mute
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19 amixer -q set 'Mic',0 0% mute
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20 amixer -q set 'Video',0 0% mute
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21 amixer -q set 'Phone',0 0% mute
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22 amixer -q set 'PC Speaker',0 0% mute
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23 amixer -q set 'Aux',0 0% mute
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24 amixer -q set 'Capture',0 50%,0%
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25 amixer -q set 'Mic Boost (+20dB)',0 1
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26 amixer -q cset iface=MIXER,name='Capture Source' 0,5
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27 amixer -q cset iface=MIXER,name='Capture Switch' 1
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28
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29 To test the acoustic echo cancellation we simulate a real telephone
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30 conversation in 5 steps:
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31 (1) record far-end speaker,
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32 (2) perform acoustic echo cancellation (this should change nothing)
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33 (3) playback far-end speaker and at the same time record near-end speaker
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34 (4) perform acoustic echo cancellation
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35 (5) playback near-end speaker (far-end speech should be cancelled)
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36
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37 # To compile the test program aec_test read file aec_test.cpp.
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38
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39 # To record 10 seconds of speech into the file b.raw enter:
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40 arecord -c 2 -t raw -f S16_LE -r 16000 -d 10 >b.raw
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41
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42 # To perform AEC at the far-end enter:
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43 ./aec_test <b.raw >b1.raw
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44
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45 # To playback file b1.raw and simultaneously record b2.raw enter both
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46 # commands in one go:
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47 aplay -c 2 -t raw -f S16_LE -r 16000 b1.raw &
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48 arecord -c 2 -t raw -f S16_LE -r 16000 -d 10 >b2.raw
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49
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50 # To perform AEC at the near-end enter:
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51 ./aec_test <b2.raw >b3.raw
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52
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53 # To playback the echo-cancelled near-end enter:
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54 aplay -c 2 -t raw -f S16_LE -r 16000 b3.raw
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