EP1121803A1

EP1121803A1 - Recording of a trick play signal on a record carrier

Info

Publication number: EP1121803A1
Application number: EP00956367A
Authority: EP
Inventors: Albert M. A. Rijckaert
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 1999-08-24
Filing date: 2000-07-31
Publication date: 2001-08-08
Also published as: TW559805B; JP2003507973A; KR20010087379A; CN1327681A; WO2001015441A1

Abstract

A recording apparatus for recording a first information signal, comprising packets of information (114) and a trick play signal comprising packets of information (116) comprise a time stamp generator (147) for generating time stamps for the packets. The first digital information signal is meant for a reproduction at a record carrier speed which equals the recording speed and the second digital signal is meant for a reproduction at a speed n1 times the recording speed. The time stamp generator derives said time stamps for the packets of said second information signal from the sync block numbers for the second sync blocks in which those packets are stored.

Description

Recording of a trick play signal on a record carrier.

The invention relates to an apparatus for recording a first and a second digital information signal in tracks on a record carrier, the first and second digital information signals being information signals comprising subsequent packets of information, the apparatus comprising - input means for receiving the first and second digital information signal,

- signal processing means for processing the first and second digital information signal into a first recording signal and a first trick play signal respectively, suitable for recording in the tracks on said record carrier, the signal processing means being adapted to generate sync blocks of information, sync blocks of the first recording signal comprising a synchronisation word, a sync block number and a number of information bytes of the first digital information signal, such that each time the information included in x transport packets of the first information signal is stored in y first sync blocks, sync blocks of the first trick play signal comprising a synchronisation word, a trick play sync block number and a number of information bytes of the second information signal, such that each time the information included in x transport packets of the second information signal is stored in y second sync blocks

- sync block number generator means for generating said sync block numbers for incorporation in said first sync blocks and for generating said trick play sync block numbers for incorporation in said second sync blocks, - time stamp generator means for generating time stamps for said transport packets of said first and second digital information signals, said signal processing means further being adapted to incorporate said time stamps for said transport packets in sync blocks of said first recording signal and said first trick play signal,

- signal combining means for combining the first and second sync blocks into a composite signal,

- writing means for writing the composite signal in the tracks at a predetermined recording speed of the record carrier, the writing means comprising a first and a second write head positioned on a rotatable head drum, said first head having a first azimuth angle and said second write head having a second azimuth angle, which is different from the first azimuth angle, the first digital information signal being meant for reproduction in a reproduction apparatus at a reproduction speed which is equal the recording speed, the second digital information signal being meant for reproduction at a trick play speed which is equal to ni times said recording speed, where ni is an integer unequal to 1 , x and y being integers for which hold x > 1 and y > x, the largest common denominator of x and y being 1. Such a recording apparatus is known from WO 98/34227- A3 (PHN 16252), which corresponds to US ser. no. 09/155724 filed on 02.02.1998.

The known apparatus takes the form of a digital video recorder for recording a digital video signal. The digital video signal may be in the form of an MPEG encoded video signal, in which packets of information of the digital video signal are included in the serial data stream of the MPEG encoded video signal. In addition to such MPEG encoded video signal, a trick play signal can be recorded in the tracks on the record carrier. Such trick play signal can be the same video signal, but reproduced at a record carrier (trick play) speed which is other than the nominal reproduction speed. Generally, a separate datastream is recorded as the trick play signal on the record carrier for enabling the reproduction at such trick play speed. The trick play signal can be derived from the MPEG encoded video signal, e.g. by selecting I-frames from the MPEG encoded video signal. This trick play signal, however, need not necessarily be a trick play signal that has a relationship with the MPEG encoded video signal, but can be a completely different signal. But, in the same way as the MPEG encoded digital video signal, the serial datastream of the trick play signal comprise packets of information of the trick play signal.

The document mentioned above describes the inclusion of time stamps in the packets in all the serial datastreams recorded on the record carrier, in order to enable a correct regeneration of the serial datastream of packets, with the correct mutual timing relationships between the subsequent packets in the serial datastream, so that a correct decoding in an MPEG decoder will be possible. In order to realize this, the time stamps are generated using a counter.

It is an object of the invention to propose a recording apparatus for recording one or more trick play signals, which is capable of generating all the time stamps for the packets in those signals in a different way. The recording apparatus in accordance with the invention is characterized in that the time stamp generator means is adapted to derive said time stamps for the packets of said second information signal from the trick play sync block numbers for the second sync blocks.

The invention is based on the following recognition. The use of time stamps is well-known in the art. At some point in the chain the MPEG packets are time stamped in order to be able to reconstruct the original timing relations further down the chain, despite all kinds of timing changes (packet shifts) between these 2 points. Time stamping is also used to correct for timing jitter in a storage device. In this case the MPEG stream is time stamped at the input of the storage device before recording. At playback the time stamps are used to reconstruct the original stream at the output of the storage device and then sent to the decoder or some other device.

This real-time time stamping functions very well for Normal play, but is more problematic for trickplay. This stems from the fact that for trickplay data there is a speed difference between record and playback. Playback is n times faster than record. During playback, the timing relations of the stream at the output of the storage device should be MPEG compliant. It is advantageous to use the same technique as for normal play, that is that the trick play MPEG packets are stored together with a time stamp. However it is difficult to use a real time stamp counter for this purpose due to the speed difference between record and playback. We must also take into account that there can be more than one special trick play stream of which some are intended for reverse trick play streams. This complicates the time stamping even more. However the only requirement is in fact that the trick play output stream is MPEG compliant and decodable. Moreover, the trick play data is not simply input data, but input data that has been subjected to modifications to reduce the bit rate and convert the input data into trick play data. Therefore one or more trick play generator(s) are present for this conversion. This also means that there is no real need for a real-time time stamping because the original relation with the input signal is lost anyway due to the trick play conversion. The time stamping of the trick play packets prior to recording can be done more intelligently by simple calculations. In this way the time stamping can easily be unified for all trick play streams. The use of the trick play sync block as a starting point for this calculation allows for a more flexible data mapping without deviating from this unified approach. The recognition that the trick play output stream only has to be MPEG compliant also leads to the conclusion that the packet distance of this stream need not be constant. This allows for simple methods to convert the trick play sync block numbers to time stamps, that can easily be implemented in hardware with a low gate cost.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereafter in the figure description.

In the figure description shows figure 1 the track format in a group of p tracks, where p equals 48, and the paths across the record carrier that two reproduction heads follow during a first trick play reproduction mode, where the record carrier speed is +4 times nominal, figure 2 the contents of a track on the record carrier, figure 3 the format of a sync block, figure 4 the format of the data header portion in the sync block of figure 3, figure 5 two subsequent sync blocks in which an MPEG packet is stored, figure 6 the contents of the packet header in the first of the two subsequent sync blocks of figure 5, which packet header comprise the time stamps, figure 7 the contents of the packet header in the first of the two subsequent trick play sync blocks of figure 5, which packet header comprise the time stamps for packets in a trick play data stream of packets, figure 8 the relation between trick play sync block numbers and trick play time stamp value, figure 9 the starting points of the trick play packets during reproduction in a trick play reproduction mode, when the time stamping algorithm as described with reference to figure 8 is used, figure 10 an embodiment of a recording apparatus in accordance with the invention, and show the figures 1 1 and 12 two other (mutually) different ways of deriving the time stamps from the trick play sync block numbers that lead to the same time stamp values.

Figure 1 shows the track format of the tracks recorded on the record carrier 1. The tracks are recorded at a slant angle with reference to the longitudinal direction of the record carrier. In figure 1 , however, the tracks are shown, for clarity reasons, at an angle transverse to the longitudinal direction of the record carrier 1. Groups of p successive tracks can be identified on the record carrier 1. One such group of p successive tracks is shown in figure 1, where p is in the present example equal to 48. During recording/reproduction, the tracks are written/read in a direction from the bottom to the top of figure 1 and from left to right in the figure.

The track format shown in figure 1 has a large resemblance with the track format of figure 1 of WO 98/34227-A3. The difference with the track format of figure 1 of WO 98/34227-A3 lies in the fact that the number of trick play sync blocks read out during one revolution of the head drum in a trick play reproduction mode is now 1 12, in which 102 trick play sync blocks comprise 51 packets of the trick play information signal and the remaining 10 trick play sync blocks comprise parity information. The track format of figure 1 enables trick play at various speeds, such as the set of trick play speeds 4x, 12x and 24x, and their reverse speeds.

Figure 2 shows the format of one track. The track is recorded and read in a direction from left to right in the figure. In the present example, the lengths of the various track portions in figure 2 are expressed in number of main sync blocks, where a main sync block has a length of 112 bytes of 8 bits each.

First, a clock run-in portion 2, denoted 'margin', is recorded, which in the present example is 2 main sync blocks long. Next, follows a preamble portion 3, which is 3 main sync blocks long. A subcode signal recording portion 4 follows the preamble portion 3 and is 4 main sync blocks long. The subcode signal recording portion 4 is meant to record a subcode signal in. The subcode signal can comprise, amongst others, absolute and/or relative time information and a table of contents.

Next, follows a postamble portion 5, which is 3 main sync blocks long, an edit gap 6, denoted 'IBG', which is 3 main sync blocks long and a preamble portion 7, which is in the present example 1 main sync block long. Next, follows an auxiliary signal recording portion 8, denoted 'AUX', which is 23 main sync blocks long. The aux signal recording portion 8 is meant for recording an auxiliary signal, such as text data, as an example. This aux signal recording portion 8 is followed by a postamble portion 9, which is 2 main sync blocks long, an edit gap 10, denoted 'IBG', which is 3 main sync blocks long and a preamble portion 11, which is 1 main sync block long. Next follows an information signal recording portion 12, denoted 'main data area', which is 307 main sync blocks long. The information signal recording portion 12 is meant to record the digital information signals in. One digital information signal can be a digital video signal and or a digital audio signal, which may have been encoded into an MPEG information signal. Further, trick play data can be included in the information signal recording portion 12. The information signal recording portion 12 is Actively divided into two parts, a first part 12a which is 277 main sync blocks long and a second part 12b, which is 30 main sync blocks long. The second part 12b comprise outer ECC parity information. The information signal recording portion 12 is followed by a postamble portion

13, which is 2 main sync blocks long and another 'margin' portion 14, the length of which is not relevant, but can be assumed to be 2 main sync blocks long, for the present example. In total, the track thus comprises 356 main sync blocks.

It should be noted here, that the auxiliary signal recording portion 8 may be optional, in the sense that in another recording mode, no auxiliary signal is recorded in the tracks and the recording portion 8, including the portions 9, 10 and 11 are added to the information signal recording portion 12 and are filled with main information.

Coming back to figure 1, the contents of the first part 12a of the information signal recording portion 12 will be further described. Figure 1 shows tracks that have been recorded using at least a first and a second write head. The first head has a gap with a first azimuth angle and the second head has a gap with a second azimuth angle, which is different from the first azimuth angle. The tracks recorded by the first write head are indicated by the slant line running from the bottom left corner of the figure to the top right comer of the figure and the tracks recorded by the second write head are indicated by the slant line running from the bottom right comer of the figure to the top left comer of the figure, see the circle in figure 1 having the reference numeral 20.

The first information signal, which may comprise packets of information of an MPEG transport stream are recorded in the tracks, more specifically, in the information signal recording portions 12 of the tracks. In an embodiment of the recording apparatus, which is in the form of a digital videorecorder of the helical scan type, the first information signal could be 'normal play' data recorded in the tracks for reproduction in a reproducing apparatus at a record carrier speed which is the same as the record carrier speed during recording. This speed is defined as the nominal record carrier speed. The first information signal is accommodated in the main sync blocks, defined above. Further, a second information signal has been recorded in specific segments in the tracks. Those segments are indicated in figure 1 by reference numerals 22.i(+4), where i runs from 1 to 12. This second information signal is meant for a reproduction in a reproduction apparatus at a reproduction speed which is 4 times the nominal reproduction speed in the forward direction. This second information signal could be an information signal which has no relationship whatsoever with the first information signal introduced above. The second information signal could have a relationship with the first information signal, in the sense that the second information signal is a trick play signal for the 4 times nominal reproduction speed, in order to obtain a reproduced (video) signal, which is a replica of the reproduced first (video) signal, but reproduced at four times the nominal speed in the forward direction.

Figure 1 further shows four scanning lines 24.1, 24.2, 26.1 and 26.2. The double arrowed scanning lines 24.1 and 24.2 show the paths that the one head, having the first azimuth angle, follow across the record carrier in the four times nominal reproduction mode, during two revolutions of the head drum. The single arrowed scanning lines 26.1 and 26.2 show the paths that the other head, having the second azimuth angle, follow across the record carrier in the four times nominal reproduction mode during the said two revolutions of the head drum. As can be seen in figure 1, the one head reads the trick play segments 22.i(+4), where i is odd, and the other head thus reads the trick play segments 22.i(+4), where i is even. The trick play segments 22.i(+4) each have a length of 56 trick play sync blocks, in the present example. From the 56 trick play sync blocks in one segment, 51 trick play sync blocks have information contents as regards the trick play information stored in those sync blocks, which could include 'dummy' sync blocks, to be described later. The other five trick play sync blocks in a segment comprise parity information, obtained from an ECC encoding step carried out on the trick play information. Thus, during each revolution of the head drum, during a four times nominal reproduction mode, 102 trick play sync blocks of information of the second information signal, which include 51 packets of the trick play information signal are read from the record carrier.

No further description of the track format of figure 1 is given, for the reason that such description runs along the same lines as the description of figure 1 in WO 98/34227- A3. But, as a general rule, it can be said that for each trick play speed in total 112 trick play sync blocks are read during one revolution of the head drum, that 102 of those trick play sync blocks comprise 51 packets of the trick play signal and 10 trick play sync blocks comprising parity information.

The 112 trick play sync blocks read during one revolution of the head drum have trick play sync block numbers and are numbered 0 to 111 inclusive, in the order in which they are read during said one revolution of the head drum in the trick play reproduction mode, where the trick play sync block 0 is the first trick play sync block read by the head having the first azimuth. The trick play sync block numbers 0 to 111 require a 7-bit count word, denoted TPSB#. The 51 packets of the trick play signal stored in 102 of those trick play sync blocks are each provided with a trick play time stamp. This trick play time stamp is well known in the art. The value of the trick play time stamp for each packet is stored as the 2-bit TSH' and the 18-bit TSL values in accordance with figure 7, to be described below. Next, the format of the trick play sync blocks will be discussed with reference to figure 3. A trick play sync block has the same length as the other sync blocks in the main data area 12 of figure 1, in which the first digital information signal is stored. A trick play sync block is 112 bytes long and comprise a sync word of 2 bytes long, an identification portion 60, denoted ID, a header portion 61, denoted 'main header', an aux byte 62, denoted 'data-aux' and a data area 64, which is 104 bytes long. The data area 64 has room for storage of 96 bytes of data of a trick play signal (one of the second to seventh information signals) and 8 parity bytes.

Figure 4 shows the two bytes 70 and 71 of the main header area 61 of figure 3. The bits b₀ to b6 of the byte 72 of the main header area 61, are available for storing a trick play sync block number TPSB# .

Next, the time stamping of trick play sync blocks will be discussed. Time stamping is well known in the art. Reference is made in this respect to US 5,579,183 (PHN 14818) and international application WO 96/30.905 (PHN15260). The documents describe the recording of MPEG packets on a record carrier, where time stamps are added to an MPEG packet upon arrival and the packet is subsequently recorded. Upon reproduction, the packet is read from the record carrier, the time stamp is retrieved from the packet and used for supplying the packet at the right moment to an output.

Figure 5 shows how an MPEG transport packet, which is 188 bytes long, is stored in two subsequent sync blocks, more specifically in the data area 64a of two subsequent sync blocks. First, a packet header 75, which is 4 bytes long, is stored in the data area 64a of the first of the two sync blocks, denoted SB_n. Next, 92 bytes of the MPEG packet are stored in the remaining portion of the data area 64a of sync block SB_n. The remaining 96 bytes of the MPEG packet are stored in the data area 64a of the second sync block SB_n+ι. The time stamp corresponding to a transport packet is stored in the packet header 75. This is shown in figure 6. More precisely, the time stamp for 'normal play' data is 22 bits long and is stored in the last 22 bits of the packet header 75.

The 22-bit time stamp for the 'normal play' data has been divided into a TSL (time stamp low) portion and a TSH (time stamp high) portion. The TSL portion is 18 bits long and runs cyclically with a modulo value of 225,000, for an apparatus in which the head drum rotates with 1800 rpm, or with a modulo value of 225,225, for an apparatus in which the head drum rotates with 1800/1.001 rpm. The TSH portion is 4 bits long and runs cyclically with a modulo value of 12. Upon each return to 0 for TSL, the TSH value is increased by one. A time stamp counter is available in the recording apparatus to be described later for the generation of time stamps for the MPEG packets for a 'normal play' information signal. The time stamp counter has a period equal to six revolutions of the head drum. The time stamp counter generates, in the present example, the 22-bit time stamps in the form of count words with a clock frequency of 27 MHz.

Trick play information for a specific trick play speed can be obtained from an MPEG data stream by retrieving packets comprising I-frames, well known in the art, from the MPEG data stream, and storing those packets in the trick play sync blocks.

A time stamp generator unit is available in the recording apparatus for the generation of trick play time stamps for the MPEG packets for a trick play information signal. The format of the trick play time stamp is shown in figure 7. The time stamp for the trick play data is made up of an 18-bit TSL (time stamp low) portion and a 2-bit TSH' (time stamp high) portion. The 20-bit trick play time stamp is stored in the packet header 75 of the first of two subsequent trick play sync blocks in which the MPEG packet corresponding to this time stamp is stored, see figure 5.

The trick play time stamp value for a packet is derived in the time stamp generator unit from the trick play sync block number of the first trick play sync block of the two trick play sync blocks in which the packet is stored. The 51 time stamps for the 51 packets stored in the 102 trick play sync blocks will therefore be derived from the trick play sync block numbers 0, 2, 4, , 98 and 100. This derivation is further explained with reference to figure 8. Figure 8 shows the (Z-) 7-bit trick play sync block numbers TPSB# generated by the trick play sync block number generator, and how the bits of this trick play sync block number is used to derive the trick play time stamp. The n'(=2) most significant bits of the trick play sync block number are used as the two bits of the TSH' portion of the trick play time stamp. Further, the A (=5) remaining (and least significant) bits of the trick play sync block number are used to derive the TSL portion of the trick play time stamp. More specifically, the most significant bit of the TSL portion as well as the 12 least significant bits of the TSL portion are taken equal to '0', and the remaining A (=5) bits of the TSL portion are taken equal to the A least significant bits of the trick play sync block number.

TSL runs cyclically with a modulo value of 225,000, for an apparatus in which the head drum rotates with 1800 rpm, or with a modulo value of 225,225, for an apparatus in which the head drum rotates with 1800/1.001 rpm. TSH' runs cyclically with a modulo value of 4. Upon each return to 0 for TSL, the TSH' value is increased by one. As a result, the period of TSL equals one quarter of a rotation of the head drum and the trick play time stamp counter is periodic with the one revolution of the head drum. The time stamp counter is synchronized with the head switch pulse, normally present in the apparatus.

A transport packet for storing in two subsequent trick play sync blocks thus has a time stamp. The two subsequent trick play sync blocks in which the transport packet is stored each have a trick play sync block number. As explained above, the said time stamp has been derived from one of those trick play sync block numbers. Next, an apparatus of the helical scan type, for recording the trick play information on a longitudinal record carrier, is described. Figure 10 shows the recording apparatus which comprises an input terminal 111 for receiving a video signal and a corresponding audio signal. The video signal and the corresponding audio signal may have been encoded into transport packets included in an MPEG serial datastream, well known in the art. The input terminal 111 is coupled to an input 112 of a 'normal play' processing unit 114. Further, a 'trick play' processing unit 116 is provided having an input 117 also coupled to the input terminal 111. Outputs 119 and 120 of the 'normal play' processing unit 114 and the 'trick play' processing unit 116 are coupled to corresponding inputs of a multiplexer 122. The 'normal play' information as well as the 'trick play' information will be recorded in the main area recording portion 12 of the track shown in figure 2.

For a further description of the 'normal play' processing unit 114 and the 'trick play' processing unit 116, reference is made to US 5,579,183.

A subcode and auxiliary signal generator 124 is present for supplying the subcode signal information for storage in the subcode signal recording portion 4, and for supplying the auxiliary signal for storage in the auxiliary signal recording portion 8, see figure 2. Outputs of the multiplexer 122 and the generator 124 are coupled to corresponding inputs of an error correction encoder unit 126. The error correction encoder unit 126 is capable of carrying out an error correction encoding step on the 'normal play' (video and audio) information and the trick play information, so as to obtain the parity information shown in the portion 12b of the main signal recording portion 12 in figure 2, and in the portions 64b of the sync blocks, see figure 3.

The recording apparatus further comprises a generator 130 for adding the sync and ID information for the sync blocks, such as shown in figure 3. After combination of the signals in the combining unit 132, the combined signal is applied to a unit 134, in which a channel encoding is carried out on the composite signal. The channel encoding carried out in the encoding unit 134 is well known in the art.

An output of the channel encoding unit 134 is coupled to an input of a writing unit 136, in which the datastream obtained with the encoding unit 134 is recorded in the slant tracks on a record carrier 140, by means of at least two write heads 142 and 144 positioned on a rotating head drum 146. The write heads 142 and 144 have head gaps with a mutually different azimuth angle, so that (e.g.) the head 142 write the tracks having an azimuth angle from bottom left to top right in figure 1 and the head 144 writes the tracks having an azimuth angle from top left to bottom right in figure 1. Further, a time stamp generator 147 is available for generating time stamps for the normal play processing unit 114 and the trick play processing unit 116.

A microprocessor unit 148 is present for controlling the functioning of the various blocks, such as:

- the control of the normal play signal processing block 114 via the control connection 150, - the control of the trick play signal processing block 116 via the control connection 152,

- the control of the subcode signal and auxiliary signal generator block 124 via the control connection 154,

- the control of the error correction encoding block 126 via the control connection 156,

- the control of the sync signal and ID signal generator block 130 via the control connection 158,

- the control of the channel encoding block 134 via the control connection 160,

- the control of the transport velocity of the record carrier 140 and the rotation of the head drum 146, via the control connection 162, and

- the control of the time stamp generator 147 via the control connection 164. The trick play processing 116 is adapted to retrieve I-frame information from the first information signal, in a way well known in the art. An additional error correction encoding step is carried out in the processing unit 116 on the trick play information in order to generate the 10 trick play sync blocks comprising the parity information.

Further, for each trick play information signal, trick play sync blocks are generated, in the sense that for each trick play sync block a trick play sync block number

TPSB# is generated and stored in the trick play sync block, and a time stamp is generated for each packet in the way explained above.

Next, the trick play sync blocks and the 'normal play' sync blocks, generated by the normal play signal processing unit 114, are combined in the multiplexer unit 122, such that, for recording information in one complete track by one of the heads, the sequence of sync blocks of the normal play information and the trick play information is such that the main data area 12 of one of the 48 tracks shown in figure 1 can be created.

Subcode data and auxiliary data is added and an error correction encoding is carried out on the combined normal play data and trick play data so as to obtain the parity information for the track portion 12b. Further, sync words and identification information is added. Next, a channel encoding step is carried out on the information prior to recording the information in the tracks.

Next, two different methods will be described with reference to the figures 11 and 12, for deriving the time stamps from the trick play sync block numbers, those method leading to the same sequence of time stamps.

In both methods, the time stamp generator means is adapted to carry out the following steps on trick play sync block numbers so as to obtain said (n'+k')-bit count values: carrying out a first operation on a trick play sync block number so as to obtain a first operation result (200,200'), derive said n' bits of said (n'+k')-bit count value from a first portion of said first operation result, carrying out a second operation on a second portion of said first operation result so as to obtain a second operation result (202,202'), derive said k' bits of said (n'+k')-bit count value from said second operation result.

More specifically, in figure 11 , the A(=6) most significant bits of a trick play sync block number TPSB# is multiplied by a first predetermined number, in the present case 5, in said step (a). Next, in said step (b), the n'(=2) most significant bits of said first operation result 200 are allocated to the n' bits of said (n'-fk')-bit count value, the TSH portion of the count value. The second operation in step (c) in figure 11 is a multiplication of the remaining portion of said first operation result 200, that is the 6 least significant bits of the result 200 by a second predetermined number, in the present case 7. Next, in said step (d) the B(=9) bits of the second operation result 202 are allocated to the B most significant bits of the k' bits of said (n'+k')-bit count value. Further, the remaining (nine) bits of said k' bits are set to '0', resulting in the TSL portion of the count values.

More specifically, in figure 12, the trick play sync block number TPSB# is multiplied by a first predetermined number, in the present case 5/4, in said step (a). In the example of figure 12, this is done by the steps indicated by the reference numerals 204 and 206 (division by 4) and the addition step. Next, in said step (b), the n'(=2) most significant bits of said first operation result 200' are allocated to the n' bits of said (n'+k')-bit count value, the TSH portion of the count value. The second operation in step (c) in figure 12 is a multiplication of the remaining portion of said first operation result 200, that is the 6 least significant bits of the result 200 by a second predetermined number, in the present case 7/8. In the example of figure 12, this is done by the steps indicated by the reference numerals 208 and 210 (division by 8) and the subtraction step. Next, in said step (d) the B(=9) bits of the second operation result 202' are allocated to the B most significant bits of the k' bits of said (n'+k')- bit count value. Further, the remaining (nine) bits of said k' bits are set to '0', resulting in the TSL portion of the count values. Both methods generate the same array of count values, with the advantage over the array of count values shown in figure 9, that the gaps 1 and 2 have roughly the same length which is moreover of the order of magnitude of the distance between subsequent count values.

Whilst the invention has been described with reference to preferred embodiments thereof, it is to be understood that these are not limitative examples. Thus, various modifications may become apparent to those skilled in the art, without departing from the scope of the invention, as defined by the claims. The first information signal thus may be another type of signal than a digital video signal and/or an audio signal, such as a data signal. Further, the trick play signal recorded in the trick play segments could be an information signal which has no relationship whatsoever with the first digital information signal. In such an embodiment, the record carrier is a recording medium on which a multiplicity of transmission channels are available for transmitting independent information signals. Further, any reference signs do not limit the scope of the claims. The invention, as far as incorporated in the error correction encoding apparatus, can be implemented by means of both hardware and software, and several "means" may be represented by the same item of hardware. The word 'comprising' does not exclude the presence of other elements or steps than those listed in a claim. Also, the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Further, the invention lies in each and every novel feature or combination of features.

Claims

CLAIMS:

1. Apparatus for recording a first and a second digital information signal in tracks on a record carrier, the first and second digital information signals being information signals comprising subsequent packets of information, the apparatus comprising

- input means for receiving the first and second digital information signal, - signal processing means for processing the first and second digital information signal into a first recording signal and a first trick play signal respectively, suitable for recording in the tracks on said record carrier, the signal processing means being adapted to generate sync blocks of information, sync blocks of the first recording signal comprising a synchronisation word, a sync block number and a number of information bytes of the first digital information signal, such that each time the information included in x transport packets of the first information signal is stored in y first sync blocks, sync blocks of the first trick play signal comprising a synchronisation word, a trick play sync block number and a number of information bytes of the second information signal, such that each time the information included in x transport packets of the second information signal is stored in y second sync blocks

- sync block number generator means for generating said sync block numbers for incorporation in said first sync blocks and for generating said trick play sync block numbers for incorporation in said second sync blocks,

- time stamp generator means for generating time stamps for said transport packets of said first and second digital information signals, said signal processing means further being adapted to incorporate said time stamps for said transport packets in sync blocks of said first recording signal and said first trick play signal,

- signal combining means for combining the first and second sync blocks into a composite signal, - writing means for writing the composite signal in the tracks at a predetermined recording speed of the record carrier, the writing means comprising a first and a second write head positioned on a rotatable head drum, said first head having a first azimuth angle and said second write head having a second azimuth angle, which is different from the first azimuth angle, the first digital information signal being meant for reproduction in a reproduction apparatus at a reproduction speed which is equal the recording speed, the second digital information signal being meant for reproduction at a trick play speed which is equal to ni times said recording speed, where ni is an integer unequal to 1, x and y being integers for which hold x > 1 and y > x, the largest common denominator of x and y being 1 , characterized in that the time stamp generator means is adapted to derive said time stamps for the packets of said second information signal from the trick play sync block numbers for the second sync blocks.

2. Apparatus as claimed in claim 1 , characterized in that the time stamp generator means is adapted to derive a time stamp for a packet of said second information signal from the trick play sync block number of the first second sync block in which said packet is stored.

3. Apparatus as claimed in claim 1 or 2, characterized in that the time stamp generator means is adapted to generate time stamps for the packets of said second information signal such that the values of subsequent time stamps are substantially equidistant.

4. Apparatus as claimed in claim 1 or 2, characterized in that the writing means are adapted to write second sync blocks of said first trick play signal in groups of p subsequent tracks such that, during reproduction of said second sync blocks in an apparatus for reproducing said second information signal with said record carrier speed nj times said recording speed, said reproducing apparatus comprising a rotatable head drum provided with at least a head with said first azimuth angle and a head with said second azimuth angle, m second sync blocks of said first trick play signal are read during one revolution of said head drum, that the sync block number generator means is adapted to generate subsequent cycles of m trick play sync block numbers for incorporation into said m second sync blocks, said m trick play sync block numbers being expressed in Z-bit digital numbers, Z being an integer number larger than 1, said time stamp generator means being adapted to generate cycles of time stamp values from said cycles of m trick play sync block numbers so as to obtain time stamp values in the form of (n'-t-k')-bit count values, where n' and k' are integers larger than 1, n' bits of said (n'+k')-bit count value being derived from a first portion of the Z-bit digital number corresponding to a trick play sync block number and k' bits of the said (n'+k')-bit count value being derived from a second portion of said Z-bit digital number.

5. Apparatus as claimed in claim 4, characterized in that Z is smaller than n'+k', but larger than n', that the n' bits of said (n'-Hk')-bit count value are taken equal to n' bits in the first portion of the Z-bit digital number.

6. Apparatus as claimed in claim 5, characterized in that the first portion of the Z- bit digital number comprises n' bits.

7. Apparatus as claimed in claim 5, characterized in that the n' bits of the (n'+k')- bit count value are the n' most significant bits of the (n'+k')-bit count value.

8. Apparatus as claimed in claim 4, characterized in that the second portion of the

Z-bit digital number has a number of bits A which is smaller than k', that A bits of the k' bits of said (n'+k')-bit count value are taken equal to said A bits of said second portion and that the remaining of said k' bits of said (n'+k')-bit count value are taken equal to '0'.

9. Apparatus as claimed in claim 8, characterized in that the most significant bit of the k' bits of said (n'+k')-bit count value is taken equal to '0', the next A most significant bits of the k' bits of said (n'+k')-bit count value is taken equal to said A bits of said second portion and that the remaining of said k' bits of said (n'+k')-bit count value are taken equal to '0'.

10. Apparatus as claimed in claim 1 or 2, characterized in that the writing means are adapted to write second sync blocks of said first trick play signal in groups of p subsequent tracks such that, during reproduction of said second sync blocks in an apparatus for reproducing said second information signal with said record carrier speed ni times said recording speed, said reproducing apparatus comprising a rotatable head drum provided with at least a head with said first azimuth angle and a head with said second azimuth angle, m second sync blocks of said first trick play signal are read during one revolution of said head drum, that the sync block number generator means is adapted to generate subsequent cycles of m trick play sync block numbers for incorporation into said m second sync blocks, said m trick play sync block numbers being expressed in Z-bit digital numbers, Z being an integer number larger than 1 , said time stamp generator means being adapted to generate cycles of time stamp values from said cycles of m trick play sync block numbers so as to obtain time stamp values in the form of (n'+k')-bit count values, where n' and k' are integers larger than 1, the time stamp generator means being adapted to carry out the following steps on trick play sync block numbers so as to obtain said (n'+k')-bit count values:

(a) carrying out a first operation on a trick play sync block number so as to obtain a first operation result,

(b) derive said n' bits of said (n'+k')-bit count value from a first portion of said first operation result, (c) carrying out a second operation on a second portion of said first operation result so as to obtain a second operation result, (d) derive said k' bits of said (n'+k')-bit count value from said second operation result.

11. Apparatus as claimed in claim 10, characterized in that said first operation is equivalent to multiplying the A most significant bits of a trick play sync block number by a first predetermined number.

12. Apparatus as claimed in claim 10, characterized in that said deriving step (b) comprises allocating the n' most significant bits of said first operation result to the n' bits of said (n'+k')-bit count value.

13. Apparatus as claimed in claim 10, characterized in that said second operation is equivalent to multiplying the remaining portion of said first operation result by a second predetermined number.

14. Apparatus as claimed in claim 10, characterized in that said deriving step (d) comprises the substep of allocating the B bits of the second operation result to the B most significant bits of the k' bits of said (n'+k')-bit count value and to make the remaining bits of said k' bits equal to '0'.

15. Apparatus as claimed in claim 4 or 10, characterized in that n'=2 and k'=18.

16. Apparatus as claimed in claim 4 or 10, characterized in that Z=7.

17. Apparatus as claimed in claim 8 or 11, characterized in that A=5.

18. Apparatus as claimed in claim 10, characterized in that the first predetermined number equals 5 or 5/4.

19. Apparatus as claimed in claim 13, characterized in that the second predetermined number equals 7 or 7/8.

20. Apparatus as claimed in claim 1, characterized in that the apparatus further comprises retrieval means for retrieving said second digital information signal from said first digital information signal and for supplying said second digital information signal to said input means.

21. Method of recording a first and a second digital information signal in tracks on a record carrier, the first and second digital information signals being information signals comprising subsequent packets of information, the method comprising the steps of

- receiving the first and second digital information signal,

- processing the first and second digital information signal into a first recording signal and a first trick play signal respectively, suitable for recording in the tracks on said record carrier, by generating sync blocks of information, sync blocks of the first recording signal comprising a synchronisation word, a sync block number and a number of information bytes of the first digital information signal, such that each time the information included in x transport packets of the first information signal is stored in y first sync blocks, sync blocks of the first trick play signal comprising a synchronisation word, a trick play sync block number and a number of information bytes of the second information signal, such that each time the information included in x transport packets of the second information signal is stored in y second sync blocks

- generating said sync block numbers for incorporation in said first sync blocks and for generating said trick play sync block numbers for incorporation in said second sync blocks,

- generating time stamps for said transport packets of said first and second digital information signals, and incorporating said time stamps for said transport packets in sync blocks of said first recording signal and said first trick play signal,

- combining the first and second sync blocks into a composite signal, - writing the composite signal in the tracks at a predetermined recording speed of the record carrier, the first digital information signal being meant for reproduction in a reproduction apparatus at a reproduction speed which is equal the recording speed, the second digital information signal being meant for reproduction at a trick play speed which is equal to ni times said recording speed, where ni is an integer unequal to 1, x and y being integers for which hold x > 1 and y > x, the largest common denominator of x and y being 1 , characterized in that the time stamp generating step comprises the substep of deriving said time stamps for the packets of said second information signal from the trick play sync block numbers for the second sync blocks.