Copy protection for hybrid digital video tape recording and

Copy protection for hybrid digital video tape recording and
US0053l54-48A
United States Patent [19]
[11] Patent Number:
Ryan
[45]
[54] COPY PROTECTION FOR HYBRID
MacPherson, Franklin & Friel
UNPROTECI‘ED SOURCE MATERIAL
[57]
.
John 0- Ryllb Cupenino, Calif-
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. .
.
analog and digital copying. The recorder (including a
digital tape deck) inputs and outputs both analog and
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digital video signals. At the analog input, a detector
[2]] App]_ NOJ 32,394
[22] Fikdl
detects conventional copy protection in the analog
input video, and in response disables recording thereof.
At the digital input, a ?rst detector detects anti-copy
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copying of such material. When another bit detector
detects anti-copy bits present in the playback digital
version, a specially adapted video recorder or playback
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vents recording. A second bit detector detects serial
copy prevention scheme bits, and in response adds an
anti_copy bit totheinput digital Strcam’prcveminglater
copy protection signal modi?es the output analog sig
nal, inhibiting copying of the output signal. In another
4,631,603 12/1986 Ryan ................................... .. 360/60
4,907,093 3/1990 Ryan ................................. .. 358/335
4,914,694 4/1990 1169mm et a1- ----- n 330/ 5
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bits present in the input material and in response pre
data stream prior to conversion to analog, an analog
References Cited
2,322;
ABSTRACI.
A hybrid digital/analog video recorder prevents both
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device copy protects video source material which for
technical reasons is not copy protectable. A copy pro
tect “flag” is provided in a predetermined location in
the video signal to be protected. The video recorder or
playback device,, upon detection of the flag at play
5I251I041 10/1993 Young et .i1"11IIIIIIIIIIiiiiiiiiifitom.1
Primary Examiner—-Donald Hajec
back’ modl?esthe Outputstandard (NTsQvideosignal
with a conventional copy protection process.
Assistant Examiner—Thomas N. Forbus, Jr.
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May 24, 1994
Attorney, Agent, or Firm-Skjerven, Morrill,
DIGITAL VIDEO TAPE RECORDING AND
[75] Invento?
[52]
Date of Patent:
5,315,448
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copies is without any signi?cant reduction in picture
COPY PROTECTION FOR HYBRID DIGITAL
VIDEO TAPE RECORDING AND UNPROTECTED
SOURCE MATERIAL
quality, unlike the case with conventional analog re
BACKGROUND OF THE INVENTION
1. Field of the Invention
This disclosure is directed to a copy protection
method and apparatus for use with (1) digital video
recording, where it is desired to copy protect both an
require special video tape.
cording technology. Current digital video recorders
(not intended for consumer purposes) use the so-called
“D-l”, “D-Z” or “D-3” video recording standards and
Future of Digital Recording
It is widely believed that digital video tape recorders
will soon be commercially available for consumer use.
analog and digital video signal associated with a digital
To maintain compatibility with analog video broadcast
signals and analog video tape recorders, it is likely that
recording or playback apparatus and (2) any video ma
terial where the original source material is not copy
protectable.
2. Description of the Prior Art
Various well known copy protection schemes for
video signals include that disclosed in US. Pat. No.
4,631,603, John 0. Ryan, Dec. 23, 1986 and assigned to
at least the ?rst generation of consumer digital video
tape recorders will be “hybrid” digital and analog sys
15
tems. Such systems will have the capabilities of current
analog video cassette recorders to record and playback
analog signals, while still having equivalent digital ca
pabilities. Thus these new hybrid digital tape recorders
Macrovision, incorporated by reference, directed to
modifying an analog video signal to inhibit making of 20 will have the capability internally to convert input ana
log signals into digital signals, and record the digital
acceptable video recordings therefrom. This discloses
signals as a digital data stream on the tape. During play
adding a plurality of pulse pairs to the otherwise unused
back the digital data stream from the tape will be avail
lines of a video signal vertical blanking interval, each
able both as a digital signal for display by a digital tele
pulse pair being a negative-going pulse followed closely
by a positive-going pulse. The effect is to confuse AGC 25 vision set (also not currently available) or be recon
verted within the hybrid video tape recorder to a con
(automatic gain control circuitry) of a VCR (video
ventional analog video signal (such as the NTSC signal
cassette recorder) recording such a signal, so that the
used in the United States.) The capability of the system
recorded signal is unviewable due to the presence of an
internally to convert the received analog signals to a
excessively dark picture when the recorded signal is
played back.
digital data stream will be important because currently
Another analog video protection scheme is disclosed
there are no sources (either tape or broadcast) of digital
in US. Pat. No. 4,914,694 issued Apr. 3, 1990, to Leon
video program material available to consumers.
ard, and assigned to Eidak Corp., incorporated by refer
Such hybrid video recorders will likely employ a
ence. The Eidak system (see Abstract) increases or
“consumer" digital recording format differing from the
decreases the length of each video ?eld from the stan 35 standards of present professional digital systems. This
dard length, either by changing the time duration of the
consumer digital video format is not yet established.
respective horizontal line intervals in each ?eld while
Such digital video recorders will likely include a con
keeping a constant, standard number of lines per frame,
ventional “front end" RF tuner and also an RF modula
or by changing the number of horizontal line intervals
tor on the output side, as do present conventional ana
which constitute a frame while maintaining the standard
log VCRs. (By analog video here is meant NTSC, PAL
duration of each line interval.
or SECAM.) The digital recording standard for con
These video protection systems modify the video
sumers is likely to be essentially a data structure that
represents the video signal as a stream of (binary) data
signal to be recorded (for instance on tape) or to be
broadcast (for instance protected pay-per-view televi
sion programs) to make copying by ordinary VCRs
dif?cult or impossible. When a video tape on which is
recorded the copy protected video signal is played back
for viewing using a VCR, the copy protection process is
essentially transparent, i.e., it does not interfere with
viewing. However, any attempt made to copy the video
45
bits along with suitable error concealment encoding,
together with a physical tape standard.
Problems Posed by Digital Recording
Since digital video tape recorders will be capable of
high ?delity reproduction which in turn will encourage
signal from the tape using a second VCR to record the
copying, it is important that such recorders for con
output of the ?rst (playback) VCR yields a picture
degraded to some extent, depending on the efficacy of
the particular copy protection system. These present
sumer use be designed to inhibit or discourage unautho
cast and recorded using current consumer video tech
video copy protection techniques are not useful in the
digital domain. Hence there is a need for a new copy
rized recording. For instance it is important to prevent
use of recorders for illegally duplicating copyrighted
video copy protection systems protect only analog $5 video material, and also to prevent playing back of such
illegally duplicated material. Currently available analog
video signals, which are the type of video signals broad
nology.
Also well known are digital video tape recorders,
although currently such digital video tape recorders
(which both record and play back digitally) are avail
able only for the professional market, due to their high
cost. Such digital systems trade distortion-free perfor
mance for substantially higher bandwidth, i.e. substan
protection system suitable for use with such hybrid
digital and analog video tape recorders, where the ma
terial recorded on the tape is a digital data stream. A
typical situation to be prevented is use of a hybrid video
tape recorder to copy an output signal from a conven
tional VHS VCR, where the tape played back from the
tially more information must be recorded per video 65 VHS VCR has a conventional copy protection process
frame. The advantage to the user of a digital recorder is
applied to it. The problem is to prevent the new hybrid
that so long as the signals are recorded and played back
digital-analog video tape recorder from copying the
in the digital domain, each successive generation of
material from such a tape. Otherwise, the existence of
3
5,315,448
such hybrid recorders would encourage copyright in
fringement.
receives a broadcast digital video signal when in the
future such signals are commercially broadcasted,, or
SUMMARY OF THE INVENTION
A hybrid digital and analog tape recorder that re
from another digital video tape recorder or digital play
back device.
Since the apparatus of FIG. 1 records a digital signal,
the analog video signal at terminal 12 is converted to
cords digitally provides copy protection in both the
digital and analog domains. For externally supplied
analog video, the recorder detects the presence of copy
protection and in response disables recording. For ex
ternally supplied digital video, both anti-copy bits and
serial copy protection bits are detected to respectively
(I) disable recording and (2) prevent later copying by a
second digital recorder. For playing back of recorded
material, the presence of anti-copy bits is detected in the
digital playback video, and the digital playback video
upon being converted to an analog signal is modi?ed by
an analog video copy protection process.
In another embodiment, analog or digital source
4
‘cated by “D”) from an external source. Terminal 14
the desired digital format by analog to digital converter
10
16. Such analog to digital converters are well known in
the video ?eld, and the construction details of analog to
digital converter 16 are determined by the nature of the
digital recording format(s) compatible with digital tape
deck 10.
The digital video data stream output from analog to
digital converter 16 is provided (via switch 18) to digital
tape deck 10. The person (or machine) operating the
recorder of FIG. 1 decides whether at any one time he
is recording an analog video input signal at terminal 12
or a digital video input signal at terminal 14. Switch 18
source) is provided with a copy protection ?ag. Detec 20 (either automatic or manually controlled) chooses from
tion of the flag by a playback device results in modi?ca
which terminal 12 or 14 the tape deck 10 receives the
tion of the played back standard video signal with an
input signal to be recorded.
analog copy protection process. This embodiment is
The input signal from switch 18 is then digitally re
suitable for playback devices where the source video
corded on tape (not shown) by tape deck 10. Subse
cannot be copy protected, but a standard (NTSC) video 25 quent playback of material recorded on the tape by tape
signal is provided of a played-back recording.
deck 10 results in a digital signal “D” at output terminal
20 of tape deck 10. The digital signal at terminal 20 is
BRIEF DESCRIPTION OF THE DRAWINGS
then (if the ultimate output signal from the recorder is to
FIG. 1 is a block diagram of a hybrid digital video
be an analog signal) provided to digital to analog con
recorder in accordance with the present invention.
30 verter 22, which converts the digital signal D to the
FIG. 2 is a block diagram of another video recorder
analog output signal A which is provided to analog
or playback device in accordance with a second em
output terminal 24. Digital to analog converter 22 (like
bodiment of the present invention.
its complementary converter 16) is conventional, the
construction details being determined by the nature of
DETAILED DESCRIPTION OF THE
35 the digital recording format and the analog output for
INVENTION
mat. Analog output terminal 24 is connected (for in
FIG. 1 shows a hybrid digital-analog video recorder
stance) on the “outputs” side of the recorder to a con
video material (either prerecorded or from an external
in accordance with the present invention. Each block
ventional television set.
includes conventional elements currently commercially
The recorder of FIG. 1 may conventionally be pro
vided with an RF tuner (not shown) on the “inputs”
side to extract video (NTSC or other) from an RF mod
available or readily constructed by one of ordinary skill
in the art in accordance with the following description.
The one possible exception is the digital tape deck me
chanics and electronics 10 which is the main subsystem
ulated video (TV) signal. Similarly on the “outputs”
side an RF modulator (not shown) may be provided to
convert the baseband (NTSC or other video signal at
video recorders include such tape deck mechanics and 45 terminal 24 to an RF modulated video signal (TV), for
electronics; however they are designed for recording
provision to the antenna input terminal of a television
of such a device. Presently available professional digital
and playback of material under current professional
set.
type digital video standards. The digital tape deck 10
The copy protection portion of the apparatus of FIG.
may be of the kind included in such present commercial
1 (when operating in the analog domain) is explained
professional systems. However, since it is envisioned 50 with regard to the above-described analog chain includ
that the hybrid system shown in FIG. 1 is chie?y (but
ing analog video input terminal 12, converter 16, switch
not exclusively) intended for consumer use, such a sys
18, converter 22 and analog output terminal 24. It is
tem will likely include different digital tape deck me
assumed that the (NTSC) analog video received at ter
chanics and electronics, of a type suitable for large scale
minal 12 may have been copy protected by one of the
production at low cost and designed in accordance with 55 above-described copy protection processes, which typi
consumer digital video format(s) not yet determined.
cally add copy protection pulses to or otherwise modify
In any case, the recorder of FIG. 1 can be con
particular portions of the video signal. The intention is
structed of presently available components including a
that the recorder of FIG. I prevent copying of such
professional type digital tape deck as now commercially
material by means of designed-in circuitry, i.e. features
available from various companies. The tape to be 60 built into the recorder by its manufacturer.
played on tape deck 10 is in the form of (l) a video
One system for adapting a video recorder to prevent
cassette or (2) reel-to-reel recording.
copying of copy protected video is described in US.
The recorder of FIG. 1 is a hybrid device capable of
Pat. No. 4,907,093 issued Mar. 6, 1990 to John 0. Ryan,
accepting at input terminal 12 a conventional analog
assigned to Macrovision Corp. and incorporated by
video signal indicated by “A”, which is an NTSC or 65 reference, the Abstract of which states:
other signal.
Also shown in FIG. 1 on the “inputs” side is digital
video input terminal 14 for receiving digital video (indi
A video signal is modi?ed so that a television receiver
will still provide a normal color picture which a
video tape recorder will detect and prohibit its being
5
5,315,448
recorded. A plurality of ordered pairs of pseudo-sync
and positive pulses are added to the video signal ver
tical blanking interval following the normal sync
pulse. A disabling circuit associated with a recorder
detects the modi?ed signal. This detection may be by
comparing the voltage differential between the pseu~
do-sync pulse tip and the positive pulse relative to the
normal voltage differential between the sync pulse tip
and the back porch of the blanking interval. Altema
tively, the modi?ed signal can be detected by identi
fying the pulse frequency of the signal in the blanking
interval. . . . Detection is also shown by peak-detect
ing the video signal and sampling this peak-detected
signal during the vertical blanking. A control signal is
produced, when the modi?ed signal is present, which
disables the recording device. If no modi?ed signal is
detected, the recording device is enabled.
The recorder of present FIG. 1 includes a similar
approach to copy protection in its upper left portion,
including ACP (anti-copy process) detector 26, which
is similar to the detection circuitry described in various
embodiments in U.S. Pat. No. 4,907,093, or alterna
tively is a detector for detecting the copy protection
6
Then, for instance, if anti-copy bit detector 32 detects
that the anti-copy bit is set high, i.e. having a value of 1,
this is interpreted as an instruction that the associated
digital video material is not to be copied. Thereupon
anti-copy bit detector 32 issues a disable recording con
trol signal on line 36 which controls operation of switch
38. In this case, the disable recording signal on line 36
opens switch 38, preventing transmission of the digital
video signal from terminal 14 to switch 18. Thus the
anti-copy bit accomplishes its purpose of preventing
copying of the associated video material input to the
recorder on digital input terminal 14.
Alternatively, the user of the recorder of FIG. 1 may
play back material from a prerecorded tape. In this case
the problem is to prevent or inhibit subsequent unautho
rized recording of the played back material. Such subse
quent unauthorized recording is not a problem if the
material played back from the tape on digital tape deck
10 is provided (in the digital domain) from output termi
20 nal 20 to digital video output terminal 42. This is be
cause then the digital video output signal could only be
recorded on another digital video recorder, which pre
sumably also is equipped with the anti-copy bit detector
32 and associated disabling circuitry.
process of US. Pat. No. 4,914,694. ACP detector 26
However, the hybrid recorder of FIG. 1 poses the
could also detect serial types of copy protection pro 25
additional copy protection problem of providing analog
cesses. When an analog (NTSC) video signal is received
video output on terminal 24. The presence of an anti
at terminal 12, ACP detector 26 detects the presence of
copy bit in the digital data stream at terminal 20 would
the copy protection, and upon detection thereof gener
have no effect (having been stripped off or ignored in
ates a disable recording control signal on line 28 which
then disables (for instance) the analog to digital con
30 the digital to analog conversion) on an analog output
signal at terminal 24. Therefore, an anti-copy (AC) bit
detector 46 is provided in the analog output chain in the
Disabling of converter 16 is somewhat different than
upper right portion of FIG. 1. AC bit detector 46 is
the disabling method described in US. Pat. No.
similar to AC copy bit detector 32, operating in the
4,907,093 (where no analog to digital converter is pres 35 digital domain to detect the anti-copy bit at its predeter
ent), and instead in accordance with the present inven
mined location. In response to the detection of the anti
tion some other feature of the recorder is disabled. As
copy bit by AC bit detector 46, an enabling signal is sent
described in US. Pat. No. 4,907,093, in the recorder of
on
line 52 t0 anti-copy process (ACP) signal generator
FIG. 1 an element other than the analog to digital con
50.
verter 16 could be disabled by the disable recording
ACP signal generator 50 is shown in one version in
signal on line 28. For instance digital tape deck 10 could
FIG. 2 of US. Pat. No. 4,631,603, and generates an
be disabled, or an additional switch (not shown) in the
analog video anti-copy signal. ACP signal generator 50
signal path could be forced to its open position. Other then adds this analog anti-copy signal to the output
means of disabling the recorder will be apparent to one
signal of digital to analog converter 22, which has con
of ordinary skill in the art. In any event, detection of a 45 verted the digital output signal from tape deck 10 to an
verter 16.
copy protection signal in the input analog video signal
disables the recording of such signal. (ACP detector 26
herein corresponds to disabler 22 in FIG. 1 of the
above-referenced patent.)
analog (for example NTSC) signal. Alternatively, ACP
signal generator 50 is as shown in above-referenced
US. Pat. No. 4,914,694 in FIG. 1 for modifying the
“TV signal source”. Thus the analog (NTSC) video
In terms of recording of copy protected material, in 50 signal at output terminal 24 is an analog video signal
the alternative situation the input signal is a digital video
modi?ed by an analog anti-copy process. This prevents
signal provided on digital input video terminal 14. In
making of acceptable video recordings on existing ana
this case, if the input signal is copy protected, typically
such copy protection is provided by a tape duplicator
facility that sets a predetermined anti-copy control bit in
log VCRs from the signal provided from the prere
sponding to the vertical blanking interval). Altemately
stances) copying of digitally recorded audio material
using commercially available DAT (digital audio tape)
corded tape.
55
FIG. 1 also includes SCPS bit detector 54, line 581,
the digital data stream recorded on the tape. This anti
and AC bit adder 60. In the ?eld of digital audio tape
copy bit will be located for instance in a particular
recording, the serial copy management system (SCMS)
location of each video frame (such as a portion corre
is well known for preventing (under certain circum
such an anti-copy bit could be located in a predeter
mined location in each video line or in some other pre
recorders. SCMS was devised jointly by the manufac
turers of digital audio tape recorders and the providers
of digital audio recorded program material, to limit
so long as it is determined by an accepted standard prior
copying of such material only in the digital domain.
to manufacture of the recorder of FIG. 1. Therefore the 65 SCMS is described for instance in US. Pat. No.
determined portion of the video signal; the exact loca
tion of this anti-copy bit is-of no particular importance
recorder manufacturer designs anti-copy (AC) bit de
5,144,658, incorporated by reference. In brief, SCMS
tector 32 to locate such an anti-copy bit by knowing its
adds a special control bit periodically to digital audio
digital address.
recorded program material which is to be copy pro
7
5,315,448
8
tected (typically copyrighted material.) In a conven
tional digital audio playback device such as a CD
terminal 24.
player, which produces both an analog output signal
and a digital output signal, the analog output signal is
terminal 42 (for instance by recording the output signal
generator 50 to copy protect the analog output signal at
Subsequent use of the output signal at digital video
not copy protected, i.e. the control bit or analog equiva
using a second recorder of the type shown in FIG. 1)
would prevent copying of this material by detection of
the set AC bit by the AC bit detector 32 of the second
recorder.
lent does not appear therein. That is to say, the control
bit is discarded internally by the digital to analog con
version process. Thus it is possible to make any number
of generations of copies by connecting analog output
from the CD player to an analog audio tape recorder. - a
However, the digital output signal from the CD
player has the SCMS bit(s) set (to high) by the duplica
tor of the recorded audio material. A digital audio tape
recorder receiving the digital output signal detects the
SCMS bit(s) and if it determines for instance that one of
these bit(s) in a particular location is high, the digital
audio tape recorder will make a recording of the mate
rial (i.e. a digital recording) and in the process of mak
Therefore the digital video recording standard in
cludes copy protection on a bit basis using particular
assigned bits in a digital video stream. Such “SCPS”
bit(s) and other anti-copy bit(s) are in one embodiment
provided for instance in each video ?eld or frame, for
copy protection on a ?eld-by-?eld or frame-by-frame
basis.
Thus the apparatus of FIG. 1 accounts for all possibil
ities of both analog and digital copy prevention. That is
to say, at the inputs side it is possible to detect the con
ing such recording (for instance) internally augments
ventional analog copy protection signals for the various
types of well known analog copy protection signals. At
the inputs side provision is also made for a digital video
copy protection system including serial copy limitation.
On the outputs side, provision is made for copy protec
that one bit with a second bit in a second location. Thus
it is possible later to playback this tape and have an
acceptable analog output signal or an acceptable digital
output signal. However, if an attempt is made later to
rerecord the tape using another DAT recorder, the
tion on the output analog side of material played back
second DAT recorder seeks the location of both bits 25 which was digitally recorded. The circuit details of
and if it detects the second bit will not make a copy
anti-copy detectors 32, 46, SCPS bit detector 54, and
thereof. Thus one is enabled to make serially one copy
AC bit adder 60 depend on the nature of future digital
in the digital domain from a particular source record
video recording protocols (formats), but given knowl
ing. It is well understood that such a system can easily
edge of such format(s) these circuits may readily be
be extended to allow two, three or four or however 30 made by one of ordinary skill in the art. Such protocols
many copies as is desired to be made serially; the inten
will be made known to both the manufacturers of digital
tion is to limit the serial copies to some particular num
video recorders and to the providers of digital video
ber, typically one in the case of SCMS.
program material.
The present inventor has determined that a similar
In another variant, ACP detector 26 rather than de
serial copy limitation system is advantageous in the 35 tecting the anti-copying signal as described in the
digital video ?eld. In the case of the present invention,
above-referenced US. Pat. No. 4,907,093, instead reacts
such a serial copy limitation system standard has not yet
directly to the analog copy protection signal. This is
been de?ned but herein is generically described as a
accomplished for example by including an automatic
“Serial Copy Protection Scheme” (SCPS) embodied in
gain control (AGC) circuit for reducing the level (am
SCPS bit detector 54. SCPS is conceptually similar to 40 plitude) of the video signal so that the copy would be
SCMS, but is in the video domain. SCPS bit detector 54
unacceptable for viewing. Most likely analog to digital
detects the serial copy protection scheme bit(s) if pres
converter 16 would of necessity include a AGC circuit,
ent in the digital video signal at terminal 14. If the ?rst
and this circuit could easily be designed to be especially
such SCPS bit for instance is detected, then an enabling
vulnerable to the anti-copying protection signals which
signal is generated on line 58 which controls AC (anti
would effect the video levels.
copy) bit adder 60 which adds (or sets to high) the
It is also to be understood that the device of FIG. 1
second (actual anti-copy) bit at its predetermined loca
need not be a record and playback device but could
tion in the digital stream. Such SCPS bit(s) may be
alternatively be a playback-only device, thus including
located for instance in the equivalent of the unused lines
only a digital playback tape deck 10 and the circuitry to
in the vertical blanking interval. The video signal then 50 the right thereof in FIG. 1, and not having the input
passes to switch 38 and then to digital tape deck 10 via
circuitry to the left thereof. In this case the output cir
cuitry is identical to that of the upper right portion and
lower right portions of FIG. 1, reacting to an anti-copy
bit present in the prerecorded digital material played
switch 18. Such a digital signal thereby including the set
(high) anti-copy bit is provided via terminal 20 on sub
sequent playback to digital video output'terminal 42.
Providers of video material (such as commercial tape 55 back on tape deck 10. Also, in yet another version, an
duplicators, broadcasters or cable TV systems) may
optical (digital) disk player is substituted for digital
choose to prevent any copying of their material (i.e. not
playback tape deck 10. Thus the upper right circuitry of
use the SCPS). In this case, such providers would set (to
the apparatus of FIG. 1 is applicable to playback-only
high) the second (anti-copy) bit in their original mate
devices for prevention of rerecording from the analog
rial. Alternatively, where it is desired to completely 60 output terminal 24 of copy protected digital video mate
rial.
prevent copying of material, an additional anti-copy bit
location (independent of the SCPS bit) could be desig
Another embodiment is for use with either digital or
analog video material which for technical or other rea
sons is not copy protected in its original form and where
nated, and such an additional AC bit also detected by
AC bit detectors 32,46, which in response would re
spectively prevent recording or provide the analog
copy protection.
Alternatively, AC bit detector 46 could detect either
of the SCPS bits and in response enable ACP signal
65
upon playback a standard video (e.g., NTSC) signal is
provided. An example is a so called “laser disc" which
is used for distribution of prerecorded video material,
by playback on a laser disc recorder. For technical
9
5,315,448
reasons, the above described copy protection schemes
10
The above description is illustrative and not limiting;
of U.S. Pat. Nos. 4,631,603 and 4,914,694 are not com
further modi?cations will be apparent to one of ordi
nary skill in the art in light of this disclosure. It is to be
understood that while at present consumer type digital
patible with laser discs, since inclusion of these copy
protection schemes on laser discs causes playability
problems.
video recording devices are not available, that digital
Therefore a copy protection scheme is needed to
video professional systems are now available, and the
above-described apparatus and method are readily
prevent unauthorized recording of material played back
from a laser disc. This is achieved by providing other
adaptable to such presently commercially available
digital video recorders.
wise conventional laser disc players to be manufactured
in accordance with ‘the invention with additional cir
I claim:
cuitry including (1) an anti-copy (AC) ?ag detector;
and (2) an ACP signal generator operationally con
nected to the anti-copy flag detector. Video material
1. An apparatus for playing back material digitally
recorded on a recording medium, comprising:
a mechanism for playing the recording medium;
recorded on a laser diseis then provided with an anti
a digital output terminal operatively connected to the
copy ?ag. The anti-copy ?ag typically is a signal of a 15
particular level in a predetermined line of each VBI in
the video material. (Analog, not digital video, is re
a digital to analog converter operatively connected to
corded on a laser disc.)
the mechanism for converting the digital signal to
an analog signal;
an analog output terminal for providing an analog
signal from the digital to analog converter;
a signal detector for detecting copy protection infor
mation present in the digital signal; and
The anti-copy flag (corresponding to the anti-copy
bit of FIG. 1) is detected by the anti-copy flag detector
in the laser disc player, and in response the ACP signal
generator modi?es the analog signal output by the laser
disc player in accordance with a conventional analog
anti-copy process. This prevents use of a video tape
recording made of the laser disc play analog output
mechanism for providing a digital signal from the
mechanism;
25
signal.
A similar modi?cation may be made to the recently
a signal generator for generating an analog copy
protection signal in response to the detected copy
protection information, and modifying the analog
signal with the generated signal.
developed “WVHS” videotape recorders for recording
2. The apparatus of claim 1, wherein the digital signal
high de?nition TV signals in the “Wide VHS” video 30 and analog signals are video signals.
format. WVHS is a video format, differing from stan
3. The apparatus of claim 2, wherein the copy protec
dard (NTSC, PAL or SECAM) video. In this case, the
modi?ed \VVHS videotape recorder senses the anti
copy flag in prerecorded material being played back on
tion information is at least one bit at a predetermined
location in the digital signal.
4. The apparatus of claim 2, wherein the generated
the WVHS videotape recorder, and in response modi 35 signal includes a pulse pair inserted into at least some
?es a played back standard video (i.e., NTSC) signal,
blanking intervals of the analog video signal, each pulse
using a conventional analog anti-copy process.
pair including a positive going pulse and a negative
This embodiment is shown in FIG. 2 which is a block
diagram of a playback-only device (such as a laser disc
player) or a record and playback device (such as a
WVHS VCR) adapted in accordance with the inven
tion.
A playback-only device includes conventional play
back mechanics/electronics 72, anticopy (AC) flag de
going pulse.
5. The apparatus of claim 1, wherein the recording
medium is magnetic tape.
6. The apparatus of claim 1, wherein the recording
medium is an optical disk.
7. The apparatus of claim 2, wherein the generated
signal includes pulses added to blanking intervals of the
tector 74, and ACP signal generator 50. Detection of 45 analog video signal.
the AC ?ag in played-back standard (e. g., NTSC) video
8. The apparatus of claim 2, wherein the generated
from mechanics/electronics 72 by detector 74 results in
signal includes alterations of the time durations of hori
the “enable” signal on line 86 to ACP signal generator
zontal line intervals in the analog video signal.
50, so that the ACP signal on line 88 is then mixed into
9. The apparatus of claim 2, wherein the generated
(or modi?es) the NTSC video output at terminal 80. A 50 signal includes alteration of the number of horizontal
second output signal on line 88 is another type of video,
line intervals per video frame.
such as HDTV (high de?nition TV) or WVHS, for
10. The apparatus of claim 3, wherein the one bit is in
which a conventional anti-copy process is not suitable.
each ?eld of the digital video signal.
Thus no ACP modi?cation is made to the video on line
11. The apparatus of claim 1, wherein the mechanism
88.
55 is also a recording mechanism, and further comprising:
For a record and playback device (such as a WVHS
VCR), also included is input video terminal 84. If the
incoming video at terminal 84 has the AC flag present,
and the AC flag is still present after recording by me
chanics and electronics 72, then the flag is detected by 60
AC ?ag detector 74 on playback and this activates ACP
signal generator 50 as before, to copy protect the
played-back NTSC video at terminal 80. (Presence of
the AC ?ag on play back depends on the particular
format of the incoming video signal and the nature of 65
a digital input terminal for receiving a digital input
signal from an external source;
means for providing the digital input signal to the
mechanism, for recording the digital input signal
on the recording medium;
a second signal detector for detecting copy protec
tion information present in the digital input signal;
means for inhibiting recording in response to detec
tion of the copy protection information present in
the digital input signal;
mechanics/electronics 72.) Similarly, playback of pre
a third signal detector for detecting serial copy pro
recorded video material having the AC ?ag activates
ACP signal generator 50.
tection information present in the digital input sig
nal; and
11
5,315,448
12
23. The method of claim 22, wherein the copy protec
a signal generator for generating a digital copy pro
tection signal in response to the detected serial
copy protection information and inserting the gen
tion information is at least one bit at a predetermined
location in the digital signal.
erated digital copy protection signal into the digital
24. The method of claim 22, wherein the generated
signal includes a pulse pair inserted into at least some
input signal.
blanking intervals of the analog video signal, each pulse
pair including a positive going pulse and a negative
12. The apparatus of claim 11, wherein the digital
input signal is a video signal.
going pulse.
13. The apparatus of claim 12, further comprising a
tuner for deriving the digital input signal from a modu
25. The method of claim 21, wherein the recording
10 medium is magnetic tape.
lated RF signal.
14. The apparatus of claim 11, further comprising:
26. The method of claim 21, wherein the recording
an analog input terminal for receiving an analog input
medium is an optical disk.
signal;
_
27. The method of claim 22, wherein the generated
an analog to digital converter for converting the
signal includes alterations of the time durations of hori
analog input signal to a converted digital signal;
zontal line intervals in the analog video signal.
means for providing the converted digital signal to
28. The method of claim 21, wherein the generated
signal includes alteration of the number of horizontal
the mechanism; and
line intervals per video frame.
an analog signal detector for detecting an analog
copy protection signal present in the analog input
signal and in response thereto inhibiting recording
of the analog input signal.
29. The method of claim 23, wherein the one bit is
located in each ?eld of the digital video signal.
30. The method of claim 22, further comprising:
receiving a digital input signal from an external
15. The apparatus of claim 14, wherein both the
means for providing are included in a switch for receiv
ing the digital input signal and the converted digital
signal and providing one or the other to the mechanism,
depending on a connection established by the switch.
source;
25
recording the digital input signal on the recording
medium;
detecting copy protection information present in the
digital input signal;
16. The apparatus of claim 14, wherein the signal
inhibiting recording in response to detection of the
detector includes an automatic gain control circuit re
sponsive to the analog copy protection signal.
copy protection information present in the digital
input signal;
17. The apparatus of claim 14, wherein the signal
detector includes a circuit responsive to the analog
copy protection signal.
18. The apparatus of claim 14, wherein the analog
signal detector includes means for detecting the analog 35
copy protection signal and generating a recording in
detecting serial copy protection information present
in the digital input signal;
generating a digital copy protection signal in re
sponse to the detected serial copy protection infor
hibiting signal in response.
mation; and
inserting the digital copy protection signal into the
19. The apparatus of claim 11, wherein the second
signal detector detects at least one bit in a predeter
31. The method of claim 30, wherein the digital input
digital input signal.
mined location in the digital input signal.
signal is a video signal.
32. The method of claim 31, further comprising deriv
20. An apparatus for playing back information re
corded digitally on a recording medium, the digitally
ing the digital input signal from an RF signal.
recorded information including copy protection por
33. The method of claim 30, further comprising:
receiving an analog input signal;
tions, comprising:
a mechanism for playing the recording medium and 45
providing a digital signal representing the recorded
a digital to analog converter for converting the digi
tal signal to an analog signal; and
means for inserting a copy protection signal into the
analog signal in response to detection of the copy
recording of the analog input signal.
34. The method of claim 22, further comprising:
providing a switch for receiving the digital input
signal and the converted digital signal; and
protection portions.
21. A method for inhibiting copying of material digi
recording one or the other signal depending on a
tally recorded on a recording medium, the material
steps of:
playing the material from the recording medium;
detecting the copy protection information in the
digital signal; and
detecting an analog copy protection signal present in
the analog input signal and in response inhibiting
information;
including copy protection information, comprising the
converting the analog input signal to a converted
55
connection established by the switch.
35. The method of claim 33, wherein the analog sig
nal detecting includes providing an automatic gain con
trol circuit directly responsive to the analog copy pro
tection signal.
played material;
36. The method of claim 33, wherein the analog sig
converting the played material from a digital signal to 60 nal detecting includes providing a circuit directly re
sponsive to the analog copy protection signal.
an analog signal;
generating an analog copy protection signal in re
37. The method of claim 33, wherein the analog sig
nal detecting includes:
sponse to the detected copy protection informa
detecting the analog copy protection signal; and
tion; and
modifying the analog signal with the generated ana 65 generating a recording inhibiting signal in response.
log copy protection signal.
22. The method of claim 21, wherein the digital signal
and analog signals are video signals.
38. The method of claim 30, wherein the serial copy
protection information comprises at least one bit in a
predetermined location in the digital input signal.
13
5,315,448
39. The method of claim 30, further comprising the
steps of inhibiting recording in response to the detected
serial copy protection information.
14
copy protection information and inserting the gen
erated digital copy protection signal into the digital
signal.
40. A method of inhibiting copying of digital re
44. The apparatus of claim 43, wherein the ?rst signal
corded material, the material including digital copy 5 detector detects at least one bit at a predetermined loca
protection portions, comprising the steps of:
tion in the digital video signal, and wherein the second
providing from a recording a digital signal represent
signal detector detects at least one bit in a location asso
ing the recorded material;
ciated with the location of the ?rst bit.
detecting the copy protection portions in the digital
45. An apparatus for playing back video material
signal;
recorded on a recording medium, comprising:
a mechanism for playing the recording medium and
converting the digital signal to an analog signal; and
modifying the analog signal with an analog copy
protection signal in response to the detection of the
providing an analog video playback signal;
a detector for detecting a copy protection flag in the
copy protection portions.
played back signal; and
41. A method of copy-protecting a video signal 15 a signal generator for generating an anti-copy signal
formed of a stream of digital data bits, the method using
in response to the detected copy protection ?ag
a serial copy protection bit detector, comprising:
and modifying the analog video playback signal
setting a ?rst serial copy protection bit to a predeter
with the generated signal.
mined value, the ?rst serial copy protection bit
46. The apparatus of claim 45, wherein the copy
occurring at a predesignated location in the stream; 20 protection ?ag is a predetermined signal level in a
determining the value of the ?rst serial copy protec
blanking interval of the analog video playback signal.
tion bit upon receipt of the video signal at the serial
47. The apparatus of claim 45, wherein the mecha
copy protection bit detector;
nism is also for recording an input analog video signal,
setting a second serial copy protection bit to a prede
and the copy protection ?ag is a predetermined signal
termined value upon determination that the value 25 level in a blanking interval of the input analog video
of the ?rst serial copy protection bit is the predeter
signal.
mined value, wherein the second serial copy pro
tection bit is in a location in the stream associated
material, comprising:
48. A method of copy protecting recorded video
with the ?rst serial copy protection bit;
detecting the second serial copy protection bit; and
providing a ?ag at a predetermined location in a
recorded video signal to be copy protected;
playing back the recorded video material as an analog
upon detection of the second serial copy protection
bit, inhibiting recording of the video signal.
42. The method of claim 41, further comprising set
ting a plurality of ?rst and second serial copy protection
bits occurring periodically in the stream.
35
43. A digital video recorder comprising:
a digital video recording mechanism;
an input terminal for receiving a digital video signal;
a ?rst signal detector for detecting copy protection
information present in the digital video signal;
means for inhibiting recording of the digital video
analog video signal with a copy protection process.
49. A method of copy protecting analog video mate
rial to be recorded comprising:
providing a ?ag at a predetermined location in the
analog video signal to be recorded;
receiving the analog video signal;
recording the analog video signal;
signal in response to detection of the copy protec
tion information;
a second signal detector for detecting serial copy
protection information present in the digital video
signal; and
video signal;
detecting the ?ag in the played back analog video
signal; and
upon detecting the ?ag, modifying the played back
45
a signal generator for generating a digital copy pro
tection signal in response to the detected serial
detecting the ?ag in the recorded video signal upon
playing back of the recorded video signal; and
in response to detection of the ?ag, modifying the
video signal with an analog copy protection pro
6685.
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