Electrical computers and digital processing systems: support – Clock control of data processing system – component – or data...
Reexamination Certificate
1999-12-08
2002-05-21
Butler, Dennis M. (Department: 2182)
Electrical computers and digital processing systems: support
Clock control of data processing system, component, or data...
C713S502000, C707S793000
Reexamination Certificate
active
06393578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of storage and retrieval of digital encoding information such as audio/video material. More specifically, the present invention relates to the field of retrieving contents of a recorded digital file without prior knowledge of the encoding format of the recorded digital file.
2. Related Art
Audio/visual (AV) material is increasingly stored, transmitted and rendered using digital data. Digital video representation of AV material facilitates its usage with computer controlled electronics and also facilitates high quality image and sound reproduction. Digital AV material is typically compressed (“encoded”) in order to reduce the computer resources required to store and transmit the digital data. The systems that transmit multimedia content encode and/or compress the content to use their transmission channel efficiently because the size of the multimedia content, especially video, is very large. Digital AV material can be encoded using a number of well known standards including; for example, the DV (Digital Video) standard, the MPEG (Motion Picture Expert Group) standard, the JPEG standard, the H.261 standard, the H.263 standard, the MiniDisk standard, the, CD standard and the Motion JPEG standard to name a few. As expected, the encoding standards also specify the associated decoding processes as well. The multimedia contents are typically stored on the storage media and are transmitted as bitstreams than can be packetized.
The MPEG format is a compression standard for audio, video and graphics information and includes, for example, MPEG1, 2, 4 and 7. it is standardized in the ISO-IEC/JTC1/SC29/WG11 documents. For instance, MPEG1 is the standard for encoding audio and video data for storage on CD-ROM devices(compact disc read only memory). The MPEG1 specification is described in the IS-11393 standard. The MPEG2 format is the standard for encoding, decoding and transmitting audio/video data for storage media, e.g., DVD (digital video disc), etc., and also for digital broadcasts. MPEG2 supports interlaced video and is therefore used for high quality video displaying on TV units. The MPEG2 specification is described in IS-13818. The MPEG4 standard is used for encoding, decoding and transmitting audio, video and computer graphics data. It supports content based bitstream manipulation and representation. The specification is described in IS14496. MPEG7, currently under standardization, pertains to meta information of multimedia (MM) contents. The example of the meta data is data that describes or is related to the MM contents, such as, identification and/or other descriptions of the author, producer information, directors, actors, etc. The draft specifications for MPEG7 are described in the ISO-IEC-JTC1/SC29/WG11 documents.
The H.261 and H.263 standards of compression are for audio and visual data. These standards are described by the ITU-T (International Telecommunication Union). The H.261 standard is used for TV conference systems, while the H.263 standard is used for mobile communication. The H.261 and H.263 standards adopt the hybrid coding of Motion Compensation (MC) and Discrete Cosine Transform (DCT). The details of these specifications are described in ITU-T recommendations which- are well known. JPEG is the compression standard used for still images. It is standardized in ISO-IEC/JTC1/SC29/WG1 documents. The JPEG standard uses transform coding (DCT) as is also used in the JPEG standard. The WG1 is standardizing JPEG2000, which is a more efficient encoding technology for still image processing. The JPEG2000 standard uses wavelet transformation. Motion JPEG is the defacto standard for video processing. In Motion JPEG, each frame of the video is encoded by JPEG. It is used in the Digital Video (DV) standard, which is used in the market today. Interframe correlation is not used for the compression.
Digital information encoded in any of the above discussed formats can be stored magnetically and/or optically on storage media often called “disk media.” The digital storage media can be removable, as in the case of a floppy disk or optical compact disk (CD) or the media can be non-removable such as the platters of a hard disk. A data retrieval problem occurs, however, when digital files of various encoding formats are allowed to be stored on the same disk. More specifically, it is very difficult to access a particular portion of a stored file (e.g., a particular location in time of the material) when files of different formats are stored on the same disk in part because the bit rates for the various encoding formats are different.
FIG. 1
illustrates a chart
10
of the average bit rates (bandwidth) for different MPEG-II encoding formats and also illustrates the bit rate for DV, MiniDisk and CD formats.
FIG. 1
also illustrates, for each format, the maximum storage for a storage medium having a capacity of 27.0 Gigabytes. As seen by these bit rates, different types of video and/or audio formats occupy a different amount of space on the hard drive because their bit rates are different. For instance, the first MPEG II format uses 2Mbit/sec and can store 30 hours, 1 minute on a media (with a 27 Gbyte capacity) but the last MPEG II format can store 3 hours, 6 minutes on the same media. Under a single retrieval format, the drive can use its knowledge of the bit rate for a particular file format to compute a location in time for that file. However, one disadvantage of this method is that a retrieval format for one encoding type will not work with other formats because the bit rates are different. This solution is not acceptable for disk systems that store files of different formats on the same disk.
Another problem is introduced when dealing with formats that have average bit rates, such as MPEG. For MPEG II, the bit rates specified in
FIG. 1
are only the average bit rates for the files and individual bit rates for various file portions can be larger or smaller than this value. As a result, the type of computation described above can be very inaccurate thereby requiring a degree of padding when seeking to a desired location in time of the file. For instance, if a disk drive knows that a particular file is encoded using a particular MPEG format (e.g., because the drive only stores files of one format), then it can use the average bit rate value to seek to a position near a desired playback location. However, because the bit rates are only average rates, the drive typically then seeks backward in the file some predetermined amount (“padding”) in order to ensure that the desired playback position is not missed. Unfortunately, using this prior art retrieval process, a certain amount of extra file contents (padding) are supplied to the decoder unit and then the decoder unit looks to discover the actual playback position. This generally creates an unwanted and noticeable delay in obtaining the desired file contents.
The type of delay described above can be reduced by including complex decoder circuits in each drive that can quickly seek to the desired location by decoding the file contents and seeking forward or backward for the desired location on the disk. However, this is a costly approach because a separate decoder circuit is required for each file format that the drive could accept. Not only is this approach costly, but it is not expandable to cover other, future, file formats not yet adopted or suggested.
SUMMARY OF THE INVENTION
Accordingly, what is needed is a generic disk drive storage and retrieval system that can accurately seek to a desired location in a digital file without knowing, prior, the encoding format of the file. A generic storage and retrieval system is well suited for disk systems that store files of different formats on the same disk. What is also needed is a generic storage and retrieval system that can accurately seek to the desired file location without causing a noticeable delay in obtaining the file contents. What is needed yet is a generic storage and retrieval system
Fairman Bruce Alan
Swidler Thomas Ulrich
Butler Dennis M.
Sony Corporation
Wagner , Murabito & Hao LLP
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