Speech Codecs and Associated PSQM Values

PSQM is a computational and modeling algorithm defined in International Telecommunications Union Recommendation ITU-T P.861 (1996) that objectively evaluates and quantifies voice quality of voice-band (300Hz - 3400 Hz) speech codecs.

PSQM uses a psychoacoustical mathematical modeling (both perceptual and cognitive) algorithm to analyze the pre and post transmitted voice signals, yielding a PSQM value which is a measure of signal quality degradation and ranges from 0 (no degradation) to 6.5 (highest degradation). In turn, this result may be translated into a Mean Opinion Score (MOS), which is an accepted measure of the perceived quality of received media on a numeric scale ranging from 1 to 5. A value of 1 indicates unacceptable, poor quality voice while a value of 5 indicates high voice quality with no perceptible issues.

The following four test sets were run on VOCAL ATA's, using different speech files and network load conditions. For further information on the exact test conditions, please contact us directly. The results provide a general indication of the relative performance of the PSQM algorithm in ranking the performance of different speech codecs under different situations.

Test Set 1

Ideal Conditions: No Network Load with Artificial Voice
	G.711u	G.711a	G.726 32kbps	G.729a	G.723.1	iLBC	GSM AMR 12.2kbps	Speex
MOS AVG (PSQM)	4.45	4.44	4.3	4.04	4.08	4.1	4.14	3.84

Test Set 2

Ideal Conditions: No Network Load with Both Gender Voice
	G.711u	G.711a	G.726 32kbps	G.729a	G.723.1	iLBC	GSM AMR 12.2kbps	Speex
MOS AVG (PSQM)	4.3	4.29	4.21	3.76	3.74	3.81	3.96	3.78

Test Set 3

Normal Conditions: 1% Packet Loss with Both Gender Voice
	G.711u	G.711a	G.726 32kbps	G.729a	G.723.1	iLBC	GSM AMR 12.2kbps	Speex
MOS AVG (PSQM)	4.24	4.25	4.14	3.74	3.75	3.82	3.94	3.79

Test Set 4

Duress: 5% Packet Loss with Both Gender Voice
	G.711u	G.711a	G.726 32kbps	G.729a	G.723.1	iLBC	GSM AMR 12.2kbps	Speex
MOS AVG (PSQM)	4.13	4.11	3.79	3.51	3.57	3.74	3.79	3.59