Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1999-03-03
2002-08-20
Kelley, Chris (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06438169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a video signal compressing method and apparatus, and a compressed data multiplexing method and apparatus, and more particularly to a video signal compressing method and apparatus, and a compressed data multiplexing method and apparatus used in a system in which an output or decode time stamp is multiplexed in a data stream to synchronize a plurality of compressed signals for transmission.
2. Description of the Related Art
The MPEG system standardized by the Working Group (WG) of the ISO/IEC JTC1/SC29 (International Organization for Standardization/International Electrotechnical Commission, Joint Technical Committee 1/Sub Committee 29) is oriented to a time-division multiplexing and transmission of a video signal, an audio signal and other data. For synchronism of the multiplexed signals with each other during time-division multiplexing and transmission, a time stamp is added to each decoding/reproduction unit of data, called “access unit”, for each of the video signal, the audio signal and the other data. The time stamp acts as time management information, and indicates when each access unit is to be decoded by a particular decoder, and also includes reproduction/presentation management information called “presentation time stamp (PTS)” and a decoding time management information called “decode time stamp (DTS)”.
In a multiplexer operating in accordance with the MPEG system during an encoding process, an access unit information (AUI) is extracted from each of the video and audio encoders and signal multiplexing is performed based upon the extracted access unit information. The conventional MPEG multiplexer uses the following variables, for example, as AUI:
picture_size
picture_type
repeat_first_field
to calculate the time stamps PTS and DTS following the procedure shown in the flow chart shown in FIG.
8
. These calculated time stamps are then added to a transmission stream.
At Step C
1
in the flow chart in
FIG. 8
, initialization is performed as follows. A DTS initial value (init_DTS) and a next DTS (next_DTS) to be transmitted are set to be equal. “i” is set to “0”. The value of i is a counting variable which counts up one for each access unit in the order of transmission. The last_IP_repeat_first_field is set to “0”. The last_IP_repeat_first_field is used to convert a 3-2 pull-down image into an inverse 3-2 pull-down image for encoding. This variable is indicative of the value (0 or 1) repeat_first_field (AUI) of a preceding I picture or P picture. Num_of_field_next_DTS is set to “0”. The num_of_field_next_DTS is the time, counted in the unit of fields, until a next DTS. Num_of_field_diff_D_P is set to “0”. The num_of_field_diff_D-P is a difference between DTS and PTS values, counted in the unit of fields, for an I or P picture.
The above variables can be calculated from access unit information AUI for a particular encoded data (picture_size, picture_type, repeat_first_field). The operation then proceeds to Step C
2
.
At Step C
2
, an access unit information (AUI) for the i-th access unit is acquired. At the next Step C
3
, a function calc_TimeStamp_infi( ) is performed following a specified procedure that will be discussed below to determine values of num_of_field_next_DTS and num_of_field_diff_D_P. The operation then proceeds to Step C
4
.
At further Step C
4
, DTS[i] is set to be equal to next_DTS. Also, PTS[i] is set to be equal to DTS[i]+SCFR/2 num_of_field_diff_D_P as will be described below. Thus DTS and PTS are determined for the i-th access unit. The operation then proceeds to Step C
5
. At the next Step C
5
, next_DTS is set to be equal to SCFR/2×num_of_field_next_DTS+DTS[i]. The value of a next DTS is calculated in this manner. The operation then proceeds to Step C
6
.
At Step C
6
, the value of the variable i is increased by one. Next, the operation returns back to Step C
2
where an AUI for a next access unit is acquired and the above processing is repeated to determine the values of DTS and PTS for the next access unit. The function calc_TimeStamp_infi( ) noted at Step C
3
in
FIG. 8
, is performed according to the procedure shown in the flow chart in FIG.
9
.
More particularly, at a first Step D
1
in the flow chart in
FIG. 9
, it is determined whether 3
—
2_pull_down_flag is set to 1 or not. The 3
—
2_pull_down_flag is indicative of whether an inverse 3-2 pull-down process has been performed. If the 3
—
2_pull_down_flag=1, encoding has been performed after an inverse 3-2 pull-down process has been performed, while if the 3
—
2_pull_down_flag is equal to 0, encoding has been performed without an inverse 3-2 pull-down process. When the result of the determination at Step D
1
is answered in the affirmative, namely, when 3
—
2_pull_down_flag is equal to 1, the operation proceeds to Step D
2
. However, when the result of the determination is answered in the negative, namely, when 3
—
2_pull_down_flag is equal to 0, the operation proceeds to Step D
6
.
At Step D
2
, it is determined whether the value of M is equal to 1. The M value is indicative of a number of pictures until a next I or P picture. When the result of the determination is answered in the affirmative, namely, when the M value is equal to 1, operation proceeds to Step D
3
. However when the result of the determination is answered in the negative, namely, if the value of M is not 1, operation preceeds to Step D
4
.
At Step D
3
, the value of num_of_field_next_DTS of the access unit is set to 2 and num_of_field_diff_D_P of the access unit is set to 0. Operation then proceeds to Step D
4
.
At Step D
4
, it is determined whether picture_type is a B picture. When the determination is answered in the affirmative, namely, picture_type represents a B picture, operation proceeds to Step D
3
. If the determination is answered in the negative, namely if picture_type does not represent a B picture, operation proceeds to Step D
5
.
At Step D
5
, the value of num_of field_next_DTS of the access unit is set to 2 and num_of_field_diff_D_P of the access unit is set to M value×2. The operation then proceeds to the return end.
At Step D
6
, it is determined whether M value is equal to 1. When the determination is answered in the affirmative, namely, when M value is equal to 1, operation proceeds to Step D
7
. If the determination is answered in the negative, namely, if M value is not 1, operation proceeds to Step D
8
.
At Step D
7
, the value of num_of_field_next_DTS of the access unit is set to 2+repeat_first_field and num_of_field_diff_D_P of the access unit is set to 0. Then the operation proceeds to the return end.
At Step D
8
, it is determined whether picture_type represents a B picture. When the determination is answered in the affirmative, namely, picture_type represents a B picture, operation proceeds to Step D
7
. If the determination is answered in the negative, namely, if picture_type dose not represent B picture, operation proceeds to Step D
9
.
At Step D
9
, it is determined whether the M value is even or not. If the determination is answered in the affirmative, namely, when the M value is even, operation preceeds to Step D
10
. When the determination is answered in the negative, namely, if the M value is not even, operation proceeds to Step D
11
.
At step D
10
, the value of num_of_field_next_DTS is set to 2+last_IP_repeat_first-field and the value of num_of_field_diff_D-P is set to 5×(M value /2). The operation then proceeds to step D
12
.
At Step D
11
, the value of num_of_field_next_DTS of the access unit is set to 2+last_IP_repeat_first_field and num_of_field_diff_D_P of the access unit is set to 5×(M/2). The operation then proceeds to Step D
12
.
At Step D
12
, the value of last_IP_repeat_first_field is set equal to repeat_first_field. This value is used as the timing for a next I or P picture.
Thus a time stamp for a video signal is calculated for each access unit in accordance with the attributes of the
Hiranaka Daisuke
Negishi Shinji
Ogura Eiji
Oishi Noriaki
Tahara Katsumi
Bugg George
Frommer William S.
Frommer & Lawrence & Haug LLP
Kelley Chris
Kessler Gordon
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