H.261 Datasheet, PDF (23/31 Pages) List of Unclassifed Manufacturers – LINE TRANSMISSION OF NON-TELEPHONE SIGNALS

Reconstruction levels (REC)
Level
1
2
3
QUANT
4
ξ
8
9
ξ
17
18
−127
−126
ξ
00−2
00−1
0000
0001
0002
0003
0004
0005
ξ
0056
0057
0058
0059
0060
ξ
0125
0126
0127
−255
−253
ξ
00−5
00−3
0000
0003
0005
0007
0009
0011
ξ
0113
0115
0117
0119
0121
ξ
0251
0253
0255
−509
−505
ξ
00−9
00−5
0000
0005
0009
0013
0017
0021
ξ
0225
0229
0233
0237
0241
ξ
0501
0505
0509
−765
−759
ξ
0−15
00−9
0000
0009
0015
0021
0027
0033
ξ
0339
0345
0351
0357
0363
ξ
0753
0759
0765
−1019
−1011
ξ
00−19
00−11
00000
00011
00019
00027
00035
00043
ξ
00451
00459
00467
00475
00483
ξ
01003
01011
01019
ξ −2039
ξ −2023
ξ
ξ
ξ 00−39
ξ 00−23
ξ 00000
ξ 00023
ξ 00039
ξ 00055
ξ 00071
ξ 00087
ξ
ξ
ξ 00903
ξ 00919
ξ 00935
ξ 00951
ξ 00967
ξ
ξ
ξ 02007
ξ 02023
ξ 02039
−2048
−2048
ξ
00−45
00−27
00000
00027
00045
00063
00081
00099
ξ
01017
01035
01053
01071
01089
ξ
02047
02047
02047
ξ −2048 −2048
ξ −2048 −2048
ξ
ξ
ξ
ξ 00−85 00−89
ξ 00−51 00−53
ξ 00000 00000
ξ 00051 00053
ξ 00085 00089
ξ 00119 00125
ξ 00153 00161
ξ 00187 00197
ξ
ξ
ξ
ξ 01921 02033
ξ 01955 02047
ξ 01989 02047
ξ 02023 02047
ξ 02047 02047
ξ
ξ
ξ
ξ 02047 02047
ξ 02047 02047
ξ 02047 02047
NOTE – Reconstruction levels are symmetrical with respect to the sign of level except for 2047/−2048.
ξ
30
ξ −2048
ξ −2048
ξ
ξ
ξ 0−149
ξ 00−89
ξ 00000
ξ 00089
ξ 00149
ξ 00209
ξ 00269
ξ 00329
ξ
ξ
ξ 02047
ξ 02047
ξ 02047
ξ 02047
ξ 02047
ξ
ξ
ξ 02047
ξ 02047
ξ 02047
31
−2048
−2048
ξ
0−155
00−93
00000
00093
00155
00217
00279
00341
ξ
02047
02047
02047
02047
02047
ξ
02047
02047
02047
For INTRA blocks the first coefficient is nominally the transform dc value linearly quantized with a step size of 8 and no
dead-zone. The resulting values are represented with 8 bits. A nominally black block will give 0001 0000 and a nominally
white one 1110 1011. The code 0000 0000 is not used. The code 1000 0000 is not used, the reconstruction level of 1024
being coded as 1111 1111 (see Table 6).
Coefficients after the last non-zero one are not transmitted. EOB (end of block code) is always the last item in blocks for
which coefficients are transmitted.
4.3 Multipoint considerations
The following facilities are provided to support switched multipoint operation.
4.3.1 Freeze picture request
Causes the decoder to freeze its displayed picture until a freeze picture release signal is received or a timeout period of at
least six seconds has expired. The transmission of this signal is via external means (for example by Recommendation H.221).
4.3.2 Fast update request
Causes the encoder to encode its next picture in INTRA mode with coding parameters such as to avoid buffer overflow. The
transmission method for this signal is via external means (for example by Recommendation H.221).
20
Recommendation H.261 (03/93)