# Patent

## Title
Method for recording and managing a multi-channel stream

## Abstract

The present invention relates to a method for recording and managing a multi-channel broadcast stream. The present method records on a recording medium such as a BD-RW a multi-channel broadcast stream where a plurality of channels are multiplexed, and creates and records management information for individual search and reproduction control of the plural channels. Consequently, this method ensures fast random access and various trick play of individual subchannel streams multiplexed in a recorded multi-channel stream at user's request.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for recording onto a recording medium such as a high-density rewritable optical disk a multi-channel broadcast stream in which data streams belonging to a plurality of channels are multiplexed, and for managing the recorded multi-channel stream.
2. Description of the Related Art
The standardization of a high-capacity rewritable optical disk, so called ‘Blu-ray Disk Rewritable’ (abbreviated ‘BD-RW’), is in rapid progress so that various products related with a BD-RW will be developed and commercialized in the near future.
FIG. 1 is a simplified block diagram of an optical disk device, which may be a VDR (Video Disk Recorder), capable of recording and reproducing signals to/from a recording medium such as a BD-RW.
The disk device of FIG. 1 comprises an optical pickup 2 for reading signals recorded on a recording medium 1 such as a BD-RW and for writing data stream processed from input signals; a VDR system 3 for restoring digital data by processing the read signals from the optical pickup 2 and for converting the input signals to data stream whose format is suitable for recording;
and an encoder 4 for encoding analog input to deliver to the VDR system 3.
The VDR system 3 of the disk device configured as FIG. 1 records an input data stream onto the placed BD-RW 1. The input data stream may be a digital TV broadcast stream provided through a tuner or be a digital data stream provided from a personal computer (PC) through a digital interface such as IEEE1394 standard.
The digital TV broadcast stream is classified into two types, one for an open broadcast stream and the other for a private broadcast stream. The open broadcast stream, which may be major TV broadcast stream formats in many countries, means that its stream syntax has been opened. Therefore, the syntax of open broadcast stream can be analyzed by a VDR system of any disk device. The well-known ATSC DTV stream in USA, DVB stream in Europe, and ARIB IDSV stream in Japan pertain to the open broadcast stream.
On the other hand, the private broadcast stream means a broadcast stream of which syntax is difficult for a DVR system of an ordinary optical device to analyze. The private broadcast stream is generally broadcasted through a cable or a satellite.
The digital TV broadcast stream may be a broadcast stream that contains program streams of a plurality of logical channels (subchannels). For instance, the ATSC D-TV format standardized in USA can accommodate a single HD-grade program stream or plural SD-grade program streams in a single physical (RF) channel, thus, a digital TV broadcast stream in which a plurality of SD-grade program streams are multiplexed is called a multi-channel broadcast stream.
Thus, the disk device must be able to record different types of data stream, namely, an open broadcast stream, a private broadcast stream, and a multi-channel broadcast stream on a BD-RW.
When the disk device records a multi-channel broadcast stream onto a BD-RW at user's request, it is preferable to write management information for individually accessing each subchannel data stream and trick play. However, what management information to create and how to write it have not been resolved yet.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of creating and recording onto a rewritable recording medium management information on effective searching and trick play for individual subchannel data stream of a multi-channel broadcast stream while recording the multi-channel broadcast stream onto the recording medium.
A method of recording and managing a multi-channel broadcast stream in accordance with the present invention is characterized in that it records on a recording medium a multi-channel broadcast stream where a plurality of channels are multiplexed, and creates and records management information for individual search and reproduction control of said plural channels.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention, illustrate the preferred embodiments of the invention, and together with the description, serve to explain the principles of the present invention.
In the drawings:
FIG. 1 is a simplified block diagram of an optical disk device such as a VDR (Video Disk Recorder);
FIG. 2 shows a flow chart of a preferable embodiment of the present invention;
FIG. 3 shows an entry point map and a time unit map that are created under file structure of a BD-RW in accordance with a multi-channel broadcast stream recording/managing method;
FIG. 4 illustrates a time unit map created in accordance with the present invention;
FIG. 5 illustrates an entry point map created in accordance with the present invention;
FIG. 6 shows a data stream example in which two subchannel streams extracted from a single physical channel are recorded in the conditional normal recording mode.



DETAILED DESCRIPTION OF THE PREFFERRED EMBODIMENT
In order that the invention may be fully understood, preferred embodiments thereof will now be described with reference to the accompanying drawings.
A method of recording and managing a multi-channel broadcast stream in accordance with the present invention is applicable to the disk device shown in FIG. 1. The VDR system 3 of the disk device records onto a placed BD-RW 1 a digital broadcast stream received through a tuner or a data stream received from a PC through a digital interface such as IEEE1394 standard. During the record, the VDR system 3 creates management information for searching and trick play of the recorded stream and writes the management information in matching way with the file structure of a BD-RW.
Now, a preferable embodiment of the present invention is described below in detail.
FIG. 2 shows a flow chart of a preferable embodiment of the present invention.
The disk device of FIG. 1 starts to record a digital broadcast stream received through a tuner as a clip file (*.m2ts) under the subdirectory ‘STREAM’ at user's request through key inputs (S10). At this time, the VDR system 3 checks the type of the received stream.
If the type is not open broadcast stream but private one whose syntax can not be known, the VDR system 3 creates search information for the recorded private broadcast stream and writes the search information in a clip information file (*.clpi) under a subdirectory ‘CLIPINF’, as shown in FIG. 3 (S16). This recording manner for a private broadcast stream is called ‘Streamer Recording’ (SR).
The search information is written in CPI (Characteristic Point Information) field reserved in a clip information file and it is a map of time units that is explained later.
If the received broadcast stream is encrypted (scrambled) with an encryption key although it is open one, the VDR system 3 applies the SR manner to the received stream, that is, the VDR system 3 records the received stream as a clip file under the subdirectory ‘STREAM’ and writes a map of time units in CPI field of a related clip information file (S16).
If the type is open and the digital broadcast stream has not been encrypted at the same time, the VDR system 3 checks user's selection on whether multi-channel recording or not. If multi-channel recording is chosen by a user (S13), the VDR system 3 records a multi-channel stream carrying a plurality of SD-grade program streams tuned by the tuner as a clip file (*.m2ts) under the subdirectory ‘STREAM’ without selecting a SD-grade subchannel from a tuned physical channel.
While recording the multi-channel stream, the VDR system 3 creates a map of time units ‘TU_map’ for the multi-channel stream and writes the map in the CPI field of a related clip information file. At the same time, the VDR system 3 creates respective entry point (EP) maps, which are for search and trick play of individual subchannel streams, and writes the EP maps in an MPD (MakersPrivateData) area reserved in the related clip information file, as shown in FIG. 3 (S17). This recording manner that creates EP maps as well as a time unit map is called ‘Conditional Normal Recording’ (CNR).
In case that the type is open and the digital broadcast stream has not been encrypted at the same time, if a user selects not a multi-channel recording but a single channel or a single subchannel recording, the VDR system 3 extracts a single chosen subchannel broadcast stream from a received physical channel (S14) and records it onto the placed BD-RW 1. This recording manner is called ‘Normal Recording’ (NR).
In the NR mode, the extracted subchannel stream is also recorded as a clip file (*.m2ts) under the subdirectory ‘STREAM’ and a single EP map, management information for search and trick play, of the recorded stream is written in the CPI field in a related clip information file (*.clpi).
FIG. 4 illustrates a time unit map and its internal entries that are created in the SR and the CNR mode. The time unit map is composed of the size information of a time unit ‘Time_Unit_Size’ and start source packet numbers (SPNs) of individual time units ‘SPN_Time_Unit_Start #k’. The SPN_Time_Unit_Start entries are used for rapid access of an arbitrary recording position on the recorded data stream in a clip file.
The VDR system 3 continuously counts successively-received source packets contained a private broadcast stream, a scrambled open broadcast stream, or a multi-channel data stream every time window set by the field ‘Time_Unit_Size’, and it writes sequentially in each SPN_Time_Unit_Start field respective sequence numbers of packets arrived first within each time window.
The time unit map is used for searching the recorded data stream. For instance, if a specific time location is entered, the entered time is divided by the value in the ‘Time_Unit_Size’ field, first. Then, a SPN_Time_Unit_Start entry that is indexed by a value resulting from the division is read and a source packet whose number is same with the value in the read entry is searched for in the recorded stream.
FIG. 5 illustrates an EP map and its internal entries that are created in the NR and the CNR mode. Each EP map is composed of an ID of stream packets ‘stream_PID’, the number of EPs ‘num_EP_entries’, plural pairs of PTS (Presentation Time Stamp) ‘PTS_EP_start’ and SPN (Source Packet Number) ‘SPN_EP_start’ of every source packet having video data that is random-accessible on the recorded data stream in a clip file.
For constructing an EP map or EP maps, the VDR system 3 examines individual source packets of a unencrypted open broadcast stream or a multi-channel stream to know whether or not they are I-picture starting ones that are accessible in random. An I-picture starting packet includes a payload where a GOP starts from head and has its TP header in which PUSI (Payload Unit Start Indicator) is set, so that the VDR system 3 reads PTS written in a PES header of a source packet whose PUSI is set.
And, the VDR system 3 identifies relative sequence number, namely, SPN of the source packet whose PUSI is set. The read PTS and the identified SPN of every PUSI-set source packet are written in the fields of ‘PTS_EP_start’ and ‘SPN_EP_start’, respectively. The number of pairs of the ‘PTS_EP_Start’ and the ‘SPN_EP_Start’ entry is written in the field ‘num_EP_entries’ and PID of source packets constituting the recorded data stream or each subchannel stream is written in the field ‘stream_PID’.
FIG. 6 shows a data stream example in which two subchannel streams extracted from a single physical channel are recorded in the CNR mode. In the example of FIG. 6, mutually-multiplexed source packet series ‘TP_Channel 1’ and ‘TP_channel 2’ pertaining to two subchannels are recorded in a clip file ‘01001.m2ts’.
A time unit map for wholly searching a data stream in the file ‘01001.m2ts’ composed of the two subchannel streams has been written in the field ‘CPI’ of the clip information file ‘01001.clpi’. And, two EP maps ‘EP_map #1’ and ‘EP_map #2’ for searching the first and the second subchannel stream individually have been written in an MPD area reserved in the clip information file ‘01001.clpi’.
A play list file named ‘01001.rpls’ has been created for playback control of the clip file ‘01001.m2ts’. The play list file ‘01001.rpls’ has several play items containing management information related with the recorded data stream in the clip file ‘01001.rpls’. The play item includes the number of subchannels of the recorded multi-channel stream, PTSs ‘IN_time_PTS’ and ‘OUT_time_PTS’, written in the EP map, of a start and an end packet of a subchannel stream interval to refer to, and a start and an end time ‘IN_time’ and ‘OUT_time’, calculated from the time unit map, of the subchannel stream interval to refer to.
The number of subchannels and the two PTSs ‘IN_time_PTS’ and ‘OUT_time_PTS’ are written in an MPD area reserved in a play item.
In the illustrative case of data stream recording in FIG. 6, if a play item, e.g., the first play item is selected from a lay list ‘01001.rpls’, the VDR system 3 identifies an entry set n an EP map related with the first subchannel with reference to information of the number of subchannels and the start and the end PTS written in the MPD area of the chosen play item.
Afterwards, the VDR system 3 searches source packets pertaining to the data stream of the first subchannel recorded in multiplexed manner in the file ‘01001.m2ts’ for I-picture starting packets or conducts a trick play of only the first-subchannel stream among the recorded multi-channel stream by selectively decoding I-pictures with reference to the information of PTS_EP_start and SPN_EP_start written in successive entries in the identified entry set.
If another play item related with a data stream of the second subchannel is selected from a play list ‘01001.rpls’, the VDR system 3 identifies an entry set in another EP map related with the second subchannel with reference to information of the number of subchannels and the start and the end PTS written in the MPD area of the chosen play item.
Afterwards, the VDR system 3 searches source packets pertaining to the data stream of the second subchannel recorded in multiplexed manner in the file ‘01001.m2ts’ for I-picture starting packets or conducts a trick play of only the second-subchannel stream among the recorded multi-channel stream by selectively decoding I-pictures with reference to the information of PTS_EP_start and SPN_EP_start written in successive entries in the identified entry set.
In the event that it is needed to search not individually but wholly the recorded multi-channel stream of the two subchannels recorded in the clip file ‘01001.m2ts’ related with the play list ‘01001.rpls’, the VDR system 3 identifies a clip information file ‘01001.clpi’ including management information about the clip file ‘01001.m2ts’ first, and then accesses fast a certain source packet located most closely to a given time location on the recorded multi-channel broadcast stream.
The above-explained method of recording and managing a multi-channel broadcast stream ensures fast random access and various trick play of individual subchannel streams multiplexed in a recorded multi-channel stream at user's request. Moreover, it makes it possible to search for a certain target point on an entire multi-channel stream fast.
While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.

## Claims

1. A storage medium, comprising:
a data area configured storing a multi-stream in which a plurality of video streams are divided into a plurality of transport packets and multiplexed, the video streams having different paths from one another; and
a navigation area storing a playlist for managing playback of the multi-stream, the playlist including a playitem indicating a playing interval of the multi-stream,
wherein the playitem includes a field representing a total number of the paths of the video streams multiplexed in the multi-stream.

2. The storage medium of claim 1, wherein the navigation area further stores an entry point map for each stream.

3. The storage medium of claim 2, wherein the entry point map is recorded in an MPD (MakersPrivateData) area reserved in a clip information file for storing information about the plurality of multiplexed streams.

4. The storage medium of claim 2, wherein the entry point map includes an ID of the transport packets pertaining to a path, the number of entry points, plural pairs of PTS (Presentation Time Stamp) and SPN (Source Packet Number) of the transport packets.

5. The storage medium of claim 4, wherein the playitem indicates a start time and an end time corresponding to the PTS.

6. The storage medium of claim 2, wherein when the playitem is selected, the entry point map related to a first path of the video streams is accessed to determine a location of transport packets of the video stream for the first path included in the multiplexed plurality of transport streams.

7. A method of recording a multi-stream, the method comprising:
recording a multi-stream in which a plurality of video streams are divided into a plurality of transport packets and multiplexed in a data area of a recording medium, the video streams having different paths from one another; and
recording a playlist for managing playback of the multi-stream in a navigation area of the recording medium, the playlist including a playitem indicating a playing interval of the multi-stream,
wherein the playitem includes a field representing a total number of the paths of the video streams multiplexed in the multi-stream.

8. The method of claim 7, further comprising:
recording an entry point map for each stream in the navigation area.

9. The method of claim 8, further comprising:
recording the entry point map in an MPD (MakersPrivateData) area reserved in a clip information file for storing information about the plurality of multiplexed streams.

10. The method of claim 8, further comprising:
recording an ID of the transport packets pertaining to a path, the number of entry points, plural pairs of PTS (Presentation Time Stamp) and SPN (Source Packet Number) of the transport packets.

11. The method of claim 10,
wherein the playitem indicates a start time and an end time corresponding to the PTS.

12. The method of claim 8, wherein when the playitem is selected, the entry point map related to a first path of the video streams is accessed to determine a location of transport packets of the video stream for the first path included in the multiplexed plurality of transport streams.

13. An apparatus for recording a multi-stream, the apparatus comprising:
a pickup configured to record a multi-stream in which a plurality of video streams are divided into a plurality of transport packets and multiplexed in a data area on a recording medium, the video streams having different paths from one another; and
a controller, operably coupled to the pickup, and configured to control the pickup to record a playlist for managing playback of the multi-stream in a navigation area of the recording medium, the playlist including a playitem indicating a playing interval of the multi-stream,
wherein the playitem includes a field representing a total number of the paths of the video streams multiplexed in the multi-stream.

14. The apparatus of claim 13, wherein the controller is further configured to control the pickup to record an entry point map for each stream in the navigation area.

15. The apparatus of claim 14, wherein the controller is further configured to control the pickup to record the entry point map in an MPD (MakersPrivateData) area reserved in a clip information file for storing information about the plurality of multiplexed streams.

16. The apparatus of claim 14, wherein the controller is further configured to control the pickup to record an ID of the transport packets pertaining to a path, the number of entry points, plural pairs of PTS (Presentation Time Stamp) and SPN (Source Packet Number) of the transport packets.

17. The apparatus of claim 16, wherein the playitem indicates a start time and an end time corresponding to the PTS in the playitem.

18. The apparatus of claim 14, wherein when the playitem is selected, the entry point map related to a first path of the video streams is accessed to determine a location of transport packets of the video stream for the first path included in the multiplexed plurality of transport streams.

19. A method of reproducing a multi-stream, the method comprising:
reading a multi-stream in which a plurality of video streams are divided into a plurality of transport packets and multiplexed in a data area of a recording medium, the video streams having different paths from one another; and
reading a playlist for managing playback of the multi-stream in a navigation area of the recording medium, the playlist including a playitem indicating a playing interval of the multi-stream,
wherein the playitem includes a field representing a total number of the paths of the video streams multiplexed in the multi-stream.

20. The method of claim 19, further comprising:
reading an entry point map for each stream from the navigation area.

21. The method of claim 20, further comprising:
reading the entry point map in an MPD (MakersPrivateData) area reserved from a clip information file for storing information about the plurality of multiplexed streams.

22. The method of claim 20, further comprising:
reading an ID of the transport packets pertaining to a path, the number of entry points, plural pairs of PTS (Presentation Time Stamp) and SPN (Source Packet Number) of the transport packets.

23. The method of claim 22,
wherein the playitem indicates a start time and an end time corresponding to the PTS.

24. The method of claim 20, wherein when the playitem is selected, the entry point map related to a first path of the video streams is accessed to determine a location of transport packets of the video stream for the first path included in the multiplexed plurality of transport streams.

25. An apparatus for reproducing a multi-stream, the apparatus comprising:
a pickup configured to read a multi-stream in which a plurality of video streams are divided into a plurality of transport packets and multiplexed in a data area on a recording medium, the video streams having different paths from one another; and
a controller, operably coupled to the pickup, and configured to control the pickup to read a playlist for managing playback of the multi-stream in a navigation area of the recording medium, the playlist including a playitem indicating a playing interval of the multi-stream,
wherein the playitem includes a field representing a total number of the paths of the video streams multiplexed in the multi-stream.

26. The apparatus of claim 25, wherein the controller is further configured to control the pickup to read an entry point map for each stream included in the navigation area.

27. The apparatus of claim 26, wherein the controller is further configured to control the pickup to read the entry point map in an MPD (MakersPrivateData) area reserved in a clip information file for storing information about the plurality of multiplexed streams.

28. The apparatus of claim 26, wherein the controller is further configured to control the pickup to read an ID of the transport packets pertaining to a path, the number of entry points, plural pairs of PTS (Presentation Time Stamp) and SPN (Source Packet Number) of the transport packets.

29. The apparatus of claim 28, wherein the controller is further configured to control the pickup to read information indicating a start time and an end time corresponding to the PTS included in the playitem.

30. The apparatus of claim 26, wherein when the playitem is selected, the entry point map related to a first path of the video streams is accessed to determine a location of transport packets of the video stream for the first path included in the multiplexed plurality of transport streams.