Video signal receiver with level limited output

Details Video signal receiver with level limited output Video signal receiver with level limited output

2001-10-23

2002-11-19

Hsia, Sherrie (Department: 2614)

Television

Image signal processing circuitry specific to television

C348S689000, C348S690000

Reexamination Certificate

active

06483549

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a video signal processing apparatus that limits the level of a received video signal when the level of the received video signal has exceeded a predetermined level by a noise or interference.
When a video signal is transmitted from an imaging apparatus or an image reproducing apparatus to a receiver for image reproduction, the video signal is generally transmitted in the form of an analog video signal or a digital video signal. During such a transmission of the video signal, there can be a case in which the level of the video signal exceeds a predetermined level for reception as a result of mixing of noise or interference with other signals including other video signals. When the level of the received video signal exceeds the predetermined level as such, there can be a case in which a pseudo-synchronization is caused. Alternatively, the excessive level of the video signal may cause a deterioration in the quality of reproduced image. Thus, there is a need to limit the level of a received video signal within a predetermined level.
FIG. 1A
shows a conventional image signal transmission system implemented in the form of a coded image transmission system, wherein the video signal transmission system includes an analog video signal output unit
301
, which may be an imaging device or a video signal recording/reproducing apparatus, an encoding and transmission unit
302
for encoding and transmitting the analog video signal from the unit
301
over a transmission path
305
, a video signal processing unit
303
receiving the encoded video signal from the unit
302
through the transmission path
305
, a video signal processing unit
303
decoding the encoded video signal thus received and converting the same into an analog video signal, and a reproducing unit
304
for reproducing the analog video signal thus recovered by the video signal processing unit
303
. As can be seen in
FIG. 1A
, the encoding and transmission unit
302
includes an A-D converter
306
for converting the input analog video signal to a digital video signal, an encoder
307
for encoding the digital video signal produced by the A-D converter
306
and an interface device
308
for transmitting the encoded video signal over the transmission path
305
. Further, the video signal processing unit
303
includes an interface unit
309
for receiving the encoded video signal from the transmission path
305
, a decoder
310
for decoding the encoded video signal thus received by the interface unit
309
, and a D-A converter
311
for converting the decoded video signal to an analog video signal.
FIG. 1B
shows another conventional image signal transmission system implemented in the form of a digital image transmission system, wherein the video signal transmission system includes an analog video signal output unit
321
, which may be an imaging device or a video signal recording/reproducing apparatus, a digital transmission unit
322
for converting the analog video signal from the unit
321
into a digital video signal and transmitting the same over a transmission path
325
, a video signal processing unit
323
receiving the digital video signal from the digital transmission unit
322
through the transmission path
305
, a video signal processing unit
323
converting the received digital video signal into an analog video signal, and a reproducing unit
324
for reproducing the analog video signal thus recovered by the video signal processing unit
323
. As can be seen in
FIG. 1B
, the transmission unit
322
includes an A-D converter
326
for converting the input analog video signal to the digital video signal and an interface device
327
for transmitting the digital video signal over the transmission path
325
. Further, the video signal processing unit
323
includes an interface unit
328
for receiving the digital video signal from the transmission path
325
and a D-A converter
329
for converting the digital video signal to an analog video signal.
FIG. 1C
shows another conventional image signal transmission system implemented in the form of an analog image transmission system, wherein the video signal transmission system includes an analog video signal output unit
331
, which may be an imaging device or a video signal recording/reproducing apparatus, an analog transmission unit
332
for transmitting the analog video signal from the unit
331
over a transmission path
335
, a video signal processing unit
333
receiving the analog video signal from the analog transmission unit
332
through the transmission path
335
, the video signal processing unit
333
receiving the an analog video signal from the transmission unit
332
via the transmission path
335
, and a reproducing unit
334
for reproducing the analog video signal thus received by the video signal processing unit
333
. As can be seen in
FIG. 1C
, the transmission unit
332
includes an A-D converter
336
for converting the input analog video signal to the digital video signal, while the video signal processing unit
333
includes an interface unit
337
for receiving the analog video signal from the transmission path
335
.
FIG. 2A
shows a 100% color bar signal that includes a synchronization pulse of −40 (IRE) level and a video signal, wherein the video signal has a level not lower than the level of the synchronization signal. The maximum level of the video signal is set to 133 (IRE) level.
When the video signal has a level lower than the −40 (IRE) level as indicated in
FIG. 2B
, it will be noted that the portion of the video signal having such a low level state is erroneously recognized as being a synchronization pulse, and there arises a problem of erroneous pseudo-synchronization. When the video signal includes a portion having a level exceeding 133 (IRE), on the other hand, the quality of the reproduced image is deteriorated as a result of saturation.
In the encoded video signal transmission system of
FIG. 1A
, it should be noted that the A-D converter
306
and the D-A converter
311
create error in the video signal associated with analog-to-digital conversion or digital-to-analog conversion of the video signal. Further, the encoder
307
and the decoder
310
create error as a result of the encoding or decoding of the video signal. Further, the transmission path
325
may pickup noise.
In the digital video signal transmission system of
FIG. 1B
, the A-D converter
326
and the D-A converter
329
create error in the video signal associated with the analog-to-digital conversion or digital-to-analog conversion of the video signal. Further, the transmission path
305
may pickup noise. In the analog video signal transmission system of
FIG. 1C
, on the other hand, the transmission path
335
may pickup noise.
As a result of the mixing of noise or conversion error, or as a result of the interference of the signals transmitted in a multiplexed mode, there can be a case in which the video signal supplied from the video signal processing unit
303
,
323
or
333
to the reproducing unit
304
,
324
or
334
contains an under-level portion or over-level portion as indicated in FIG.
2
B. When this is the case, the under-level portion of the video signal may be erroneously recognized as being a synchronization pulse, and there occurs a problem of pseudo-synchronization. When the video signal contains an over-level portion, on the other hand, the quality of the reproduced image may be deteriorated.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful video signal processing apparatus wherein the foregoing problems are eliminated.
Another and more specific object of the present invention is to provide a video signal processing apparatus producing an output video signal in response to a received video signal, which may be any of an encoded image signal, a digital image signal or an analog image signal, such that the level of the output video signal does not fall below a predetermined lower limit lev

Affiliated with

Also associated with

Rating

Video signal receiver with level limited output does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Video signal receiver with level limited output, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Video signal receiver with level limited output will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2958699