Patent Publication Number: US-8539092-B2

Title: Video streaming using multiple channels

Description:
The present application claims the benefit of U.S. Provisional application, Ser. No. 61/079,373, filed Jul. 9, 2008, entitled “Video Streaming Using Multiple Channels.” The disclosure of this application is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The hypertext transfer protocol (HTTP) is a request/response protocol used to send data, most often text and images, from a server to a client. In conventional operation, an HTTP client sends, over the Transmission Control Protocol (TCP), a request for a specific resource to a server. The server processes the request and returns a response that includes a status or error message and, if available, the requested resource. Conventional HTTP communication sessions include a single channel between a server and a client to transmit data between the two. The channel can be used for multiple requests. 
     An HTTP connection can be used to transmit a variety of data from a server to a client. When an HTTP session is used to stream video or other data that is sensitive to delays in transmission or bandwidth available to the client, the client may receive delayed or incomplete video data. Generally, the backoff and retransmission mechanisms built into TCP can lead to undesirable delays that violate the timeliness requirement for streaming media. The client also may be required to buffer a considerable amount of video data before presenting the video to a user at an acceptable quality, in order to mitigate later-occurring effects such as communication delays or changes in available bandwidth. 
     The connectivity issues may be exacerbated given that the stream is usually received over a single channel, such structure also generally precluding the possibility of scaling or shaping the video transmission on-the-fly. Further, where on-the-fly scaling and transmission controls are implemented, they are generally server-side, and the client essentially takes what it can get. 
     Accordingly, it would be desirable to mitigate some of the transmission errors and delays currently inherent in video streaming by coordinating the stream between multiple HTTP channels, and shifting control of the stream from the servers to the clients. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified block diagram illustrating how multi-channel HTTP streaming may be employed according to an embodiment of the invention. 
         FIG. 2  illustrates a client node in connection with remote nodes. 
         FIG. 3  is a flow diagram of multi-channel HTTP streaming according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Detailed descriptions of one or more embodiments of the invention follow, examples of which may be graphically illustrated in the drawings. Each example and embodiment is provided by way of explanation of the invention, and is not meant as a limitation of the invention. For example, features described as part of one embodiment may be utilized with another embodiment to yield still a further embodiment. It is intended that the present invention include these and other modifications and variations. 
     Systems and methods for streaming video over multiple HTTP channels are provided. The client may have control over multiple channels (each associated with a distinct client port), allowing the client to control the amount and source of data received. Data requested by the client may be separated into a set of layers, with each layer being assigned to a separate channel. The client may adjust the number of layers requested based on a variety of factors. For example, as the client&#39;s available bandwidth changes, the client can drop or request additional layers. Layers may be requested from multiple remote sources, providing the client with additional control over the specific bandwidth profile of received data. 
     Embodiments of the invention may allow a client to more fully control the amount and quality of streaming video received. After requesting an initial base layer of streaming video, the client may open additional channels to request enhancement layers that provide increased quality or quantity of video. As the client encounters environmental changes such as increased or decreased processing power or bandwidth, fewer or more enhancement layers may be requested. The client may decode the base layer and as many enhancement layers as are received and may generate a recovered video signal therefrom. The recovered video signal may be output to a display device or stored for later use at the client. 
     Throughout this disclosure, reference is made to a “channel,” which may be defined as a single HTTP connection over an Internet socket. As is known, an Internet socket is generally composed of the protocol used (e.g., TCP, etc.), a local Internet Protocol (IP) address (i.e., the client&#39;s IP address), a port on the client machine, a remote IP address, and a port on the remote machine. 
       FIG. 1  is a simplified functional block diagram illustrating a system for receiving video data over multiple channels. A client node  110  may connect to one or more remote nodes  120 . Each remote node may be a server, such as a content server, or it may be a peer of the client node. The client node may receive a base layer  122  of a video stream from a remote node. Typically, the base layer includes a minimum amount of data sufficient to decode and/or provide audio/video content to a user of the client node. For example, a base layer may include video data encoded at a minimum resolution, audio data encoded at a minimum bitrate, an initial portion of a video, and/or other data sufficient to provide a base quality or quantity of content. 
     The client node also may receive one or more enhancement layers  123 ,  125  from a remote node. Enhancement layers may provide additional data to the client node that can be incorporated with the base layer to increase the quality and/or quantity of the video data. 
     Each layer received by the client node may be received over a single channel between the client node and a remote node. The ports associated with each channel may be those ports having generally standardized functions and those that are generally allocated dynamically. For example, a layer may be received over a channel comprising a remote node&#39;s TCP port  80 , which is typically reserved for HTTP data, and any of the client node&#39;s port numbers other than 0-1023, which are generally reserved by the operating system and various applications. Other TCP ports may be used. Typically, each layer is received over a separate port, though a specific port may be used to receive a first layer during one time domain, and a second layer during another time domain (i.e., a particular layer is not mapped—beyond a session—to a particular port). Each layer may be provided by a separate remote node, or a single remote node may provide multiple layers. For example, where the remote node is a content server, the content server may provide each layer to a client node as the layers are requested by the client node (i.e., the client node may not need to use multiple remote nodes to satisfy its requirements, but can instead establish multiple channels to a single remote node capable of providing the requested data). 
     To manage reception of video data over multiple channels, the client node may include a port manager  105 . The port manager can allow the client node to receive additional video layers by opening connections to additional remote nodes, and can disable the reception of layers by closing the ports over which those layers are received, effectively stopping communication with the remote nodes (over at least those particular ports). 
     The client node may manage received layers using a variety of criteria. For example, the client node may monitor the network bandwidth available to the client node; when additional bandwidth is available, the client node may request additional enhancement layers. If the client node experiences reduced bandwidth, enhancement layers may be dropped by closing the ports over which the layers are received. The client node also may request and drop enhancement layers based on input received from a user of the client node, such as where a user indicates that a higher resolution of a video stream is desired, or that he would now like to see closed-captioning information. 
     The client node also may adjust the number of requested layers based on how efficiently the client node is able to process the layers. For example, the video stream may require decoding by the client node before presentation to a user, such as where the video stream is compressed to reduce transmission bandwidth. The client node may include a processing unit  150  to decode or perform other processing of the received video stream. Data received from remote nodes may be initially processed by one or more input buffers  130 ,  135 . In an embodiment, the base layer may be processed by a first input butter  130  and enhancement layers processed by a second input buffer  135 . Multiple input buffers may be used for the enhancement layers. It will be appreciated that the number of input buffers and their association with a layer or layers may vary widely between embodiments, and that these permutations and combinations are not critical to the invention. 
     The processing unit may transmit processed video data to one or more output buffers  160 ,  165 . The output buffers may receive post-processing video data and configure it for the output  180 . For example, where the processing unit  150  provides decoded data faster than is required for display by the client node, the output buffers may store the decoded data and provide it at a rate appropriate for display by an output device  180 . Separate output buffers may be used for the base layer and for enhancement layers, if present. Multiple output buffers may be used for the enhancement layers. As with the input buffers, it will be appreciated that the number of output buffers and their association with a layer or layers may vary widely between embodiments, and that these permutations and combinations are not critical to the invention. The output  180  may be any appropriate display or interface, such as a television, monitor, projection screen, or other device. 
     The client node may include buffer monitors  140 ,  170  to track the progress of the various layers through the system. Depending on the amount and speed of data being processed, the client node may adjust the layers requested from remote nodes. For example, where too much data is received or data is received too quickly at the input buffers, the client node may drop one or more enhancement layers. Similarly, if the processing unit can successfully process more data (i.e., the input buffers are storing little data), the client node may request one or more additional layers. The client node also may adjust the number of layers requested based on data from a buffer monitor  170  that tracks the relationship between processed data and output data. For example, if the output buffers are storing a large amount of data, such as where they may be nearing capacity, the client node may drop one or more enhancement layers. If the output buffers are storing a relatively small amount of data over time, the client node may request additional enhancement layers. 
     A client node may request streaming video layers from a variety of remote nodes. In an embodiment, the remote nodes from which a client node requests streaming video layers may be network peers.  FIG. 2  shows a client node  200  in a communication network. The network may include one or more servers  210  to provide content such as streaming video. In some cases, the client node may not be able to communicate directly with the server, or it may be more efficient to communicate with peer client nodes  220 ,  224 ,  228  on the network than directly with the server  210 . In this configuration, the client node may identify and request streaming video layers from servers, peer nodes, or both. The client node may select remote nodes from which to request layers based on a variety of factors, such as available bandwidth between the client node and the remote nodes, communication latency between the various remote nodes, or the physical geography of the remote nodes. Different criteria may be applied to different layers. For example, the client node may request a base layer from the first remote node to respond to a series of requests sent to multiple remote nodes, so that the client node can begin processing the base layer as soon as possible. Similarly, the client node may request enhancement layers from the available remote nodes that are best suited to deliver them, such as where the enhancement layers are known to have much larger bandwidth requirements than the base layer. Depending on various factors affecting a remote node (e.g., available bandwidth, latency, processor load, etc.), the remote node may respond to a client node&#39;s request to create and deliver a layer in a various ways. For example, if the remote node determines it is capable of delivering the layer as requested, it may do so. However, if the remote node determines it cannot provide the layer as requested, for example due to loading or bandwidth limitations, it may refuse the request and not provide a layer at all. Alternatively, the remote node may provide a layer of a smaller size than requested, which typically involves compression at lower quality. Similarly, if the remote node determines that it is permissible to deliver a layer of larger size than requested by the client node, which typically involves higher quality coding, it may attempt to do so. In any case, the client node may accept or reject a layer provided by the remote node. 
       FIG. 3  is a flow diagram of multi-channel HTTP streaming according to an embodiment of the invention. At block  300 , a client node begins receiving a base layer of video on a first channel established between the client node and a first remote node. Depending on various factors, such as, for example, network conditions as monitored by the client node, the client node determines whether it can handle the reception of an enhancement layer, as shown at block  310 . If no, the client node continues receiving just the base layer and ultimately outputs the received video to an appropriate display or interface, as illustrated by block  340 . If the client node determines that it can receive an enhancement layer, a port manager at the client node opens a port on the client node and a second channel is established between the client node and a second remote node, as shown at block  320 . At block  330 , the client node receives both the base layer and the enhancement layer, each on a separate channel. The base layer and the enhancement layer are decoded, and the recovered video is output to an appropriate display or interface, as illustrated by block  340 . 
     Each client node may manage and monitor its own network conditions, so that the remote nodes may not need to be aware of how much data each client node can accept. For example, a client node that has a large amount of bandwidth relative to other client nodes may request a base layer and several enhancement layers, while a client node with a relatively small amount of bandwidth might request only the base layer or fewer enhancement layers. Thus, each client node is able to manage its own network resources, and the remote node can remain effectively ignorant of what the client node&#39;s capabilities and requirements are, other than that the client node needs the particular layer currently being requested. 
     Similarly, and in addition to monitoring network conditions, the client node may monitor its power conditions, and use such conditions, either alone or together with network conditions, to determine what and how much data the client node can accept. For example, if a client node is implemented in a mobile device subject to various and shifting power constraints (e.g., a discharging battery), the client node may choose to receive only a base layer; however, if the client node begins receiving constant power (e.g., from a power supply plugged into an electrical outlet), it may request to receive one or more enhancement layers. 
     The client node also may use various information about the video stream (i.e., metadata), which may be supplied together with a layer of the video stream or over a separate, independent channel, to determine which enhancement layers to request and when to request them. For example, the metadata may describe, or otherwise make known to the client node, an upcoming portion of the video that would be well served by one or more enhancement layers, and such sections may be “pre-loaded” so that they are available to the client node when playback of the video reaches the subject portion. 
     The multi-layer, multi-channel streaming techniques and their control by the client node as described herein, may allow for delivery methods not available using conventional techniques. For example, video content may be provided or sold in different qualities and through different mediums. In this configuration, the base layer may be provided at an initial cost or for no cost, and additional enhancement layers offered for additional cost. Thus, a user could instruct the client node to receive only the base layer initially, and if the user wishes to receive a higher-quality version of the streamed content, one or more enhancement layers may be requested, possibly for additional cost. Thus, each user or client node can select the quality level appropriate for the viewing device, user desires, or other constraint. 
     For example, the base layer may be sold on an optical disc (e.g., a DVD) or other medium, and the user of the client node may be given the option to view enhancement layers for additional cost. Such an implementation may be advantageous to a user who wishes to watch the majority of a movie at only a base-layer quality, but who wants to receive at least part of the movie at an enhanced quality (which may be more expensive). It will be appreciated that in such a configuration, the base layer, received from, for example, a DVD, may not reach the processing unit via the port manager, but rather by way of some other communication mechanism adapted for the particular medium. 
     As described herein, the client node communicates with remote nodes using multiple channels, and this configuration may provide advantages over both other protocols and conventional single-channel HTTP streaming techniques. The use of HTTP may simplify client node design, since it is a common and well-utilized protocol. It may also provide enhanced control for client nodes when compared to conventional streaming techniques that use a single channel for communications and thus force requests and responses to occur in series. In contrast, the multi-channel streaming systems and methods described herein allow multiple layers to be requested and managed in parallel, providing greater flexibility to the client node. 
     Multi-channel HTTP streaming as described herein, including the shifting of much of the control of the stream(s) to the client node, shall not hinder a remote node&#39;s ability to dynamically load-balance the bandwidth used by the remote node. For example, if many client nodes are requesting enhancement layers and the resulting total bandwidth used to provide the enhancement layers is undesirable, the remote node may block some of the enhancement layers and force some or all users to connect at a lower bandwidth cost. The remote node may allow some clients to use enhancement layers and restrict other client nodes to base layers, or client nodes may be allotted a specific amount of bandwidth and restricted to base and enhancement layers that can fit in the allotted bandwidth. Other techniques and algorithms may be used. 
     The various computer systems described herein may each include a storage component for storing machine-readable instructions for performing the various processes as described and illustrated. The storage component may be any type of machine-readable medium (i.e., one capable of being read by a machine) such as hard drive memory, flash memory, floppy disk memory, optically-encoded memory (e.g., a compact disk, DVD-ROM, DVD±R, CD-ROM, CD±R, holographic disk), a thermomechanical memory (e.g., scanning-probe-based data-storage), or any type of machine readable (computer-readable) storing medium. Each computer system may also include addressable memory (e.g., random access memory, cache memory) to store data and/or sets of instructions that may be included within, or be generated by, the machine-readable instructions when they are executed by a processor on the respective platform. The methods and systems described herein may also be implemented as machine-readable instructions stored on or embodied in any of the above-described storage mechanisms. 
     The sequence and numbering of blocks depicted in  FIG. 3  is not intended to imply an order of operations to the exclusion of other possibilities. Although the present invention has been described with reference to particular examples and embodiments, it is understood that the present invention is not limited to those examples and embodiments. The present invention as claimed therefore includes variations from the specific examples and embodiments described herein, as will be apparent to one of skill in the art.