Bug 183375 – Audio quality received at Safari degrades significantly when injecting network impairment jitter >= 300ms

• Component: WebRTC
• Status: NEW

[Ju-Chiang Wang]

We suppose Safari may not handle jitter buffer well. In our end-to-end audio quality test, we injected network impairment with jitter and found the audio quality degraded a lot on Safari as a receiver. The jitter impairment greater than 300 ms can easily cause Safari drop rtp packages, leading to crappy sound.

We compared the result among different browsers and found Safari->Safari and Chrome->Safari were poor audio quality. However, Firefox->Safari was good.

Details:
Safari->Safari	
Impairment case			MOS	Delay(ms)
jitter 100ms downlink UDP	4.2	228
jitter 200ms downlink UDP	4.08	536
jitter 300ms downlink UDP	2.36	373
jitter 400ms downlink UDP	2.54	515
jitter 500ms downlink UDP	1.85	386
jitter 500ms uplink UDP	        1.98	525
jitter 400ms uplink UDP	        2.03	474
jitter 300ms uplink UDP	        2.04	427
jitter 200ms uplink UDP	        4.17	595
jitter 100ms uplink UDP	        4.18	319

Chrome->Safari	
Impairment case			MOS	Delay(ms)	
jitter 100ms downlink UDP	4.29	201
jitter 200ms downlink UDP	4.04	461
jitter 300ms downlink UDP	2.33	417
jitter 400ms downlink UDP	1.86	417
jitter 500ms downlink UDP	1.72	474
jitter 500ms uplink UDP	        1.64	366
jitter 400ms uplink UDP	        1.93	484
jitter 300ms uplink UDP	        3	460
jitter 200ms uplink UDP	        4.24	759
jitter 100ms uplink UDP	        4.21	315

Firefox->Safari
Impairment case			MOS	Delay(ms)
jitter 100ms downlink UDP	4.51	157
jitter 200ms downlink UDP	4.47	337
jitter 300ms downlink UDP	4.47	428
jitter 400ms downlink UDP	4.49	568
jitter 500ms downlink UDP	4.49	672
jitter 500ms uplink UDP	        4.5	730
jitter 400ms uplink UDP	        4.47	570
jitter 300ms uplink UDP	        4.46	440
jitter 200ms uplink UDP	        4.48	336
jitter 100ms uplink UDP	        4.46	233