CMUSphinx implements keyword spotting in pocketsphinx engine, see for details the FAQ entry.
To recognize a single keyphrase you can run decoder in “keyphrase search” mode.
From command line try:
pocketsphinx_continuous -infile file.wav -keyphrase “oh mighty computer” -kws_threshold 1e-20
From the code:
ps_set_keyphrase(ps, "keyphrase_search", "oh mighty computer");
ps_set_search(ps, "keyphrase_search);
ps_start_utt();
/* process data */
You can also find examples for Python and Android/Java in our sources. Python code looks like this, full example here:
# Process audio chunk by chunk. On keyphrase detected perform action and restart search
decoder = Decoder(config)
decoder.start_utt()
while True:
buf = stream.read(1024)
if buf:
decoder.process_raw(buf, False, False)
else:
break
if decoder.hyp() != None:
print ([(seg.word, seg.prob, seg.start_frame, seg.end_frame) for seg in decoder.seg()])
print ("Detected keyphrase, restarting search")
decoder.end_utt()
decoder.start_utt()
Threshold must be tuned for every keyphrase on a test data to get the right balance missed detections and false alarms. You can try values like 1e-5 to 1e-50.
For the best accuracy it is better to have keyphrase with 3-4 syllables. Too short phrases are easily confused.
You can also search for multiple keyphrase, create a file keyphrase.list like this:
oh mighty computer /1e-40/
hello world /1e-30/
other_phrase /other_phrase_threshold/
And use it in decoder with -kws configuration option.
pocketsphinx_continuous -inmic yes -kws keyphrase_list
This feature is not yet implemented in sphinx4 decoder.
