Patent Description:
One important type of measurement in the context of packet-based data stream quality assessment is the determination of jitter associated with the data packets of the packet-based data stream, i.e. of the variation of the arrival time with respect to the transmission time of the individual data packets.

Usually, one of the data packets is used as a reference in order to extract the jitter from the arrival times of the data packets. For example, it is known to use the arrival time of the first packet in the packet-based data stream to set the time reference and compute the relative arrival times for each of the following packets from that reference time.

However, such an approach does not consider possible global delays that could occur for example when several packets are stuck in the network and then released suddenly. In that case, it is possible that some arrival times in the jitter file are set to values that are below their theoretical minimum arrival time, i.e. below the sending time plus the minimum possible one-way delay.

<CIT> discloses a system with a first device and a second device that are connected to each other via a network. The second device comprises a de-jitter buffer and de-jitter buffer control circuitry. The de-jitter buffer control circuitry is configured to adjust a target delay of the de-jitter buffer based on an arrival delay value, which corresponds to a mean delay value, i.e. an estimated average network delay of transmissions between the first device and the second device. An audio stream played back by the second device is delayed according to the target delay by means of the de-jitter buffer.

Thus, there is a need for a jitter determination method, a jitter determination module, and a packet-based data stream receiver that allow for correctly determining the jitter when global delays are present.

Embodiments of the present disclosure provide a jitter determination method for determining jitter associated with a packet-based data stream according to claim <NUM>.

Therein, the actual arrival time of the data packet not selected to be the reference data packet may be measured relative to the reference data packet. It is emphasized that the reference data packet does not need to be the first data packet of the packet-based data stream.

Accordingly, the actual arrival time of the data packet not selected to be the reference data packet may be smaller than zero if the corresponding packet arrives before the reference data packet, equal to zero if the corresponding packet arrives at the same time as the reference data packet, or bigger than zero if the corresponding packet arrives after the reference data packet. As mentioned above, the actual arrival time may be a relative time, namely relative to the reference data packet.

The expected arrival time may correspond to the arrival time of the respective data packet without any perturbations present in the network, i.e. without jitter and/or any global delays.

The jitter determination method according to the present disclosure is based on the idea to determine discrepancies between the expected arrival time(s) and the actual arrival time(s) of the data packets, particularly of the at least one data packet not selected to be the reference data packet.

Based on these determined discrepancies, the time bias is determined. The time bias accounts for global delays of the data packets, for example if some or all of the data packets were stuck in the transmission network over a certain time and are released simultaneously.

Thus, the jitter associated with the packet-based data stream can be determined correctly by means of the jitter determination method according to the present disclosure even in the presence of global delays as described above.

It is noted that the jitter data may also be called "jitter vector" in the context of jitter analysis on packet-based data streams.

The time bias is determined based on respective deviations between the expected arrival times and the actual arrival times of the data packets not selected to be the reference data packet. In other words, the time bias, e.g. due to global delays, is reconstructed based on the discrepancies between the actual arrival time(s) and the expected arrival time(s). By comparing the actual arrival time(s) and the expected arrival time(s) of the data packet(s) not selected to be the reference data packet, conclusions about potential global delays can be drawn.

The time bias is a maximum deviation between the expected arrival times and the actual arrival times of the data packet not selected to be the reference data packet, particularly the expected arrival times and the actual arrival times across the at least two data packets. In other words, the deviation between the expected arrival time and the actual arrival time is determined for each data packet not selected to be the reference data packet. The time bias is the biggest one of these deviations. It has turned out that by correcting the jitter data this way, no (corrected) arrival time in the corrected jitter data is before the expected arrival time or before a minimum arrival time of the respective data packet.

The determined time bias is added to the arrival times of the data packets, respectively, in order to obtain the corrected jitter data. In other words, the arrival time of each data packet is corrected in the jitter data by adding the time bias to the respective arrival time. Accordingly, the corrected arrival time of each data packet equals the actual arrival time plus the determined time bias.

According to an aspect of the present disclosure, the expected arrival time is determined based on packet sequence numbers of the at least two data packets, based on the standard used for data transmission and/or based on durations of the at least two data packets. For example, the expected arrival time may be equal to the sending time (i.e. the time at which the packet is sent by the transmitter) plus the minimum one-way delay, i.e. plus the minimum travel time of the respective data packet through the respective transmission network.

In general, the packet sequence numbers determine the correct order of the different data packets, particularly according to the standard used for data transmission. More precisely, the data packets have increasing packet sequence numbers, such that packets sent earlier have a lower packet sequence number than packets sent later.

The expected arrival time may be determined based on a linear function that increases linearly from the actual arrival time of the reference data packet. More precisely, an expected arrival time tn of a data packet with packet number n may be determined according to the function tn = tr + (n - r) · Tp, wherein r is the packet sequence number of the reference data packet, tr is the actual arrival time of the reference data packet, and Tp is a packet duration, i.e. the duration of one data packet in case the packet duration is the same for all packets in the packet-based data stream.

The packet sequence numbers may be determined from the headers of the respective data packets, as the headers usually comprise the packet sequence number.

The packet duration may depend on the standard used for data transmission, as the standard may specify the packet rate fp and thus the packet duration TP = <NUM>/fp in case the packet duration is the same for all packets in the packet-based data stream.

The packet duration can also be derived from timestamps that may be present in the headers according to Ti = (ti+<NUM> - ti)/F, wherein Ti is the duration of packet i (in seconds), ti is the timestamp corresponding to packet i (in timestamp units) and F is the clock rate according to the corresponding data transport protocol (in Hz).

In a further embodiment of the present disclosure, the corrected jitter data is equal to the initial jitter data if the determined time bias is below a predefined threshold, wherein the corrected jitter data is different from the initial jitter data if the determined time bias is above a predefined threshold. In other words, the jitter data is only corrected if the determined time bias is above the predefined threshold. For example, the predefined threshold may be equal to half a data packet duration, one data packet duration, or m data packet durations, wherein m is an integer greater than or equal to two.

Particularly, the expected arrival times are determined based on the reference data packet. For example, the actual arrival time of the reference data packet may be used as a fix point, wherein the actual arrival time of the reference data packet equals the expected arrival time.

The expected arrival time of the at least one data packet not selected as reference data packet may be determined based on a linear function that increases linearly from the expected arrival time of the reference data packet. More precisely, an expected arrival time tn of a data packet with packet number n may be determined according to the formula tn = tr + (n - r) · Tp, wherein r is the packet number of the reference data packet, tr is the actual arrival time of the reference data packet, and Tp is a packet duration, i.e. the duration of one data packet in case the packet duration is the same for all packets in the packet-based data stream.

The packet duration can also be derived from timestamps that may be present in the headers according to Ti = (ti+<NUM> - ti)/F, wherein Ti is the duration of packet i (in seconds), ti is the timestamp corresponding to packet i (in timestamp units) and F is the clock rate according to the corresponding transport protocol (in Hz).

In a further embodiment of the present disclosure, the time bias is determined if at least one actual arrival time is before the corresponding expected arrival time. Accordingly, the time bias may only be determined if there is a need to correct the jitter data, namely due to the at least one actual arrival time being before the corresponding expected arrival time. On the other hand, the time bias may not be determined if there is no need to correct the jitter data, as all actual arrival times are already equal to or after the respective expected arrival times.

The packet-based data stream may be based on the Real-Time Transport Protocol (RTP), the QUIC protocol, and/or the Transmission Control Protocol (TCP), particularly wherein the packet-based data stream is a voice data stream, an image data stream, a video data stream, a music data stream and/or a media data stream. Particularly, the packet-based data stream may comprise an arbitrary combination of voice data streams, image data streams, video data streams, music data streams and/or media data streams.

According to an aspect of the present disclosure, a quality of the packet-based data stream can be assessed based on the corrected jitter data. The corrected jitter data comprises additional information on the time bias, and thus additional information on potential global delays of the packet-based data stream. Thus, the quality of the packet-based data stream can be assessed more precisely based on the additional information regarding the time bias.

Particularly, a voice quality, an image quality, a video quality, a data quality, a music quality and/or a media quality may be assessed.

According to another aspect of the present disclosure, minimum arrival times of the at least two data packets are determined, wherein the corrected jitter data is determined based on the determined minimum arrival times. For example, the minimum arrival time may be equal to the sending time (i.e. the time at which the packet is sent by the transmitter) plus the minimum one-way delay, i.e. plus the minimum travel time of the respective data packet. Accordingly, the minimum arrival time may be used as the expected arrival time for the respective data packet.

Embodiments of the present disclosure further provide a jitter determination module for determining jitter associated with a packet-based data stream according to claim <NUM>.

Particularly, the jitter determination module may be configured to perform the jitter determination method described above.

Regarding the advantages and further properties of the jitter determination module, reference is made to the explanations given above with respect to the jitter determination method, which also hold for the jitter determination module and vice versa.

According to an aspect of the present disclosure, the corrected jitter data is equal to the initial jitter data if the determined time bias is below a predefined threshold, wherein the corrected jitter data is different from the initial jitter data if the determined time bias is above a predefined threshold. In other words, the jitter data is only corrected if the determined time bias is above the predefined threshold. For example, the predefined threshold may be equal to half a data packet duration, one data packet duration, or m data packet durations, wherein m is an integer greater than or equal to two.

Embodiments of the present disclosure further provide a packet-based data stream receiver. The packet-based data stream receiver comprises at least one signal input and a jitter determination module described above.

Particularly, the packet-based data stream receiver may be configured to perform the jitter determination method described above.

Regarding the advantages and further properties of the packet-based data stream receiver, reference is made to the explanations given above with respect to the jitter determination method and the jitter determination module, which also hold for the packet-based data streamreceiver and vice versa.

In an embodiment of the present disclosure, the jitter determination module is located downstream of the at least one signal input. Accordingly, the jitter determination module is integrated into the packet-based data streamreceiver. Particularly, the packet-based data stream receiver may comprise a housing, and the jitter determination module may be arranged within the housing.

<FIG> schematically shows an packet-based data receiver <NUM>. In general, the packet-based data receiver <NUM> is configured to receive and process packet-based data streams.

The packet-based data streams may each be based on the Real-Time Transport Protocol (RTP), the QUIC protocol, and/or the Transmission Control Protocol /TCP).

For example, the packet-based data streams may each be a voice data stream, an image data stream, a video data stream, a music data stream and/or a media data stream. Particularly, the packet-based data streams may comprise an arbitrary combination of voice data streams, image data streams, video data streams, music data streams and/or media data streams.

The packet-based data streamreceiver <NUM> may be connected to a data transmission network, such as a computer network and/or a server network, particularly to the world wide web.

The packet-based data stream receiver <NUM> comprises at least one signal input <NUM> and a jitter determination module <NUM>.

Therein and in the following, the term "(sub-)module" is understood to describe suitable hardware, suitable software, or a combination of hardware and software that is configured to have a certain functionality.

The hardware may, inter alia, comprise a CPU, a GPU, an FPGA, an ASIC, or other types of electronic circuitry.

The jitter determination module <NUM> is connected to the at least one signal input <NUM>, wherein the jitter determination module <NUM> is located downstream of the at least one signal input <NUM>.

The jitter determination module <NUM> may be connected to the at least one signal input <NUM> directly or via other electronic components of the packet-based data stream receiver <NUM>.

The jitter determination module <NUM> comprises a signal input <NUM>, an initial jitter submodule <NUM>, a time bias submodule <NUM>, and a correction submodule <NUM>.

The packet-based data stream receiver <NUM> or rather the jitter determination module <NUM> is configured to determine jitter associated with at least one packet-based data stream received by the packet-based data stream receiver <NUM>.

More precisely, the jitter determination module <NUM> is configured to perform a jitter determination method for for determining jitter associated with a packet-based data stream that is described in the following with reference to <FIG>.

At least one packet-based data stream is received by means of the signal input <NUM> of the jitter determination module <NUM> (step S1).

Beforehand, the packet-based data stream may be received by means of the at least one signal input <NUM> of the packet-based data stream receiver <NUM>, optionally pre-processed by means of further electronic components of the packet-based data stream receiver <NUM>, and forwarded to the jitter determination module <NUM>.

Initial jitter data is determined by means of the initial jitter submodule <NUM> (step S2).

The initial jitter data comprises information on actual arrival times of the data packets associated with the at least one packet-based data stream received.

In other words, the actual arrival times of the received data packets are determined in order to determine the initial jitter data.

Therein, one of the received data packets is selected to be a reference data packet. The actual arrival times of the data packets not selected as reference data packet may be measured relative to the arrival time of the reference data packet.

For example, the actual arrival time of the reference data packet may be set to zero. Accordingly, the actual arrival times of the data packets not selected to be the reference data packet may be smaller than zero if the corresponding packet arrives before the reference data packet, equal to zero if the corresponding packet arrives at the same time as the reference data packet, or bigger than zero if the corresponding packet arrives after the reference data packet.

This is illustrated in <FIG>, which shows a plot of the actual arrival times (labelled as "initial arrival time") of the data packets plotted against the packet sequence number.

In the particular example shown in <FIG>, the data packet with packet sequence number <NUM> is selected to be the reference data packet. However, it is to be understood that any one of the other data packets may be selected as reference data packet instead.

Expected arrival times of the received data packets not selected to be the reference data packet are determined by means of the time bias submodule <NUM> (step S3).

In general, the expected arrival times may correspond to the arrival times of the respective data packets without any perturbations present in the transmission network, i.e. without jitter or and/or global delays.

Thus, the expected arrival times may be equal to the respective sending times (i.e. the time at which the respective packet is sent by the transmitter) plus the minimum one-way delay, i.e. plus the minimum travel time of the respective data packet.

This is illustrated in <FIG>, which shows a plot of the expected arrival times (labelled as "minimum arrival time") of the data packets plotted against the packet sequence number.

<FIG> further shows a plot of the sending times (labelled as "relative sending time") of the data packets plotted against the packet sequence number.

The expected arrival time may be a linear function that increases linearly from the actual arrival time of the reference data packet. Thus, for the reference data packet, the expected arrival time may be set to be equal to the actual arrival time.

More precisely, an expected arrival time tn of a data packet with packet number n may be determined according to the formula tn = tr + (n - r) · Tp, wherein r is the packet sequence number of the reference data packet, tr is the actual arrival time of the reference data packet, and Tp is a packet duration, i.e. the duration of one data packet in case the packet duration is the same for all packets in the packet-based data stream.

A time bias associated with the packet-based data stream is determined by means of the time bias submodule <NUM> based on determined expected arrival times of the received data packets and based on the determined actual arrival times of the data packets not selected to be the reference data packet (step S4).

In general, the actual arrival times and the expected arrival times of the data packets, particularly of the data packets not selected as a reference data packet, are compared in order to determine the time bias.

Particularly, the time bias is a maximum deviation between the expected arrival times and the actual arrival times of the data packet not selected to be the reference data packet, particularly the expected arrival times and the actual arrival times across all of the received data packets.

In other words, the respective deviation between the expected arrival time and the actual arrival time is determined for each data packet not selected to be the reference data packet.

As is illustrated in <FIG>, the time bias is determined to be the biggest one of these deviations.

Optionally, the time bias may only be determined if at least one of the actual arrival time is smaller than the corresponding expected arrival time.

Accordingly, the time bias may only be determined if there is a need to correct the jitter data, namely due to the at least one actual arrival time being before the corresponding expected arrival time. On the other hand, the time bias may not be determined if there is no need to correct the jitter data, as all actual arrival times are already equal to or after the respective expected arrival times.

Corrected jitter data is determined by means of the correction submodule based on the determined initial jitter data and the determined time bias by means of the correction submodule <NUM> (step S5).

More precisely, the determined time bias is added to the arrival times of the data packets, respectively, in order to obtain the corrected jitter data.

In other words, the arrival time of each data packet is corrected in the jitter data by adding the time bias to the respective arrival time. Accordingly, the corrected arrival time of each data packet equals the actual arrival time plus the determined time bias.

This is illustrated in <FIG>, which shows a plot of the corrected arrival times (labelled as "corrected arrival time in jitter vector") of the data packets plotted against the packet sequence number.

In the resulting corrected jitter data, no (corrected) arrival time is below the corresponding expected arrival time.

Thus, global delays are correctly accounted for in the corrected jitter data, such that no corrected arrival time is before the expected arrival time or even before the sending time.

Optionally, the corrected jitter data may only be determined if the determined time bias is above a predefined threshold. Accordingly, the initial jitter data may only be corrected if there is a need to correct the jitter data.

For example, the predefined threshold may be equal to half a data packet duration, one data packet duration, or m data packet durations, wherein m is an integer greater than or equal to two.

A quality of the packet-based data stream may be assessed based on the corrected jitter data (step S6).

It is noted that the quality of the packet-based data stream may be assessed based on the initial jitter data if the time bias has not been determined because no actual arrival time was before the expected arrival time, or if the time bias was below the predefined threshold.

The corrected jitter data comprises additional information on the time bias, and thus additional information on potential global delays of the packet-based data stream. Thus, the quality of the packet-based data stream can be assessed more precisely based on the additional information regarding the time bias.

Certain embodiments disclosed herein, particularly the respective module(s), utilize circuitry (e.g., one or more circuits) in order to implement standards, protocols, methodologies or technologies disclosed herein, operably couple two or more components, generate information, process information, analyze information, generate signals, encode/decode signals, convert signals, transmit and/or receive signals, control other devices, etc. Circuitry of any type can be used.

Claim 1:
A jitter determination method for determining jitter associated with a packet-based data stream, wherein the packet-based data stream comprises several data packets, wherein the jitter determination method comprises the following steps:
- receiving at least two data packets associated with the packet-based data stream;
- selecting one data packet of the at least two data packets to be a reference data packet;
- determining initial jitter data based on the at least two data packets, wherein the initial jitter data comprises information on actual arrival times of the at least two data packets, respectively;
- determining expected arrival times for the at least two data packets, respectively;
- determining a time bias associated with the packet-based data stream based on at least the determined expected arrival time and based on at least the actual arrival time of the data packet not selected to be the reference data packet; and
- determining corrected jitter data based on the initial jitter data and based on the determined time bias;
wherein the time bias is determined based on respective deviations between the expected arrival times and the actual arrival times of data packets not selected to be the reference data packet,
wherein the time bias is a maximum deviation between the expected arrival times and the actual arrival times of the data packets not selected to be the reference data packet, and
wherein the determined time bias is added to the arrival times of the data packets, respectively, in order to obtain the corrected jitter data.