Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
2000-03-24
2004-09-28
Tran, Thai (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C360S039000
Reexamination Certificate
active
06798978
ABSTRACT:
The invention relates to a method of encoding an input information stream in one operation, which input information stream comprises a stream of information units [
IN
], comprising an encoding step of converting the input information stream into an output information stream, said output information stream comprising a variable stream of information units [R
ENC
], the variable stream of information units being between a minimum value R
ENC,MIN
and a maximum value R
ENC,MAX
, while the effect of the encoding step can be influenced by means of at least one control signal [R].
The invention also relates to an encoding device for encoding an input information stream comprising a steam of information units [R
IN
] into an output information stream, said output information stream comprising a variable stream of information units [R
ENC
] which is between a minimum value [R
ENC,MIN
] and a maximum value [R
ENC,MAX
].
The invention further relates to a recording device for recording an information stream on a record carrier, said device comprising recording means for recording an information stream on the record carrier.
Such a method, encoding device and recording device are known from European patent application EP 0 802 682 (“Video encoder and recording device”, publication date 22-10-1997). This application discloses a system for encoding video information, in which the encoded information is recorded on a disc such as, for example, the digital video disc (DVD). To this end, the system comprises a compression unit having a variable output information stream (Variable Bit Rate, VBR). An example of such a compression unit is a unit operating in accordance with the MPEG2 method which is described, inter alia, in IEEE Transactions on Consumer Electronics, Vol. 41, No. 3, August 1995, pp. 504-509, “Video disc system using variable bit rate”. The system, which is known from the above-mentioned application, is suitable for encoding the information stream in one operation. Due to the variable output information stream, rendering the quantity of storage space required for recording the video information unknown in advance, and the fixed quantity of storage space present on a disc, the compression unit is operated in the limited variable output information stream mode (constraint VBR). The variation of the output stream is dynamically limited in such a way that the quantity of storage space on a disc is sufficient for storing the desired quantity of video information. The variation of the output stream is limited by controlling quality-defining parameters of the compression unit such as, for example, the maximum value of the variable stream of information units [R
MAX
], the minimum value of the variable stream of information units [R
MIN
] and the quantization scale [QSC]. It is known that a compression unit with a variable output information stream yields a more efficient encoding at the same picture quality than a compression unit with a constant output information steam (Constant Bit Rate, CBR).
A problem in the known system is that there is no linear relation between the storage space on a disc, expressed in information units, and the quantity of information, expressed in length of time, which can be stored on the disc. This is very confusing to a user, because he does not know at any moment during recording how much storage capacity, expressed in length of time, is left. Moreover, it is confusing that, if a block of information having a given length of time is erased, information may be stored in the erased block whose -length of time significantly deviates from the length of time of the erased block comprising information.
It is an object of the invention to provide a method of encoding an information stream into a variable stream of information units, in which for a user a substantially linear relation appears to exist between the length of time of the encoded information stream and the storage space required for storing the encoded information stream.
According to the invention, this object is achieved by means of a method of encoding an input information stream, which is characterized in that the method comprises a measuring step in which, at any instant T, a quantity of information units [ENC
OUT
(T)] generated in the encoding step, reduced by a chosen average value of the variable stream of information units in the output information stream [R
ENC,AVER
] multiplied by the instant T, is recorded in accordance with the formula [ENC
OUT
(T)−R
ENC,AVER
·T], and a comparison step in which the quantity of information units [ENC
OUT
(T)−R
ENC,AVER
·T] recorded in the measuring step is compared with at least one criterion, and in which at least one signalizing signal [S] is generated, and a control step in which at least one control signal [R] is generated, in which the state of the control signal depends on the state of at least one of the signalizing signals [S] generated in the comparison step, and which control signal influences the effect of the encoding step.
At any instant T, the quantity of information units ENC
OUT
(T) generated in the encoding step is recorded. This quantity is reduced by a chosen average value of the variable stream of information units in the output information stream, R
ENC,AVER
, multiplied by the time T. By means of these data, the variable stream (Variable Bit Rate) of information units generated in the encoding step and ranging between a minimum value R
ENC,MIN
and a maximum value R
ENC,MAX
can be represented at any instant T by a constant stream (Constant Bit Rate) of information units having a chosen value R
ENC,AVER
and a quantity of [ENC
OUT
(T)−R
ENC,AVER
·T] information units which are stored in an imaginary buffer (referred to as virtual buffer). Due to the constant stream of information units, a linear relation can be established between the storage space on a disc, expressed in information units D
SIZE
, and the quantity of information expressed in length of time T
DISC
that can be stored on the disc, namely T
DISC
=D
SIZE
/R
ENC,AVER
. Since the stream of information units generated in the encoding step is actually a variable stream, T
DISC
is actually an approximation. The deviation of the approximated value of T
DISC
from the real value of T
DISC
is (ENC
OUT
(T)−R
ENC,AVER
·T)/R
ENC,AVER
.
In a comparison step, the quantity of information units stored in the virtual buffer is compared with at least one criterion, and at least one signalizing signal is generated, with the state of the signalizing signals being dependent on the result of the comparisons. Subsequently, control signals influencing the effect of the encoding step and hence the quantity of information units ENC
OUT
(T) generated in this encoding step are generated in dependence upon the signalizing signal. Via the mechanism of signalizing signals and control signals, the quantity of information units stored in the virtual buffer, and hence the deviation from the approximated value T
DISC
with respect to the real value of T
DISC
can be influenced.
The comparison step criteria may be fixed criteria which are always identical at the start of the method. However, it is alternatively possible to modify the criteria in dependence upon previous executions of the method. These so-called self-learning criteria do not always need to be identical at the start of the method.
An embodiment of the method according to the invention is characterized in that a first criterion is −&agr;·T
VB
·R
ENC,AVER
and a second criterion is &agr;·T
VB
·R
ENC,AVER
, in which T
VB
represents a chosen time constant and in which &agr; represents a constant chosen value, and in that a first signalizing signal [S
UNDER
] acquires a predetermined value if the equation ENC
OUT
(T)−[R
ENC,AVER
]·T≦−&agr;·T
VB
·R
ENC,AVER
is true, and in that a second signal
Brüls Wilhelmus H. A.
De Haan Wiebe
Morris Octavius J.
Belk Michael E.
Koninklijke Philips Electronics , N.V.
Onuaku Christopher
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