Patent GB-1410843-A (GB)
Title: Sound information reproducing apparatus for use in a still picture broadcasting system
IPC: G11B20/02
Filed: 1973-10-05
Abstract: 1410843 Television; speech compression SANYO ELECTRIC CO Ltd 5 Oct 1973 [6 Oct 1972] 46656/73 Headings F4F and H4R In a transmission system in which a plurality of "still" pictures each accompanied by respective sound information (representative of a description of the particular still picture) are repeatedly transmitted, the "time-base" of the sound being compressed, receiving apparatus comprises gate means for selecting and storing in a main store a desired "still" picture together with its accompanying sound information and auxiliary memory means comprising two readwrite stores into which are alternately written, during successive read-outs of the main store, successive different portions of the stored sound information each store then being read-out alternately, at a rate which is lower than the writing rate so that the "time-base" of the sound information is expanded to allow the original sound to be obtained. Fig. 2, shows the transmitting end of the system in which a computer 4 controls a gate 1 to pass video signals (from a programme source 3) representative of one frame of a "still" picture via a F.M. modulator to a recording head 5a associated with a magnetic disc memory 5 rotating at 1800 r.p.m. The computer also opens gate 7 for a period of 8À7 sec. to pass sound information, related to the description of one whole "still' picture, to an A-D converter 8. which, in response to 10À489 kHz sampling pulses from generator 9, produces six-bit signals per sampling pulse and supplies them to a memoy 10 in which they are stored in response to writein pulses of 62À9 kHz pulses from generator 11. The stored signals are then read out and supplied to a binary-to-octal converter 13 under the control of 17À9 MHz pulses from generator 12 and via a  divider 14 pulses of 4À475 MHz are derived and employed to read-out converter 13 into a mixer 15<1> to which some of the 4À475 MHz pulses are supplied via gate 19 controlled by pulses HS of one half the video horizontal frequency from generator 16 to provide "framesound" synch. signals PFP (see Fig. 3), the composite signals from mixer 15<1> then being supplied to a further mixer 15 to which the pulses HS are added. The output of mixer 15 then comprises a set of sound signals A1.1, A1.2, A3.3 ... A1.262 (Fig. 3) which occupies 1/30 sec. (i.e. the 8À7 sec. sound signal has been compressed into 1/30 sec.) and this set is supplied via FM modulator 17 to recording head 5b associated with the memory 5. The video signals and the corresponding sound signals are then "played-back" via respective heads 5c, 5d and transmitted via circuit 18. Video signals and corresponding sound signals related to other "still" pictures are processed in a similar manner and a suitable address code is associated with each pair of signals. Fig. 6, shows a receiving circuit suitable for receiving the signals transmitted by the circuit of Fig. 2 and for expanding the compressed sound signal. In operation, the address code of the "still" picture and accompanying sound which it is desired to receive is set up on a keyboard and supplied to gates 21, 21<1> which gate for 1/30 sec. the sound and video signals from circuit 20 to respective recording heads 23b, 23a associated with a 1800 r.p.m. magnetic disc main memory 23 the set of sound signals being recorded as shown in Fig. 5. The video information is "read" by head 23c and the sound information which is read by head 23d is supplied to FM demodulator 25 and to synch. separator 26. The output of the former (demodulator 25) is supplied to an octal-to-binary converter 30 and to a separator 42 which separates out the "frame synch." signals PFP whilst the output of the latter (synch. separator 26) comprising the half (video) line frequency pulses HS1,HS2 .. HS262 is supplied to a counter 27. The output of the latter counter together with the output of a counter 29, which responds to each revolution of the disc 23, then operate a gate selector 28 (detailed in Fig. 7, not shown) controlling distributing gates 31, 32 to which the output of converter 30 is supplied and controlling respective gates 33, 34. In operation, during the first revolution of disc 23, distributing gate 31 is conditioned by the 1 output of selector 28 to supply the sound signals section Al. 1 (Fig. 5) to auxiliary memory 36 in which it is written by 17À9 MHz pulses supplied via gate 33 from pulse generator 35. At the commencement of the second revolution of disc 23 the 01 output of selector 28 disappears and the 02 output is produced and an output G1 of a gate 39 supplies read-out 62À9 kHz pulses from generator 38 to memory 36 which supplies its contents via a mixer 40 to a D-A converter 41 from which the sound signal corresponding to section A1.1 is derived. The production of the 02 output of selector 28 causes distributing gate 32 to supply the sound signal section A1.2 to memory 37 in which it is written by the 17À9 MHz pulses from generator 35 via gate 34 and at the commencement of the third revolution of disc 23 gate 39 supplies the 62À9 kHz read-out pulses from generator 33 via output G2 to readout the contents of memory 37 into mixer 40. The operation continues in this manner until at the end of 8À7 sec. all of the sound information contained in the 262 sections has been reproduced. In a modification a single distributing gate and auxiliary memory only are employed the auxiliary memory being operative to store successive sections A1.1; A1.2 &c. during successive revolutions of the disc 23 and to read out the stored sections during the periods between-successive storings. This involves interrupting the reproduced sound for the brief storage duration and results in a loss of fidelity which, however, may be acceptable in some circumstances (Fig. 8, not shown).