Brian White CS529 SPEAK WITH FORWARD ERROR CORRECTION: IMPLEMENTATION AND EVALUATION

 Perceptual Evaluation of Speech Technology (ITU-T P.862)  Standard methodology for analysis of voice quality  “Full Reference” Test – original vs. degrade  Produces a mean opinion score (MOS)  Temporal alignment  Sample by sample comparison  ITU provides a reference implementation PESQ: WHAT IS IT?

WHAT DOES PESQ DETECT?

 Media Specific Forward Error Correction  Include fully redundant data in next packet  Sequence Number  Primary Audio  Secondary Audio SPEAK FEC IMPLEMENTATION A[N]A[N+1]N+1A[N-1]A[N]N

 Handling packet loss (packet N) SPEAK FEC IMPLEMENTATION A[N]A[N+1]N+1A[N-1]A[N]NA[N-2]A[N-1]N-1 A[N-1]A[N]A[N+1]

 Subjective evaluation with 5 test subjects  22 seconds audio played through a Speak application channel.  With and Without FEC  Various error rates (0%,5%,7%,10%,12%,15%)  The audio of each session was recorded and run through PESQ  3 Questions on quality  Overall quality  Impression vs. landline  Impression vs. cellphone EVALUATION

SO HOW WELL DOES FEC PERFORM?

COMPARISON TO LANDLINE PHONE

PESQ EVALUATION

 FEC is valuable for networks that expect moderate loss  To fully work, an adaptive buffering scheme should be adopted  Work with speech detection  Future work to evaluate FEC implementation in a two-way conversation test.  Expand on informal evaluation of PESQ as a testing methodology. Are there cases were PESQ diverges from subjective results? CONCLUSION