Methods for changing the size of a jitter buffer and for time alignment, communications system, receiving end, and transcoder
First Claim
1. Method for changing the size of a jitter buffer, which jitter buffer is employed at a receiving end in a communications system including a packet network for buffering received packets containing audio data in order to enable a compensation of varying delays of said received packets, the method comprising:
- determining whether a current jitter buffer size should be increased or decreased by evaluating current overall delay and jitter in received packets; and
in case it was determined that the current jitter buffer size is to be increased, increasing the jitter buffer size and compensating the resulting empty jitter buffer space by generating additional data based on audio data contained in received packets.
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Accused Products
Abstract
The invention relates to a method for changing the size of a jitter buffer, which jitter buffer is employed at a receiving end in a communications system including a packet network for buffering received packets containing audio data in order to enable a compensation of varying delays of said received packets. In order to enable a faster change of the jitter buffer size it is proposed that in case it is determined that the current jitter buffer size has to be changed, the jitter buffer size is expanded by generating additional data based on the received data or decreased by compacting the received data. A proposed communications system, receiving end and processing unit include corresponding means. The invention equally relates to a method for time alignment in a radio communications system based on existing speech data. A further proposed communications system, transceiver unit and processing unit include the corresponding means.
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Citations
45 Claims
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1. Method for changing the size of a jitter buffer, which jitter buffer is employed at a receiving end in a communications system including a packet network for buffering received packets containing audio data in order to enable a compensation of varying delays of said received packets, the method comprising:
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determining whether a current jitter buffer size should be increased or decreased by evaluating current overall delay and jitter in received packets; and
in case it was determined that the current jitter buffer size is to be increased, increasing the jitter buffer size and compensating the resulting empty jitter buffer space by generating additional data based on audio data contained in received packets. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. Communications system comprising a packet network and at least one possible receiving end, the receiving end including:
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a jitter buffer for buffering received packets containing audio data;
processing means for compensating varying delays of received packets buffered in said jitter buffer;
processing means for determining whether the size of said jitter buffer should be increased or decreased-based on the current overall delay and the current variation of delay between the different packets; and
processing means for changing the current size of said jitter buffer according to one of the methods 1 to 22. - View Dependent Claims (24)
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25. Receiving end for a communications system including a packet network, which receiving end comprises:
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a jitter buffer for buffering received packets containing audio data;
processing means for compensating varying delays of received packets buffered in said jitter buffer;
processing means for determining whether the size of said jitter buffer should be increased or decreased based on the current overall delay and the current variation of delay between the different packets; and
processing means for changing the current size of said jitter buffer according to one of the methods 1 to 22. - View Dependent Claims (26)
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27. Processing means for a receiving end of a communications system including a packet network, which processing means are designed for changing the current size of a jitter buffer according to one of the methods 1 to 22.
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28. Method for carrying out a time alignment in a network transcoder (145) of a radio communications system, which time alignment is used for decreasing a buffering delay in downlink direction, said buffering delay resulting from buffering downlink speech data encoded by said transcoder (145) before transmitting said speech data over a radio interface of said radio communications system in order to compensate for a phase shift in downlink framing of speech data at said transcoder (145) and at said radio interface, the method comprising:
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determining whether a time alignment has to be carried out; and
in case it was determined that a time alignment has to be carried out, expanding or compacting selected speech data with a time scaling method for achieving the required time alignment. - View Dependent Claims (29, 30, 31, 32, 33, 34)
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35. Method for carrying out a time alignment in a network transcoder of a radio communications system, which time alignment is used for decreasing a buffering delay in downlink direction, said buffering delay resulting from buffering downlink speech data encoded by said transcoder before transmitting said speech data over a radio interface of said radio communications system in order to compensate for a phase shift in a downlink framing of said speech data in said transcoder and at said radio interface, the method comprising:
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determining whether a time alignment has to be carried out; and
in case it was determined that a time alignment has to be carried out, expanding selected speech data for achieving the required time alignment by inserting an empty space within said selected speech data and by compensating said empty space by a bad frame handling. - View Dependent Claims (36, 37, 38)
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39. Method for carrying out a time alignment in a network transcoder of a radio communications system, which time alignment is used for decreasing a buffering delay in downlink direction, said buffering delay resulting from buffering downlink speech data encoded by said transcoder before transmitting said speech data over a radio interface of said radio communications system in order to compensate for a phase shift in a downlink framing of said speech data in said transcoder and at said radio interface, the method comprising:
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determining whether a time alignment has to be carried out; and
in case it was determined that a time alignment has to be carried out, condensing speech data for achieving the required time alignment by overlapping a selected first portion of speech data and a selected second portion of speech data and by discarding the speech data in between said first and said second selected portion of the speech data. - View Dependent Claims (40)
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41. Method for carrying out a time alignment in a network transcoder of a radio communications system, which time alignment is used for decreasing a buffering delay in downlink direction, said buffering delay resulting from buffering downlink speech data encoded by said transcoder before transmitting said speech data over a radio interface of said radio communications system in order to compensate for a phase shift in a downlink framing of said speech data in said transcoder and at said radio interface, the method comprising:
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determining whether a time alignment has to be carried out; and
in case it was determined that a time alignment has to be carried out, condensing speech data for achieving the required time alignment by discarding at least one frame of speech data, wherein gain parameters and Linear Predictive Coding (LPC) coefficients of frames of speech data surrounding the at least one discarded frame are modified to smoothly combine the frames surrounding the at least one discarded frame.
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42. Method for carrying out a time alignment in a network transcoder of a radio communications system, which time alignment is used for decreasing a buffering delay in downlink direction, said buffering delay resulting from buffering downlink speech data encoded by said transcoder before transmitting said speech data over a radio interface of said radio communications system in order to compensate for a phase shift in a downlink framing of said speech data in said transcoder and at said radio interface, the method comprising:
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determining whether a time alignment has to be carried out; and
in case it was determined that a time alignment has to be carried out, expanding speech data for achieving the required time alignment by interpolating additional audio data from selected speech data.
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43. Method for carrying out a time alignment in a network transcoder of a radio communications system, which time alignment is used for decreasing a buffering delay in downlink direction, said buffering delay resulting from buffering downlink speech data encoded by said transcoder before transmitting said speech data over a radio interface of said radio communications system in order to compensate for a phase shift in a downlink framing of said speech data in said transcoder and at said radio interface, the method comprising:
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determining whether a time alignment has to be carried out; and
in case it was determined that a time alignment has to be carried out, expanding speech data for achieving the required time alignment by interpolating selected adjacent or spaced apart speech data into reduced speech data.
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44. Radio communications system comprising
at least one radio interface for transmitting encoded speech data in a downlink direction; -
at least one network transcoder (145), which network transcoder (145) includes at least one encoder (146) for encoding speech data to be used for a downlink transmission via said radio interface, and which network transcoder (145) further includes processing means (147) for carrying out a time alignment on encoded speech samples according to one of methods 28 to 43; and
buffering means (143) arranged between said radio interface and said network transcoder (145) for buffering downlink speech data encoded by said transcoder (145) before transmitting said encoded speech data via said radio interface in order to compensate for a phase shift in a downlink framing of said speech data by said transcoder (145) and by said radio interface; and
processing means (143) for determining whether and to which extend the speech samples encoded by said encoder (146) have to be time aligned before transmission in order to minimize a buffering delay for encoded speech data resulting from a buffering by said buffering means (143).
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45. Network transcoder (145) for a radio communications system comprising:
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at least one encoder (146) for encoding speech data to be used for a downlink transmission via a radio interface of said radio communications system; and
processing means (147) for carrying out a time alignment according to one of the methods 28 to 43.
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Specification