I. Field of the Invention
The present invention relates to a digital signal protocol and process for communicating signals between a host communications device and a client audio/visual presentation device at high data rates. More specifically, the present invention relates to a technique for transferring multimedia and other types of digital signals from a wireless device to a micro-display unit or other presentation device using a low power high data rate transfer mechanism.
II. Related Art
Computers, electronic game related products, and various video technologies (for example DVD""s and High Definition VCRs) have advanced significantly over the last few years to provide for presentation of increasingly higher resolution still, video, video-on-demand, and graphics images, even when including some types of text, to end users of such equipment. These advances in turn mandated the use of higher resolution electronic viewing devices such as high definition video monitors, HDTV monitors, or specialized image projection elements. Combining such visual images with high-definition or -quality audio data, such as when using CD type sound reproduction, DVDs, and other devices also having associated audio signal outputs, is used to create a more realistic, content rich, or true multimedia experience for an end user. In addition, highly mobile, high quality sound systems and music transport mechanisms, such as MP3 players, have been developed for audio only presentations to end users.
In a typical video presentation scenario, video data is typically transferred using current techniques at a rate that could be best termed as slow or medium, being on the order of one to tens of kilobits per second. This data is then either buffered or stored in transient or longer term memory devices, for delayed (later) play out on a desired viewing device. For example, images may be transferred xe2x80x9cacrossxe2x80x9d or using the Internet using a program resident on a computer having a modem or internet connection device, to receive or transmit data useful in digitally representing an image. A similar transfer can take place using wireless devices such as portable computers equipped with wireless modems, or wireless Personal Data Assistants (PDAs), or wireless telephones.
Once received, the data is stored locally in memory elements, circuits, or devices, such as RAM or flash memory, including external storage devices, for playback. Depending on the amount of data and the image resolution, the playback might begin relatively quickly, or be presented with longer term delay. That is, in some instances, image presentation allows for a certain degree of real time playback for very small or low resolution images not requiring much data, or using some type of buffering, so that after a small delay, some material is presented while more material is being transferred. Provided there are no interruptions in the transfer link, once the presentation begins the transfer is reasonably transparent to the end user of the viewing device.
The data used to create either still images or motion video are often compressed using one of several well known techniques such as those specified by the Joint Photographic Experts Group (JPEG), the Motion Picture Experts Group (MPEG), and other well known standards organizations or companies for in the media, computer, and communications industries to speed the transfer of data over a communication link. This allows transferring images or data faster by using a smaller number of bits to transfer a given amount of information.
Once the data is transferred to a xe2x80x9clocalxe2x80x9d device such as a computer or other device, the resulting information is un-compressed (or played using special decoding players) and prepared for appropriate presentation based on the corresponding available presentation resolution and control elements. For example, a typical computer video resolution in terms of a screen resolution of X by Y pixels typically ranges from as low as 480xc3x97640, through 600xc3x97800 to 1024xc3x971024, although a variety of other resolutions are generally possible, either as desired or needed.
Image presentation is also affected by the image content and the ability of given video controllers to manipulate the image in terms of certain predefined color levels or color depth (bits per pixel used to generate colors) and intensities, and any additional overhead bits being employed. For example, a typical computer presentation would anticipate anywhere from around 8 to 32, or more, bits per pixel to represent various colors (shades and hues), although other values are encountered.
From the above values, one can see that a given screen image is going to require the transfer of anywhere from 2.45 Megabits (Mb) to around 33.55 Mb of data over the range from the lowest to highest typical resolutions and depth, respectively. When viewing video or motion type images at a rate of 30 frames per second, the amount of data required is around 73.7 to 1,006 Megabits of data per second (Mbps), or around 9.21 to 125.75 Megabytes per second (MBps). In addition, one may desire to present audio data in conjunction with images, such as for a multimedia presentation, or as a separate high resolution audio presentation, such as CD quality music. Additional signals dealing with interactive commands, controls, or signals may also be employed. Each of these options adding even more data to be transferred. In any case, when one desires to transfer high quality or high resolution image data and high quality audio information or data signals to an end user to create a content rich experience, a high data transfer rate link is required between presentation elements and the source or host device that is configured to provide such types of data.
Data rates of around 115 Kilobytes (KBps) or 920 Kilobits per second (Kbps) can be routinely handled by modern serial interfaces. Other interfaces such as USB serial interfaces, can accommodate data transfers at rates as high as 12 MBps, and specialized high speed transfers such as those configured using the Institute of Electrical and Electronics Engineers (IEEE) 1394 standard, can occur at rates on the order of 50 to 100 MBps. Unfortunately, these rates fall short of the desired high data rates discussed above which are contemplated for use with future wireless data devices and services for providing high resolution, content rich, output signals for driving portable video displays or audio devices. In addition, these interfaces require the use of a significant amount of host or system and client software to operate. Their software protocol stacks also create an undesirably large amount of overhead, especially where mobile wireless devices or telephone applications are contemplated. Furthermore, some of these interfaces utilize bulky cables which are too heavy and unsatisfactory for highly aesthetic oriented mobile applications, complex connectors which add cost, or simply consume too much power.
There are other known interfaces such as the Analog Video Graphics Array (VGA), Digital Video Interactive (DVI) or Gigabit Video Interface (GVIF) interfaces. The first two of these are parallel type interfaces which process data at higher transfer rates, but also employ heavy cables and consume large amounts of power, on the order of several watts. Neither of these characteristics are amenable to use with portable consumer electronic devices. Even the third interface consumes too much power and uses expensive or bulky connectors.
For some of the above interfaces, and other very high rate data systems/protocols or transfer mechanisms associated with data transfers for fixed installation computer equipment, there is another major drawback. To accommodate the desired data transfer rates also requires substantial amounts of power and/or operation at high current levels. This greatly reduces the usefulness of such techniques for highly mobile consumer oriented products.
Generally, to accommodate such data transfer rates using alternatives such as say optical fiber type connections and transfer elements, also requires a number of additional converters and elements that introduce much more complexity and cost, than desired for a truly commercial consumer oriented product. Aside from the generally expensive nature of optical systems as yet, their power requirements and complexity prevents general use for lightweight, low power, portable applications.
What is lacking in the industry for portable or mobile applications, is a technique to provide a high quality presentation experience, whether it be audio, video, or multimedia based, for highly mobile end users. That is, when using portable computers, wireless phones, PDAs, or other highly mobile communication devices or equipment, the current video and audio presentation systems or devices being used simply cannot deliver output at the desired high quality level. Often, the perceived quality that is lacking is the result of unobtainable high data rates needed to transfer the high quality presentation data. Therefore, a new transfer mechanism is needed to increase data throughput between host devices providing the data and client display devices or elements presenting an output to end users.
The above drawback, and others, existent in the art are addressed by embodiments of the current invention in which a new protocol and data transfer mechanism has been developed for transferring data between a host device and a recipient client device at high data rates.
An advantage of embodiments of the invention is that a technique is provided for data transfer that is low in complexity, low cost, has high reliability, fits well within the environment of use, and is very robust, while remaining very flexible.
Embodiments for the invention are directed to a Mobile Digital Data Interface (MDDI) for transferring digital data at a high rate between a host device and a client device over a communication path which employees a plurality or series of packet structures linked together to form a communication protocol for communicating a pre-selected set of digital control and presentation data between the host and client devices. The signal communications protocol or link layer is used by a physical layer of host or client link controllers. At least one link controller residing in the host device is coupled to the client device through the communications path or link, and is configured to generate, transmit, and receive packets forming the communications protocol, and to form digital presentation data into one or more types of data packets. The interface provides for bi-directional transfer of information between the host and client.
In further aspects of embodiments of the invention, at least one client link controller, or client receiver, is disposed in the client device and is coupled to the host device through the communications path or link. The client link controller is also configured to generate, transmit, and receive packets forming the communications protocol, and to form digital presentation data into one or more types of data packets. Generally, the host or link controller employs a state machine for processing data packets used in commands or certain types of signal preparation and inquiry processing, but can use a slower general purpose processor to manipulate data and some of the less complex packets used in the communication protocol. The host controller comprises one or more differential line drivers; while the client receiver comprises one or more differential line receivers coupled to the communication path.
The packets are grouped together within media frames that are communicated between the host and client devices having a pre-defined fixed length with a pre-determined number of packets having different variable lengths. The packets each comprise a packet length field, one or more packet data fields, and a cyclic redundancy check field. A Sub-frame Header Packet is transferred or positioned at the beginning of transfers of other packets from the host link controller. One or more Video Stream type packets and Audio Stream type packets are used by the communications protocol to transfer video type data and audio type data, respectively, from the host to the client over a forward link for presentation to a client device user. One or more Reverse Link Encapsulation type packets are used by the communications protocol to transfer data from the client device to the host link controller.
Filler type packets are generated by the host link controller to occupy periods of forward link transmission that do not have data. A plurality of other packets are used by the communications protocol to transfer video information. Such packets include Color Map, Bit Block Transfer, Bitmap Area Fill, Bitmap Pattern Fill, and Transparent Color Enable type packets. User-Defined Stream type packets are used by the communications protocol to transfer interface-user defined data. Keyboard Data and Pointing Device Data type packets are used by the communications protocol to transfer data to or from user input devices associated with said client device. A Link Shutdown type packet is used by the communications protocol to terminate the transfer of data in either direction over said communication path.
The communication path generally comprises or employs a cable having a series of four or more conductors and a shield. In some embodiments the link controllers comprise a USB data interface and the cable uses a USB type interface along with the other conductors. In addition, printed wires or flexible conductors can be used, as desired.
The host link controller requests display capabilities information from the client device in order to determine what type of data and data rates said client is capable of accommodating through said interface. The client link controller communicates display or presentation capabilities to the host link controller using at least one Display Capability type packet. Multiple transfer modes are used by the communications protocol with each allowing the transfer of different maximum numbers of bits of data in parallel over a given time period, with each mode selectable by negotiation between the host and client link controllers. These transfer modes are dynamically adjustable during transfer of data, and the same mode need not be used on the reverse link as is used on the forward link.
In other aspects of some embodiments of the invention, the host device comprises a wireless communications device, such as a wireless telephone, a wireless PDA, or a portable computer having a wireless modem disposed therein. A typical client device comprises a portable video display such as a micro-display device, and/or a portable audio presentation system. Furthermore, the host may use storage means or elements to store presentation or multimedia data to be transferred to be presented to a client device user.