Pulse or digital communications – Bandwidth reduction or expansion
Reexamination Certificate
1999-06-14
2002-05-07
Kelley, Chris (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
C386S349000, C386S349000
Reexamination Certificate
active
06385240
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a progressive image signal transmitting apparatus, a progressive image signal receiving apparatus, and a method and a medium each using a bitstream obtained by encoding, e.g., a progressive video signal (sequential scanning signal) based on the MPEG2 formats.
BACKGROUND ART
In recent years, the international standardization of MPEG2 (Moving Picture Experts Group the 17-th phase 2) (registration in ISO/IEC 13818-1, 2, 3) has increased the importance of a digital transmission/reception system and method using digital high-efficiency encoding. The use of the MPEG2 encoding scheme has raised expectations for channel multiplexing, improved user interface, and diversified service based on the prospect of additional data transmission, while enabling simultaneous transmission of signals with various image qualities (resolutions) from a single transmitter. As a result, a sequential scanning signal with high image quality (progressive signal) can be transmitted in digital broadcasting.
Below, a description will be given to a conventional progressive signal transmission/reception system.
FIG. 13
is a block diagram showing the structure of the conventional progressive signal transmitting/receiving apparatus.
It is to be noted that, in the following description, an image structure is expressed by using signs i (interlace) and p (progressive) as abbreviations in order to distinguish whether the image structure is interlace or progressive and express a frame rate in a comprehensible manner. By way of example, a progressive signal at a rate of 24 frames per second may be described as
24
p
and an interlace signal at a rate of 60 frames per second may be described as
60
i.
In
FIG. 15
, a reference numeral
1301
denotes a view diagrammatically showing the structure of a video material recorded at a sampling rate of 24 frames per second, which is represented by a cinematic film material or the like. A reference numeral
1302
denotes a
24
p
/
60
i
converter for converting a picture at the rate of 24 frames/second to a normal NTSC television signal at a rate of 60 fields/second. A reference numeral
1303
denotes an MPEG2 video encoder for encoding the aforesaid signal at the rate of 60 fields/second to a bitstream in accordance with the description in ISO 13818-2 (MPEG2-Video). A reference numeral
1304
denotes an MPEG2 video decoder for receiving the aforesaid bitstream and reversely converting the received bitstream to the
60
i
signal at the rate of 60 fields/second. A reference numeral
1305
denotes a double rate converter for doubling the horizontal scanning rate of the
60
i
signal.
A description will be given to the operation of the conventional progressive signal transmission/reception system thus structured. Since the film material with the rate of 24 frames/second with no alteration normally requires a special-purpose reproducing device or recording device, it is initially converted to the
60
i
signal at the rate of 60 fields/second, which is mostly stored in a D
1
or S-VHS tape afterward and-distributed.
The
24
p
/
60
i
converter
1302
operates to convert the signal at the rate of 24 frames/second to a signal at the rate of 60 fields/second by appropriately inserting field repeats in the signal at the rate of 24 frames/second.
FIG. 16
is a view for illustrating the operation of the
24
/
60
i
converter. In
FIG. 16
, it is assumed that a sign A
1
represents a field image consisting of the odd-numbered lines (lines
1
,
3
,
5
, . . . ) of a frame A sampled at a time 0 and a sign A
2
represents a field image consisting of the even-numbered lines (lines
2
,
4
,
6
, . . . ) of the same frame A.
It is also assumed that a sign B
1
represents a field image consisting of the odd-numbered lines of a frame B sampled at a time 1 and a sign B
2
represents a field image consisting of the even-numbered lines of the frame B.
The difference between the sampling times 0 and 1 is {fraction (1/24)} seconds in the case of the film material.
Likewise, a sign C
1
represents a field image consisting of the odd-numbered lines of a frame C at a time 2 and a sign C
2
represents a field image consisting of the even-numbered lines of the frame C.
On the other hand, a sign D
1
represents a field image consisting of the odd-numbered lines of a frame D at a time 3 and a sign D
2
represents a field image consisting of the even-numbered lines of the frame D.
An example of an output from the
24
p
/
60
i
converter
1302
is such an output signal as shown in FIG.
16
. Specifically, the
24
p
/
60
i
converter
1302
operates to obtain output images (A
1
, A
2
), (A
1
, B
2
), (B
1
, C
2
), (C
1
, C
2
), and (D
1
, D
2
) having a 5-frame field structure from input images A, B, C, D having a 4-frame frame structure by inserting a field repeat in each of the frames A and C. A sign (f
1
, f
2
) is assumed to indicate that a pair of fields f
1
and f
2
constitute one frame. A sign f
1
represents an image consisting of the odd-numbered lines of the frame, while a sign f
2
represents an image consisting of the even-numbered lines thereof. The output signal forms a signal at the rate of 60 fields/second.
The signal at the rate of 60 fields/second is inputted to the MPEG2 video encoder
1303
.
The MPEG2 video encoder
1303
operates to convert the. inputted video signal to a bitstream compliant with the format described in ISO/IEC 13818-2 and output the bitstream. The bitstream output is connected to the MPEG2 video decoder
1304
via a transmission system.
At this time, there are cases where the MPEG2 video encoder
1303
encodes the entire frames (30 frames per second) of the inputted signal
60
i
and outputs the encoded frames without any alterations and where the MPEG2 video encoder
1303
detects a field repeat at the encoder side, performs internal processing so as not to transmit the repeated field, and transmits only data at the rate of 24 frames per second.
In the case where the MPEG video encoder
1303
encodes all the frames of the inputted signal
60
i
and outputs the encoded frames, the MPEG2 decoder
1303
encodes each frame of the video signal inputted thereto into a bitstream and outputs the bitstream.
In the case where the MPEG2 video encoder
1303
detects the field repeat at the encoder side, performs processing so as not to transmit the repeated field, and transmits only data at the rate of n 24 frames per second, the MPEG2 video encoder
1303
transmits only signals representing the 4 frames of A, B, C, and D but converts each of the signals representing the frames A and C to a bitstream in a form obtained by adding 1 to the repeat_first_field flag bit in accordance with the format described in ISO/IEC 13818-2 and outputs the bitstream.
The MPEG2 video decoder
1304
receives the bitstream produced in accordance with the foregoing procedure and performs a reverse operation in accordance with the grammar described in MPEG2 to reconstruct the video signal from the bitstream.
In the case where the MPEG2 video encoder
1303
detects the field repeat in the input signal, performs processing not to transmit the repeated field, and transmits only data at the rate of 24 frames per second, the MPEG2 video decoder
1304
operates as follows.
In the case where the repeat_first_field flag is
1
in the input bitstream, one field of the target frame is repeatedly outputted. In the case where the repeat_first_field flag is 0, the image signal is outputted without performing a field repeat.
Consequently, the output of the MPEG2 video decoder
1304
is the same signal at the rate of 60 fields/second in either of the cases where the entire frames of the input signal
60
i
are encoded and outputted and the case where the field repeat is detected at the encoder side, processing is performed not to transmit the repeated field, and only data at the rate of 24 frames per second is outputted, resulting in no difference in terms of frame rate and internally constructed image.
The rate doubling unit
1305
receives the output of the MPEG2 vid
An Shawn S.
Kelley Chris
Matsushita Electric Industrial Co Ltd.
Ratner & Prestia
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