<s>
Enhanced	B-Algorithm
Voice	I-Algorithm
Services	I-Algorithm
(	O
EVS	O
)	O
is	O
a	O
superwideband	B-Algorithm
speech	B-Application
audio	O
coding	O
standard	O
that	O
was	O
developed	O
for	O
VoLTE	O
.	O
</s>
<s>
It	O
offers	O
up	O
to	O
20kHz	O
audio	O
bandwidth	O
and	O
has	O
high	O
robustness	O
to	O
delay	O
jitter	O
and	O
packet	B-Protocol
losses	I-Protocol
due	O
to	O
its	O
channel	O
aware	O
coding	O
and	O
improved	O
packet	B-Protocol
loss	I-Protocol
concealment	O
.	O
</s>
<s>
Samsung	B-Application
uses	O
the	O
term	O
HD+	O
when	O
doing	O
a	O
call	O
using	O
EVS	O
.	O
</s>
<s>
Other	O
contributors	O
included	O
Huawei	O
,	O
Nokia	O
,	O
Orange	O
,	O
Qualcomm	O
,	O
Samsung	B-Application
Electronics	O
,	O
VoiceAge	O
,	O
and	O
ZTE	O
Corporation	O
.	O
</s>
<s>
EVS	O
employs	O
similar	O
concepts	O
to	O
its	O
predecessors	O
,	O
such	O
as	O
AMR-WB	B-Algorithm
,	O
to	O
which	O
it	O
retains	O
backward-compatibility	O
.	O
</s>
<s>
It	O
switches	O
between	O
speech	B-Application
and	O
audio	O
compression	O
modes	O
depending	O
on	O
the	O
content	O
,	O
using	O
ACELP	B-Algorithm
and	O
MDCT	O
.	O
</s>
<s>
Subjective	O
listening	O
tests	O
conducted	O
by	O
Nokia	O
concluded	O
that	O
EVS	O
offers	O
significantly	O
improved	O
quality	O
over	O
AMR	B-Algorithm
and	O
AMR-WB	B-Algorithm
at	O
all	O
operating	O
points	O
.	O
</s>
<s>
Inter-carrier	O
interoperability	O
is	O
a	O
problem	O
,	O
as	O
calls	O
are	O
by	O
default	O
routed	O
over	O
narrowband	O
connections	O
which	O
downgrades	O
the	O
voice	O
to	O
narrowband	O
quality	O
instead	O
of	O
EVS	O
and	O
HD	B-Algorithm
Voice	I-Algorithm
even	O
if	O
the	O
individual	O
phones	O
and	O
carrier	O
networks	O
all	O
support	O
EVS	O
.	O
</s>
<s>
Thus	O
,	O
users	O
are	O
encouraged	O
to	O
switch	O
from	O
phone	O
calls	O
to	O
pure	O
VoIP	O
apps	O
such	O
as	O
FaceTime	B-Operating_System
,	O
Google	B-Application
Duo	I-Application
,	O
WhatsApp	B-Application
,	O
Facebook	B-Protocol
Messenger	I-Protocol
,	O
and/or	O
Telegram	B-Application
when	O
voice	O
call	O
quality	O
remains	O
poor	O
despite	O
good	O
network	O
connectivity	O
.	O
</s>
<s>
EVS	O
,	O
like	O
AMR-WB	B-Algorithm
and	O
AMR-WB	B-Algorithm
+	O
,	O
incorporates	O
several	O
patents	O
.	O
</s>
