Method and apparatus for multiplexing television signals
First Claim
1. A decoder for separating an encoded television frame representing odd and even field lines of an unencoded television frame, the decoder comprising:
- (a) means for receiving an input signal containing the encoded television frame comprising a plurality of sum and difference signal pairs,wherein each of said signal pairs comprises a sum signal indicative of the sum of respective pair of field lines of the unencoded television frame,and a time-compressed difference signal indicative of the time-compressed bandlimited difference between a respective pair of field lines of the unencoded television frame;
(b) first means for sampling and holding the sum signals of the signal pairs at a first effective rate;
(c) second means for effectively sampling and holding the time-compressed difference signals of the signal pairs at a second effective rate which is a non-unity multiple of said first effective rate to produce respective time-expanded difference signals;
(d) means for adding the sampled and held sum signals to the time-expanded difference signals to substantially recover one of the paired field lines of each of the field line pairs; and
(e) means for differencing the sampled and held sum signals and the time-expanded difference signals to substantially recover the other of the field lines of each of the field line pairs.
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Accused Products
Abstract
A decoder for use in a multiplexing system wherein the adjacent frame lines of a first program are summed and differenced, and the sum signal and time-compressed difference signal of each line pair is transmitted during the period allotted for transmission of a single line, thereby transmitting data for two lines in the time allotted for a single line. The decoder avoids a need for complex digital wall filters at the input by sampling the timed-compressed difference signals at a non-unity multiple of the rate used for sampling the sum signals. The multiple is sufficiently fast to enable the standard "front-end" low pass filter of the decoder to function as an interpolation filter, eliminating the artifacts which would otherwise require the use of the complex filter. The disclosed decoder additionally includes a first memory-sharing arrangement wherein memory addresses are accessed during each operating cycle in a manner which permits data to be written into memory prior to the complete reading out of data from the previous operating cycle. A second memory-sharing arrangement is included wherein memory addresses are accessed during each operating cycle in a manner which permits data to be read out of the memory prior to the complete writing of data for that operating cycle, enabling re-use of certain memory addresses during the operating cycle.
18 Citations
23 Claims
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1. A decoder for separating an encoded television frame representing odd and even field lines of an unencoded television frame, the decoder comprising:
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(a) means for receiving an input signal containing the encoded television frame comprising a plurality of sum and difference signal pairs, wherein each of said signal pairs comprises a sum signal indicative of the sum of respective pair of field lines of the unencoded television frame, and a time-compressed difference signal indicative of the time-compressed bandlimited difference between a respective pair of field lines of the unencoded television frame; (b) first means for sampling and holding the sum signals of the signal pairs at a first effective rate; (c) second means for effectively sampling and holding the time-compressed difference signals of the signal pairs at a second effective rate which is a non-unity multiple of said first effective rate to produce respective time-expanded difference signals; (d) means for adding the sampled and held sum signals to the time-expanded difference signals to substantially recover one of the paired field lines of each of the field line pairs; and (e) means for differencing the sampled and held sum signals and the time-expanded difference signals to substantially recover the other of the field lines of each of the field line pairs. - View Dependent Claims (2, 3, 4, 7, 8, 9, 10, 11)
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5. A decoder for separating an encoded television frame representing odd and even field lines of an unencoded television frame, the decoder comprising:
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(a) means for receiving an input signal containing the encoded television frame comprising a plurality of sum and difference signal pairs, wherein each of said signal pairs comprises a sum signal indicative of the sum of a respective pair of field lines of the unencoded television frame, and a time compressed bandlimited difference signal indicative of the time-compressed bandlimited difference between a respective pair of field lines of the unencoded television frame; (b) first means for sampling and holding the sum signals of the signal pairs at a first effective rate; (c) second means for effectively sampling and holding the time-compressed difference signals of the respective signal pairs at a second effective rate which is a multiple of said first effective rate to produce respective time-expanded difference signals, said multiple being proportional to the compression ratio of the difference signals to the sum signals; (d) memory means for storing the sampled and held values of the time-expanded difference signals in uniquely addressable memory locations, (e) means for adding the sampled and held sum signals to the time-expanded difference signals for each field line pair to substantially recover one field lines of each pair; (f) means for differencing the sampled and held sum signals and time-expanded difference signals for each field line pair to substantially recover the other of the field lines of each pair; and (g) means for applying the sampled and held sum signals and the stored time-expanded difference signals in a time-aligned manner to the adding means and the differencing means as the sum signals are sampled by the first sample and hold means. - View Dependent Claims (6, 12)
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13. A decoder for separating an encoded television frame representing odd and even field lines of an unencoded television frame, the decoder comprising:
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(a) means for receiving an input signal containing the encoded television frame comprising a plurality of sum and difference signal pairs, wherein each of said signal pairs comprises a sum signal indicative of the sum of a respective pair of field lines of the unencoded television frame, and a time-compressed difference signal indicative of the time-compressed difference between the a respective pair of field lines of the unencoded television frame; (b) means for effectively sampling and holding the sum signals of the signals pairs at a first effective rate; (c) means for effectively sampling and holding the time-compressed difference signals of the signal pairs at a second effective rate which is a multiple of said first effective rate to produce respective time-expanded difference signals; (d) means for time expanding the sampled and held difference signals to establish a number of samples substantially equal to the number of samples of the sampled and held sum signals; (e) means for adding the sampled and held sum signals to the time-expanded difference signals to substantially recover one of the paired field lines of each of the field line pairs; (f) means for differencing the sampled and held sum signals and the time-expanded difference signals to substantially recover the other of the paired field lines of each of the field line pairs; (g) first memory means having uniquely addressable locations for storing the recovered line signals for at least a portion of one of the fields; (h) second memory means having uniquely addressable locations for storing the the recovered line signals of the other field; and (i) means for accessing the first and second memory means to output the recovered line signals for the frame. - View Dependent Claims (14)
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15. A decoder for separating a pair of multiplexed television programs, each program comprising a plurality of encoded television frames which respectively represent odd and even field lines of an unencoded television frame, the decoder comprising:
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(a) means for receiving an input signal containing a succession of the encoded television frames, each encoded frame comprising a plurality of sum and difference signal pairs, wherein each of said signals pairs comprises a sum signal indicative of the sum of a respective pair of field lines of the respective unencoded television frame, and a time-compressed difference signal indicative of the time-compressed difference between the respective pair of field lines in the respective unencoded television frame; (b) means for effectively sampling and holding the sum signals of the signal pairs at a first effective rate; (c) means for effectively sampling and holding the time-compressed difference signals of the signal pairs; (d) means for time-expanding the sampled and held difference signals to re-establish their pre-compression time base; (e) means for adding the sampled and held sum signals to the time-expanded difference signals to substantially recover one of the paired field lines of each of the field line pairs of the unencoded television frames; (f) means for differencing the sampled and held sum signals and the time-expanded difference signals to substantially recover the the other of the paired field lines of each of the field line pairs of the unencoded television frames; (g) first memory means having uniquely addressable locations for storing the recovered line signals for at least a portion of one of the fields; (h) second memory means having uniquely addressable locations for storing the recovered line signals of other of the fields; and (i) means for accessing the first and second memory means to output the recovered line signals to produce recovered unencoded frames. - View Dependent Claims (16, 17)
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18. In a video multiplexing system wherein data for each of a plurality of video frames, each comprising a first field and second field is received within a field interval during each of succession of operating cycles, and wherein each field of each frame is to be produced within a field interval during a respective one of said cycles, a method for buffering the data comprising the steps of:
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(a) sizing a first memory to store at least a portion of the data from one of the fields; (b) sizing a second memory to store substantially all the data from one of the fields; (c) structuring the first and second memories so that each may be simultaneously written into and read from; and (d) within each said operating cycles, (1) writing the data for the first field of an incoming frame into successively addressed locations of the first memory; (2) reading the written data for the first field from the successively addressed locations of the first memory during a field interval, the writing of the data being commenced prior to the start of the reading of the data; (3) reading previous data which was written for a second field during the previous operating cycle from successively addressed locations of the second memory; and (4) writing the data for the second field of the incoming frame in the successively addressed locations of the second memory from which the previous data has been read. - View Dependent Claims (19, 20, 21, 22, 23)
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Specification