Scrambling system for an audio frequency signal

• US 4,683,586 A
• Filed: 12/29/1983
• Issued: 07/28/1987
• Est. Priority Date: 01/11/1983
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sugita, Takehiro, Fukami, Takeshi, Sakamoto, Akira, Toyoshima, Masakatsu
• Primary Examiner(s): Cangialosi, Salvatore
• Assistant Examiner(s): Lewis, Aaron J.
• Application Number:
  US06/566,899
• Time in Patent Office: 1,307 Days
• Field of Search: 370/109, 381/34, 381/32, 178/22.17, 178/22.04, 375/116, 375/112
• US Class Current: 380/237
• CPC Class Codes: H04K 1/06 by transmitting the information or elements thereof at unnatural speeds or in jumbled order or backwards

Abstract

A scrambling system for an audio frequency signal is disclosed which employs a timebase-compressing and/or expanding system to measure the compressed and/or expanded amount of a segment time length caused in a transmission recording and reproducing system. In the scrambling system of the present invention, a marker signal is inserted into a portion between the adjoining segments and transmitted from an encoder side to a decoder side, while at the decoder side, this marker signal is detected, the synchronization is achieved by this marker signal along the compression and expansion of the segment length and the respective segments are rearranged to the original correct order. Thus, the connected portion between the segments can be made smooth so that it is possible to obtain the scrambling system for an audio frequency signal having high accuracy and high reliability.

Claims

1. Apparatus for scrambling and unscrambling an audio frequency analog signal which is digitized and divided into blocks, each block consisting of a plurality of adjoining multiple-bit segments arranged in an original order;

said apparatus comprising;

encoding means for providing at an end of each of said segments a redundant signal portion from an adjacent end of one of said adjoining segments, thereby to form enlarged segments, rearranging and uniformly timebase-compressing by a selected amount said enlarged segments to form rearranged segments of the same duration as the original segments, and inserting a marker signal in place of each of said redundant signal portions to form an encoded signal on a predetermined time base for transmission to a decoding means, during which transmission the rearranged segments of said encoded signal may be randomly timebase-compressed or timebase-expanded relative to said predetermined time base; and

said decoding means receiving said encoded signal for detecting successive ones of said marker signals in said received encoded signal, for measuring the respective separations between successive ones of said marker signals as detected, and for uniformly timebase-expanding said segments by the reciprocal of said selected amount used in said encoding means for said uniformly timebase-compressing and restoring the segments to said original order of said segments prior to the encoding thereof, said segments, as restored to the original order by said decoding means, each having a respective length proportional to the respective one of said separations measured between the preceding and succeeding marker signals in said decoding means, said decoding means comprising first memory means having a plurality of addresses for storing data representing respective segments of the received encoded signal corresponding to one of said blocks;

second memory means for storing data representing the addresses in said first memory means at which said segments of said one of said blocks are stored;

third memory means for storing data representing a duration of time for each of said segments stored in said first memory means; and

means for reading out from said first memory means the data stored at said addresses in an order determined by data from said second memory means and during a time determined by data from said third memory means.

2. Apparatus for scrambling and unscrambling an audio frequency analog signal which is digitized and divided into blocks, each block consisting of a plurality of adjoining multiple-bit segments arranged in an original order;

said apparatus comprising;

encoding means for providing at an end of each of said segments a redundant signal portion from an adjacent end of one of said adjoining segments, thereby to form enlarged segments, rearranging and uniformly time-base-compressing by a selected amount said enlarged segments to form rearranged segments of the same duration as the original segments, and inserting a marker signal in place of each of said redundant signal portions to form an encoded signal on a predetermined time base for transmission to a decoding means, during which transmission the rearranged segments of said encoded signal may be randomly time-base-compressed or timebase-expanded relative to said predetermined time base;

said encoding means comprising generator means for generating said marker signals;

gain control means for adjusting the gain of said audio frequency signal;

switch means selectively connectable to one of said generator means and said gain control means for transmitting one of said marker signals or said audio signal to said decoding means; and

timing controller means for periodically actuating said generator means, said gain control means and said switch means so that said gain control means reduces the gain of said audio frequency signal during each said redundant signal portion and said switch means is connected at that time to said generator means for transmitting one of said marker signals to said decoding means and, after each said redundant signal portion, said switch means is connected to said gain control means and said gain control means then increases the gain of said audio frequency signal; and

said decoding means receiving said encoded signal for detecting successive ones of said marker signals in said received encoded signal, for measuring the respective separations between successive ones of said marker signals as detected, and for uniformly timebase-expanding said segments by the reciprocal of said selected amount used in said encoding means for said uniformly timebase-compressing and restoring the segments to said original order of said segments prior to encoding thereof, said segments, as restored to the original order by said decoding means, each having a respective length proportional to the respective one of said separations measured between the preceding and succeeding marker signals in said decoding means.

3. An apparatus for transmitting in scrambled form an audio signal that has associated with it a corresponding video signal, in which the audio signal is divided into blocks with each block being formed of a plurality of adjoining segments arranged in an original order, said apparatus comprising:

an encoder including means for inserting at an end of each of said segments a signal portion from an adjacent end of one of said adjoining segments, means for uniformly timebase-compressing said segments including said adjacent signal portions by a selected amount and for rearranging the order of said timebase-compressed segments relative to said original order, means for inserting a marker signal into each of said segments in place of said signal portion from said adjacent end of an adjoining segment to form an encoded signal of rearranged segments on a predetermined time base;

a decoder; and

means for transmitting the encoded rearranged signal to said decoder during which transmission said rearranged segments of said encoded signal may become randomly timebase-varied relative to said predetermined time base; and

said decoder including means for detecting said marker signals in said encoded signal received from the transmitting means, means for establishing synchronization of said segments relative to said corresponding video signal using said marker signals present in said timebase-varied segments, means for measuring respective lengths between successive detected marker signals, means for restoring said segments to said original order with the lengths of the segments, as restored to said original order, being proportional to the respective measured lengths between successive detected marker signals, and means for uniformly timebase-expanding said segments in said encoded received signal by the reciprocal of said selected amount used in said encoder for said uniformly timebase-compressing.