 |
Description  |
|
|
CROSS REFERENCE TO RELATED APPLICATION
This application is closely related to the applicant's co-filed, copending
patent application Ser. No. 637,552 filed Dec. 4, 1975, entitled A
Playback Technique For A Stored Audio-Video Program which is assigned to
the assignee of the present invention.
BACKGROUND OF THE INVENTION
The time compression of audio information into video bandwidth information
and the further processing of time-compressed audio information into
pseudo video information of a format comparable to a television line is
disclosed in U.S. Pat. No. 3,789,137 issued Jan. 29, 1974, assigned to the
assignee of the present invention and incorporated herein by reference.
The technique discloses in the above-referenced U.S. patent, permits video
transmission of many minutes of audio information in a few seconds. In the
system of the above-identified U.S. patent, a single frame or field of
video information is recorded on a separate recording track of a magnetic
disc via a single moving head immediately prior to the recording of an
accompanying audio track. A suitable technique for achieving the recording
of audio and video tracks is described in U.S. Pat. No. 3,878,560, issued
to W. W. Ramage on Apr. 15, 1975, assigned to the assignee of the present
invention and incorporated herein by reference. During playback of the
system of U.S. Pat. No. 3,789,137, each video frame is displayed for the
entire period required to play back the corresponding audio track. In this
system, pictures cannot be changed during an audio track playback.
SUMMARY OF THE INVENTION
There is disclosed herein with reference to the accompanying drawings an
improved audio-video program recording technique which permits recording
of successive video frames in an audio-video program with little or no
audio discontinuity. The term audio lines as used hereafter, refers to the
time-compressed audio lines of the type developed in accordance with the
teachings of U.S. Pat. No. 3,789,137. Picture-change cue signals are
recorded with selected audio lines so that picture changes can be made at
any point in the recording of an audio track. This contrasts with the
present program recorders which limit picture changes to the end of an
audio track.
It is an object of the invention to provide a program recording system for
interleaved video (single frames or fields) and audio fields or frames, in
which the audio is recorded on separate sections or tracks of a magnetic
recording medium, such as a disc or drum, leaving adjacent blank tracks in
the audio recording for the later insertion of video signals having a
program association with the audio lines of the preceding recorded audio
track.
Furthermore it is an object of the invention to produce the above program
recording system in which a large number of successive video frames may be
recorded with little or no loss of audio continuity.
Another object of the above invention is to produce a program recording
system in which the picture-change cue signals may be introduced in
connection with the numerous audio lines on an audio track, rather than
only at the end of an audio track. The picture-change cue signals recorded
with the audio functions to control video presentation associated with the
audio program during playback.
It is a further object of the above invention to provide a program
recording system wherein the audio lines and video signals can be recorded
simultaneously on separate tracks of a magnetic recording medium.
DESCRIPTION OF THE DRAWINGS
The invention will become more readily apparent from the following
exemplary description in connection with the accompanying drawings:
FIG. 1 is a schematic illustration of a technique for adding picture-change
cue signals to recorded audio lines;
FIG. 2 is a waveform illustration of the recorded audio lines of FIG. 1;
and
FIG. 3 is a schematic illustration of a technique for recording video
information in combination with the audio lines of FIG. 1.
DESCRIPTION OF THE INVENTION
Referring to FIG. 1 there is schematically illustrated an audio recording
system 10 for processing time-compressed audio lines produced by the audio
compression circuit A in accordance with the teachings of the above
referenced U.S. Pat. No. 3,789,137. The audio lines are recorded on the
audio tracks of the disc D of a conventional record/playback R. As
described in detail in U.S. Pat. No. 3,789,137, the audio compression
circuit A accepts conventional audio information and television signal
information and generates an audio line output signal, as illustrated in
FIG. 1, consisting of a compressed audio segment T of a duration
corresponding to the active portion of a television line, a television
sync signal S and blank level B. The audio line, like a television line,
is approximately 53 microseconds in duration.
The object of the invention is to permit the insertion of video cue signals
Q during the blank signal B of selected audio lines recorded on an audio
track of the disc D and to provide a number of blank tracks following the
recorded audio track sufficient to accommodate the recording of video
information corresponding to the number of video cue signals Q introduced
in the audio lines of an audio track. For example, if three of the audio
lines of the first recorded audio track each include a video cue signal Q,
then the next three tracks of the disc D would be left blank to
accommodate subsequent video information corresponding to the three video
cue signals Q. The recording of the audio information would continue on
the fifth track of the disc D. The schematic illustration of FIG. 1
represents a typical embodiment of a technique for introducing the video
cue signals Q into selected audio lines and further providing the
necessary blank recording tracks for the later recording of associated
video information.
The audio line outputs from the audio line compression circuit A are
supplied to sync detector circuit 11 and adder circuit 22. The sync
detector circuit 11 responds to the presence of the sync pulse S of each
audio line by generating an output signal which is delayed by the .DELTA.T
delay circuit 12 and subsequently applied to the video cue pulse
mono-stable circuit 13 which responds by transmitting a video cue pulse of
a predetermined width to a first input of the AND gate 14. Typically the
width of the video cue pulse Q is 1 microsecond. The video cue signals Q
are continuously produced in response to the sync signals of successive
audio lines and supplied to the first input of the AND gate 14. The gating
of a video cue pulse Q through the AND gate 14 to an input of the adder
circuit 22 is controlled by the video cue pulse initiator circuit 16,
herein illustrated as consisting of switch SW. While numerous techniques
may be employed to automatically program the generation of gate signals to
the second input of the AND gate 14 to gate video cue signals Q for
inclusion with appropriate audio lines in the adder circuit 22, the manual
switch SW represents a simplified approach suitable for the purposes of a
clear understanding of the invention. The closing of switch SW of the
video cue initiator circuit 16 causes flip-flop circuit 18 to gate the
video cue pulse Q produced by the video cue pulse circuit 13 through the
AND gate 14 to the adder circuit 22. The video cue pulse output from the
AND gate 14 functions to reset the flip-flop 18 thereby removing the
gating input signal to the AND gate 14 so as to prevent the gating of
further video cue pulses Q through the AND gate 14 until a subsequent
actuation of the switch SW. The adder circuit 22 functions to sum or
combine the video cue pulse Q from the AND gate 14 with the audio line
input signal from the audio compression circuit A to produce the resultant
output waveform as illustrated. The function of the .DELTA.T delay circuit
12, as is apparent from the output waveform of the adder circuit 22, is to
position the video cue pulse Q at a location in the blank signal B of the
audio line corresponding to the time duration .DELTA.T, typically 10
microseconds, as measured from the leading edge of the sync pulse S. The
output waveform of the adder circuit 22 in the absence of a Q pulse output
from the AND gate 14 corresponds to the audio line output waveform of the
audio compression circuit A. The audio line output information from the
adder circuit 22 is supplied to the record input of the conventional
record/playback unit R where it is supplied to a modulator circuit M for
application to the recording head H for recording on an audio track of the
disc D. Thus, the number of audio lines in a recorded audio track which
includes a video cue pulse Q is determined by the number of actuations of
switch SW. Thus a recorded audio track may include audio lines of which
none include a video cue signal Q while other audio tracks may include one
or more audio lines with video cue signals Q.
In order to determine the exact number of video cue signals introduced in
audio track so that a corresponding number of adjacent blank tracks on the
disc D can be allocated for the recording of associated video information,
the video cue pulse output from the AND gate 14 is supplied to the upcount
input UC of the up/down counter 24. Up/down counter 24 is a commercially
available circuit available from suppliers such as Texas Instruments.
The up/down counter 24 counts in an upward sequence in response to each of
the video cue pulse output signals from the AND gate 14 to a total count
value corresponding to the total number of video cue pulses Q introduced
in the audio lines of an audio track recorded on the disc D. The total
video cue pulse count stored in the up/down counter 24 corresponds to the
number of adjacent tracks in the disc D which are to be skipped by the
head H before commencing further recording of audio lines. The head
stepping signals applied to the head step input of the record/playback
unit R are applied to the head step motor HM to achieve the desired
movement of the head H across a number of disc tracks required for later
recording of the video information associated with the recorded audio
track.
At the conclusion of each track of compressed audio information developed
by the audio compression circuit A, the audio compression circuit A
generates a head step signal which is supplied as an input signal to the
delay mono-stable circuit 26 and as a first input to the adder circuit 36.
The head step signal triggers the delay mono-stable circuit 26 which
generates an output signal to set the flip-flop circuit 28 in the absence
of a reset signal from the zero count detector 32. The set condition of
the flip-flop circuit 28 functions to open the AND gate 30 for the
transmission of output pulses from the pulse generator 34 to a second
input of the adder circuit 36.
The head step signal produced by the audio compression circuit A is
transmitted through the adder circuit 36 to the head step input of the
record/playback R to move the recording head H to the next track on the
disc D. Additional head step input signals from the adder circuit 36, in
the form of output pulses from pulse generator 34, is a function of the up
count stored in the up/down counter 24. A zero count in the counter 24,
corresponding to an audio track in which no video cue signals Q have been
inserted, will result in a reset of flip-flop circuit 28 and no additional
head step signals being transmitted through the adder circuit 36. In this
instance, continuing audio information is recorded on the track of disc D
which is immediately adjacent to the previously recorded audio track.
However, assuming an up count value in counter 24 of three, corresponding
to three video cue signals Q on the previously recorded audio track, there
will be no reset output signal from the zero count detector 32, and the
set condition of the flip-flop circuit 28 will cause AND gate 30 to
transmit output pulses from pulse generator 34 through the AND gate 30 and
the adder circuit 36 to serve as additional head step input signals to the
record/playback unit R. Output pulses from the pulse generator 34, at a
typical pulse repetition rate of 250 hertz have proven appropriate for
establishing head stepping input pulses to the record/playback unit R.
Each of the output pulses produced by the pulse generator 34 and gated to
the AND gate 30 by the set condition of flip-flop circuit 38 is not only
supplied as a head step input signal to the record/playback unit R but
also serves an input signal to the down count input DC of the up/down
counter 24. Thus, assuming the previous condition of an up count of three
in the up/down counter 24, three successive output pulses from the pulse
train generator 34 will cause the up/down counter 24 to count down to a
zero count. Zero count detector 32 in turn repsonds to the zero count
condition in the up/down counter 24 by applying a reset signal to the
flip-flop 28 thus blocking any further transmission of output pulses from
the pulse generator 34 through the AND gate 30. Thus a total of four head
steps input signals will be supplied to the record/playback unit under
these conditions, one head step input signal from the audio compression
circuit A and three head step input signals from the output of AND gate
30. The total of four head step input signals will cause the head motor HM
to step the head motor HM to step the head H four tracks, three
corresponding to the three tracks set aside for subsequent recording of
video information and one to position the head H on the next track
available for continuing the recording of audio information. Following the
completion of recording of the next audio track, the head step sequence is
again initiated in the manner described above.
As shown in FIG. 2, the time between the last audio line T1 recorded on an
audio track n and the first audio line T2 recorded on the next audio track
n + 1 is approximately 1/30 of a second. It is during this 1/30 of a
second that the head stepping signals from the adder circuit 36 are
generated. Inasmuch as the stepping of the head H takes place between
recordings of audio lines, there is no loss in audio circuitry.
The recording of video information on the blank tracks provided by the
operation of the audio recording technique of FIG. 1, is typically
illustrated in the schematic embodiment of FIG. 3. The video information V
supplied to the record input of the record/playback unit R and to the sync
detector unit 68 can take the form of live television information from a
camera, recorded video information from another disc recorder, recorded
video information from different tracks on the same disc D from which the
audio has been recorded, etc. The recording of the video information V
onto the specified tracks of the disc D of the record/playback unit R is
controlled by the video record initiator circuit 51, herein illustrated as
consisting of switch SW2. The actuation of the switch SW2 sets flip-flop
50 thereby causing AND gate 52 to transmit output pulses from the pulse
generator 54 which serve as both input pulses to the delay mono-stable
circuit 56 and head step pulses to the head step input of the
record/playback unit R. Each output pulse transmitted from the AND gate 52
triggers the delay mono-stable circuit 56 which in turn triggers the pulse
mono-stable circuit 58. The output of the pulse mono-stable circuit 58 is
inhibited by signals transmitted from the playback output of the
record/playback unit R through the amplifier 60 and level detector 62 in
the event the track being monitored is a recorded track. The presence of a
recorded information on a track as amplified by amplifier 60 causes the
level detector 62 to transmit and inhibit signal to the pulse mono-stable
circuit 58. Once, however, the head H has been stepped to a blank track of
the disc D, the output from the amplifier 60 will be insufficient to cause
the level detector 62 to generate and inhibit signal, and an output signal
from the pulse mono-stable circuit is transmitted to the reset input of
the flip-flop circuit 50 and to the set input of flip-flop circuit 64. The
resetting of flip-flop 50 terminates the transmission of output pulses
from pulse generator 54 as head stepping input signals to record/playback
unit R. Thus, recording head H is positioned on the first blank track
encountered in the disc D suitable for recording video information. The
setting of the flip-flop circuit 64 opens AND gate 66 to transmit the
output pulses generated by the sync detector circuit 68 in response to the
presence of sync pulses in the video information V. The output pulses from
the sync detector circuit 68, which are gated through AND gate 66 by the
set condition of flip-flop 64, are applied as input signals to the
mono-stable circuit 70. Mono-stable circuit 70 responds to each output
signal from the sync detector 68 gated through the AND gate 66 by
resetting flip-flop 64 and transmitting a 1/30 of a second output pulse to
the record gate input of the record/playback unit R. The 1/30 of a second
output pulse from the mono-stable circuit 70 corresponds to one video
frame and thus enables record/playback unit R to record one video frame of
the video information V on the blank track. The resetting of the flip-flop
64 terminates the gate signal to the AND gate 66 and thus terminates the
passage of sync detector signals to the mono-stable circuit 70. Thus, a
single video frame is recorded on the first available blank track of the
disc D in response to an actuation of the switch SW2. A second actuation
of the switch SW2 will cause the recording head to be stepped to the next
blank track and a second video frame will be recorded on the second blank
track in a similar manner. This video recording process is repeated by
subsequent actuations of switch SW2 until the recording of the video
information V is completed. Once again, while the video record initiator
circuit has been simply illustrated as consisting of a switch SW2 for the
purpose of a clear understanding of the video recording mode, it is
apparent that the video record initiator circuit 51 can be designed to
automatically initiate the video record signals.
* * * * *
|
|
 |
|
 |
Description |
|
