Patent Publication Number: US-6990202-B2

Title: Packetizing devices for secure scalable data streaming

Description:
TECHNICAL FIELD 
     The present claimed invention relates to the field of streaming media data, particularly scalably encoded and progressively encrypted data. More specifically, the present claimed invention relates to the packetizing of such data. 
     BACKGROUND ART 
     Wireless streaming environments present many challenges for the system designer. For instance, clients can have different display, power, communication, and computational capabilities. In addition, wireless communication links can have different maximum bandwidths, quality levels, and time-varying characteristics. A successful wireless video streaming system must be able to stream video to heterogeneous clients over time-varying wireless communication links, and this streaming must be performed in a scalable and secure manner. Scalability is needed to enable streaming to a multitude of clients with different device capabilities. Security is particularly important in wireless networks to protect content from eavesdroppers. 
     In order to achieve scalability and efficiency in wireless streaming environments, one must be able to easily adapt or transcode the compressed video stream at intermediate network nodes. A transcoder takes a compressed video system as the input, then processes it to produce another compressed video stream as the output. Sample transcoding operations include bitrate reduction, rate shaping, spatial downsampling, frame rate reduction, and changing compression formats. Network transcoding can improve system scalability and efficiency, for example, by adapting the spatial resolution of a video stream for a particular client&#39;s display capabilities or by dynamically adjusting the bitrate of a video stream to match a wireless channel&#39;s time-varying characteristics. 
     While network transcoding facilitates scalability in video streaming systems, it also presents a number of challenges. First, while computationally efficient transcoding algorithms have been developed, even these are not well-suited for processing hundreds or thousands of streams at intermediate wired network nodes or even a few streams at intermediate low-power wireless networking relay nodes. Furthermore, network transcoding poses a serious threat to the security of the streaming system because conventional transcoding operations performed on encrypted streams generally require decrypting the stream, transcoding the decrypted stream, and then re-encrypting the result. Because every transcoder must decrypt the stream, each network transcoding node presents a possible breach in the security of the entire system. 
     More specifically, in conventional video streaming approaches employing application-level encryption, video is first encoded into a bitstream using interframe compression algorithms. These algorithms include, for example, the Moving Picture Experts Group (MPEG) standard, the International Telecommunications Union (ITU) standard, H.263, or intraframe compression algorithms such as, for example, the Joint Photographic Experts Group (JPEG) or JPEG2000 standards. The resulting bitstream is then encrypted, and the resulting encrypted stream is packetized and transmitted over the network using a transport protocol such as user datagram protocol (UDP). Prior Art  FIG. 1  is a block diagram  100  which illustrates the order in which conventional application-level encryption is performed (e.g., Encode  102 , Encrypt  104 , and Packetize  106 ). One difficulty with this conventional approach arises when a packet is lost. Specifically, error recovery is difficult because without the data from the lost packet, decryption and/or decoding may be difficult if not impossible. 
     Prior Art  FIG. 2  is a block diagram  200  illustrating another conventional secure video streaming system that uses network-level encryption (e.g., Encode  202 , Packetize  204 , and Encrypt  206  ). The system of Prior Art  FIG. 2  can use the same video compression algorithms as the system of Prior Art  FIG. 1 . However, in the system of Prior Art  FIG. 2 , the packetization can be performed in a manner that considers the content of the coded video and thus results in better error recovery, a concept known to the networking community as application-level framing. For example, a common approach is to use MPEG compression with the real-time transport protocol (RTP) which is built on UDP. RTP provides streaming parameters such as time stamps, and suggests methods for packetizing MPEG payload data to ease error recovery in the case of lost or delayed packets. However, error recovery is still difficult and, without data from a lost packet, decryption and/or decoding is still difficult if not impossible. 
     Both of the conventional approaches of Prior Art  FIG. 1  and Prior Art  FIG. 2  are secure in that they transport the video data in encrypted form. However, with these conventional approaches, if network transcoding is needed, it must be performed in accordance with the method of Prior Art  FIG. 3 . That is, as shown in block diagram  300 , the necessary transcoding operation is a decrypt  302 , decode  304 , process  306 , re-encode  308 , and re-encrypt  310  process. As shown in the block diagram  400  of Prior Art  FIG. 4 , in another conventional approach, the computational requirements of the operation of Prior Art  FIG. 3  are reduced to a decrypt  402 , transcode  404 , and re-encrypt  406  process. Specifically, this computational reduction is achieved by incorporating an efficient transcoding algorithm (e.g., transcode module  404 ) in place of the decode  304 , process  306 , and re-encode  308  modules of Prior Art  FIG. 3 . However, even such improved conventional transcoding algorithms have computational requirements that are not well-suited for transcoding many streams in a network node. Furthermore, a more critical drawback stems from the basic need to decrypt the stream for every transcoding operation. As mentioned above, each time the stream is decrypted, it opens another possible attack point and thus increases the vulnerability of the system. Thus, each transcoder further threatens the security of the overall system. 
     As yet another concern, wireless streaming systems are limited by wireless bandwidth and client resources. Wireless bandwidth is scarce because of its shared nature and the fundamental limitations of the wireless spectrum. Client resources are often practically limited by power constraints and by display, communication, and computational capabilities. As an example, wireless transmission and even wireless reception alone typically consume large power budgets. In order to make the most efficient use of wireless bandwidth and client resources, it is desirable to send clients the lowest bandwidth video streams that match their display and communication capabilities. In wireless streaming systems where a sender streams video to a number of heterogeneous clients with different resources, network transcoders can be used to help achieve end-to-end system efficiency and scalability. 
     In hybrid wired/wireless networks, it is often necessary to simultaneously stream video to fixed clients on a wired network and to mobile clients on a wireless network. In such a hybrid system, it may often be desirable to send a full-bandwidth, high-resolution video stream to the fixed wired client, and a lower-bandwidth, medium-resolution video stream to the mobile wireless receiver. Conventional video streaming approaches, however, do not achieve the efficiency, security, and scalability necessary to readily accommodate the video streaming corresponding to hybrid wired/wireless networks. 
     Yet another example of the drawbacks associated with conventional video streaming approaches is demonstrated in conjunction with wireless appliance networks. In many wireless appliance networks, mobile senders and receivers communicate with one another over wireless links. A sender&#39;s coverage area is limited by the power of the transmitted signal. Relay devices can be used to extend the wireless coverage area when intended receivers are beyond the immediate coverage area of the sender. However, in the case of heterogeneous clients within the same wireless network, it may be desired to provide a higher bandwidth, high-resolution video stream to the high power wireless receivers, and a lower bandwidth, low-resolution video stream to the low power wireless receivers. Once again, conventional video streaming approaches do not achieve the efficiency, security, and scalability necessary to readily accommodate such video streaming demands in wireless appliance networks. 
     Although the above-listed discussion specifically mentions the shortcomings of prior art approaches with respect to the streaming of video data, such shortcomings are not limited solely to the streaming of video data. Instead, the problems of the prior art span various types of media including, but not limited to, audio-based data, image-based data, graphic data, web page-based data, and the like. 
     Accordingly, what is needed is a method and/or system that can allow media data to be streamed in a secure and computationally efficient manner. What is also needed is a method and/or system that can satisfy the above need and that can also allow media data to be streamed to heterogeneous clients (“receiving nodes”) that may have different display, power, communication and computational capabilities and characteristics. The present invention provides a novel solution to these needs. 
     DISCLOSURE OF THE INVENTION 
     The present invention provides, in one embodiment, a secure and computationally efficient method and system allowing media data to be streamed to a variety of receiving nodes having different capabilities and characteristics. In another embodiment, the present invention provides a secure and computationally efficient method and system for allowing media data to be streamed according to attributes of the communication channel. These and other technical advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments that are illustrated in the various drawing figures. 
     The present invention pertains to a device and method thereof for packetizing scalably encoded and progressively encrypted data. The data can be any type of media data including video data, audio data, image data, graphic data, and web page data. 
     The packetizing device includes a receiver adapted to receive a stream of data from an encoding and encrypting device, in which some or all of the data are scalably encoded and progressively encrypted. The device also includes a packetizer adapted to packetize some or all of the data into secure and scalable data packets. In one embodiment, the device includes a memory unit for storing the data received from the encoding and encrypting device prior to packetization of the data. In another embodiment, the device includes a memory unit for storing the secure and scalable data packets. In yet another embodiment, the device includes a transmitter for transmitting some or all of the data packets to a downstream device. 
     The packetizing device can receive data from a storage unit of the encoding and encrypting device, or the packetizing device can receive data in real time as the data are output from the encoding and encrypting device. The data may include header data and payload data. The header data includes information corresponding to the payload data, and may be encrypted or unencrypted. The information in the header data allows a transcoder to transcode secure and scalable data packets without having to decrypt and decode those data packets. 
     The packetizing device may receive all or a subset of the data processed by the encoding and encrypting device. Similarly, the packetizing device may packetize all or a subset of the encoded and encrypted data. Likewise, the packetizing device may transmit all or a subset of the secure and scalable data packets. In each of these cases, the amount of data processed by the packetizing device depends on, for example, the attributes and capabilities of downstream devices and channels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       PRIOR ART  FIG. 1  a block diagram which illustrates the order in which conventional application-level encryption is performed. 
       PRIOR ART  FIG. 2  is a block diagram which illustrates another conventional secure streaming system using network-level encryption. 
       PRIOR ART  FIG. 3  is block diagram illustrating a conventional transcoding method. 
       PRIOR ART  FIG. 4  is block diagram illustrating another conventional transcoding method. 
         FIG. 5  is a schematic diagram of an exemplary computer system used to perform steps of the present method in accordance with various embodiments of the present claimed invention. 
         FIG. 6  is a flowchart of steps performed in a secure and scalable encoding method in accordance with one embodiment of the present claimed invention. 
         FIG. 7  is a block diagram of an encoding system in accordance with one embodiment of the present claimed invention. 
         FIG. 8  is a block diagram of an encoding system having a video prediction unit coupled thereto in accordance with one embodiment of the present claimed invention. 
         FIG. 9  is a block diagram of an encoding system having a video prediction unit integral therewith in accordance with one embodiment of the present claimed invention. 
         FIG. 10A  is a schematic depiction of a frame of video data in accordance with one embodiment of the present claimed invention. 
         FIG. 10B  is a schematic depiction of the frame of video data of  FIG. 10A  after segmentation into corresponding regions in accordance with one embodiment of the present claimed invention. 
         FIG. 10C  is a schematic depiction of the frame of video data of  FIG. 10A  after segmentation into corresponding non-rectangular regions in accordance with one embodiment of the present claimed invention. 
         FIG. 10D  is a schematic depiction of the frame of video data of  FIG. 10A  after segmentation into corresponding overlapping non-rectangular regions in accordance with one embodiment of the present claimed invention. 
         FIG. 11  is a flowchart of a process for decoding data which has been securely and scalably encoded in accordance with one embodiment of the present claimed invention. 
         FIG. 12  is a block diagram of a decoding system in accordance with one embodiment of the present claimed invention. 
         FIG. 13  is a block diagram of a decoding system having a video prediction unit coupled thereto in accordance with one embodiment of the present claimed invention. 
         FIG. 14  is a block diagram of a decoding system having a video prediction unit integral therewith in accordance with one embodiment of the present claimed invention. 
         FIG. 15A  is a block diagram of an exemplary hybrid wired/wireless network upon which embodiments of the present invention may be practiced. 
         FIG. 15B  is a block diagram of an exemplary wireless network upon which embodiments of the present invention may be practiced. 
         FIG. 16  is a block diagram of a source node, an intermediate (transcoder) node, and a receiving node in accordance with one embodiment of the present invention. 
         FIG. 17  is a block diagram of one embodiment of a transcoder device upon which embodiments of the present invention may be practiced in accordance with one embodiment of the present claimed invention. 
         FIGS. 18A ,  18 B,  18 C,  18 D and  18 E are data flow diagrams illustrating various embodiments of a method for transcoding data packets in accordance with one embodiment of the present claimed invention. 
         FIG. 19  is a flowchart of a process for transcoding data packets in accordance with one embodiment of the present claimed invention. 
         FIG. 20  is a schematic representation of a data packet including header data and scalably encoded, progressively encrypted data in accordance with one embodiment of the present claimed invention. 
         FIG. 21  is a schematic representation of a data packet including scalably encoded, progressively encrypted data in accordance with one embodiment of the present claimed invention. 
         FIGS. 22A and 22B  are block diagrams of devices for encoding and encrypting data in accordance with various embodiments of the present claimed invention. 
         FIG. 23  is a flowchart of the steps in a process for encoding and encrypting data in accordance with one embodiment of the present claimed invention. 
         FIG. 24  is a flowchart of the steps in a process for packetizing data in accordance with one embodiment of the present claimed invention. 
         FIGS. 25A ,  25 B,  25 C and  25 D are block diagrams of devices for packetizing data in accordance with various embodiments of the present claimed invention. 
     
    
    
     The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted. 
     BEST MODES FOR CARRYING OUT THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as “receiving,” “segmenting,” “encoding,” “encrypting,” “storing,” “sending,” “generating,” “providing,” “packetizing” or the like, refer to the actions and processes of a computer system, or similar electronic computing device. The computer system or similar electronic computing device manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices. The present invention is also well suited to the use of other computer systems such as, for example, optical and mechanical computers. 
     Computer System Environment of the Present Secure Scalable Streaming Invention 
     With reference now to  FIG. 5 , portions of the present invention method and system are comprised of computer-readable and computer-executable instructions which reside, for example, in computer-usable media of a computer system.  FIG. 5  illustrates an exemplary computer system  500  used in accordance with one embodiment of the present secure scalable streaming invention. It is appreciated that system  500  of  FIG. 5  is exemplary only and that the present invention can operate on or within a number of different computer systems including general purpose networked computer systems, embedded computer systems, routers, switches, server devices, client devices, various intermediate devices/nodes, stand alone computer systems, and the like. Additionally, computer system  500  of  FIG. 5  is well adapted to having computer readable media such as a floppy disk, a compact disc, and the like coupled thereto. Such computer readable media are not shown coupled to computer system  500  in  FIG. 5  for purposes of clarity. 
     System  500  of  FIG. 5  includes an address/data bus  502  for communicating information, and a central processor unit  504  coupled to bus  502  for processing information and instructions. System  500  also includes data storage features such as a computer usable volatile memory  506 , e.g. random access memory (RAM), coupled to bus  502  for storing information and instructions for central processor unit  504 , computer usable non-volatile memory  508  (e.g. read only memory, ROM) coupled to bus  502  for storing static information and instructions for the central processor unit  504 , and a data storage unit  510  (e.g., a magnetic or optical disk and disk drive) coupled to bus  502  for storing information and instructions. System  500  of the present invention also includes an optional alphanumeric input device  512  including alphanumeric and function keys coupled to bus  502  for communicating information and command selections to central processor unit  504 . System  500  also optionally includes an optional cursor control device  514  coupled to bus  502  for communicating user input information and command selections to central processor unit  504 . System  500  of the present embodiment also includes an optional display device  516  coupled to bus  502  for displaying information. 
     Referring still to  FIG. 5 , optional display device  516  may be a liquid crystal device, cathode ray tube, or other display device suitable for creating graphic images and alphanumeric characters recognizable to a user. Optional cursor control device  514  allows the computer user to dynamically signal the two dimensional movement of a visible symbol (cursor) on a display screen of display device  516 . Many implementations of cursor control device  514  are known in the art including a trackball, mouse, touch pad, joystick or special keys on alphanumeric input device  512  capable of signaling movement of a given direction or manner of displacement. Alternatively, it will be appreciated that a cursor can be directed and/or activated via input from alphanumeric input device  512  using special keys and key sequence commands. The present invention is also well suited to directing a cursor by other means such as, for example, voice commands. A more detailed discussion of the present secure scalable streaming invention is found below. 
     General Description of the Present Secure Scalable Streaming Invention 
     With reference next to  FIG. 6 ,  FIG. 11 , and  FIG. 19 , flowcharts  600 ,  1100  and  1900 , respectively, illustrate exemplary steps used by the various embodiments of the present invention. Flowcharts  600 ,  1100  and  1900  include processes of the present invention which, in one embodiment, are carried out by a processor under the control of computer-readable and computer-executable instructions. The computer-readable and computer-executable instructions reside, for example, in data storage features such as computer usable volatile memory  506 , computer usable non-volatile memory  508 , and/or data storage device  510  of  FIG. 5 . The computer-readable and computer-executable instructions are used to control or operate in conjunction with, for example, central processing unit  504  of  FIG. 5 . 
     As an overview, the present invention is directed towards any data which can be scalably encoded and, specifically, any data that combine scalable encoding with progressive encryption. For purposes of the present application, scalable coding is defined as a process which takes original data as input and creates scalably coded data as output, where the scalably coded data have the property that portions of it can be used to reconstruct the original data with various quality levels. Specifically, the scalably coded data are often thought of as an embedded bitstream. The first portion of the bitstream can be used to decode a baseline-quality reconstruction of the original data, without requiring any information from the remainder of the bitstream, and progressively larger portions of the bitstream can be used to decode improved reconstructions of the original data. For purposes of the present application, progressive encryption is defined as a process which takes original data (plain text) as input and creates progressively encrypted data (cipher text) as output, where the progressively encrypted data have the property that the first portion can be decrypted alone, without requiring information from the remainder of the original data; and progressively larger portions can be decrypted with this same property, in which decryption can require data from earlier but not later portions of the bitstream. 
     Encoding Method and System 
     Although specific steps are disclosed in flowchart  600  of  FIG. 6 , such steps are exemplary. That is, the present invention is well suited to performing various other steps or variations of the steps recited in  FIG. 6 . Additionally, for purposes of clarity and brevity, the following discussion and examples will specifically deal with video data. The present invention, however, is not limited solely to use with video data. Instead, the present invention is well suited to use with audio-based data, image-based data, web page-based data, graphic data and the like (“media data”). Specifically, the present invention is directed towards any data in which scalable coding is combined with progressive encryption. In step  602  of  FIG. 6 , in one embodiment, the present invention recites receiving video data. In one embodiment, the video data are comprised of a stream of uncompressed video frames which are received by segmenter  702  of the encoder system  700  of  FIG. 7 . 
     In another embodiment of the present invention, the video data are comprised of prediction error video data generated by a video prediction unit (VPU). As shown  FIG. 8 , in one embodiment of the present invention encoder system  700  has a VPU  800  coupled thereto. VPU  800  generates and forwards prediction error video data to segmenter  702  of encoder system  700 . Although VPU  800  of  FIG. 8  is disposed outside of encoding system  700 , the present invention is also well suited to having VPU  800  integral with encoding system  700 .  FIG. 9  illustrates one embodiment of the present invention in which VPU  800  is integral with encoding system  700 . 
     With reference now to step  604  of  FIG. 6 , the present embodiment of the present invention then segments the received video data into corresponding regions.  FIG. 10A  provides a schematic depiction of a video frame  1000 . Video data corresponding to video frame  1000  are received by segmenter  702  of  FIGS. 7 ,  8 , and  9 .  FIG. 10B  depicts the same video frame  1000  after segmenter  702  has segmented video frame  1000  into corresponding regions  1002 ,  1004 ,  1006 ,  1008 ,  1010 , and  1012 . Although such a quantity and configuration of regions is shown in  FIG. 10B , such a tiling quantity and configuration is intended to be exemplary only. As one example,  FIG. 10C  illustrates another example of segmentation in which segmenter  702  has segmented video frame  100  into various non-rectangular regions  1014 ,  1016 ,  1018 ,  1020 , and  1022 . As another example,  FIG. 10D  illustrates another example of segmentation in which segmenter  702  has segmented video frame  100  into various non-rectangular and overlapping regions  1024 ,  1026 ,  1028 ,  1030 , and  1032 . The overlapping portions are denoted by dotted lines. The present invention is also well suited to an approach in which segmenter  702  has various rectangular regions configured in an overlapping arrangement. Furthermore, the present invention is also well suited to an embodiment in which the regions change from frame to frame. Such an embodiment is employed, for example, to track a foreground person as they move. 
     Referring now to step  606 , encoder  704  of  FIGS. 7 ,  8  and  9  then scalably encodes the regions into scalable video data. For purposes of the present application, scalable coding is defined as a process which takes original data as input and creates scalably coded data as output, where the scalably coded data have the property that portions of it can be used to reconstruct the original data with various quality levels. Specifically, the scalably coded data are often thought of as an embedded bitstream. The first portion of the bitstream can be used to decode a baseline-quality reconstruction of the original data, without requiring any information from the remainder of the bitstream, and progressively larger portions of the bitstream can be used to decode improved reconstructions of the original data. That is, a separate region or regions of a video frame are encoded into one or more data packets. The scalable video data generated by the present embodiment have the property that a first small portion of the data can be decoded into baseline quality video, and larger portions can be decoded into improved quality video. It is this property that allows data packets to be transcoded to lower bitrates or spatial resolutions simply by truncating the data packet. This process of truncation will be discussed in further detail below. 
     With reference still to step  606 , in one embodiment of the present invention, each region is coded by encoder  704  into two portions: header data and scalable video data. Hence, in such an embodiment, each data packet contains header data and scalable video data. The header data describe, for example, the region (e.g., the location of the region within the video frame) that the data packet represents and other information used for subsequent transcoding and decoding operations in accordance with the present invention. Furthermore, in one embodiment, the header data contain information including a series of recommended truncation points for data packet transcoders. The scalable video data contain the actual coded video. In the case of intraframe coding, the video data may be the coded pixels; while in the case of interframe coding, it may be the motion vectors and coded residuals that result from motion-compensated prediction. In the present embodiments, scalable coding techniques are used in both cases to create an embedded or scalable data packet that can be truncated to lower the resolution or fidelity of the coded video data. In still another embodiment of the present invention, the scalably encoded video data are prepared by encoder  704  without corresponding header data. 
     As recited in step  608 , the present embodiment then progressively encrypts the scalable video data to generate progressively encrypted scalable video data. That is, packetizer and encrypter  706  of  FIGS. 7 ,  8 , and  9  employ progressive encryption techniques to encrypt the scalable video data. For purposes of the present application, progressive encryption is defined as a process which takes original data (plain text) as input and creates progressively encrypted data (cipher text) as output, where the progressively encrypted data have the property that the first portion can be decrypted alone, without requiring information from the remainder of the original data; and progressively larger portions can be decrypted with this same property, in which decryption can require data from earlier but not later portions of the bitstream. Progressive encryption techniques include, for example, cipher block chains or stream ciphers. These progressive encryption methods have the property that the first portion of the data is encrypted independently, then later portions are encrypted based on earlier portions. When properly matched with scalable coding and packetization, progressive encryption preserves the ability to transcode data packets with simple data packet truncation. More specifically, progressive encryption methods have the property that smaller blocks of data are encrypted progressively. While block code encryption with small block sizes is not very secure, progressive encryption methods add a degree of security by feeding encrypted data of earlier blocks into the encryption of a later block. Decryption can then be performed progressively as well. In one embodiment, the first small block of cipher text is decrypted into plain text by itself while later blocks of cipher text depend on the decrypted plain text from earlier blocks. Thus, earlier blocks of cipher text can be decrypted without knowledge of the entire cipher text segment. This progressive nature of cipher block chains and stream ciphers matches nicely with the progressive or embedded nature of scalable coding. Although encoding system  700  depicts a combined packetizer and encrypter module  706 , such a depiction is exemplary only, as encoding system  700  of the present invention is well suited to having separate and distinct packetizer and encrypter modules. 
     In prior art approaches, entire data packets were encrypted with one long block code. As a result, decryption was not possible unless the data packet was received in its entirety. However, the present invention is using scalable data packets and it is desired to transcode the stream of scalable data packets by data packet truncation. Therefore, the present invention encrypts the data packets in a similarly progressive manner. Hence, unlike conventional approaches, the present invention is data packet loss resilient. That is, should a data packet be lost, decryption of the remaining data packets is not further complicated and is still readily achievable. This combination of scalable encoding and progressive encryption enables the advantageous transcoding operations described in detail below. 
     With reference still to step  608 , in one embodiment of the present invention, while the payload data (e.g., the scalable video data) are encrypted progressively, the header data are left unencrypted so that transcoding nodes can use this information to make transcoding decisions. For example, in one embodiment, the unencrypted header contains information such as recommended truncation points within the encrypted payload data. In another embodiment, these header data are used to achieve near rate distortion (RD)-optimal bitrate reduction by intermediate transcoding nodes. Moreover, in the present embodiment, the transcoding nodes can use the header data to make transcoding decisions without requiring decryption of the progressively encrypted scalable video data or the header data. In yet another embodiment of the present invention, the header data are encrypted to add additional security. 
     Referring now to step  610 , the present invention then packetizes the progressively encrypted scalable video data. In one embodiment, a packetizer and encrypter  706  of  FIGS. 7 ,  8 , and  9  combines and packetizes the unencrypted header data with the progressively encrypted scalable video data. The resulting secure scalable data packets are then available to be streamed to desired receivers. In another embodiment, packetizer and encrypter  706  packetizes the progressively encrypted scalable video data and the encrypted header data. Furthermore, in an embodiment which does not include header data, packetizer and encrypter  706  packetizes only the progressively encrypted scalable video data. 
     Encoding system  700  securely and scalably encodes video data. More specifically, encoding system  700  combines scalable coding with progressive encryption techniques. The resulting scalably encoded, progressively encrypted, and packetized video streams have the feature that subsequent transcoding operations such as bitrate reduction and spatial downsampling can be performed (via data packet truncation or data packet elimination, for example) without decrypting the packetized data and thus while maintaining the security of the system. The present invention is also well suited to an embodiment in which only some, but not all, of the regions formed by segmenter  702  are ultimately forwarded from encoding system  700 . As an example, in one embodiment, the foreground of a video data image is forwarded, as the background image may not have changed since a previous transmission, or perhaps the background image does not contain data of interest. 
     Decoding Method and System 
     Although specific steps are disclosed in flowchart  1100  of  FIG. 11 , such steps are exemplary. That is, the present invention is well suited to performing various other steps or variations of the steps recited in  FIG. 11 . In step  1102  of  FIG. 11 , the present invention receives a data packet containing progressively encrypted and scalably encoded video data. More specifically, decrypter  1202  of decoding system  1200  ( FIG. 12 ) receives the data packet containing progressively encrypted and scalably encoded video data. In one embodiment, the received data packet also includes header data wherein the header data provide information corresponding to the scalably encoded video data. In yet another embodiment, the received data packet also includes encrypted header data providing information corresponding to the scalably encoded video data. 
     As recited in step  1104 , the present invention then decrypts the data packet containing the progressively encrypted and scalably encoded video data to generate scalably encoded regions. That is, decrypter  1202  of  FIG. 12  decrypts the progressively encrypted and scalably encoded video data to generate scalably encoded regions. Furthermore, in an embodiment in which the received data packet includes encrypted header data, decrypter  1202  also decrypts the encrypted header data. 
     Referring now to step  1106 , the present embodiment then decodes the scalably encoded regions to provide decoded regions. As described above in conjunction with the description of encoding system  700  of  FIGS. 7 ,  8 , and  9 , a video frame  1000  as shown in  FIG. 10A  can be segmented in multiple corresponding regions  1002 ,  1004 ,  1006 ,  1008 ,  1010 , and  1012  as shown in  FIG. 10B . 
     At step  1108 , the present invention then assembles the decoded regions to provide video data. Moreover, assembler  1206  of decoding system  1200  of  FIG. 12  assembles the decoded regions to provide video data. In one embodiment of the present invention, decoding system  1200  then provides, as output, video data in the form of an uncompressed video stream. In another embodiment of the present invention, assembler  1206  outputs video data comprised of prediction error video data suitable for use by a video prediction unit (VPU). As shown  FIG. 13 , in one embodiment of the present invention, decoder system  1200  has a VPU  1300  coupled thereto. VPU  1300  uses the output of assembler  1206  to ultimately provide an uncompressed stream of video frame data. Although VPU  1300  of  FIG. 13  is disposed outside of decoding system  1200 , the present invention is also well suited to having VPU  1300  integral with decoding system  1200 .  FIG. 14  illustrates one embodiment of the present invention in which VPU  1300  is integral with decoding system  1200 . Hence, the present invention provides a method and system for decoding video data which has been securely and scalably encoded. 
     Transcoding Method and System 
       FIG. 15A  is a block diagram of an exemplary hybrid wired/wireless network  1500  upon which embodiments of the present invention may be practiced. In hybrid wired/wireless network  1500 , media (e.g., video) data are streamed to fixed clients (stationary receiving nodes) via a wired link and to mobile clients (moving receiving nodes) via a wireless link. 
     In the present embodiment, hybrid wired/wireless network  1500  includes a wired sender (source  1510 ), a wired high-resolution receiver  1520 , and a wireless medium-resolution receiver  1540 . In this system, source  1510  generates a full-bandwidth, high-resolution video stream  1550   a  that is sent to high-resolution receiver  1520 . A transcoder  1530 , placed either at source  1510 , at medium-resolution receiver  1540 , or at an intermediate node such as a wired/wireless gateway, transcodes the stream  1550   a  into a lower-bandwidth, medium-resolution video stream  1550   b  which is then sent to medium-resolution receiver  1540 . 
       FIG. 15B  is a block diagram of an exemplary wireless network  1501  (e.g., a wireless appliance network) upon which embodiments of the present invention may be practiced. In wireless appliance networks, mobile senders and receivers communicate with one another over wireless links. A sender&#39;s coverage area is limited by the power of the transmitted signal. Relay devices can be used to extend the wireless coverage area when intended receivers are beyond the immediate coverage area of the sender. In the case of heterogeneous receivers (e.g., receiving nodes having different display, power, computational, and communication characteristics and capabilities), transcoders can be used to adapt a video stream for a particular receiver or communication link. Transcoding can be performed in a relay device or in a receiver which also acts as a relay. Transcoding can also be performed by the sender or by the receiving node. 
     In the present embodiment, wireless network  1501  includes a wireless sender (source  1510 ), a high-resolution receiver and transcoder  1560 , and a medium-resolution (lower bandwidth) receiver  1540 . In wireless network  1501 , the high-resolution receiver  1560  receives and transcodes the high-resolution video stream  1550   a , and relays the resulting lower-bandwidth stream  1550   b  to the medium-resolution receiver  1540 . 
     Referring to  FIGS. 15A and 15B , both hybrid wired/wireless network  1500  and wireless network  1501  use network transcoders to transcode video streams  1550   a  into lower bandwidth streams  1550   b  that match the display capabilities of the target wireless nodes (e.g., medium-resolution receiver  1540 ). Generally speaking, these networks illustrate how network transcoding can enable efficient use of wireless spectrum and receiver resources by transcoding media (e.g., video) streams into formats better suited for transmission over particular channels and for the capabilities of the receiving nodes. 
       FIG. 16  is a block diagram of a system  1600  including a source node  1610 , an intermediate (transcoder) node  1620 , and a receiving node  1630  in accordance with one embodiment of the present invention. In this embodiment, transcoder  1620  is a separate node transposed between source node  1610  and receiving node  1630 . However, the functions performed by transcoder  1620  may instead be performed by source node  1610  or by receiving node  1630 . 
     In the present embodiment, source node  1610  encodes and/or encrypts a stream of data packets and sends these data packets to transcoder  1620 , as described above. In one embodiment, each of the data packets in the stream has a header portion and a payload portion (see  FIG. 20 , below); in another embodiment, the data packet has only a payload portion (see  FIG. 21 , below). The payload portion carries the data, while the header portion carries information that is used by transcoder  1620  to transcode the payload portion. A data packet, including the information carried by the header portion, and the transcoding method used by transcoder  1620  are further described below. In one embodiment, only the payload portion is encrypted and encoded. In another embodiment, the payload portion is encrypted and encoded, and the header portion is also encrypted. 
     In the present embodiment, transcoder  1620  performs a transcoding function on the data packets received from source node  1610 . The transcoding function performed by transcoder  1620  is described in conjunction with  FIG. 19 , below. The purpose of the transcoding function is to configure the stream of data packets according to the attributes downstream of transcoder  1620 , such as the attributes of the receiving node  1630  or the attributes of communication channel  1625  linking transcoder  1620  and receiving node  1630 . The transcoding function can include, for example, truncation of the data packets or elimination of certain data packets from the stream. In the case in which the stream is already configured for the receiving node  1630  or for communication channel  1625 , the transcoding function consists of a pass-through of the data packets in the stream without modification. 
     Of particular significance, in accordance with the present invention, transcoder  1620  performs a transcoding function without decrypting and/or decoding the data packets (specifically, the media data in the data packets). In the embodiment in which the data packets have a header portion and a payload portion, and where the header portion is encrypted, transcoder  1620  only decrypts the header portion. In either case, in comparison to a conventional transcoder, transcoder  1620  of the present invention requires less computational resources because there is no need to decrypt the media data. In addition, the present invention provides end-to-end security while enabling very low complexity transcoding to be performed at intermediate, possibly untrusted, nodes without compromising the security of the media data. 
     Continuing with reference to  FIG. 16 , transcoder  1620  has knowledge of the attributes of receiving node  1630  and/or communication channel  1625 . These attributes include, but are not limited to, the display, power, communication and computational capabilities and characteristics of receiving node  1630  or the available bandwidth on communication channel  1625 . For example, in one embodiment, transcoder  1620  receives the attribute information from receiving node  1630 , or transcoder  1620  reads this information from receiving node  1630 . In another embodiment, transcoder  1620  may be implemented as a router in a network; the router can determine if there is congestion on the next “hop” and transcode the stream of data packets accordingly. 
     In the present embodiment, after transcoding, transcoder  1620  sends the resultant stream of data packets, comprising the encoded and encrypted data packets, to receiving node  1630 . 
       FIG. 17  is a block diagram of one embodiment of a transcoder device  1620  upon which embodiments of the present invention may be practiced. In this embodiment, transcoder  1620  includes a receiver  1710  and a transmitter  1720  for receiving a stream of data packets from source node  1610  ( FIG. 16 ) and for sending a stream of data packets to receiving node  1630  ( FIG. 16 ), respectively. Receiver  1710  and transmitter  1720  are capable of either wired or wireless communication. Separate receivers and transmitters, one for wired communication and one for wireless communication, may also be used. It is appreciated that receiver  1710  and transmitter  1720  may be integrated as a single device (e.g., a transceiver). 
     Continuing with reference to  FIG. 17 , transcoder device  1620  may include an optional controller  1730  (e.g., a processor or microprocessor), an optional decrypter  1740 , and an optional memory  1750 , or a combination thereof. In one embodiment, decrypter  1740  is used to decrypt header information. In another embodiment, memory  1750  is used to accumulate data packets received from source node  1610  before they are forwarded to receiving node  1630  ( FIG. 16 ). 
       FIGS. 18A ,  18 B,  18 C,  18 D and  18 E are data flow diagrams illustrating various embodiments of a method for transcoding data packets in accordance with the present invention. In the embodiments of  FIGS. 18A–18D , the data packets each have a header portion and a payload portion; in the embodiment of  FIG. 18E , the data packets do not have a header portion. In each of the embodiments of  FIGS. 18A–18E , the data packets (specifically, the media data) are encrypted and may be encoded. The embodiments of  FIGS. 18A–18E  are separately described in order to more clearly describe certain aspects of the present invention; however, it is appreciated that the present invention may be implemented by combining elements of these embodiments. 
     In accordance with the present invention, the method for transcoding data packets is performed on the encrypted data packets; that is, the media data are not decrypted. Transcoding functions can include truncation of the data packets (specifically, the payload portions of the data packets), eliminating certain data packets from the stream, or passing the data packets through without modification. 
     With reference first to  FIG. 18A , incoming encrypted and/or encoded data packets are received by transcoder  1620 . In this embodiment, the header portion of each data packet is not encrypted. Transcoder  1620  reads the header portion, which contains information that can be used to make transcoding decisions. In one embodiment, the information in the header portion includes specification of the truncation points. In another embodiment, the truncation points are derived from the information provided in the header. 
     For example, the header portion may contain information specifying recommended points (e.g., a number of a bit) for truncating the payload portion of the data packets. It is appreciated that each data packet may have a different truncation point. The recommended truncation point can be selected using a variety of techniques. In one embodiment, the truncation point for each data packet is specified according to an analysis such as a rate-distortion (RD) analysis, so that the stream of data packets can be compressed to a rate that is RD optimal or near-RD optimal. In another embodiment, the header portion contains information that describes the RD curves generated by the RD analysis, and the truncation points are derived from further analysis of the RD curves. 
     In the present embodiment, RD optimal coding is achieved by generating an RD plot for each region of a video image, and then operating on all regions at the same slope that generates the desired total bitrate. Near optimal transcoding can be achieved at the data packet level by placing the optimal RD cutoff points for a number of quality levels in the header portions of the data packets. Then, transcoder  1620  ( FIG. 16 ) can truncate each packet at the appropriate cutoff point; thus, the resulting packets will contain the appropriate number of bits for each region of the image for the desired quality level. Transcoder  1620  reads each packet header, then truncates the packet at the appropriate point. For example, if three regions in an image are coded into separate packets, for each region three RD optimal truncation points are identified and their locations placed in the respective packet header. Transcoder  1620  can choose to operate at any of the three RD points (or points in between), and then can truncate each packet at the appropriate cutoff point. 
     The header portion may also contain information identifying each data packet by number, for example. Accordingly, transcoder  1620  can eliminate certain data packets from the stream; for example, if every other packet is to be eliminated (e.g., the odd-numbered packets), transcoder  1620  can use the header information to identify the odd-numbered data packets and eliminate those from the stream of data packets. 
     The embodiment of  FIG. 18B  is similar to that of  FIG. 18A , except that the header portion of each data packet is encrypted. In this case, transcoder  1620  first decrypts the header portion before reading the header information and operating on the stream of data packets as described above. 
     In the embodiment of  FIG. 18C , data packets are accumulated in memory. That is, instead of a first-in/first-out type of approach, a subset of the data packets in the stream is accumulated and stored in memory (e.g., memory  1750  of  FIG. 17 ) before they are forwarded to the receiving node. In this embodiment, the header information for all of the accumulated data packets in the subset is used to make transcoding decisions. The transcoding decisions are made based on the attributes of the receiving node  1630  or the attributes of the communication channel  1625  ( FIG. 16 ), as described previously herein. It may be possible, and perhaps desirable, to configure the stream of data packets according to the attributes of the receiving node or communication channel without operating on every data packet in the stream. For example, instead of truncating all of the data packets in the subset, a decision may be made to truncate only a portion of the packets in the subset, or to truncate the packets at a point other than the recommended truncation point. 
     In the embodiment of  FIG. 18D , transcoder  1620  receives information from the downstream receiving node (e.g., receiving node  1630  of  FIG. 16 ). In one embodiment, the information describes attributes of receiving node  1630 , such as its display, power, computational and communication capabilities and characteristics. Based on the information received from receiving node  1630 , transcoder  1620  can make transcoding decisions based on the information in the header portions of the data packets. For example, transcoder  1620  can pick a truncation point depending on whether receiving node  1630  is a medium- or low-resolution device, and transcoder  1620  can choose not to modify the stream of data packets if receiving node  1630  is a high-resolution device. Similarly, transcoder  1620  can receive information describing the attributes of communication channel  1625  ( FIG. 16 ). 
     In the embodiment of  FIG. 18E , the incoming data packets do not have a header portion. Accordingly, transcoder  1620  makes transcoding decisions based on a pre-defined set of rules. That is, instead of truncating each data packet at a different point specified by the information in the header portion, transcoder  1620  may truncate all data packets in the stream at the same point, depending on the attributes of the receiving node or communication channel. 
       FIG. 19  is a flowchart of the steps in a process  1900  for transcoding data packets in accordance with one embodiment of the present invention. In one embodiment, process  1900  is implemented by transcoder device  1620  ( FIG. 17 ) as computer-readable program instructions stored in memory  1750  and executed by controller  1730 . Although specific steps are disclosed in of  FIG. 19 , such steps are exemplary. That is, the present invention is well suited to performing various other steps or variations of the steps recited in  FIG. 19 . 
     In step  1910  of  FIG. 19 , a stream of data packets is received from a source node (e.g., source  1610  of  FIG. 16 ). In the present embodiment, the data packets include encrypted data. In one embodiment, the data are also encoded. In another embodiment, the data packets include a header portion and a payload portion. In one embodiment, the header portion is also encrypted. 
     In step  1915  of  FIG. 19 , in one embodiment, information describing the attributes of a downstream receiving node (e.g., receiving node  1630  of  FIG. 16 ) or communication channel (e.g., communication channel  1625  of  FIG. 16 ) is received. In another embodiment, the attributes of receiving node  1630  or communication channel  1625  are already known. 
     In step  1920  of  FIG. 19 , a transcoding function is performed on the stream of data packets to configure the stream according to the attributes of receiving node  1630 . Significantly, the transcoding function is performed without decrypting the data in the data packets. In one embodiment, the transcoding function is performed on information provided by the header portion of each data packet. In one such embodiment, the header information provides recommended truncation points for the payload portion of the respective data packet. In another embodiment, the truncation points are derived from the information provided in the header portion. 
     In step  1922 , in one embodiment, the transcoding function eliminates certain data packets from the stream. In step  1924 , in one embodiment, the transcoding function truncates the data in the data packets. It is appreciated that each data packet may have a different truncation point. In step  1926 , in one embodiment, the transcoding function passes the data packets through without modification. 
     In step  1930 , the transcoded data packets (still encrypted and/or encoded) are sent to receiving node  1630 . 
     In summary, the above-listed embodiment of the present invention provides a secure method and system for transcoding data for a variety of downstream attributes, such as the attributes of receiving nodes having different capabilities and characteristics or the attributes of the communication between the transcoder and a receiving node. Because the encrypted data do not need to be decrypted and then encrypted again, the computational resources needed for transcoding the stream of data packets is significantly reduced, and the security of the data is not compromised. 
     Secure Scalable Data Packet 
     With reference now to  FIG. 20 , a schematic representation of a data packet  2000  formed in accordance with one embodiment of the present invention is shown. Furthermore, as mentioned above, for purposes of clarity and brevity, the following discussion and examples will specifically deal with video data. The present invention, however, is not limited solely to use with video data. Instead, the present invention is well suited to use with audio-based data, image-based data, web page-based data, and the like. It will be understood that in the present embodiments, data packet  2000  is generated by encoding system  700  of  FIGS. 7 ,  8 , and  9 , operated on by transcoder  1620  of  FIGS. 16 ,  18 A,  18 B,  18 C,  18 D, and  18 E, and then ultimately forwarded to decoding system  1200  of  FIGS. 12 ,  13 , and  14 . During the aforementioned process, data packet  2000  is stored on computer readable media residing in, and causes a functional change or directs the operation of, the devices (e.g., general purpose networked computer systems, embedded computer systems, routers, switches, server devices, client devices, various intermediate devices/nodes, stand alone computer systems, and the like) in which, for example, transcoder  1620  and/or decoder  1200  are implemented. 
     In the embodiment of  FIG. 20 , data packet  2000  includes header data portion  2002  and scalably encoded, progressively encrypted video data portion  2004 . As mentioned above, header data portion  2002  includes information that is used by transcoder  1620  to transcode the scalably encoded, progressively encrypted video data portion  2004 . For example, header data portion  2002  may contain information specifying recommended points (e.g., a number of a bit) for truncating the payload portion (e.g., the scalably encoded, progressively encrypted video data portion  2004 ) of data packet  2000 . Header data portion  2002  may also contain information identifying each data packet by number, for example. Accordingly, transcoder  1620  can eliminate certain data packets from the stream; for example, if every other packet is to be eliminated (e.g., the odd-numbered packets), transcoder  1620  can use the information in header data portion  2002  to identify the odd-numbered data packets and eliminate those from the stream of data packets. 
     With reference still to  FIG. 20 , data packet  2000  also includes potential truncation points  2006 ,  2008 , and  2010  within scalably encoded, progressively encrypted video data portion  2004 . Although such truncation points are shown in  FIG. 20 , the configuration of truncation points  2006 ,  2008 , and  2010  is exemplary only. That is, the present invention is well suited to having a lesser or greater number of truncation points, and to having the truncation points located other than where shown in  FIG. 20 . Again, as mentioned above, truncation points  2006 ,  2008 , and  2010  are used by transcoder  1620  during its operation on packet  2000 . Additionally, in one embodiment of the present invention, header data portion  2002  is encrypted. 
     In the embodiment of  FIG. 21 , data packet  2100  does not include a header data portion, and instead includes only scalably encoded, progressively encrypted video data portion  2104 . With reference still to  FIG. 21 , data packet  2100  also includes potential truncation points  2104 ,  2106 , and  2108  within scalably encoded, progressively encrypted video data portion  2104 . Although such truncation points are shown in  FIG. 21 , the configuration of truncation points  2104 ,  2106 , and  2108 , is exemplary only. That is, the present invention is well suited to having a lesser or greater number of truncation points, and to having the truncation points located other than where shown in  FIG. 21 . Again, as mentioned above, truncation points  2104 ,  2106 , and  2108  are used by transcoder  1620  during its operation on packet  2100 . 
     Thus, the present invention provides, in one embodiment, a secure and scalable encoding method and system for use in the streaming of data. The present invention further provides, in one embodiment, a method for decoding data which has been securely and scalably encoded. 
     Encoding and Encrypting Devices for Secure Scalable Data Streaming 
       FIG. 22A  is a block diagram of a device  2200  for scalably encoding and progressively encrypting data in accordance with one embodiment of the present claimed invention. As an overview, the present invention is directed towards any data which can be scalably encoded and, specifically, any data that combine scalable encoding with progressive encryption. For purposes of the present application, scalable coding is defined as a process which takes original data as input and creates scalably coded data as output, where the scalably coded data have the property that portions of it can be used to reconstruct the original data with various quality levels. Specifically, the scalably coded data are often thought of as an embedded bitstream. The first portion of the bitstream can be used to decode a baseline-quality reconstruction of the original data, without requiring any information from the remainder of the bitstream, and progressively larger portions of the bitstream can be used to decode improved reconstructions of the original data. For purposes of the present application, progressive encryption is defined as a process which takes original data (plain text) as input and creates progressively encrypted data (cipher text) as output, where the progressively encrypted data have the property that the first portion can be decrypted alone, without requiring information from the remainder of the original data; and progressively larger portions can be decrypted with this same property, in which decryption can require data from earlier but not later portions of the bitstream. 
     In the present embodiment, device  2200  includes a segmenter  2202  coupled to an encoder  2204 , which in turn is coupled to an encrypter  2206 . The functionality of device  2200  is described in conjunction with  FIG. 23 , below. 
     Significantly, in this embodiment, device  2200  of  FIG. 22A  does not include packetizing device  2208  as an integrated unit; instead, device  2200  is coupled to packetizing device  2208  disposed outside of device  2200 . As such, different types of packetization methods can be used with device  2200 , depending on the capabilities of downstream channels and devices, for example. In the present embodiment, packetizing device  2208  receives data from device  2200  in real time, that is, as the data are encoded and encrypted. 
       FIG. 22B  is a block diagram of a device  2200   a  for scalably encoding and progressively encrypting data in accordance with another embodiment of the present claimed invention. In this embodiment, device  2200   a  includes a storage unit  2210  for storing encoded and encrypted data (specifically, scalably encoded and progressively encrypted data) that are output from encoder  2206 . Thus, packetizing device  2208  can receive data from device  2200   a  in real time as the data are encoded and encrypted, or at a later time packetizing device  2208  can receive data from device  2200   a  that are stored in storage unit  2210 . In the latter case, packetizing device  2208  can receive all of or a selected portion of the data in storage unit  2210 . Thus, for example, the data can be packetized for different types of channels (e.g., channels having different bandwidth), for different types of downstream devices (e.g., receiving nodes having different display, power, computational and communication characteristics and capabilities), or using different packetization methods. Additional information is provided in conjunction with  FIG. 24 , below. 
       FIG. 23  is a flowchart of the steps in a process  2300  for encoding and encrypting data in accordance with one embodiment of the present claimed invention. Although specific steps are illustrated in  FIG. 23 , such steps are exemplary, and the present invention is well suited to performing various other steps or variations of the steps included in process  2300 . Process  2300  is, in one embodiment, carried out by a processor under the control of computer-readable and computer-executable instructions. The computer-readable and computer-executable instructions reside, for example, in data storage features such as computer usable volatile memory  506 , computer usable non-volatile memory  508 , and/or data storage device  510  of  FIG. 5 . The computer-readable and computer-executable instructions are used to control or operate in conjunction with, for example, central processing unit  504  of  FIG. 5  coupled to or integrated with device  2200  (or  2200   a ) of  FIGS. 22A and 22B . 
     For purposes of clarity and brevity, the following discussion and examples will specifically deal with video data. The present invention, however, is not limited solely to use with video data. Instead, the present invention is well suited to use with audio-based data, image-based data, web page-based data, graphic data and the like (“media data”). 
     In step  2310  of  FIG. 23 , in the present embodiment, device  2200  (or  2200   a ) receives video data comprised of a stream of uncompressed video frames. In one embodiment, the video data also are comprised of prediction error video data generated by a video prediction unit (VPU). As shown by  FIGS. 8 and 9 , respectively, the devices  2200  and  2200   a  may be coupled to a VPU or the VPU may be integral with devices  2200  and  2200   a.    
     In step  2320  of  FIG. 23 , in the present embodiment, the video data are segmented into various regions by segmenter  2202  ( FIGS. 22A and 22B ). Segmentation of video data is described above in conjunction with  FIGS. 6  (step  604 ),  10 A,  10 B,  10 C and  10 D. As described, the video data can be segmented into rectangular regions, non-rectangular regions, and overlapping regions, for example. 
     In step  2330  of  FIG. 23 , in the present embodiment, at least one of the regions (or all of the regions) are scalably encoded by encoder  2204  ( FIGS. 22A and 22B ). In one embodiment, each encoded region is encoded into two portions: a header portion comprising header data and a payload portion comprising scalable video data. The header data provide information about the video data, such as the region within the video frame that the video data represent. The header data can also include information that allows a transcoder to transcode the video data without decrypting and decoding the data, as described previously herein. Scalable encoding is described above in conjunction with  FIG. 6  (step  606 ). 
     In step  2340  of  FIG. 23 , in the present embodiment, the scalably encoded video data are progressively encrypted by encrypter  2206  ( FIGS. 22A and 22B ). In the embodiment in which data are encoded into a header portion, the header portion may or may not be encrypted. Progressive encryption is described above in conjunction with  FIG. 6  (step  608 ). 
     In step  2350  of  FIG. 23 , in one embodiment, the scalably encoded and progressively encrypted video data are stored in storage unit  2210  ( FIG. 22B ) prior to packetization. 
     In step  2360  of  FIG. 23 , in the present embodiment, the scalably encoded and progressively encrypted video data are provided to a packetizing device  2208  disposed outside of devices  2200  and  2200   a  ( FIGS. 22A and 22B ). The data can be pushed to packetizing device  2208  or pulled by packetizing device  2208 . In the embodiment in which data are not stored, the data are provided to packetizing device  2208  in real time (as the data are scalably encoded and progressively encrypted). In the embodiment in which the data are stored, the data are provided to packetizing device  2208  after storage. 
     The data provided to packetizing device  2208  may represent the entire set of data that was received by devices  2200  and  2200   a  or a portion thereof. That is, in the real time embodiment, at any one of the stages in device  2200 , the data may be reduced because of factors such as the type of channels or the type of downstream devices. Similarly, in the storage embodiment, the data may be reduced at any one of the stages in device  2200   a . Also in the storage embodiment, only a portion of the data in storage unit  2210  may be provided to packetizing device  2208 . 
     Packetizing Devices for Secure Scalable Data Streaming 
     With reference to  FIGS. 24 ,  25 A,  25 B,  25 C and  25 D, a process  2400  for packetizing data in accordance with various embodiments of the present claimed invention is described. Although specific steps are illustrated in  FIG. 24 , such steps are exemplary, and the present invention is well suited to performing various other steps or variations of the steps included in process  2400 . Process  2400  is, in one embodiment, carried out by a processor under the control of computer-readable and computer-executable instructions. Process  2400  is performed by a packetizer device disposed external to devices  2200  and  2200   a  ( FIGS. 22A and 22B , respectively). 
       FIGS. 25A–25D  show various embodiments of a packetizing device upon which process  2400  of  FIG. 24  may be implemented. Each of these embodiments includes a receiver  2502  for receiving a stream of scalably encoded and progressively encrypted data from encoding and encrypting device  2200  or  2200   a  of  FIGS. 22A and 22B , respectively. Each of these embodiments also includes a packetizer  2506  for packetizing the scalably encoded and progressively encrypted data (or a portion thereof) into data packets. Packetizing device  2208   b  of  FIG. 25B  includes a memory unit  2504  for storing scalably encoded and progressively encrypted data prior to packetization. Packetizing device  2208   c  of  FIG. 25C  includes a memory unit  2508  for storing secure and scalable data packets subsequent to packetization. Packetizing device  2208   d  of  FIG. 25D  includes a transmitter  2510  for transmitting secure and scalable data packets to a downstream device (e.g., a transcoder such as transcoder  1620  of  FIG. 17 ). Although the embodiments of  FIGS. 25A–25D  are separately described in order to more clearly illustrate certain aspects of the present invention, it is appreciated that combinations of these embodiments may also be used. 
     In step  2410  of  FIG. 24 , with reference also to  FIGS. 25A–25D , the data are streamed from encoding and encrypting device  2200  or  2200   a  to packetizing device  2208   a–d  using either a push or a pull approach. The data may be received by packetizing device  2208   a–d  either in real time as they are encoded and encrypted by device  2200  or  2200   a , or after storage on those devices. Only a portion of the data may be extracted by or sent to packetizing device  2208   a–d . For example, packetizing device  2208   a–d  may extract only the amount of data appropriate to the attributes of a downstream channel or device. 
     In one embodiment, the data received from encoding and encrypting device  2200  or  2200   a  are stored in memory unit  2504  prior to packetization. In this embodiment, packetizer  2206  may packetize only a subset of the data stored in memory unit  2504 , depending on the attributes of downstream channels or devices. 
     In step  2420  of  FIG. 24 , again with reference also to  FIGS. 25A–25D , the data received from devices  2200  and  2200   a  are formed into data packets by packetizer  2206 . In the embodiment in which the data include a header portion as well as a payload portion, the header portion (scalably encoded and either encrypted or unencrypted) is combined and packetized with the payload portion (scalably encoded and progressively encrypted). Packetizer  2208   a–d  may only packetize a subset of the data, depending on the attributes of downstream channels or devices, for example. 
     In one embodiment, the data packets received from packetizer  2206  are stored in memory unit  2508 . In this case, a subset of the data packets may be retrieved from memory unit  2508 , depending on the attributes of downstream receiving devices or channels, for example. 
     In step  2430  of  FIG. 24 , with reference also to  FIGS. 25A–25D , the secure and scaled data packets can be transmitted (streamed) to downstream receiving devices as described previously herein. In one embodiment, the data packets are transmitted to downstream devices using transmitter  2510 . As described above, only a subset of the data packets may be sent depending on downstream attributes and capabilities. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.