WO2007007264A2 - Method and apparatus for recording an input signal with a decrease of the level of resolution during temporarily suspension of the recording - Google Patents

Method and apparatus for recording an input signal with a decrease of the level of resolution during temporarily suspension of the recording Download PDF

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Publication number
WO2007007264A2
WO2007007264A2 PCT/IB2006/052310 IB2006052310W WO2007007264A2 WO 2007007264 A2 WO2007007264 A2 WO 2007007264A2 IB 2006052310 W IB2006052310 W IB 2006052310W WO 2007007264 A2 WO2007007264 A2 WO 2007007264A2
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WO
WIPO (PCT)
Prior art keywords
recording
level
resolution
input signal
digital signal
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Application number
PCT/IB2006/052310
Other languages
French (fr)
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WO2007007264A3 (en
Inventor
Pawel A. Konieczny
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Koninklijke Philips Electronics N.V.
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Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2007007264A2 publication Critical patent/WO2007007264A2/en
Publication of WO2007007264A3 publication Critical patent/WO2007007264A3/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/79—Processing of colour television signals in connection with recording
    • H04N9/7921—Processing of colour television signals in connection with recording for more than one processing mode
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10527—Audio or video recording; Data buffering arrangements
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/36—Monitoring, i.e. supervising the progress of recording or reproducing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10527—Audio or video recording; Data buffering arrangements
    • G11B2020/1062—Data buffering arrangements, e.g. recording or playback buffers
    • G11B2020/10675—Data buffering arrangements, e.g. recording or playback buffers aspects of buffer control
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10527—Audio or video recording; Data buffering arrangements
    • G11B2020/1062—Data buffering arrangements, e.g. recording or playback buffers
    • G11B2020/10675—Data buffering arrangements, e.g. recording or playback buffers aspects of buffer control
    • G11B2020/10685—Data buffering arrangements, e.g. recording or playback buffers aspects of buffer control input interface, i.e. the way data enter the buffer, e.g. by informing the sender that the buffer is busy
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10527—Audio or video recording; Data buffering arrangements
    • G11B2020/1062—Data buffering arrangements, e.g. recording or playback buffers
    • G11B2020/10675—Data buffering arrangements, e.g. recording or playback buffers aspects of buffer control
    • G11B2020/10731—Data buffering arrangements, e.g. recording or playback buffers aspects of buffer control wherein the buffer I/O can be temporarily suspended, e.g. by refusing to accept further data to be buffered
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10527—Audio or video recording; Data buffering arrangements
    • G11B2020/1062—Data buffering arrangements, e.g. recording or playback buffers
    • G11B2020/10675—Data buffering arrangements, e.g. recording or playback buffers aspects of buffer control
    • G11B2020/1074—Data buffering arrangements, e.g. recording or playback buffers aspects of buffer control involving a specific threshold value
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10527—Audio or video recording; Data buffering arrangements
    • G11B2020/1062—Data buffering arrangements, e.g. recording or playback buffers
    • G11B2020/1075—Data buffering arrangements, e.g. recording or playback buffers the usage of the buffer being restricted to a specific kind of data
    • G11B2020/10759—Data buffering arrangements, e.g. recording or playback buffers the usage of the buffer being restricted to a specific kind of data content data
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10527—Audio or video recording; Data buffering arrangements
    • G11B2020/1062—Data buffering arrangements, e.g. recording or playback buffers
    • G11B2020/10805—Data buffering arrangements, e.g. recording or playback buffers involving specific measures to prevent a buffer overflow
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10527—Audio or video recording; Data buffering arrangements
    • G11B2020/1062—Data buffering arrangements, e.g. recording or playback buffers
    • G11B2020/10824—Data buffering arrangements, e.g. recording or playback buffers the buffer being used to prevent vibrations or shocks from causing delays
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B2020/10935—Digital recording or reproducing wherein a time constraint must be met
    • G11B2020/10972—Management of interruptions, e.g. due to editing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/20—Disc-shaped record carriers
    • G11B2220/23—Disc-shaped record carriers characterised in that the disc has a specific layer structure
    • G11B2220/235—Multilayer discs, i.e. multiple recording layers accessed from the same side
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/84—Television signal recording using optical recording
    • H04N5/85—Television signal recording using optical recording on discs or drums
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/79—Processing of colour television signals in connection with recording
    • H04N9/80—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
    • H04N9/804—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback involving pulse code modulation of the colour picture signal components
    • H04N9/8042—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback involving pulse code modulation of the colour picture signal components involving data reduction

Definitions

  • the invention relates to a method and an apparatus for recording an input signal on an information carrier.
  • a method of recording of the type indicated in the opening paragraph is known from US5737481, which describes the operation of a digital video-camera recording a real-time audio/video signal on an optical disc.
  • the real-time audio/video signal, or input information is encoded and stored in a buffer memory, from which it is then read and recorded on the optical disk.
  • a buffer memory In order to be able to continuously record the input information without loss, even if the digital video-camera falls into a recording-disable state due to a shock externally applied, causing the recording operation to be interrupted, the coding rate of the input information is temporarily reduced, while at the same time the remaining capacity in the buffer memory is monitored.
  • This method has the problem that it leads to an abrupt reduction in the resolution of the encoded input information, which is particularly visible and annoying for the end-user during a subsequent reproduction of the recorded input information.
  • the object is achieved by a method as claimed in claim 1, and by an apparatus as claimed in claim 9.
  • a gradual reduction of the level of resolution is less perceptible during a subsequent replay of the recorded input signal because the end-user has more time to get used to a slightly reduced resolution before a further reduction takes place.
  • the reduction can take place in a plurality of small intermediate steps or continuously from the initial value to the lower value.
  • the same gradual variation can be used for restoring the initial value, once the temporary suspension is over, preferably after the level of filling in the buffer has diminished to a safe level.
  • Fig. 1 shows a known apparatus for recording an input signal on an information carrier
  • Fig. 2 shows the level of filling in the buffer while recording a digital signal, including a temporary suspension of the recording, resulting from the application of the known method of recording an input signal on a record carrier,
  • Fig. 3 shows the level of filling in the buffer while recording a digital signal, including a temporary suspension of the recording, resulting from the application of the method of recording according to the invention
  • Fig. 4 shows the level of filling in the buffer while recording a digital signal, including a temporary suspension of the recording, resulting from the application of another embodiment of the method of recording according to the invention.
  • Fig. 1 shows a known apparatus for recording an input signal on an information carrier.
  • the apparatus comprises processing means 20 for encoding the input signal 21 into a digital signal 10, which digital signal 10 temporarily stored in a buffer 11 at a storing rate Rs.
  • the digital signal 10 is subsequently fetched from the buffer 11 to be recorded at a recording rate Rr on the information carrier 12, which in this case is a multilayer information carrier, with a first layer 13 and a second layer 14.
  • the digital signal 10 is in fact a digital representation of digital data.
  • the buffer is filled at a level 15 which may vary reflecting a difference between the storing rate Rs and the recording rate Rr.
  • the storing rate Rs may be constant or variable; if it is variable, it may be constrained variable, i.e.
  • Rr is equal to the average of Rs in a given interval of time, so that a buffer overflow or underflow can be prevented. More commonly Rr is higher in value than the storing rate Rs in average, and the recording can be repeatedly activated / deactivated, so that the recording is effected in recording packets.
  • the recording When the recording is not activated the level 15 of filling in the buffer 11 increases at a rate equal to the storing rate Rs; when the recording is activated the level 15 of filling in the buffer 11 decreases at a rate equal to Rr - Rs; the recording is controlled to be activated when the level 15 has increased up to a predetermined high level 16 and deactivated when the level 15 has decreased down to a predetermined low level 17.
  • the predetermined high level 16 and the predetermined low level 17 may be close to a situation of buffer full and empty, respectively, however other choices are possible.
  • the predetermined high level 16 for example could be chosen as a level where 90% or more of the buffer is full, but not 100%, otherwise a buffer overflow could not be prevented anymore.
  • the optimal determination of the predetermined high level 16 reflects design considerations like the time requested to activate the recording, the maximum storing rate and the buffer size. Similar considerations can be applied to the predetermined low level 17 as well, except for the fact that in some situations the condition of buffer empty can be perfectly acceptable or even desirable, so that fixing the predetermined low level 17 to 0% is in general possible.
  • the apparatus further comprises a recording unit 18, for recording the digital signal 10 stored in the buffer 11 on the information carrier, and may further comprise a start/stop unit 19, to activate / deactivate, the recording unit 18, upon reaching the predetermined high level 16 / low level 17 in the buffer 11.
  • the apparatus also comprises an encoding resolution control unit 25, controlling the level of resolution with which the input signal 21 is encoded in the processing means 20, and a recording control unit 24 which in response to an event forces a deactivation of the recording unit 18 and the encoding resolution control unit 25 to decrease the level of resolution with which the input signal 21 is encoded in the digital signal 10 to a lower value.
  • the event might be any event causing or requiring a temporary suspension of the recording, like for example a shock, the need for replacing the information carrier, or fresh power supply, or, in the case of a multi- layer information carrier, the need for a layer jump.
  • the input signal 21 may be itself another digital signal or an analogue signal, particularly a real-time audio/video signal.
  • Fig. 2 shows the level of filling in the buffer while recording the digital signal in the situation in which the storing rate Rs is a constrained variable rate.
  • the first line represents the storing rate Rs having a constrained variable value.
  • the second line represents the level 15 of filling in the buffer 11 : apart from the initial value the level 15 of filling in the buffer 11 is the integral of the storing rate minus the recording rate Rs - Rr; consequently, the level 15 in the buffer 11 has some variations reflecting the variations in the storing rate.
  • a situation is represented where the recording takes place continuously, however what is described is valid also in the situation of recording in packets.
  • the recording indicated by the third line, is suspended at a time te due to some event, like for example the storage space available on the first layer of a multilayer information carrier being exhausted and a layer jump having to take place; then the recording is resumed at a time tr. Therefore in this example the temporary suspension of the recording is effected in order to allow the layer jump to take place, however it is stressed that other reasons may be behind the need for a temporary suspension of the recording, like for example a momentary inability to record due to a shock.
  • the digital signal 10 has to be stored in the buffer 11, therefore the storing rate Rs is reduced to a lower level, so as to reduce the rate at which the buffer is filled up, thereby reducing the possibility of a buffer overflow.
  • the consequences of a buffer overflow may be particularly severe because part of the digital signal may be completely lost.
  • the higher initial value of the storing rate can be restored.
  • the higher initial value of the storing rate is not restored before the buffer level has decreased down to a safe level.
  • Fig. 3 shows the level of filling in the buffer while recording the digital signal in the same situation discussed with reference to Fig 2 by applying the method according to the invention.
  • the storing rate Rs is not decreased abruptly but gradually, i.e. varying in continuously or in intermediate steps from the initial value to the lower value.
  • the change in resolution is less noticeable, and thus less disturbing during replay of the recorded signal.
  • the adjustment unit 25 is adapted for decreasing the storing rate gradually when a temporary suspension of recording is taking place.
  • the need for a temporary suspension of the recording can be either unpredictable, like a shock, or predictable, like a layer jump in relation to a multi- layer information carrier.
  • the storing rate Rs can be reduced before the temporary suspension of the recording, for example when in proximity of the storage space available on the first layer being filled, as shown in Fig. 4.
  • the condition of proximity to the storage space available on the first layer being filled can be defined for example as the remaining storage space available on the first layer falling below a given threshold.
  • the recording unit 18 can calculate the storage space available remaining at a given moment on the basis for example of a current recording address and the total storage space.
  • This method can be further improved if the storing rate Rs is decreased to a value calculated so that the time interval during which the recording is suspended begins with the buffer 11 substantially empty, because also this concurs to provide a longer time before a buffer overflow may occur, or similarly, to allow for a buffer of reduced size.
  • the earlier the storing rate Rs is decreased the smaller is the decrease in Rs which is required.
  • the situation may be given in which the digital signal derives from the processing of an input signal, which input signal is generally not under control: that is the input signal cannot be slowed down, accelerated, or stopped.
  • the input signal is an analogue signal, for example a realtime audio/video signal, which recording cannot be stopped, the sanction being the loss of the audio/video signal during an interval of time.
  • the digital signal derives from the digitalization of the input signal and it is possible to decrease the rate at which the digital signal is generated for example by decreasing the sampling rate of the analogue signal and/or the resolution of the samples.
  • the digital signal can be obtained by use of an MPEG encoder, which allows different levels of resolution: in this case the rate at which the digital signal is generated, sometimes referred to as bit rate, can be decreased by decreasing the level of resolution.
  • bit rate the rate at which the digital signal is generated
  • the constrained variable bit rate is a bit rate which can vary within a range around a nominal value, so as to optimize the visual perception.
  • the method according to the invention can be exploited by a digital video camera using a dual- layer recordable DVD as storage medium.
  • a method is disclosed of recording an input signal on an information carrier, comprising the steps of: - encoding the input signal so as to obtain a digital signal, with a level of resolution at an initial value, storing the digital signal in a buffer, recording the digital signal stored in the buffer on the information carrier, temporarily suspending the recording, and - while the recording is temporarily suspended, having the level of resolution decreased to a lower value in encoding the input signal, characterized in that in decreasing the level of resolution to the lower value, said level of resolution is decreased gradually. In this way it is obtained that the decrease in the level of resolution is less perceptible during reproduction of the input signal.

Abstract

A method is disclosed of recording an input signal 21 on an information carrier 12, comprising the steps of: - encoding the input signal so as to obtain a digital signal 10, with a level of resolution at an initial value, - storing the digital signal in a buffer 11, - recording the digital signal stored in the buffer on the information carrier, - temporarily suspending the recording, and - while the recording is temporarily suspended, having the level of resolution decreased to a lower value in encoding the input signal, wherein in decreasing the level of resolution to the lower value, said level of resolution is decreased gradually. In this way it is obtained that the decrease in the level of resolution is less perceptible during reproduction of the input signal.

Description

Method and apparatus for recording an input signal.
The invention relates to a method and an apparatus for recording an input signal on an information carrier.
A method of recording of the type indicated in the opening paragraph is known from US5737481, which describes the operation of a digital video-camera recording a real-time audio/video signal on an optical disc.
The real-time audio/video signal, or input information, is encoded and stored in a buffer memory, from which it is then read and recorded on the optical disk. In order to be able to continuously record the input information without loss, even if the digital video-camera falls into a recording-disable state due to a shock externally applied, causing the recording operation to be interrupted, the coding rate of the input information is temporarily reduced, while at the same time the remaining capacity in the buffer memory is monitored. This method has the problem that it leads to an abrupt reduction in the resolution of the encoded input information, which is particularly visible and annoying for the end-user during a subsequent reproduction of the recorded input information.
It is an object of the present invention to provide a method and an apparatus of the type described in the opening paragraph by which a temporary suspension of the recording is managed in a way that is less perceptible during a subsequent replay of the recorded input information.
According to the invention the object is achieved by a method as claimed in claim 1, and by an apparatus as claimed in claim 9.
In fact, a gradual reduction of the level of resolution is less perceptible during a subsequent replay of the recorded input signal because the end-user has more time to get used to a slightly reduced resolution before a further reduction takes place. The reduction can take place in a plurality of small intermediate steps or continuously from the initial value to the lower value. The same gradual variation can be used for restoring the initial value, once the temporary suspension is over, preferably after the level of filling in the buffer has diminished to a safe level. Advantageous embodiments of the method according to the invention are claimed in the dependent claims. All optional features of the method according to the invention defined in the dependent claims can be translated into corresponding optional features for the apparatus according to the invention.
These and other aspects of the method and apparatus according to the invention will be further elucidated and described with reference to the drawings. In the drawings:
Fig. 1 shows a known apparatus for recording an input signal on an information carrier,
Fig. 2 shows the level of filling in the buffer while recording a digital signal, including a temporary suspension of the recording, resulting from the application of the known method of recording an input signal on a record carrier,
Fig. 3 shows the level of filling in the buffer while recording a digital signal, including a temporary suspension of the recording, resulting from the application of the method of recording according to the invention,
Fig. 4 shows the level of filling in the buffer while recording a digital signal, including a temporary suspension of the recording, resulting from the application of another embodiment of the method of recording according to the invention.
Fig. 1 shows a known apparatus for recording an input signal on an information carrier. The apparatus comprises processing means 20 for encoding the input signal 21 into a digital signal 10, which digital signal 10 temporarily stored in a buffer 11 at a storing rate Rs. The digital signal 10 is subsequently fetched from the buffer 11 to be recorded at a recording rate Rr on the information carrier 12, which in this case is a multilayer information carrier, with a first layer 13 and a second layer 14. The digital signal 10 is in fact a digital representation of digital data. At a given moment the buffer is filled at a level 15 which may vary reflecting a difference between the storing rate Rs and the recording rate Rr. The storing rate Rs may be constant or variable; if it is variable, it may be constrained variable, i.e. variable within a range around a nominal value, or fully variable. Generally the system has to be designed in such a way that Rr is equal to the average of Rs in a given interval of time, so that a buffer overflow or underflow can be prevented. More commonly Rr is higher in value than the storing rate Rs in average, and the recording can be repeatedly activated / deactivated, so that the recording is effected in recording packets. When the recording is not activated the level 15 of filling in the buffer 11 increases at a rate equal to the storing rate Rs; when the recording is activated the level 15 of filling in the buffer 11 decreases at a rate equal to Rr - Rs; the recording is controlled to be activated when the level 15 has increased up to a predetermined high level 16 and deactivated when the level 15 has decreased down to a predetermined low level 17. The predetermined high level 16 and the predetermined low level 17 may be close to a situation of buffer full and empty, respectively, however other choices are possible. The predetermined high level 16 for example could be chosen as a level where 90% or more of the buffer is full, but not 100%, otherwise a buffer overflow could not be prevented anymore. The optimal determination of the predetermined high level 16 reflects design considerations like the time requested to activate the recording, the maximum storing rate and the buffer size. Similar considerations can be applied to the predetermined low level 17 as well, except for the fact that in some situations the condition of buffer empty can be perfectly acceptable or even desirable, so that fixing the predetermined low level 17 to 0% is in general possible. The apparatus further comprises a recording unit 18, for recording the digital signal 10 stored in the buffer 11 on the information carrier, and may further comprise a start/stop unit 19, to activate / deactivate, the recording unit 18, upon reaching the predetermined high level 16 / low level 17 in the buffer 11. The apparatus also comprises an encoding resolution control unit 25, controlling the level of resolution with which the input signal 21 is encoded in the processing means 20, and a recording control unit 24 which in response to an event forces a deactivation of the recording unit 18 and the encoding resolution control unit 25 to decrease the level of resolution with which the input signal 21 is encoded in the digital signal 10 to a lower value. The event might be any event causing or requiring a temporary suspension of the recording, like for example a shock, the need for replacing the information carrier, or fresh power supply, or, in the case of a multi- layer information carrier, the need for a layer jump. The input signal 21 may be itself another digital signal or an analogue signal, particularly a real-time audio/video signal.
Fig. 2 shows the level of filling in the buffer while recording the digital signal in the situation in which the storing rate Rs is a constrained variable rate. The first line represents the storing rate Rs having a constrained variable value. The second line represents the level 15 of filling in the buffer 11 : apart from the initial value the level 15 of filling in the buffer 11 is the integral of the storing rate minus the recording rate Rs - Rr; consequently, the level 15 in the buffer 11 has some variations reflecting the variations in the storing rate.
For the sake of simplicity, a situation is represented where the recording takes place continuously, however what is described is valid also in the situation of recording in packets. The recording, indicated by the third line, is suspended at a time te due to some event, like for example the storage space available on the first layer of a multilayer information carrier being exhausted and a layer jump having to take place; then the recording is resumed at a time tr. Therefore in this example the temporary suspension of the recording is effected in order to allow the layer jump to take place, however it is stressed that other reasons may be behind the need for a temporary suspension of the recording, like for example a momentary inability to record due to a shock. During the temporary suspension of the recording, the digital signal 10 has to be stored in the buffer 11, therefore the storing rate Rs is reduced to a lower level, so as to reduce the rate at which the buffer is filled up, thereby reducing the possibility of a buffer overflow. In fact, the consequences of a buffer overflow may be particularly severe because part of the digital signal may be completely lost. After the recording has resumed, the higher initial value of the storing rate can be restored. Preferably the higher initial value of the storing rate is not restored before the buffer level has decreased down to a safe level.
Fig. 3 shows the level of filling in the buffer while recording the digital signal in the same situation discussed with reference to Fig 2 by applying the method according to the invention. What is done differently from in Fig. 2a is that the storing rate Rs is not decreased abruptly but gradually, i.e. varying in continuously or in intermediate steps from the initial value to the lower value. What is obtained is that the change in resolution is less noticeable, and thus less disturbing during replay of the recorded signal.
Similarly, in an apparatus according to the invention, differently from what already shown in Fig. 1, the adjustment unit 25 is adapted for decreasing the storing rate gradually when a temporary suspension of recording is taking place.
The need for a temporary suspension of the recording can be either unpredictable, like a shock, or predictable, like a layer jump in relation to a multi- layer information carrier. In an advantageous embodiment, when confronted with a temporary suspension of the recording of predictable type, the storing rate Rs can be reduced before the temporary suspension of the recording, for example when in proximity of the storage space available on the first layer being filled, as shown in Fig. 4. The condition of proximity to the storage space available on the first layer being filled can be defined for example as the remaining storage space available on the first layer falling below a given threshold. Clearly the recording unit 18 can calculate the storage space available remaining at a given moment on the basis for example of a current recording address and the total storage space. This method can be further improved if the storing rate Rs is decreased to a value calculated so that the time interval during which the recording is suspended begins with the buffer 11 substantially empty, because also this concurs to provide a longer time before a buffer overflow may occur, or similarly, to allow for a buffer of reduced size. Generally, the earlier the storing rate Rs is decreased, the smaller is the decrease in Rs which is required. As it has been introduced above, the situation may be given in which the digital signal derives from the processing of an input signal, which input signal is generally not under control: that is the input signal cannot be slowed down, accelerated, or stopped. In a particularly relevant embodiment the input signal is an analogue signal, for example a realtime audio/video signal, which recording cannot be stopped, the sanction being the loss of the audio/video signal during an interval of time. In this case the digital signal derives from the digitalization of the input signal and it is possible to decrease the rate at which the digital signal is generated for example by decreasing the sampling rate of the analogue signal and/or the resolution of the samples.
If the input signal is real-time audio/video signal the digital signal can be obtained by use of an MPEG encoder, which allows different levels of resolution: in this case the rate at which the digital signal is generated, sometimes referred to as bit rate, can be decreased by decreasing the level of resolution. According to some MPEG encoding methods it is possible to select a constrained variable bit rate instead of a constant bit rate. The constrained variable bit rate is a bit rate which can vary within a range around a nominal value, so as to optimize the visual perception.
Clearly, the method according to the invention can be exploited by a digital video camera using a dual- layer recordable DVD as storage medium.
It must be noted that the term "comprises/comprising" when used in this specification, including the claims, is taken to specify the presence of stated features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or groups thereof. It must also be noted that the word "a" or "an" preceding an element in a claim does not exclude the presence of a plurality of such elements. Moreover, any reference signs do not limit the scope of the claims; the invention can be implemented by means of both hardware and software, and several "means" may be represented by the same item of hardware. Furthermore, the invention resides in each and every novel feature or combination of features.
The invention can be summarized as follows. A method is disclosed of recording an input signal on an information carrier, comprising the steps of: - encoding the input signal so as to obtain a digital signal, with a level of resolution at an initial value, storing the digital signal in a buffer, recording the digital signal stored in the buffer on the information carrier, temporarily suspending the recording, and - while the recording is temporarily suspended, having the level of resolution decreased to a lower value in encoding the input signal, characterized in that in decreasing the level of resolution to the lower value, said level of resolution is decreased gradually. In this way it is obtained that the decrease in the level of resolution is less perceptible during reproduction of the input signal.

Claims

CLAIMS:
1. Method of recording an input signal (21) on an information carrier (12), comprising the steps of: encoding the input signal so as to obtain a digital signal (10), with a level of resolution at an initial value, - storing the digital signal in a buffer (11), recording the digital signal stored in the buffer on the information carrier, temporarily suspending the recording, and while the recording is temporarily suspended, having the level of resolution decreased to a lower value in encoding the input signal, characterized in that in decreasing the level of resolution to the lower value, said level of resolution is decreased gradually.
2. Method as claimed in claim 1, characterized in that the digital signal is recorded on an information carrier (12) comprising a first layer (13) and a second layer (14), and while the recording is temporarily suspended a layer jump is effected.
3. Method as claimed in claim 2, characterized by decreasing the level of resolution before the recording is temporarily suspended.
4. Method as claimed in claim 3, characterized by decreasing the level of resolution to a value so selected that the buffer is substantially empty when the recording is temporarily suspended.
5. Method as claimed in claim 1, characterized in that the input signal (21) is an analogue signal, in particular a real-time audio/video signal.
6. Method as claimed in claim 5, characterized in that in encoding the input signal (21) an MPEG encoder is used.
7. Method as claimed in claim 6, characterized in that the MPEG encoder is used in a mode where the bit rate (Rs) of the digital signal is a variable constrained rate.
8. Method as claimed in claim 7, characterized by comprising the step of switching the variable constrained rate to a fixed rate.
9. Apparatus for recording an input signal (21) on an information carrier (12), comprising: an encoder (20), for encoding the input signal so as to obtain a digital signal (10), with a selectable level of resolution, a buffer (11) for the storage of the digital signal, a recording unit (18), for recording the digital signal stored in the buffer on the information carrier, a recording control unit (24) for controlling the recording unit to temporarily suspending the recording, an encoding resolution control unit (25), for controlling the encoder to have the level of resolution decreased to a value lower than an initial value in encoding the input signal, while the recording is temporarily suspended, characterized in that the encoding resolution control unit (25) is adapted for decreasing gradually the level of resolution to the lower value.
10. Apparatus as claimed in claim 9, wherein the a recording unit (18) is configured for recording the digital signal on an information carrier (12) comprising a first layer (13) and a second layer (14) and for effecting a layer jump, and wherein the recording control unit (24) is configured for controlling the recording unit to temporarily suspending the recording when the layer jump is effected.
PCT/IB2006/052310 2005-07-13 2006-07-07 Method and apparatus for recording an input signal with a decrease of the level of resolution during temporarily suspension of the recording WO2007007264A2 (en)

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