<s>
H.120	B-Algorithm
was	O
the	O
first	O
digital	O
video	B-Algorithm
compression	I-Algorithm
standard	I-Algorithm
.	O
</s>
<s>
The	O
video	O
turned	O
out	O
not	O
to	O
be	O
of	O
adequate	O
quality	O
,	O
there	O
were	O
few	O
implementations	O
,	O
and	O
there	O
are	O
no	O
existing	O
codecs	B-General_Concept
for	O
the	O
format	O
,	O
but	O
it	O
provided	O
important	O
knowledge	O
leading	O
directly	O
to	O
its	O
practical	O
successors	O
,	O
such	O
as	O
H.261	B-Algorithm
.	O
</s>
<s>
H.120	B-Algorithm
streams	O
ran	O
at	O
1544	O
kbit/s	O
for	O
NTSC	O
and	O
2048	O
kbit/s	O
for	O
PAL	B-Language
.	O
</s>
<s>
Version	O
1	O
(	O
1984	O
)	O
featured	O
conditional	O
replenishment	O
,	O
differential	B-General_Concept
pulse-code	I-General_Concept
modulation	I-General_Concept
(	O
DPCM	B-General_Concept
)	O
,	O
scalar	B-Algorithm
quantization	I-Algorithm
,	O
variable-length	B-Algorithm
coding	I-Algorithm
and	O
a	O
switch	O
for	O
sampling	B-Algorithm
.	O
</s>
<s>
H.120	B-Algorithm
video	O
was	O
not	O
of	O
good	O
enough	O
quality	O
for	O
practical	O
use	O
it	O
had	O
very	O
good	O
spatial	O
resolution	O
(	O
as	O
differential	B-General_Concept
PCM	I-General_Concept
works	O
on	O
a	O
pixel-by-pixel	O
basis	O
)	O
,	O
but	O
very	O
poor	O
temporal	O
quality	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
(	O
DCT	B-General_Concept
)	O
block-based	O
codecs	B-General_Concept
that	O
followed	O
H.120	B-Algorithm
,	O
such	O
as	O
H.261	B-Algorithm
,	O
the	O
first	O
practical	O
video	O
encoding	O
standard	O
.	O
</s>
