<s>
TwinVQ	B-Algorithm
(	O
transform-domain	O
weighted	O
interleave	O
vector	B-Algorithm
quantization	I-Algorithm
)	O
is	O
an	O
audio	O
compression	O
technique	O
developed	O
by	O
Nippon	O
Telegraph	O
and	O
Telephone	O
Corporation	O
(	O
NTT	O
)	O
Human	O
Interface	O
Laboratories	O
(	O
now	O
Cyber	O
Space	O
Laboratories	O
)	O
in	O
1994	O
.	O
</s>
<s>
The	O
compression	O
technique	O
has	O
been	O
used	O
in	O
both	O
standardized	O
and	O
proprietary	B-Application
designs	O
.	O
</s>
<s>
In	O
the	O
context	O
of	O
the	O
MPEG-4	B-Algorithm
Audio	I-Algorithm
(	O
MPEG-4	B-Algorithm
Part	I-Algorithm
3	I-Algorithm
)	O
,	O
TwinVQ	B-Algorithm
is	O
an	O
audio	O
codec	B-General_Concept
optimized	O
for	O
audio	O
coding	O
at	O
ultra	O
low	O
bitrates	O
around	O
8	O
kbit/s	O
.	O
</s>
<s>
TwinVQ	B-Algorithm
is	O
one	O
of	O
the	O
object	O
types	O
defined	O
in	O
MPEG-4	B-Algorithm
Audio	I-Algorithm
,	O
published	O
as	O
subpart	O
4	O
of	O
ISO/IEC	B-Algorithm
14496-3	I-Algorithm
(	O
for	O
the	O
first	O
time	O
in	O
1999	O
-	O
a.k.a.	O
</s>
<s>
MPEG-4	B-Algorithm
Audio	I-Algorithm
version	O
1	O
)	O
.	O
</s>
<s>
This	O
object	O
type	O
is	O
based	O
on	O
a	O
general	O
audio	O
transform	O
coding	O
scheme	O
which	O
is	O
integrated	O
with	O
the	O
AAC	O
coding	O
frame	O
work	O
,	O
a	O
spectral	O
flattening	O
module	O
,	O
and	O
a	O
weighted	O
interleave	O
vector	B-Algorithm
quantization	I-Algorithm
module	O
.	O
</s>
<s>
It	O
supports	O
bitrate	O
scalability	O
,	O
both	O
by	O
means	O
of	O
layered	O
TwinVQ	B-Algorithm
coding	O
and	O
in	O
combination	O
with	O
the	O
scalable	O
AAC	O
.	O
</s>
<s>
Note	O
that	O
some	O
commercialized	O
products	O
such	O
as	O
Metasound	O
(	O
Voxware	O
)	O
,	O
SoundVQ	B-Algorithm
(	O
Yamaha	O
)	O
,	O
and	O
SolidAudio	O
(	O
Hagiwara	O
)	O
are	O
also	O
based	O
on	O
the	O
TwinVQ	B-Algorithm
technology	O
,	O
but	O
the	O
configurations	O
are	O
different	O
from	O
the	O
MPEG-4	B-Algorithm
TwinVQ	B-Algorithm
.	O
</s>
<s>
A	O
proprietary	B-Application
audio	O
compression	O
format	O
called	O
TwinVQ	B-Algorithm
was	O
developed	O
by	O
Nippon	O
Telegraph	O
and	O
Telephone	O
Corporation	O
(	O
NTT	O
)	O
(	O
in	O
NTT	O
's	O
Human	O
Interface	O
Laboratories	O
)	O
and	O
marketed	O
by	O
Yamaha	O
under	O
the	O
name	O
SoundVQ	B-Algorithm
.	O
</s>
<s>
The	O
NTT	O
also	O
offered	O
a	O
TwinVQ	B-Algorithm
demonstration	O
software	O
for	O
non-commercial	O
purposes	O
-	O
NTT	O
TwinVQ	B-Algorithm
Encoder	O
and	O
TwinVQ	B-Algorithm
Player	O
,	O
encoder	O
API	B-General_Concept
,	O
decoder	O
API	B-General_Concept
and	O
header	O
file	O
format	O
.	O
</s>
<s>
The	O
filename	O
extension	O
is	O
.vqf	B-Algorithm
.	O
</s>
<s>
TwinVQ	B-Algorithm
uses	O
Twin	B-General_Concept
vector	I-General_Concept
quantization	I-General_Concept
.	O
</s>
<s>
The	O
proprietary	B-Application
TwinVQ	B-Algorithm
codec	B-General_Concept
supports	O
constant	B-General_Concept
bit	I-General_Concept
rate	I-General_Concept
encoding	O
at	O
80	O
,	O
96	O
,	O
112	O
,	O
128	O
,	O
160	O
and	O
192	O
kbit/s	O
.	O
</s>
<s>
It	O
was	O
claimed	O
that	O
TwinVQ	B-Algorithm
files	O
are	O
about	O
30	O
to	O
35%	O
smaller	O
than	O
MP3	B-Application
files	I-Application
of	O
adequate	O
quality	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
96	O
kbit/s	O
TwinVQ	B-Algorithm
file	O
allegedly	O
has	O
roughly	O
the	O
same	O
quality	O
as	O
a	O
128	O
kbit/s	O
MP3	B-Application
file	I-Application
.	O
</s>
<s>
Yamaha	O
marketed	O
TwinVQ	B-Algorithm
as	O
an	O
alternative	O
to	O
MP3	B-Application
,	O
but	O
the	O
format	O
never	O
became	O
very	O
popular	O
.	O
</s>
<s>
This	O
could	O
be	O
attributed	O
to	O
the	O
proprietary	B-Application
nature	O
of	O
the	O
format	O
—	O
third	O
party	O
software	O
was	O
scarce	O
and	O
there	O
was	O
no	O
hardware	O
support	O
.	O
</s>
<s>
Also	O
the	O
encoding	O
was	O
extremely	O
slow	O
and	O
there	O
was	O
not	O
much	O
music	O
available	O
in	O
TwinVQ	B-Algorithm
format	O
.	O
</s>
<s>
As	O
other	O
MP3	B-Application
alternatives	O
emerged	O
,	O
TwinVQ	B-Algorithm
quickly	O
became	O
obsolete	O
.	O
</s>
<s>
The	O
proprietary	B-Application
version	O
of	O
TwinVQ	B-Algorithm
can	O
be	O
also	O
used	O
for	O
speech	B-Application
encoding	I-Application
.	O
</s>
<s>
The	O
NTT	O
TwinVQ	B-Algorithm
implementation	O
supported	O
sampling	B-Algorithm
frequencies	I-Algorithm
from	O
8kHz	O
or	O
11.025kHz	O
and	O
bit	O
rate	O
from	O
8	O
kbit/s	O
.	O
</s>
<s>
Yamaha	O
released	O
an	O
English	O
player	O
application	O
called	O
SoundVQ	B-Algorithm
.	O
</s>
<s>
The	O
format	O
was	O
reverse-engineered	O
in	O
2009	O
by	O
the	O
FFmpeg	B-Library
project	O
and	O
decoding	O
of	O
vqf	B-Algorithm
files	O
is	O
supported	O
by	O
the	O
open-source	O
libavcodec	B-Language
library	O
,	O
which	O
makes	O
it	O
supported	O
in	O
players	O
that	O
utilize	O
the	O
library	O
,	O
such	O
as	O
VLC	B-Application
media	I-Application
player	I-Application
.	O
</s>
<s>
Some	O
older	O
versions	O
of	O
Nero	B-Application
Burning	I-Application
ROM	I-Application
are	O
able	O
to	O
encode	O
to	O
TwinVQ/VQF	O
.	O
</s>
<s>
Some	O
CD-Ripping/Converter	O
software	O
also	O
support	O
encoding	O
to	O
.vqf	B-Algorithm
format	O
.	O
</s>
