Optical disc optical disc recording and reproducing...

Details Optical disc optical disc recording and reproducing... Optical disc optical disc recording and reproducing...

2000-03-09

2002-10-22

Boccio, Vincent (Department: 2615)

Motion video signal processing for recording or reproducing

Local trick play processing

With randomly accessible medium

C386S349000, C386S349000

Reexamination Certificate

active

06470140

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a readable and writable optical disc, and to a method for recording and a method for reproducing this optical disc. More particularly, our invention relates to an optical disc for recording multimedia data including moving picture data, still image data, and audio data, and to a method for recording and a method for reproducing this optical disc.
2. Description of the Related Art
Rewritable optical discs have for years had a maximum storage capacity of approximately 650 MB, but this has changed by the development of phase change type DVD-RAM discs with a capacity of several gigabytes. Combined with the adoption of MPEG, and particularly MPEG-2, standards for encoding digital AV data, DVD-RAM is widely anticipated as a recording and reproducing medium with applications in the AV industry, as well as the computer industry. More specifically, DVD-RAM media are expected to replace magnetic tape as the storage medium of choice for AV recordings.
A. DVD-RAM
Increases in the storage density of rewritable optical disc media over the last few years has made it possible to use such media for applications ranging from storing computer data and recording audio data to recording image data, including movies.
The signal recording surface of a conventional optical disc is typically formatted with lands and grooves, one of which is used as a guide groove for signal recording and reproducing. The data signal is then recorded using only the land or the groove. With the advent of the land and groove recording method, however, it became possible to record signals to both the land and groove. This development approximately doubled the storage capacity of the disc (see Japanese Unexamined Patent Application (kokai) 8-7282).
The further development of a zone CLV (constant linear velocity) method simplified and made it easy to implement a CLV recording and reproducing technique, which is an effective means of further increasing the recording density. (See Japanese Unexamined Patent Application (kokai) 7-93873).
A major topic left for future development is how to use such a potentially high capacity optical disc media to record AV data containing image data to achieve new functions and performance far surpassing conventional AV products.
With the introduction of high capacity rewritable optical disc media, optical discs are widely expected to replace conventional tape media for recording and reproducing AV content. The transition from tape to disc recording media is also expected to greatly affect both the performance and functions of AV recording and reproducing products.
One of the greatest benefits of a transition to disc is a significant improvement in random access performance. While random access to tape content is possible, it generally takes on the order of minutes to rewind a full tape. This is several orders slower than the typical seek time of optical disc media, which is on the order of at most several tens of milliseconds. Tape is therefore considered, for practical purposes, not to be a random access medium.
The random access capability of optical disc media has also made possible distributed, that is, noncontiguous, recording of AV data, which is not possible with conventional tape.
FIG. 38
is a block diagram of the drive device of a DVD recorder. As shown in
FIG. 38
, this DVD recorder comprises an optical pickup
11
for reading data from a disc
10
, an ECC (error correction code) processor
12
, track buffer
13
, switch
14
for changing between track buffer input/output, encoder
15
, and decoder
16
. An enlarged view of a disc format
17
is also shown.
As indicated by the disc format
17
, the smallest unit used for recording data to a DVD-RAM disc is a sector, which is 2 KB. Sixteen sectors are combined as one ECC block, to which the ECC processor
12
applies error correction coding.
The track buffer
13
is used for recording AV data at a variable bit rate in order to record AV data to a DVD-RAM disc more efficiently. While the read/write rate (Va) to a DVD-RAM disc is fixed, the bit rate (Vb) of the AV data is variable, based on the complexity of the AV data content (e.g., images if the AV data is video). The track buffer
13
is used to absorb this bit rate difference. This means that the track buffer
13
is unnecessary if the AV data bit rate is also fixed, as it is in the Video CD format.
This track buffer
13
can be even more effectively used by dispersed placement of the AV data on the disc. This is explained with reference to FIGS.
39
(
a
) and (
b
).
FIG. 39
(
a
) shows the disc address space. If the AV data recorded is divided between contiguous area A
1
between addresses a
1
and a
2
, and contiguous area A
2
between a
3
and a
4
, as shown in
FIG. 39
(
a
), the AV data can be continuously reproduced by supplying data accumulated in the track buffer
13
to the decoder while the optical head seeks from a
2
to a
3
. This is shown in
FIG. 39
(
b
).
Once reading AV data starts from al at time t
1
, it is both input to the track buffer
13
and output from the track buffer
13
with data accumulating in the track buffer at the rate (Va-Vb), that is, the difference between the input rate Va to the track buffer and the output rate Vb from the track buffer. This continues to address a
2
at time t
2
. Assuming that the data volume accumulated to the track buffer at this time is B(t
2
), data supply to the decoder can continue until the data B(t
2
) accumulated to the track buffer is depleted at time t
3
at which reading resumes from address a
3
.
In other words, if it is assured that a certain volume of data ([a
1
, a
2
]) is read before a seek operation is performed, AV data can be continuously supplied to the decoder while the seek is in progress.
It should be noted that this example considers reading, that is, reproducing, data from DVD-RAM, but the same concept applies for writing or recording data to DVD-RAM.
It will thus be obvious that insofar as a specified amount of data is recorded continuously to a DVD-RAM disc, continuous reproduction and recording is possible even if the AV data is noncontiguously recorded to the disc.
B. MPEG
A common AV data format is described next below.
As noted above, AV data is recorded to DVD-RAM media using the MPEG international standard, also known as ISO/IEC 13818.
Even though DVD-RAM discs have a large, plural gigabyte, capacity, this is still not sufficient for recording uncompressed digital AV data. A way to compress and record AV data is therefore necessary. MPEG (ISO/IEC 13818) is now widely used around the world for AV data compression. MPEG decoders (compression/decompression ICs) have also been realized with advances in IC devices. This has enabled the DVD recorder to handle MPEG compression and decompression internally.
MPEG signal processing is able to achieve high efficiency data compression chiefly as a result of the following two features.
First is that compression using a time correlation characteristic between frames (known as pictures in MPEG) is used in conjunction with conventional compression using a spatial frequency characteristic for moving picture data compression. Each video sequence of an MPEG video signal stream is divided into one or more groups of pictures, each group of pictures comprising one or more pictures of three different types: I-pictures (intraframe coded pictures), P-pictures (predictive-coded pictures, that is, intracoded with reference to a preceding picture), and B-pictures (bidirectionally predictive-coded pictures, that is, intraframe coded with reference to preceding and following pictures).
FIG. 40
shows the relationship between I, P, and B pictures. As shown in
FIG. 40
, P-pictures refer to temporally preceding I- or P-pictures in the sequence, while B-pictures refer to the first preceding and following I- or P-pictures. It should also be noted that because B-pictures reference an upcoming I- or P-picture, the display order of the pictures may not match the coding order of

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