[M4IF Technotes] Mpeg-4 audio/video quality measurement

[Bhaskar Sherigar]

Hi,
The video data that can be deviated from the Reference data and all
other error percentages are mentioned in IEEE-1180 Standard Specification.
This is basically for MPEG2, in addition to this following needs to be met.
The N by N inverse discrete transform shall conform to IEEE Standard
Specification for the Implementations of 8 by
8 Inverse Discrete Cosine Transform, Std 1180-1990, December 6, 1990, with the
following modifications:
1) In item (1) of subclause 3.2 of the IEEE specification, the last sentence is
replaced by: <<Data sets of 1 000 000
(one million) blocks each should be generated for (L=256, H=255), (L=H=5) and
(L=384, H=383). >>
2) The text of subclause 3.3 of the IEEE specification is replaced by : <<For
any pixel location, the peak error shall
not exceed 2 in magnitude. There is no other accuracy requirement for this
test.>>
3) Let F be the set of 4096 blocks Bi[y][x] (i=0..4095) defined as follows :
a) Bi[0][0] = i - 2048
b) Bi[7][7] = 1 if Bi[0][0] is even, Bi[7][7] = 0 if Bi[0][0] is odd
c) All other coefficients Bi[y][x] other than Bi[0][0] and Bi[7][7] are equal to
0
For each block Bi[y][x] that belongs to set F defined above, an IDCT that claims
to be compliant shall output a block
f[y][x] that as a peak error of 1 or less compared to the reference saturated
mathematical integer-number IDCT
fíí(x,y). In other words, | f[y][x] - fíí(x,y)| shall be <= 1 for all x and
y.?ISO/IEC 14496-2:2001(E)
NOTE 1 lause 2.3 Std 1180-1990 “Considerations of Specifying IDCT Mismatch
Errors” requires the specification
of periodic intra-picture coding in order to control the accumulation of
mismatch errors. Every macroblock is
required to be refreshed before it is coded 132 times as predictive macroblocks.
Macroblocks in B-pictures (and
skipped macroblocks in P-pictures) are excluded from the counting because they
do not lead to the accumulation of
mismatch errors. This requirement is the same as indicated in 1180-1990 for
visual telephony according to ITU-T
Recommendation H.261.
NOTE 2 Whilst the IEEE IDCT standard mentioned above is a necessary condition
for the satisfactory
implementation of the IDCT function it should be understood that this is not
sufficient. In particular attention is
drawn to the following sentence from subclause 5.4: “Where arithmetic precision
is not specified, such as the
calculation of the IDCT, the precision shall be sufficient so that significant
errors do not occur in the final integer
values.”
-Bhaskar
harisha V wrote:
> Hi all
>
> Can any one tell how much  decoded MPEG-4 audio/video data should be
> deviated from Reference decoded sequences.
>
> How the difference is measured when decoded file compared with reference
> file.
> Is there any Tool measure such difference
>
> Harisha
>
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