Method and apparatus for an adaptive de-jitter buffer in a wireless communication system

• US 20060056383A1
• Filed: 08/30/2005
• Published: 03/16/2006
• Est. Priority Date: 08/30/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kapoor, Rohit, Black, Peter John, Yavuz, Mehmet, Spindola, Serafin Diaz
• Granted Patent: US 7,826,441 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/2416 Real-time traffic
• CPC Class Codes: H04L 47/28 in relation to timing considerations
• CPC Class Codes: H04L 47/29 using a combination of thresholds
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/9094 Arrangements for simultaneous transmit and receive, e.g. simultaneous reading/writing from/to the storage element
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/752 adapting media to network capabilities
• CPC Class Codes: H04L 65/80 Responding to QoS

Abstract

Adaptive De-Jitter Buffer for Voice over IP (VoIP) for packet switch communications. The de-jitter buffer methods and apparatus presented avoid playback of underflows while balancing end-to-end delay. In one example, the de-jitter buffer is recalculated at the beginning of each talkspurt. In another example, talkspurt packets are compressed upon receipt of all remaining packets.

Claims

1. An apparatus, comprising:

a memory storage unit configured to store packets of data; and

a first controller adapted to determine a target delay length for the memory storage unit, and to initiate compression of at least one packet when a number of stored packets exceeds the target delay length.

2. The apparatus as in claim 1, wherein the first controller is further configured to maintain a given percentage of underflows due to delayed packets.

3. The apparatus as in claim 2, wherein the first controller is further configured to calculate the target delay length as:

 

If (PER_delay <

TARGET_VALUE) then  

 

DEJITTER_DELAY = DEJITTER_DELAY −

CONSTANT;

 

If (PER_delay >

TARGET_VALUE &

&

PER_delay >

= last_PER_delay) then  

 

DEJITTER_DELAY = DEJITTER_DELAY + CONSTANT;

 

Set DEJITTER_DELAY = MAX (MIN_JITTER,  

DEJITTER_DELAY);

 

 

 

 

 

 

 

 

 

 

and DEJITTER_DELAY = MIN (MAX_JITTER, DEJITTER_DELAY),

wherein PER_delay is a rate of underflows due to delayed packets, TARGET_VALUE is a targeted rate of delayed packets, DEJITTER_DELAY is the target delay length of the adaptive de-jitter buffer, CONSTANT is a pre-defined value, and MAX_JITTER and MIN_JITTER are pre-defined values representing the maximum and minimum target delay lengths respectively.

4. The apparatus as in 3, wherein the first controller is configured to calculate the PER_delay as:

PER_delay=PER_CONSTANT×

PER_delay+(1−

PER_CONSTANT)×

Current_—

PER_delay

wherein PER_CONSTANT is the time constant for the filter used to estimate PER_delay.

5. The apparatus as in claim 4, wherein the first controller comprises:

a packet error calculation unit configured to calculate the Current_PER_delay as a rate of delayed packets, wherein delayed packets are received after an anticipated playback time, and wherein the Current_PER_delay.

6. The apparatus as in claim 5, wherein the packet error calculation unit is configured to calculate the Current_PER_delay as a ratio of delayed packets to total packets received, including delayed packets, measured from a last update of PER_delay to a current update, and calculated as:

${\mathrm{Current\_PER}}_{\mathrm{delay}}=\frac{\mathrm{Number}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Delayed}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Underflows}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Since}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Last}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Update}}{\mathrm{Number}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Packets}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Received}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Since}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Last}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Update}}.$

7. The apparatus as in claim 6, wherein the first controller is configured to identify a first portion of received packets, wherein the first portion corresponds to a talkspurt, and wherein the talkspurt comprises a plurality of sequential packets.

8. The apparatus as in claim 7, wherein the first controller is configured to identify the first portion by encoding of the first portion.

9. The apparatus as in claim 8, wherein the first controller is configured to determine an anticipated playback time for a first packet of the talkspurt, and to initiate playback of the first packet of the talkspurt before the anticipated playback time.

10. The apparatus as in claim 9, the first controller further configured to initiate expansion of subsequent packets after playback of the first packet.

11. The apparatus as in claim 10, wherein the first controller is configured to identify the beginning and the end of a talkspurt.

12. The apparatus as in claim 11, wherein the first controller is configured to identify an end portion of the talkspurt, and compress at least one packet in the end portion of the talkspurt.

13. The apparatus as in claim 12, wherein the first controller is configured to identify the end portion of the talkspurt by an encoding rate of received packets.

14. The apparatus as in claim 13, wherein the first controller is configured to identify the end portion of the talkspurt by a silence indicator.

15. The apparatus as in claim 14, wherein the first controller is configured to identify the end portion of the talkspurt by an end-of-talkspurt indicator.

16. A method for processing packetized data, comprising:

storing packets of data in a memory storage unit;

determining a target delay length for the memory storage unit;

evaluating a status of the memory storage unit with respect to the target delay length, wherein the status of the memory storage unit is a measure of data stored in the memory storage unit; and

initiating time warping of at least one packet from the memory storage unit if the status of the memory storage violates the target delay length.

17. The method of claim 16, further comprising:

calculating the target delay length as;

If (PER_delay <

TARGET_VALUE) then 

 

DEJITTER_DELAY = DEJITTER_DELAY −

CONSTANT;

 

If (PER_delay >

TARGET_VALUE &

&

PER_delay >

= last_PER_delay) then 

 

DEJITTER_DELAY = DEJITTER_DELAY + CONSTANT;

 

Set DEJITTER_DELAY = MAX (MIN_JITTER, 

DEJITTER_DELAY);

 

 

 

 

 

 

 

 

 

 

andDEJITTER_DELAY = MIN (MAX_JITTER, DEJITTER_DELAY),

wherein PER_delay is a rate of underflows due to delayed packets, the TARGET_VALUE is a targeted rate of delayed packets, the DEJITTER_DELAY is the target delay length of the adaptive de-jitter buffer, the CONSTANT is a pre-defined value, and the MAX_JITTER and MIN_JITTER are pre-defined values which are the maximum and minimum target delay lengths respectively.

18. The method as in claim 17, further comprising:

generating a time warp control signal;

receiving a plurality of sequential packets; and

add-overlapping segments in response to the time warp control signal.

19. The method as in claim 18, wherein the add-overlapping comprises:

combining at least two of the plurality of segments as;

$\begin{array}{cc}a)& \mathrm{OutSegment}<br><br>\left[i\right]=\frac{(\mathrm{Segment1}<br><br>\left(i\right)*\left(\mathrm{WindowSize}-i\right)+\left(\mathrm{Segment2}<br><br>\left(i\right)*i\right)}{\mathrm{WindowSize}}\\ b)& \mathrm{OutSegment}<br><br>\left[i\right]=\frac{(\mathrm{Segment2}<br><br>\left(i\right)*\left(\mathrm{WindowSize}-i\right)+\left(\mathrm{Segment1}<br><br>\left(i\right)*i\right)}{\mathrm{WindowSize}}\\ \text{\hspace{1em}<br><br>}& \begin{array}{ccc}i=0<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{WindowSize}-1& \text{\hspace{1em}<br><br>}& \mathrm{WindowSize}=\mathrm{RWindowSize}\end{array}\end{array}$

wherein OutSegment is a resulting add-overlapped segment, Segment1 and Segment2 are the segments to be add-overlapped, WindowSize corresponds to a first segment, and RWindowSize corresponds to a second segment.

20. The method of claim 19, wherein the add-overlapping further comprises:

identifying a portion of maximum correlation between the first segment and the second segment.

21. The method of claim 20, wherein identifying the portion of maximum correlation between the first segment and the second segment further comprises:

identifying the portion of maximum correlation by calculating maximum correlation as;

$\mathrm{Corr}<br><br>\left(d\right)=\frac{\underset{i}{\sum <br><br>}<br><br>\left[\left(x<br><br>\left(i\right)-\mathrm{mx}\right)\times <br><br>\left(y<br><br>\left(i-d\right)-\mathrm{my}\right)\right]}{\sqrt{\underset{i}{\sum <br><br>}<br><br>\left(x<br><br>\left(i\right)-\mathrm{mx}\right)^2}<br><br>\text{\hspace{1em}<br><br>}<br><br>\sqrt{\underset{i}{\sum <br><br>}<br><br>\left(y<br><br>\left(i-d\right)-\mathrm{my}\right)^2}},$

wherein x represents the first segment, y represents the second segment of speech,

m represents the correlation window, i is an index value, and

d represents the correlation portion.

22. The method as in claim 16, further comprising:

time warping a plurality of sequential packets;

inhibiting time warping for at least one sequential packet, wherein the at least one sequential packet is subsequent to the plurality of sequential packets; and

enabling time warping subsequent to the at least one sequential packet.

23. The method as in claim 16, further comprising:

calculating a time warping rate, wherein the time warping rate is a number of time warped packets over a time window; and

initiating time warping of packets as a function of the time warping rate.

24. A computer-readable storage medium containing a set of instructions, the set of instructions comprising:

an input routine for storing packets of data in a memory storage unit;

a target delay length calculation routine for determining a target delay length for the memory storage unit;

a first routine for evaluating a status of the memory storage unit with respect to the target delay length, wherein the status of the memory storage unit is a measure of data stored in the memory storage unit; and

a second routine initiating time warping of at least one packet from the memory storage unit if the status of the memory storage violates the target delay length.