Apparatus for generating and restoring RTP packet and method thereof

• US 20030185245A1
• Filed: 03/31/2003
• Published: 10/02/2003
• Est. Priority Date: 04/01/2002
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lobo, Austin, Kang, Sang-Ug
• Granted Patent: US 7,366,204 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/65 Network streaming protocols, e.g. real-time transport protocol [RTP] or real-time control protocol [RTCP]
• CPC Class Codes: H04L 65/70 Media network packetisation
• CPC Class Codes: H04L 69/22 Parsing or analysis of headers

Abstract

An apparatus and method to generate and restore an RTP (Real-Time Transmission Protocol) packet. A setting unit assigns a CTS (Composition TimeStamp), a DTS (Decoding TimeStamp), and a PSN (Packet Sequence Number) that sequentially increase according to a packet generation order for each of a plurality of SL (Synchronization Layer) packets, extracting a time stamp length and a packet sequence number length from an SLCD (SL Configuration Descriptor) within each SL packet. A packet generating unit generates a header of the SL packet accommodated in an RTP packet header and the RTP packet based on the CTS, the DTS, the PSN, the time stamp length and the packet sequence number length. Since only difference values in the CTS, the DTS, and the PSN information between a previous SL packet and the present SL packet, are recorded, a number of bits can be reduced if the CTS value rolls over and a multiple SL packet can be made for the SL packet having a time stamp length greater than 32 bits. Also, a condition that a DTS delta value should always be a positive number is met.

Claims

1. An apparatus for restoring an RTP (Real-Time Transport Protocol) packet comprising:

a setting unit assigning a CTS (Composition TimeStamp), a DTS (Decoding TimeStamp), and a PSN (Packet Sequence Number) that sequentially increase according to a packet generation order for each of a plurality of SL (Synchronization Layer) packets, and extracting a time stamp length and a packet sequence number length from an SLCD (SL Configuration Descriptor) within each SL packet; and

a packet generating unit generating a header of each SL packet accommodated in an RTP packet header and the RTP packet based on the CTS, the DTS, the PSN, the time stamp length and the packet sequence number length.

2. The apparatus according to claim 1, wherein the setting unit comprises:

a CTS generating unit assigning the CTS that sequentially increases from one according to a packet generation order for each of the SL packets;

a DTS generating unit assigning the DTS that increases from zero according to the packet generation order for each of the SL packets;

a PSN generating unit assigning the PSN that increases from zero according to the packet generation order for each of the SL packets; and

an extracting unit extracting the time stamp length and the packet sequence number from the SLCD within each of the SL packets.

3. The apparatus according to claim 1, wherein the packet generating unit comprises:

an RTP packet header generating unit generating an RTP packet header including an RTP time stamp calculated based on the CTS;

a CTS delta generating unit generating a CTS delta based on the CTS and the RTP time stamp;

a DTS delta generating unit generating a DTS delta based on the CTS and the DTS; and

an index/index delta generating unit receiving the PSN, an index length, and an index delta length and generating an index/index delta.

4. A method of generating an RTP packet, comprising:

assigning a CTS (Composition TimeStamp), a DTS (Decoding TimeStamp), and a PSN (PacketSequenceNumber) that sequentially increase according to a packet generation order for each of a plurality of SL (Synchronization Layer) packets;

extracting a time stamp length and a packet sequence number length from a SLCD (SL ConfigurationDescriptor) within each SL packet; and

generating a header of each SL packet accommodated in an RTP packet header and the RTP packet based on the CTS, the DTS, the PSN, the time stamp length and the packet sequence number length.

5. The method according to claim 4, wherein the assigning comprises:

a first determining of an RTP time stamp recorded on a header of the RTP packet based on the CTS of each SL packet accommodated first in the RTP packet; and

a second determining of a CTS delta, a DTS delta and an index/index delta recorded on a header of each SL packet based on the RTP time stamp determined, the CTS, the DCT, the PSN and the index delta length.

6. The method according to claim 5, wherein the first determining comprises the RTP time stamp according to the following formula, in which:

RTP time stamp=(CTS of first SL packet)%(RTP time stamp length)

7. The method according to claim 5, wherein the second determining comprises the CTS delta, the DTS delta, the index, and the index delta according to the following formula, in which:

CTS delta(i)=CTS(i)−

RTP time stamp DTS delta(i)=CTS(i)−

DTS(i) Index(O)=PSN(O)% 2^{index length} Index delta(i)=(PSN(i)−

PSN(i))% 2^{index delta length}

where i stands for a packet sequence number of each SL packet.

17. An article of manufacture comprising a computer-readable medium having stored thereon computer-executable instructions for performing the method of claim 4.

8. An apparatus of restoring an RTP (Real-Time Transmission Protocol) packet comprising:

a first restoring unit restoring an RTP time stamp;

a second restoring unit restoring a CTS (Composition TimeStamp) of a first SL packet from the RTP time stamp and a CTS delta of the first SL packet, restoring a CTS of remaining SL packets from a CTS of a restored first SL packet and a CTS delta of the remaining SL packets;

a third restoring unit restoring a DTS (Decoding TimeStamp) of each of the SL packets from a CTS and a DTS delta; and

a fourth restoring unit restoring a PSN (Packet Sequence Number) of the first SL packet from an index of the first SL packet, restoring a PSN of the remaining SL packets from a PSN of the restored first SL packet and an index delta of the remaining SL packets.

9. The apparatus according to claim 8, further comprising:

a first changing unit changing the CTS and the DTS based on a set time stamp length; and

a second changing unit changing the PSN based on a set packet sequence number length.

10. A method of restoring an RTP (Real-Time Transmission Protocol) packet comprising:

extracting an RTP time stamp from a received RTP packet, restoring a CTS (Composition TimeStamp) for each of a plurality of SL packets within a payload of the received RTP packet;

restoring a DTS (Decoding TimeStamp) from a DTS delta extracted from the CTS and each of the SL packets; and

restoring a PSN (Packet Sequence Number) based on an index and an index delta extracted from each of the SL packets.

11. The method according to claim 10, wherein the restoring of the CTS comprises restoring the CTS according to a first formula], restoring the DTS comprises restoring the DTS according to a second formula], and restoring the PSN comprises restoring the PSN according to a third formula], respectively, in which:

the first formula comprises;

CTS(1)=RTPtime stamp; and

CTS(i)=CTS(1)+CTS delta(i);

the second formula comprises;

DTS(i)=CTS(i)−

DTSdelta(i); and

the third formula comprises;

PSN(1)=index; and

PSN(i)=PSN(i−

1)+index delta(i)+1;

where i stands for a packet sequence number of each SL packet.

12. The method according to claim 10, further comprising:

a first changing of the CTS and the DTS based on a set time stamp length; and

a second changing of the PSN based on a set packet sequence number length.

13. The method according to claim 12, wherein the first changing comprises changing the CTS and the DTS according to a first formula], and the second changing comprises changing the PSN according to a second formula], respectively, in which:

the first formula comprises;

CTS′

(i)=CTS(i)%time stamp length; and

DTS′

(i)=DTS(i)%time stamp length; and

the second formula comprises;

PSN′

(i)=PSN(i)%packet sequence number length; and

where i stands for a packet sequence number of the SL packet.

18. An article of manufacture comprising a computer-readable medium having stored thereon computer-readable instructions for performing the method of claim 10.

14. An apparatus for restoring an RTP (Real-Time Transport Protocol) packet, comprising:

a setting unit, setting preselected time and sequence information for, and obtaining preselected SLCD (SL Configuration Descriptor) information from, a plurality of SL (Synchronization Layer) packets; and

a packet generating unit, generating a header of each SL packet in the RTP packet using the preselected time and sequence information and the preselected SLCD information.

15. The apparatus according to claim 14, wherein the preselected time and sequence information for the plurality of SL packets includes a CTS (Composition TimeStamp), a DTS (Decoding TimeStamp), and a PSN (Packet Sequence Number) that sequentially increase according to a packet generation order for each of the plurality of SL packets.

16. The apparatus according to claim 14, wherein the preselected SLCD information includes a time stamp length and a packet sequence number length from a SLCD (SL Configuration Descriptor) within each SL packet.

19. An apparatus for generating a multiple SL (Synchronization Layer) RTP (Real-Time Transport Protocol) packet from a plurality of SL packets, comprising:

a multiple SL packet layer unit, configuring a CTS (Composition TimeStamp), a DTS (Decoding TimeStamp) and a PSN (Packet Sequence Number) having lengths according to a time stamp of an SLCD (SL Configuration Descriptor) within each SL packet;

a generating value layer unit, generating a generated CTS, a generated DTS and a generated PSN based on the CTS, the DTS and the PSN of the multiple SL packet layer; and

a multiple SL layer unit, generating a multiple SL packet header of a multiple SL packet accommodated in an RTP packet header and the RTP packet based on a CTS delta/RTP time stamp, a DTS delta, and an index/index delta.

20. An apparatus for restoring a multiple SL (Synchronization Layer) RTP (Real-Time Transport Protocol) packet having a plurality of SL packets, comprising:

a multiple SL layer restoring unit, restoring a CTS (Composition TimeStamp) delta/RTP time stamp, a DTS (Decoding TimeStamp) delta, and an index/index delta from a multiple SL packet header of a multiple SL packet accommodated in an RTP packet header and the RTP packet;

a generating value layer restoring unit, restoring a generated CTS, a generated DTS and a generated PSN (Packet Sequence Number) based on the CTS delta/RTP time stamp, the DTS delta, and the index/index delta from the multiple SL packet header of the multiple SL packet; and

a multiple SL packet layer restoring unit, restoring a CTS, a DTS and a PSN for each SL packet of the multiple SL packet.