WO2001052530A2

WO2001052530A2 - Recording/reproducing apparatus having writing means for recording and/or reading means and detector means for reproducing an information signal in resp. from at least one track on a record carrier

Info

Publication number: WO2001052530A2
Application number: PCT/EP2000/013222
Authority: WO
Inventors: Marinus A. H. Looijkens
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2000-01-10
Filing date: 2000-12-27
Publication date: 2001-07-19
Also published as: US20010024336A1; US6490107B2; DE60044673D1; WO2001052530A3; EP1190570B1; ATE474420T1; EP1190570A2; JP2003520385A

Abstract

Recording/reproducing apparatus for recording/reproducing a serial information stream of A/V signals comprising packets of information signals, such as MPEG Transport Packets, on/from a recording medium (6). The apparatus comprises time stamping means (3) for time stamping received information packets in accordance with a time stamping clock reference, writing means (5) for recording the information packets in accordance with a write clock reference and reading means (10) for reproducing the information packets in accordance with a read clock reference. All clock references are derived from a single crystal clock reference (17). The read clock reference has a frequency equal to the frequency of the single crystal clock reference (17), which frequency is an integer multiple of the frequency of the write clock reference. The time stamp clock reference has a frequency derived from the single crystal clock reference (17) by digital counter means.

Description

Recording/reproducing apparatus having writing means for recording and/or reading means and detector means for reproducing an information signal in resp. from at least one track on a record carrier.

The invention relates to an apparatus having receiving means for receiving an information signal comprising packets of information signals that occur regularly as a function of time in a serial data stream of the received information signal, time stamping means for time stamping the packets comprised in the received information signal employing a time stamp clock reference, writing means for recording the time stamped packets in at least one track of a record carrier, employing a write clock reference for synchronizing the writing means, and reading means linked with detector means for reproducing the recorded time stamped information signal from the at least one track of the record carrier employing a read clock reference for sampling the recorded information signal. In current day practice use is made of at least two different and independent

X-tal clock generators, one for sampling the information signal which is retrieved from the record carrier and for generation of a first stamp reference clock, and one separate X-tal clock which is used for synchronizing the writing means. Particularly the synchronizing frequency of the latter clock requires accuracy in the choice of frequency in order to conform to the information signal channel bit rate.

It is the aim of the invention to reduce the number of components used in the known apparatus without comprising the requirements of the recording and reproducing process of the known apparatus.

According to a first aspect of the invention, the apparatus comprises clock generating means with a single reference crystal for generating the clock reference signals.

Advantageously, the single reference crystal is chosen to generate a single reference signal of a frequency of an integer multiple of the write clock reference signal.

This provides the opportunity to maintain the required accuracy of the writing operation by applying a divider in order to generate the required write clock signal derived from the single reference signal from the clock generating means, which satisfies the writing frequency.

Particularly when the frequency of the single clock reference is chosen at three times the frequency of the write clock signal, the clock generating means provide a frequency in a reproducing mode with an oversampling factor of 3, which facilitates an improvement in respect of the signal quality.

A further advantageous embodiment of a recording/reproducing apparatus wherein the received information signal comprises program clock reference (PCR) signals is characterized in that the apparatus comprises counter means for generating the time stamp clock reference employing the received program clock reference (PCR) signals and the single clock reference signal.

Preferably a counter of the type as described in the international application with application number IB99/00980 (PHN 16.942), filed at 31-05-99, is used. A further embodiment is characterized in that the counter means provides a time stamp reference signal with a frequency of 27 MHz.

These and other aspects of the invention will be apparent from and elucidated further with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which Figure 1 shows a known recording/reproducing apparatus; Figure 2 shows schematically a preferred embodiment of a recording/reproducing apparatus according to the invention; Figure 3 shows a counter of Fig. 2 in more detail and

Figure 4 shows circuitry to be used in another embodiment of the invention. Corresponding elements in different Figures have identical reference numerals.

Fig. 1 shows a known recording/reproducing apparatus. This may be an apparatus of the type as disclosed in the international patent application with application number IB99/00980 (PHN 16.942) filed on 31-05-99 or international patent application with publication number WO 96/30905 (PHN 15.260).

A received information signal received at an input terminal 1 with receiving means 2 comprises packets of information signals according to the MPEG- standard, according to ISO/TEC 13.818, part 1 'Systems', IS O/IEC 13.818, part 2 'Video' and ISO/TEC 13.818, part 3 'Audio'. The packets, called Transport Packets, are received at regular time intervals. In order to reproduce this time relation when reproducing, these packets are time stamped with time stamping circuitry 3, employing a time stamp clock reference signal fl, with a frequency of 27 MHz. It is noted that this time stamp reference signal fl is locked to the external time base used for generating the received information signals, by locking to simultaneously and regularly transmitted Program Clock References (PCR).

The time stamped packets are further channel encoded with channel encoding means 4 and submitted to writing means 5. In case of recording on a magnetic tape 6 according to a D-VHS standard, this recording has to be done with a fixed writing frequency of 19,138560 MHz. For this purpose a write clock reference signal f3 is supplied to the writing means 5.

The information signals are written on tracks 7 of a magnetic tape 6 using writing heads of the magnetic type. Although also a recording medium suits as a disc, either of the optically or magnetically readable/recordable type may be employed. Suitable tape drive means 8 are controlled by central control means 9, which control all other units, as indicated with dashed lines. Detecting means 10 detect the magnetized areas on the magnetic tape 6, with a sampling rate of 54 MHz, given by the read clock reference signal £3. Reading means 11 finally decode the detected channel coded signal. Finally, suitable decoding means 12 decode the packets of information signals to audio/video signals. Herewith the time relationship between the originally received packets is restored mean while using the time stamp reference signal fl. First clock reference means 13, comprising a crystal-clock 14 generating a 54 MHz clock frequency are used to generate the time stamp clock reference signal fl with a frequency of 27 MHz and the read reference clock reference β with a frequency of 54 MHz. The second clock reference means 15, comprising a second crystal clock 16 generating a 19,138560 MHz frequency are used to generate the write clock reference signal f2 with a frequency of 54 MHz.

Fig. 2 shows a recording/reproducing device according to a preferred embodiment of the invention. Identical numerals refer to corresponding elements in Fig.1 , which will not be discussed again. Signal clock reference generating means 17 are shown, for generating the clock reference signals fl, £2 and β. One single crystal clock 18 is provided, generating a single clock reference signal with a frequency of 57,4155 MHz. This frequency is preferably chosen to be three times the channel bit rate or frequency of the write clock reference signal f2, being 19,138560 MHz. This write clock reference signal may easily be obtained with frequency dividing means, not shown in the figure. The single clock reference signal is used to generate the read clock reference signal β, providing an oversampling over 3. Finally, the time stamp clock reference signal fl is also derived from this single clock reference signal of a frequency of 57,4155 MHz. This will be explained with reference to Fig.3.

Fig. 3 A shows a system time counter (STC) 19 of the type as disclosed in the international patent application with the application number IB 99/00980 (PHN 16.942), which is incorporated herein by reference. The single reference signal, which is also used as the read clock reference signal β, is supplied with received Program clock Reference (PCR) signals to the System Time Counter (STC) 19. These Program Clock Reference (PCR) signals contain the time base of the received information signals when generated and are being transmitted regularly with the information signals. The System Time Counter (STC) 19, generates a time stamps clock reference fl locked to the time base of the received information signals.

Fig. 3B illustrates the System Time Counter (STC) 19 of Fig. 3 A, in more detail. A comparator 20 compares the Program Clock Reference (PCR) signal with a current count value of the System Time counter. The output of the comparator 20 is coupled to a generating unit 21 which supplies a System Time Clock increment value to an adder unit 22. The single reference clock signal β is also supplied to the adder unit 22. The generator System Time Clock reference signal, corresponding with the required time stamp reference clock is obtained from adder unit 22, in a manner as described in the mentioned international patent application, which will not be discussed further.

Fig. 4 finally discloses circuitry embodying the single clock reference generating means 17 of Fig. 2, comprising a single crystal 18, a System Time Clock 19 and a frequency divider 23.

Whilst the invention has been derived with reference to preferred embodiments thereof, it is to be understood that these are not limitative examples. Thus, various modification will become apparent to those skilled in the art, without departing from the scope of the invention, as defined by the claims. Further, the invention lies in each and every novel feature or combination of features.

Claims

CLAIMS:

1. Recording/reproducing apparatus having receiving means for receiving an information signal, the received information signal comprising packets of information signals that occur regularly as a function of time in a serial data stream of the received information signal, time stamping means for time stamping the packets comprised in the received information signal employing a time stamp clock reference, writing means for recording the time stamped packets in at least one track of a record carrier, employing a write clock reference for synchronizing the writing means, and reading means linked with detector means for reproducing the recorded time stamped information signal from at least one track of the record carrier employing a read clock reference for sampling the recorded information signal, characterized in that, the apparatus comprises clock generating means with a single reference crystal for generating the clock reference signals.

2. Recording/reproducing apparatus according to claim 1, characterized in that the single reference crystal is chosen to generate a single reference signal of a frequency of an integer multiple of the write clock reference signal.

3. Recording/reproducing apparatus according to claim 2, characterized in that the frequency of the single clock reference is chosen at three times the frequency of the write clock signal.

4. Recording/reproducing apparatus according to claim 1, wherein the received information signal comprises program clock reference (PCR) signals, characterized in that the apparatus comprises counter means for generating the time stamp clock reference employing the received program clock reference (PCR) signals and the single clock reference signal.

5. Recording/reproducing apparatus according to claim 4, characterized in that the counter means provides a time stamp reference signal with a frequency of 27 MHz.

6. Recording/reproducing apparatus according to claim 2, characterized in that the frequency of the single reference signal is 57,4155 MHz.

7. Recording/reproducing apparatus according to claim 1, characterized in that the apparatus is adapted to interface with a record carrier executed as magnetically readable tape.

8. Circuit means suited for use in a recording/reproducing apparatus according to one of the claims 1-7, comprising clock generating means with a single reference crystal and counter means that are capable to provide a) a read clock reference signal for the detector means of said apparatus; b) a write clock reference signal for synchronization the writing means of said apparatus; c) a time stamp clock reference signal.