Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1997-07-31
2002-08-13
Tran, Thai (Department: 2715)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000
Reexamination Certificate
active
06434321
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording and reproducing method for slow-motion reproduction of video and audio signals recorded on a video tape of, for example, a DV (digital video) format and a magnetic recording and reproducing apparatus capable of slow-motion reproduction of the video and audio signals, said magnetic recording and reproducing apparatus being frequently incorporated in a laptop editor or installed as a part of studio editing equipment.
2. Description of the Prior Art
FIGS.
4
(
a
) and
4
(
b
) show block diagrams of a conventional magnetic recording and reproducing apparatus.
FIG.
4
(
a
) is a block diagram of a recording system. FIG.
4
(
b
) is a block diagram of a reproducing system.
Referring to FIG.
4
(
a
), an A/D (analog-to-digital) converter
11
has a function to convert an analog video input from a television camera or other video tape recorders into a digital signal. A data shuffling circuit
12
has a function to selectively capture the output data from the A/D converter
11
and a digital video data input from a digital video tape recorder or a digital camera to perform data shuffling. A data compressing circuit
13
has a function to compress the output data of the data shuffling circuit
12
through two-dimensional discrete cosine transformation.
An A/D converter
14
has a function to convert an analog audio input from a microphone amplifier or other video tape recorders into a digital signal. A sampling frequency converting circuit
15
has a function to selectively capture the output data from the A/D converter
14
and a digital audio data input from a digital video tape recorder or other digital sound sources to perform sampling frequency conversion.
An error correcting code adding circuit
16
has a function to add an error correcting code to the output of the data compressing circuit
13
and the output of the sampling frequency converting circuit
15
. A variable length coding circuit
17
has a function to code the output of the error correcting code adding circuit
16
. The output of the variable length coding circuit
17
is sent to a magnetic head (not shown), so that the video and audio signals are recorded on a magnetic tape in frame units, for example, in the DV format.
Referring to FIG.
4
(
b
), a detecting circuit
21
has a function to detect a signal outputted from the magnetic head (not shown) sliding over the magnetic tape. An error correcting circuit
22
has a function to perform error correction on the digital signal outputted from the detecting circuit
21
. A decoding circuit
23
has a function to decode the video data included in the digital signal outputted from the error correcting circuit
22
. A data deshuffling circuit
24
has a function to deshuffle the data outputted from the decoding circuit
23
. The data deshuffling circuit
24
outputs digital video data which are used for digital dubbing.
A D/A (digital-to-analog) converter
25
has a function to convert the output data of the data deshuffling circuit
24
into an analog signal. The analog video output is sent to a video monitor or used for analog dubbing. To the error correcting circuit
22
, a frame control signal in slow-motion reproduction is added to control the error correcting operation in slow-motion reproduction.
A sampling frequency converting circuit
26
has a function to perform sampling frequency conversion on the audio data included in the digital signal outputted from the error correcting circuit
22
. The sampling frequency converting circuit
26
outputs digital audio data which are used for digital dubbing.
A D/A converter
27
has a function to convert the output data of the sampling frequency converting circuit
25
into an analog signal. The analog audio output is sent to an audio monitor or used for analog dubbing.
In the magnetic recording and reproducing apparatus shown in
FIG. 4
, in the case of the signal processing in recording, the video signal is delayed by a total of two frames: one frame in the data shuffling operation and one frame in the error correcting code adding operation, whereas the audio signal is delayed only by one frame in the error correcting code adding operation. For this reason, although not shown in the circuit of
FIG. 4
, a means for delaying the audio signal by one frame is provided in order to synchronize the recording timing of the video and audio signals.
Likewise, in the case of the signal processing in reproduction, the video signal is delayed by a total of two frames: one frame in the data deshuffling operation and one frame in the error correcting operation, whereas the audio signal is delayed only by one frame. For this reason, although not shown in the circuit of
FIG. 4
, a means for delaying the audio signal by one frame is provided in order to synchronize the reproduction timing of the video and audio signals. The signal processing is performed in frame units.
FIG. 5
shows the timing in the recording and reproduction of the video and audio signals. FIG.
5
(
a
) shows the timing in recording. FIG.
5
(
b
) shows the timing in normal reproduction (normal-speed reproduction). Reference characters A, B, C, D and E in the figures represent frames. FIG.
5
(
a
) shows that when the video input and the audio input are added in synchronism with each other to the frames A, B, C, . . . , the recording by the magnetic head is performed on the frames A, B, C, . . . with a delay of two frames from the video and audio inputs. FIG.
5
(
b
) shows that when the reproduction by the magnetic head is performed on the frames A, B, C, . . . , the video output and the audio output are performed on the frames A, B, C, . . . with a delay of two frames from the reproduction by the magnetic head.
The magnetic recording and reproducing apparatus is capable of a 1
-speed slow-motion reproduction in which the average transport speed of the magnetic tape is 1
that of the normal reproduction. Here, n is an integer not less than 2 but not more than approximately 30. In the 1
-speed slow-motion reproduction, a slow-motion reproduction at a speed 1
the normal reproduction speed is performed by reproducing video and audio signals recorded on a magnetic tape in a digital format such as the DV format at a speed 1
that of the normal reproduction and repetitively outputting a video signal of the same frame over n frame periods. The magnetic recording and reproducing apparatus is also capable of a variable speed slow-motion reproduction in which the speed of the slow-motion reproduction is variable from ½ (n=2) to approximately 1/30 (n=30).
The repetitive output of a video signal of the same frame over n frame periods is realized by storing one frame of the data obtained by the error correcting circuit
22
in an error correction interpolating memory
29
and outputting the one frame of the data stored in the error correction interpolating memory
29
n times. When the magnetic tape is transported to reproduce the data of the next frame, the data in the error correction interpolating memory
29
are updated. The frame control in the slow-motion reproduction is performed based on a control signal (speed information) for sending the same signal n times.
Referring now to
FIG. 6
, there is shown a difference in video and audio signals between the normal-speed reproduction and a ⅓-speed reproduction. FIG.
6
(
a
) shows the manner of the video output and the audio output in the normal-speed reproduction and indicates that the frames of the video and audio outputs are changed to A, B, C, . . . every frame period. FIG.
6
(
b
) shows the manner of the video output and the audio output in the ⅓-speed reproduction and indicates that the frames of the video and audio outputs are changed to A, A, A, B, B, B, C, C, C, . . . every frame period, i.e. video and audio outputs of the same frame are repetitively outputted over three consecutive frame periods.
The above-described conventional magnetic recording and reproducing app
Matsushita Electric - Industrial Co., Ltd.
Stevens Davis Miller & Mosher LLP
Tran Thai
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