Patent Description:
Immersive teleconferencing provides in-person, high definition video and audio experience for conferences. It supports real-time, multi-connection streaming of the immersive video on head mounted device (HMD) devices/ video player. Immersive teleconferencing allows to experience a life-like communication with high definition video and audio services. It aims to creates an immersive experience for users participating in the conference remotely.

The VR support in multimedia telephony service for IMS (MTSI) and IMS-based telepresence enables the support of an immersive experience for remote terminals joining teleconferencing and telepresence sessions. This enables two-way audio and one-way immersive video e.g. a remote user wearing an HMD participates in a conference and receives an immersive audio and video captured by omnidirectional camera in a conference room, whereas only sends audio and optionally 2D video.

Bandwidth and other technical limitations have precluded improved delivery of immersive video with respect to viewpoint margin update as the HMD spatial orientation is updated remotely in real time. An example for a multimedia telephony service system which supports VR assets is disclosed in <NPL>. Further, the document <CIT> discloses a system for providing panoramic video content to mobile devices from an edge server. The system supports transmitting <NUM>° video content from an edge server to remote VR assets.

Therefore, there is a desire for a technical solution to such problems involving network overhead and server computational overheads.

To address one or more different technical problems, this disclosure provides technical solutions to reduce network overhead and server computational overheads while delivering immersive video with respect to one or more viewport margin updates according to exemplary embodiments.

There is included a method and apparatus comprising memory configured to store computer program code and a processor or processors configured to access the computer program code and operate as instructed by the computer program code. The computer program code includes controlling code configured to cause the at least one processor to control a delivery of a video conference call to a viewport, setting code configured to cause the at least one processor to set an event-based threshold with respect to the video conference call, determining code configured to cause the at least one processor to determine whether the event-based threshold has been triggered based on an event and whether an amount of time having elapsed from another event is less than a predetermined amount of time, further controlling code configured to cause the at least one processor to further control the delivery of the video conference call to the viewport based on determining whether the event-based threshold has been triggered and whether the amount of time having elapsed from the other event is less than the predetermined amount of time.

According to exemplary embodiments, the event-based threshold comprises at least a degree of change in a spatial orientation of the viewport.

According to exemplary embodiments, determining whether the event-based threshold has been triggered comprises determining whether the spatial orientation of the viewport has been changed by more than the degree of change of the event-based threshold.

According to exemplary embodiments, further controlling the delivery of the video conference call to the viewport comprises delivering at least an additional margin of the video conference call to the viewport in a case in which it is determined that the spatial orientation of the viewport has been changed by more than the degree of change of the event-based threshold.

According to exemplary embodiments, further controlling the delivery of the video conference call to the viewport comprises processing different length packets depending on whether a timer has been triggered or whether the event-based threshold has been triggered.

According to exemplary embodiments, wherein of the different length packets, a first packet that the timer has been triggered is longer than a second packet that the event-based threshold has been triggered.

According to exemplary embodiments, the computer program code further includes further determining code configured to cause the at least one processor to determine whether a frequency at which the event triggers the event-based threshold exceeds a frequency threshold based on whether the amount of time having elapsed from the other event is less than the predetermined amount of time.

According to exemplary embodiments, the computer program code further includes updating code configured to cause the at least one processor to update a timer in response to determining that the frequency at which the event triggers the event-based threshold exceeds the frequency threshold.

According to exemplary embodiments, the viewport is a display of at least one of a headset and a handheld mobile device (HMD).

Further features, nature, and various advantages of the disclosed subject matter will be more apparent from the following detailed description and the accompanying drawings in which:.

The proposed features discussed below may be used separately or combined in any order. Further, the embodiments may be implemented by processing circuitry (e.g., one or more processors or one or more integrated circuits). In one example, the one or more processors execute a program that is stored in a non-transitory computer-readable medium.

<FIG> illustrates a simplified block diagram of a communication system <NUM> according to an embodiment of the present disclosure. The communication system <NUM> may include at least two terminals <NUM> and <NUM> interconnected via a network <NUM>. For unidirectional transmission of data, a first terminal <NUM> may code video data at a local location for transmission to the other terminal <NUM> via the network <NUM>. The second terminal <NUM> may receive the coded video data of the other terminal from the network <NUM>, decode the coded data and display the recovered video data.

<FIG> illustrates a second pair of terminals <NUM> and <NUM> provided to support bidirectional transmission of coded video that may occur, for example, during videoconferencing. For bidirectional transmission of data, each terminal <NUM> and <NUM> may code video data captured at a local location for transmission to the other terminal via the network <NUM>. Each terminal <NUM> and <NUM> also may receive the coded video data transmitted by the other terminal, may decode the coded data and may display the recovered video data at a local display device.

In <FIG>, the terminals <NUM>, <NUM>, <NUM> and <NUM> may be illustrated as servers, personal computers and smart phones but the principles of the present disclosure are not so limited. The network <NUM> represents any number of networks that convey coded video data among the terminals <NUM>, <NUM>, <NUM> and <NUM>, including for example wireline and/or wireless communication networks. The communication network <NUM> may exchange data in circuit-switched and/or packet-switched channels. For the purposes of the present discussion, the architecture and topology of the network <NUM> may be immaterial to the operation of the present disclosure unless explained herein below.

<FIG> illustrates, as an example for an application for the disclosed subject matter, the placement of a video encoder and decoder in a streaming environment.

A streaming system may include a capture subsystem <NUM>, that can include a video source <NUM>, for example a digital camera, creating, for example, an uncompressed video sample stream <NUM>. That sample stream <NUM> may be emphasized as a high data volume when compared to encoded video bitstreams and can be processed by an encoder <NUM> coupled to the camera <NUM>. The encoder <NUM> can include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter as described in more detail below. The encoded video bitstream <NUM>, which may be emphasized as a lower data volume when compared to the sample stream, can be stored on a streaming server <NUM> for future use. One or more streaming clients <NUM> and <NUM> can access the streaming server <NUM> to retrieve copies <NUM> and <NUM> of the encoded video bitstream <NUM>. A client <NUM> can include a video decoder <NUM> which decodes the incoming copy of the encoded video bitstream <NUM> and creates an outgoing video sample stream <NUM> that can be rendered on a display <NUM> or other rendering device (not depicted). In some streaming systems, the video bitstreams <NUM>, <NUM> and <NUM> can be encoded according to certain video coding/compression standards. Examples of those standards are noted above and described further herein.

<FIG> may be a functional block diagram of a video decoder <NUM> according to an embodiment of the present invention.

A receiver <NUM> may receive one or more codec video sequences to be decoded by the decoder <NUM>; in the same or another embodiment, one coded video sequence at a time, where the decoding of each coded video sequence is independent from other coded video sequences. The coded video sequence may be received from a channel <NUM>, which may be a hardware/software link to a storage device which stores the encoded video data. The receiver <NUM> may receive the encoded video data with other data, for example, coded audio data and/or ancillary data streams, that may be forwarded to their respective using entities (not depicted). The receiver <NUM> may separate the coded video sequence from the other data. To combat network jitter, a buffer memory <NUM> may be coupled in between receiver <NUM> and entropy decoder / parser <NUM> ("parser" henceforth). When receiver <NUM> is receiving data from a store/forward device of sufficient bandwidth and controllability, or from an isosychronous network, the buffer <NUM> may not be needed, or can be small. For use on best effort packet networks such as the Internet, the buffer <NUM> may be required, can be comparatively large and can advantageously of adaptive size.

The video decoder <NUM> may include a parser <NUM> to reconstruct symbols <NUM> from the entropy coded video sequence. Categories of those symbols include information used to manage operation of the decoder <NUM>, and potentially information to control a rendering device such as a display <NUM> that is not an integral part of the decoder but can be coupled to it. The control information for the rendering device(s) may be in the form of Supplementary Enhancement Information (SEI messages) or Video Usability Information parameter set fragments (not depicted). The parser <NUM> may parse / entropy-decode the coded video sequence received. The coding of the coded video sequence can be in accordance with a video coding technology or standard, and can follow principles well known to a person skilled in the art, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and so forth. The parser <NUM> may extract from the coded video sequence, a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder, based upon at least one parameters corresponding to the group. The entropy decoder / parser may also extract from the coded video sequence information such as transform coefficients, quantizer parameter values, motion vectors, and so forth.

The parser <NUM> may perform entropy decoding / parsing operation on the video sequence received from the buffer <NUM>, so to create symbols <NUM>. The parser <NUM> may receive encoded data, and selectively decode particular symbols <NUM>. Further, the parser <NUM> may determine whether the particular symbols <NUM> are to be provided to a Motion Compensation Prediction unit <NUM>, a scaler / inverse transform unit <NUM>, an Intra Prediction Unit <NUM>, or a loop filter <NUM>.

Reconstruction of the symbols <NUM> can involve multiple different units depending on the type of the coded video picture or parts thereof (such as: inter and intra picture, inter and intra block), and other factors. Which units are involved, and how, can be controlled by the subgroup control information that was parsed from the coded video sequence by the parser <NUM>. The flow of such subgroup control information between the parser <NUM> and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder <NUM> can be conceptually subdivided into a number of functional units as described below.

A first unit is the scaler / inverse transform unit <NUM>. The scaler / inverse transform unit <NUM> receives quantized transform coefficient as well as control information, including which transform to use, block size, quantization factor, quantization scaling matrices, etc. as symbol(s) <NUM> from the parser <NUM>. It can output blocks comprising sample values, that can be input into aggregator <NUM>.

In some cases, the output samples of the scaler / inverse transform <NUM> can pertain to an intra coded block; that is: a block that is not using predictive information from previously reconstructed pictures, but can use predictive information from previously reconstructed parts of the current picture. Such predictive information can be provided by an intra picture prediction unit <NUM>. In some cases, the intra picture prediction unit <NUM> generates a block of the same size and shape of the block under reconstruction, using surrounding already reconstructed information fetched from the current (partly reconstructed) picture <NUM>. The aggregator <NUM>, in some cases, adds, on a per sample basis, the prediction information the intra prediction unit <NUM> has generated to the output sample information as provided by the scaler / inverse transform unit <NUM>.

In other cases, the output samples of the scaler / inverse transform unit <NUM> can pertain to an inter coded, and potentially motion compensated block. In such a case, a Motion Compensation Prediction unit <NUM> can access reference picture memory <NUM> to fetch samples used for prediction. After motion compensating the fetched samples in accordance with the symbols <NUM> pertaining to the block, these samples can be added by the aggregator <NUM> to the output of the scaler / inverse transform unit (in this case called the residual samples or residual signal) so to generate output sample information. The addresses within the reference picture memory form where the motion compensation unit fetches prediction samples can be controlled by motion vectors, available to the motion compensation unit in the form of symbols <NUM> that can have, for example X, Y, and reference picture components. Motion compensation also can include interpolation of sample values as fetched from the reference picture memory when subsample exact motion vectors are in use, motion vector prediction mechanisms, and so forth.

The output samples of the aggregator <NUM> can be subject to various loop filtering techniques in the loop filter unit <NUM>. Video compression technologies can include in-loop filter technologies that are controlled by parameters included in the coded video bitstream and made available to the loop filter unit <NUM> as symbols <NUM> from the parser <NUM>, but can also be responsive to meta-information obtained during the decoding of previous (in decoding order) parts of the coded picture or coded video sequence, as well as responsive to previously reconstructed and loop-filtered sample values.

The output of the loop filter unit <NUM> can be a sample stream that can be output to the render device <NUM> as well as stored in the reference picture memory <NUM> for use in future interpicture prediction.

Once a coded picture is fully reconstructed and the coded picture has been identified as a reference picture (by, for example, parser <NUM>), the current reference picture <NUM> can become part of the reference picture buffer <NUM>, and a fresh current picture memory can be reallocated before commencing the reconstruction of the following coded picture.

The video decoder <NUM> may perform decoding operations according to a predetermined video compression technology that may be documented in a standard, such as ITU-T Rec. The coded video sequence may conform to a syntax specified by the video compression technology or standard being used, in the sense that it adheres to the syntax of the video compression technology or standard, as specified in the video compression technology document or standard and specifically in the profiles document therein.

In an embodiment, the receiver <NUM> may receive additional (redundant) data with the encoded video. The additional data may be used by the video decoder <NUM> to properly decode the data and/or to more accurately reconstruct the original video data. Additional data can be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, and so on.

<FIG> may be a functional block diagram of a video encoder <NUM> according to an embodiment of the present disclosure.

The encoder <NUM> may receive video samples from a video source <NUM> (that is not part of the encoder) that may capture video image(s) to be coded by the encoder <NUM>.

The video source <NUM> may provide the source video sequence to be coded by the encoder (<NUM>) in the form of a digital video sample stream that can be of any suitable bit depth (for example: <NUM> bit, <NUM> bit, <NUM> bit,. <NUM> Y CrCB, RGB,. ) and any suitable sampling structure (for example Y CrCb <NUM>:<NUM>:<NUM>, Y CrCb <NUM>:<NUM>:<NUM>). In a media serving system, the video source <NUM> may be a storage device storing previously prepared video. In a videoconferencing system, the video source <NUM> may be a camera that captures local image information as a video sequence.

According to an embodiment, the encoder <NUM> may code and compress the pictures of the source video sequence into a coded video sequence <NUM> in real time or under any other time constraints as required by the application. Enforcing appropriate coding speed is one function of Controller <NUM>. Controller controls other functional units as described below and is functionally coupled to these units. Parameters set by controller can include rate control related parameters (picture skip, quantizer, lambda value of rate-distortion optimization techniques,. A person skilled in the art can readily identify other functions of controller <NUM> as they may pertain to video encoder <NUM> optimized for a certain system design.

Some video encoders operate in what a person skilled in the art readily recognizes as a "coding loop. " As an oversimplified description, a coding loop can consist of the encoding part of an encoder <NUM> ("source coder" henceforth) (responsible for creating symbols based on an input picture to be coded, and a reference picture(s)), and a (local) decoder <NUM> embedded in the encoder <NUM> that reconstructs the symbols to create the sample data that a (remote) decoder also would create (as any compression between symbols and coded video bitstream is lossless in the video compression technologies considered in the disclosed subject matter). That reconstructed sample stream is input to the reference picture memory <NUM>. As the decoding of a symbol stream leads to bit-exact results independent of decoder location (local or remote), the reference picture buffer content is also bit exact between local encoder and remote encoder. This fundamental principle of reference picture synchronicity (and resulting drift, if synchronicity cannot be maintained, for example because of channel errors) is well known to a person skilled in the art.

The operation of the "local" decoder <NUM> can be the same as of a "remote" decoder <NUM>, which has already been described in detail above in conjunction with <FIG>. Briefly referring also to <FIG>, however, as symbols are available and en/decoding of symbols to a coded video sequence by entropy coder <NUM> and parser <NUM> can be lossless, the entropy decoding parts of decoder <NUM>, including channel <NUM>, receiver <NUM>, buffer <NUM>, and parser <NUM> may not be fully implemented in local decoder <NUM>.

As part of its operation, the source coder <NUM> may perform motion compensated predictive coding, which codes an input frame predictively with reference to one or more previously-coded frames from the video sequence that were designated as "reference frames. " In this manner, the coding engine <NUM> codes differences between pixel blocks of an input frame and pixel blocks of reference frame(s) that may be selected as prediction reference(s) to the input frame.

The local video decoder <NUM> may decode coded video data of frames that may be designated as reference frames, based on symbols created by the source coder <NUM>. Operations of the coding engine <NUM> may advantageously be lossy processes. When the coded video data may be decoded at a video decoder (not shown in <FIG>), the reconstructed video sequence typically may be a replica of the source video sequence with some errors. The local video decoder <NUM> replicates decoding processes that may be performed by the video decoder on reference frames and may cause reconstructed reference frames to be stored in the reference picture cache <NUM>. In this manner, the encoder <NUM> may store copies of reconstructed reference frames locally that have common content as the reconstructed reference frames that will be obtained by a far-end video decoder (absent transmission errors).

The predictor <NUM> may perform prediction searches for the coding engine <NUM>. That is, for a new frame to be coded, the predictor <NUM> may search the reference picture memory <NUM> for sample data (as candidate reference pixel blocks) or certain metadata such as reference picture motion vectors, block shapes, and so on, that may serve as an appropriate prediction reference for the new pictures. The predictor <NUM> may operate on a sample block-by-pixel block basis to find appropriate prediction references. In some cases, as determined by search results obtained by the predictor <NUM>, an input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory <NUM>.

The controller <NUM> may manage coding operations of the video coder <NUM>, including, for example, setting of parameters and subgroup parameters used for encoding the video data.

Output of all aforementioned functional units may be subjected to entropy coding in the entropy coder <NUM>. The entropy coder translates the symbols as generated by the various functional units into a coded video sequence, by loss-less compressing the symbols according to technologies known to a person skilled in the art as, for example Huffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter <NUM> may buffer the coded video sequence(s) as created by the entropy coder <NUM> to prepare it for transmission via a communication channel <NUM>, which may be a hardware/software link to a storage device which would store the encoded video data. The transmitter <NUM> may merge coded video data from the video coder <NUM> with other data to be transmitted, for example, coded audio data and/or ancillary data streams (sources not shown).

The controller <NUM> may manage operation of the encoder <NUM>. During coding, the controller <NUM> may assign to each coded picture a certain coded picture type, which may affect the coding techniques that may be applied to the respective picture. For example, pictures often may be assigned as one of the following frame types:.

Source pictures commonly may be subdivided spatially into a plurality of sample blocks (for example, blocks of <NUM> x <NUM>, <NUM> x <NUM>, <NUM> x <NUM>, or <NUM> x <NUM> samples each) and coded on a block-byblock basis. Pixel blocks of P pictures may be coded non-predictively, via spatial prediction or via temporal prediction with reference to one previously coded reference pictures. Blocks of B pictures may be coded non-predictively, via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

The video coder <NUM> may perform coding operations according to a predetermined video coding technology or standard, such as ITU-T Rec. In its operation, the video coder <NUM> may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence.

In an embodiment, the transmitter <NUM> may transmit additional data with the encoded video. The source coder <NUM> may include such data as part of the coded video sequence. Additional data may comprise temporal/spatial/SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, Supplementary Enhancement Information (SEI) messages, Visual Usability Information (VUI) parameter set fragments, and so on.

<FIG> illustrates a call <NUM>, such as a <NUM>-degree conference call according to exemplary embodiments. Referring to <FIG>, a conference call is being organized in room <NUM>. The room <NUM> consists of people physically present in the room <NUM>, an omnidirectional camera <NUM> and a view screen <NUM>. Two other persons <NUM> and <NUM> join the meeting, and according to exemplary embodiments, person <NUM> may be using a VR and/or AR headset and the person <NUM> may be using a smartphone or tablet. The persons <NUM> and <NUM> receive a <NUM>-degree view of the conference room via the omnidirectional camera <NUM>, and the views received may be respective to the persons <NUM> and <NUM> which may or may not be viewing different portions of the <NUM>-degree view relative to their specific view-screen orientations for example. The remote participants, persons <NUM> and <NUM> for example, also have the option of bringing into focus each other's camera feed. In <FIG>, persons <NUM> and <NUM>, send their viewport information <NUM> and <NUM> respectively to the room <NUM>, or other networked devices relative to the omnidirectional camera <NUM> and view screen <NUM>, which in turn sends them the viewport dependent video <NUM> and <NUM> respectively.

A remote user, person <NUM> for example, wearing a head mount display (HMD) joining the conference remotely receives stereo or immersive voice/audio and immersive video from the conference room captured by an omnidirectional camera. The person <NUM> may also wear a HMD or use a handheld mobile device such as a smartphone or tablet.

According to exemplary embodiments, Omnidirectional Media format (OMAF) defines two types of media profile (i) viewport-independent, and (ii) viewport-dependent. When using a viewport-independent streaming (VIS), the whole video is transmitted at a high quality irrespective of the user's viewport. When VIS is used, no latency is experienced during the HMD movement; however the bandwidth requirement may be relatively high.

Streaming the whole high-resolution immersive videos in desirable quality may be less efficient due to the limitations on the network bandwidth, decoding complexities and the computing constraints of the end devices, since the user's field of view (FoV) may be limited. Therefore, according to exemplary embodiments viewport-dependent streaming (VDS) has been defined in Omnidirectional Media format (OMAF). When VDS is used, only the user's current viewport is streamed in high-quality, while rest is streamed at comparatively lower quality. This helps to save considerable amount of bandwidth.

While using VDS, the remote users, persons <NUM> and <NUM> for example, can send their viewport orientation information via RTCP reports. These reports can be sent at fixed intervals, event-based triggers or using a hybrid scheme comprising of the regular interval and event-based triggers.

According to exemplary embodiments, the event-based feedback is triggered whenever the viewport changes and an immediate feedback is sent. The frequency of the RTCP report will be dependent on the speed of the HMD and will increase as the HMD speed increases.

Now, if the HMD speed is large and the feedback trigger angle is relatively short, a large number of event-based RTCP reports will be generated and sent to the server. This may result in the required bandwidth exceeding the RTCP <NUM>% bandwidth limitations. For example, refer to <FIG>, for an illustration <NUM> of a point to point scenario for <NUM> Mbps video, when the feedback trigger is <NUM> degrees and the HMD speed exceed <NUM> degree per seconds, the bandwidth required for the RTCP reports to be sent exceeds the RTCP bandwidth limitation of <NUM> Mbps. <FIG> refers to event-based RTCP feedback generated per second for <NUM>, <NUM>, <NUM> and <NUM> degrees triggers.

The initial viewport orientation of the user, decoding/rendering metadata and the captured field-of-view is signaled in the session description protocol (SDP) during the call setup in addition to the normal multimedia telephony service for IMS (MTSI) call signaling, such as at S803 in <FIG>, between a conference room <NUM> and a remote user <NUM>. After the call establishment, the remote parties send their viewport orientation information via the RTCP reports.

The RTCP feedback may follow the <NUM>% bandwidth usage rule according to exemplary embodiments. Therefore, the frequency of the RTCP depends on the group size or the number of remote participants. As the group size increases, the feedback can be sent less frequently to abide by the bandwidth usage limitations. Immediate feedback can be used when the number of remote participants is small. As the number of participants increases, early RTCP feedback can be used. However, if the group size becomes large, regular RTCP feedback should be sent. As per internet engineering task force (IETF) request for comments (RFC) <NUM> the minimum transmission interval for RTCP may be five seconds. As the group size increases, the RTCP feedback interval can also increase resulting in additional delay. According to exemplary embodiments herein and for use in immersive video for example, the RTCP reports can be sent according to any of a fixed interval-basis and on an event-basis, which can be triggered by the change in viewport orientation per remote person, such as person <NUM> and/or person <NUM> in <FIG>.

According to exemplary embodiments, RTCP Feedback Packets may be compound packets which consists of a status report and feedback (FB) messages. Further, sender report (SR)/received report(RR) packets contain the status reports which are transmitted at regular intervals as a part of the compound RTCP packets which includes the sources description besides other messages.

According to exemplary embodiments, an order of the RTCP packets in the compound RTCP packets containing the FB messages are:.

In the compound packet, the FB messages may be placed after the RR and source description RTCP packets (SDES).

Two compound RTCP packets carrying feedback packets can be described: Minimal Compound RTCP feedback packet and Full compound RTCP feedback packet.

The RTCP feedback messages are specified in IETF <NUM>. It can be identified by the PT (payload type) = PSFB (<NUM>) which refers to payload-specific feedback message. According to exemplary embodiments, the feedback message may involve signaling of the viewport information for both regular interval and event based.

When any remote participant, such as one of the person <NUM> and person <NUM> in <FIG>, changes its respective viewport (such as by changing a spatial orientation of their respective display device), the RTCP viewport feedback should be timely delivered, else it would cause delay and affect the high-quality VR experience for that user. As the number of remote participants increases, the RTCP feedback interval increases. If the regular RTCP feedback interval is sent, such as on a <NUM> second basis alone, it may be delayed as the number of remote participants increases. Therefore, according to exemplary embodiments, the RTCP interval may be a combination of the regular feedback interval and an event-based interval so as to improve over such technical deficiencies.

According to exemplary embodiments, a regular RTCP feedback interval should be sent as a compound RTCP packets complying by the RTP rules where the minimum RTCP interval (Tmin) between consecutive transmission should be five seconds. This RTCP interval can be derived from the RTCP packet size and the RTCP bandwidth available. Full compound packet contains any additional RTCP packets such as additional receiver reports, additional SDES items, etc..

When the viewport changes, the event-based feedback is triggered. In this case a minimal compound RTCP packet may be sent. Minimal compound RTCP feedback packet contains only the mandatory information such as the necessary encryption prefix, exactly one SR or RR, exactly one SDES (with only CNAME item present), and the FB message(s). This helps to minimize the RTCP packet transmitted for the feedback, hence will have minimal effect on the bandwidth. The event-based feedback is not affected by the group size unlike the regular RTCP feedback interval.

When the user changes the viewport <NUM>, as in <FIG>, the event-based feedback is triggered, and the regular feedback interval should start after the minimum interval (Tmin). Now, if the user changes its viewport <NUM> before the minimum interval, the event-based feedback is triggered again. This might affect the <NUM>% bandwidth rule if these events occur successively. However, putting a minimum interval constraint on the event-based feedbacks will degrade the user's experience. Hence, there should be no minimum interval defined for the event-based feedbacks to be sent. To respect the bandwidth usage for the RTCP feedback, the interval for the regular feedbacks can be increased and therefore it should be dependent on the frequency of the event-based feedbacks and the intervals between them.

In view of exemplary embodiments described herein, the user is able to request additional higher quality margins, such as <NUM> in the illustration <NUM> of <FIG>, around the viewport <NUM> so as to minimize delay, such as an M2HQdelay, and enhance the user experience. The viewport <NUM> may be the viewport of any of the devices of remote persons <NUM> and <NUM> in <FIG>. This is significantly useful when one of the remote persons <NUM> and <NUM> is performing small head motion perturbations. However, during a call, such as at S805 in <FIG>, when the user moves his head by a (negligibly) small degree which is out of the viewport margin <NUM>, an event-based feedback should not be triggered since the out-of-margin viewport area is comparatively negligible and hence should wait for regular feedback to be transmitted. Therefore, there may be some degree of tolerance <NUM> defined for yaw, pitch and roll before an event-based feedback can be triggered, for example, see in <FIG> at S804 where tolerance information may be transmitted from the remote user <NUM> to the conference room <NUM>. This degree of tolerance <NUM>, tolerance information including an event-based feedback tolerance margin <NUM>, can be defined as one or more of a rotation angle yaw (tyaw), pitch (tpitch) and roll (troll) from the user's viewport. Such information can be negotiated during the initial SDP session S804, as in <FIG>, or in-between the session according to embodiments, such as at S806.

<FIG> illustrates a format <NUM> for such feedback messages described herein according to exemplary embodiments.

<FIG> shows an RTCP feedback message format <NUM>. In <FIG>, FMT denotes the feedback message type, whereas PT denotes the payload type. For an RTCP feedback message, the FMT may be set to value '<NUM>' whereas the PT is set to <NUM>. The FCI (feedback message control information) contains the viewport information and is composed of the following parameters: Viewport_azimuth; Viewport_elevation; Viewport_tilt; Viewport_azimuth_range; Viewport_elevation_range; Viewport_stereoscopic according to exemplary embodiments.

<FIG> illustrates a flowchart <NUM>. As S901 there is a call setup <NUM>, including initialization such as at S803 in <FIG>, and according to embodiments there is provision of information including viewport orientation of the user, decoding/rendering metadata and the captured field-of-view is signaled in the session description protocol (SDP) during the call setup in addition to the normal multimedia telephony service for IMS (MTSI) call signaling. A degree of tolerance, as described above, may be set at this S901.

After the call establishment, at S902, the remote parties send their viewport orientation information via the RTCP reports along with the beginning of the call. Then, at S903, it may be determined whether there is an event-based feedback that is triggered and whether the regular feedback interval is triggered. The regular feedback interval may be triggered by determining whether some time period has passed, such as <NUM> seconds for example, as a time-based feedback. The event-based feedback may be determined by whether a remote user's viewport has been changed in spatial orientation, and if so, whether that change is within or beyond the preset tolerance ranges, such as with respect to the tolerance margins <NUM> in <FIG>.

If the time-based feedback is determined at S905, then a compound RTCP packet may be sent. According to exemplary embodiments, a regular RTCP feedback interval should be sent as a compound RTCP packets complying by the RTP rules where the minimum RTCP interval (Tmin) between consecutive transmission should be five seconds. This RTCP interval can be derived from the RTCP packet size and the RTCP bandwidth available. Full compound packet contains any additional RTCP packets such as additional receiver reports, additional SDES items, etc. Afterwards, it may be determined at S904 whether there is a user input or other input of some update to the tolerance information, and if not, the process may loop or otherwise proceed with the call at S902 in accordance with any communications received with respect to the compound RTCP packet of S905. This S905 may also reset the timer to count another time period, such as <NUM> seconds.

If the event-based feedback is determined at S906, then a minimal RTCP packet may be sent. For example, when the viewport changes, the event-based feedback is triggered. In this case a minimal compound RTCP packet may be sent. Minimal compound RTCP feedback packet contains only the mandatory information such as the necessary encryption prefix, exactly one SR or RR, exactly one SDES (with only CNAME item present), and the FB message(s). This helps to minimize the RTCP packet transmitted for the feedback, hence will have minimal effect on the bandwidth. The event-based feedback is not affected by the group size unlike the regular RTCP feedback interval. Afterwards, it may be determined at S904 whether there is a user input or other input of some update to the tolerance information, and if not, the process may loop or otherwise proceed with the call at S902 in accordance with any communications received with respect to the minimal RTCP packet of S906. This S906 may also reset the timer to count another time period, such as <NUM> seconds. Further, it may also be determined at S904, from S906, whether to update the timer to count an increased elapsed time in a case in which it is also determined at S906 that a frequency of the event-based triggering exceeds a threshold, such as contributing to an excess of a <NUM>% bandwidth rule of RTCP for example according to embodiments such as described further with respect to <FIG>, <FIG>, <FIG>, and <FIG>.

Exemplary embodiments introduce a parameter for defining the minimum interval between two consecutive event-based RTCP feedbacks, S906 to S906 without an intermediate S905 for example, such that the bandwidth requirement does not exceed the RTCP bandwidth limitation and may be accounted for by update or otherwise at S904.

When a relatively short feedback trigger at S906 is used for a large HMD motion, the RTCP bandwidth requirement may exceed the RTCP bandwidth limitations. Hence, the bandwidth requirement for the event-based RTCP reports may be dependent on the HMD speed and the feedback trigger degree according to exemplary embodiments.

The event-based feedback interval is the time interval between two consecutive triggers. As the HMD speed increases, the event-based feedback interval decreases, resulting in increase in the bandwidth requirement. The event-based feedback can be defined as below: <MAT>.

Therefore, to limit the bandwidth requirement so as to comply by the <NUM>% RTCP rule, a threshold parameter is defined. This threshold parameter may be dependent on the event-based feedback interval.

The following assumptions may be made according to exemplary embodiments: <MAT> <MAT> <MAT> <MAT>.

The RTCP bandwidth should not exceed the <NUM>% bandwidth as per the RTCP rule. Therefore, <MAT>.

Whereas, Imin can be stated as below, <MAT>.

Assuming total bandwidth of 20Mbps, when the feedback degree is <NUM> degree and the HMD speed is over <NUM> degree/sec, the bandwidth values exceed the <NUM>% RTCP bandwidth limitations. As can be seen from the illustration <NUM> in <FIG>. However, this value is well within the limitations when the trigger increases to <NUM>, <NUM> and <NUM>.

The number of event-based RTCP feedbacks sent per second for <NUM>, <NUM>, <NUM> and <NUM> degree triggers are shown in the illustration <NUM> in <FIG>. Therefore, to respect the RTCP bandwidth limitation, exemplary embodiments may increase the RTCP event-based feedback interval and introduce a parameter Imin which can be defined as the minimum interval between two consecutive RTCP feedbacks and can be chosen such that <MAT>.

When the HMD speed increases, the number of triggers per second increases as well resulting in the decrease of the trigger interval and increase of the RTCP bitrate. When the trigger interval reaches a minimum point Imin, it should not be further decreased, and therefore the maximum number of triggers/sec is reached as in shown in the illustration <NUM> of <FIG> with the dotted curve. <FIG> refers to an event-based RTCP feedback generated per second for <NUM>, <NUM>, <NUM>, and <NUM> degrees triggers after the Imin parameter is introduced according to embodiments. This minimum point will be reached when RTCP bandwidth (RB) is close to <NUM>% of the bandwidth but not greater. Therefore, Imin parameter will be dependent on the allowed RTCP bandwidth. The bitrate before and after introduction of the I min parameter for <NUM>-degree trigger is shown in the illustration <NUM> of <FIG>. Hence, after the minimum point Imin is reached, the curve flattens.

Referring further to <FIG>, I min is calculated for a constant head speed and refers to a bit rate for <NUM> degree trigger before and after the Imin parameter is introduced according to embodiments. However due to relatively short travel time of the head, the difference between average and constant head speed is negligent.

According to exemplary embodiments, when such a hybrid reporting scheme, consisting of the regular interval and event-based triggers, is used:.

One or more of such calculations described above with respect to <FIG>, <FIG>, <FIG>, and <FIG> may be performed at S904 in <FIG>.

Accordingly, by exemplary embodiments described herein, the technical problems noted above may be advantageously improved upon by one or more of these technical solutions. For example, A parameter Imin, which is defined as the minimum interval between two consecutive triggers, should be introduced for event-based RTCP feedbacks. This helps to restrain the bandwidth requirement by limiting the number of event-based triggers sent per second. Hence, as the head motion increases and the RTCP interval reaches min (Imin) value, the bit rate is saturated and does not increase further.

The techniques described above, can be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media or by a specifically configured one or more hardware processors. For example, <FIG> shows a computer system <NUM> suitable for implementing certain embodiments of the disclosed subject matter.

The components shown in <FIG> for computer system <NUM> are exemplary in nature and are not intended to suggest any limitation as to the functionality of the computer software implementing embodiments of the present disclosure. Neither should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiment of a computer system <NUM>.

Input human interface devices may include one or more of (only one of each depicted): keyboard <NUM>, mouse <NUM>, trackpad <NUM>, touch screen <NUM>, joystick <NUM>, microphone <NUM>, scanner <NUM>, camera <NUM>.

Computer system <NUM> may also include certain human interface output devices. Such human interface output devices may include tactile output devices (for example tactile feedback by the touch-screen <NUM>, or joystick <NUM>, but there can also be tactile feedback devices that do not serve as input devices), audio output devices (such as: speakers <NUM>, headphones (not depicted)), visual output devices (such as screens <NUM> to include CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch-screen input capability, each with or without tactile feedback capability-some of which may be capable to output two dimensional visual output or more than three dimensional output through means such as stereographic output; virtual-reality glasses (not depicted), holographic displays and smoke tanks (not depicted)), and printers (not depicted).

Computer system <NUM> can also include human accessible storage devices and their associated media such as optical media including CD/DVD ROM/RW <NUM> with CD/DVD <NUM> or the like media, thumb-drive <NUM>, removable hard drive or solid state drive <NUM>, legacy magnetic media such as tape and floppy disc (not depicted), specialized ROM/ASIC/PLD based devices such as security dongles (not depicted), and the like.

Computer system <NUM> can also include interface <NUM> to one or more communication networks <NUM>. Networks <NUM> can for example be wireless, wireline, optical. Networks <NUM> can further be local, wide-area, metropolitan, vehicular and industrial, real-time, delay-tolerant, and so on. Examples of networks <NUM> include local area networks such as Ethernet, wireless LANs, cellular networks to include GSM, <NUM>, <NUM>, <NUM>, LTE and the like, TV wireline or wireless wide area digital networks to include cable TV, satellite TV, and terrestrial broadcast TV, vehicular and industrial to include CANBus, and so forth. Certain networks <NUM> commonly require external network interface adapters that attached to certain general-purpose data ports or peripheral buses (<NUM> and <NUM>) (such as, for example USB ports of the computer system <NUM>; others are commonly integrated into the core of the computer system <NUM> by attachment to a system bus as described below (for example Ethernet interface into a PC computer system or cellular network interface into a smartphone computer system). Using any of these networks <NUM>, computer system <NUM> can communicate with other entities. Such communication can be uni-directional, receive only (for example, broadcast TV), uni-directional send-only (for example CANbusto certain CANbus devices), or bi-directional, for example to other computer systems using local or wide area digital networks. Certain protocols and protocol stacks can be used on each of those networks and network interfaces as described above.

Aforementioned human interface devices, human-accessible storage devices, and network interfaces can be attached to a core <NUM> of the computer system <NUM>.

The core <NUM> can include one or more Central Processing Units (CPU) <NUM>, Graphics Processing Units (GPU) <NUM>, a graphics adapter <NUM>, specialized programmable processing units in the form of Field Programmable Gate Areas (FPGA) <NUM>, hardware accelerators for certain tasks <NUM>, and so forth. These devices, along with Read-only memory (ROM) <NUM>, Random-access memory <NUM>, internal mass storage such as internal non-user accessible hard drives, SSDs, and the like <NUM>, may be connected through a system bus <NUM>. In some computer systems, the system bus <NUM> can be accessible in the form of one or more physical plugs to enable extensions by additional CPUs, GPU, and the like. The peripheral devices can be attached either directly to the core's system bus <NUM>, or through a peripheral bus <NUM>.

CPUs <NUM>, GPUs <NUM>, FPGAs <NUM>, and accelerators <NUM> can execute certain instructions that, in combination, can make up the aforementioned computer code. That computer code can be stored in ROM <NUM> or RAM <NUM>. Transitional data can be also be stored in RAM <NUM>, whereas permanent data can be stored for example, in the internal mass storage <NUM>. Fast storage and retrieval to any of the memory devices can be enabled through the use of cache memory, that can be closely associated with one or more CPU <NUM>, GPU <NUM>, mass storage <NUM>, ROM <NUM>, RAM <NUM>, and the like.

Claim 1:
A method for viewport dependent video streaming (VDS), the method performed by at least one processor and comprising:
- sending a viewport dependent video (<NUM>) from a video capture subsystem (<NUM>) to a streaming client (<NUM>, <NUM>) having a viewport;
wherein the method is characterized in
- setting a threshold for a degree of change in a spatial orientation of the viewport;
- determining whether a degree of change in a spatial orientation of the viewport exceeds the threshold and whether an amount of time having elapsed from regularly signaling viewport information from the streaming client (<NUM>, <NUM>) to the video capture subsystem (<NUM>) is less than a predetermined amount of time; and
- signaling viewport information from the streaming client (<NUM>, <NUM>) to the video capture subsystem (<NUM>) based on determining whether the threshold for the degree of change in a spatial orientation of the viewport has been exceeded and whether the amount of time having elapsed from regularly signaling viewport information from the streaming client (<NUM>, <NUM>) to the video capture subsystem (<NUM>) is less than the predetermined amount of time.