Video encoding device

Details Video encoding device Video encoding device

2002-01-31

2004-06-29

Diep, Nhon (Department: 2613)

Pulse or digital communications

Bandwidth reduction or expansion

Television or motion video signal

C375S240010

Reexamination Certificate

active

06757329

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to video encoding devices in general and to single chip video encoding devices, in particular.
BACKGROUND OF THE INVENTION
Methods for encoding an audio-visual signal are known in the art. According to these methods, a video signal is digitized, analyzed and encoded in a compressed manner. These methods are implemented in computer systems, either in software, hardware or a combined software-hardware form.
Most hardware encoding systems consist of a set of semiconductor circuits, which are arranged on a large circuit board. State of the art encoding systems include a single semiconductor circuit, which is based on a high power processor.
Reference is now made to
FIG. 1
, which is a schematic illustration of a video encoding circuit, referenced
10
, which is known in the art.
Circuit
10
includes a motion estimation processor
12
, a motion estimation memory unit
14
connected to the motion estimation processor
12
, a Reduced Instruction Set Computer (RISC) processor
16
connected to the motion estimation processor
12
and an image buffer
18
, connected to RISC processor
16
.
RISC processor
16
transfers a portion of video signal from image buffer
18
to memory unit
14
. Motion estimation processor
12
analyzes the motion of the video signal. Motion estimation processor
12
utilizes memory unit
14
as a storage area for the video signal portion which is currently processed by it. When the motion estimation processor
12
completed analyzing the motion of a video signal portion, it transfers the results of the motion estimation analysis to the RISC processor
16
.
The RISC processor
16
performs all other processing and encoding tasks which the video signal has to undergo, such as discrete COSINE transform (DCT), quantization, entropy encoding, bit-stream production and the like. The RISC processor
16
utilizes the image buffer
18
as a storage area for the video signal portion which is currently processed by it, and as a temporary storage for its computational purposes.
It will be appreciated by those skilled in the art that such encoding systems have several disadvantages. For example, one disadvantage of circuit
10
is that each of the processing units
12
and
16
have a separate storage area. Accordingly, each of the processed portions of video signal, such as and ISO/IEC 13818 (MPEG-2) macro-blocks, have to be transferred to both memory unit
14
and image buffer
18
. RISC processor
16
has to access image buffer
18
for the same data, each time this data is required. Such Retrieval of large data blocks, many times, greatly increases data traffic volume over the encoding system data transmission lines.
Another disadvantage is that circuit
10
is able to execute all processing and encoding tasks in a serial manner, thereby capable of processing only a single macro-block at a time, requiring high operational processor frequencies. Circuit
10
receives a macro-block, processes it and produces an encoded bit-stream. Internally, the RISC processor
16
operates in the same manner.
Hence, as long as the RISC processor
10
hasn't completed transmitting the encoded bit-stream of a selected macro-block, it cannot receive the next macro-block.
It will be appreciated by those skilled in the art that the operational frequency of circuit
10
has a direct affect over the heat produced by it, thereby requiring large cooling elements as well as massive cooling devices such as fans and the like.
It will be appreciated by those skilled in the art that such circuit structure requires that input-output (I/O) operations have to be performed extremely fast, thereby greatly increasing the storage memory bandwidth requirements.
Another disadvantage of such systems is that all processing and encoding procedures (excluding motion estimation) are executed by the same RISC processor. In this case, the same circuit performs various types of computations, which makes the utilization of the processor's hardware resources very inefficient.
Methods for estimating motion in a video signal are known in the art. According to these methods a frame is compared with previous frames. The difference between the frames is used to estimate a level of motion. These methods analyze a frame and map it, thereby indicating areas in frame which have no motion over previous frames and areas in the frame which are assigned with a motion level.
According to one such like method each pixel in the search area is analyzed. This method requires a vast number of estimation operations and is thereby extremely resource consuming. This method is also called a full exhaustive search.
According to another method, known in the art, the search area is scanned in a center weighted manner, which can be logarithmic, and the like, whereby the center of the search area is scanned thoroughly at full resolution and the rest of the search area is scanned at lower resolution. Areas which detected as having some motion, in the low resolution search, are scanned again in full resolution. This reduces the overall number of estimation operations.
Reference is now made to
FIG. 2
, which is a schematic illustration of a Digital Signal Processing (DSP) processor, referenced
50
, which is known in the art.
DSP processor
50
is of a single instruction multiple data (SIMD) type machine. It includes a plurality of identical processing units (P.U.)
52
,
56
,
60
,
64
.
68
and
72
, and a random access memory (RAM)
61
. RAM
61
is divided into segments
54
,
58
.
62
,
66
,
70
and
74
.
Each memory segment is exclusively assigned and connected to a processing unit, whereas RAM segment units
54
,
58
,
62
,
66
,
70
and
74
are assigned to and connected to processing units (P.U.)
52
,
56
,
60
,
64
,
68
and
72
, respectively.
This structure has several disadvantages. One disadvantage of such machine is that the same operation is performed by all of the processing units at same time.
Another disadvantage of the SIMD machine is that the data is not shared among the processing units. For example, processing unit
56
can access data contained in RAM segment
66
via processing unit
64
only. It cannot do so directly. It will be appreciated by those skilled in the art that such a configuration is inefficient.
A further disadvantage is that individual operations that vary for different data items cannot be efficiently performed by an SIMD machine. The programming of such operations into the processing units, is very difficult. Such individual operations can be only performed in a serial manner, while masking all irrelevant data, resulting in shutting off most of the processing units. The utilization of the hardware resources in an SIMD machine during such programming operations is very low, and performance of the machine are dramatically decreased.
Another disadvantage relates to the interconnection structure between the processing units. It will be appreciated that, a processing unit within an SIMD machine is connected to a limited number of neighboring processing units. Hence communication between such a processing unit and a processing unit not connected thereto, is often a complex operation.
Bit-stream processing and generation, in a conventional encoding circuit, is performed by a general purpose processor. Bit-stream generation requires some specific operations, which can not be performed efficiently by a general purpose processor. In order to perform such special operation, a general purpose processor uses a small portion of its processing resources, while shutting off rest of them. Therefore, the disadvantage is that the resources of such processor are not utilized efficiently.
SUMMARY OF THE PRESENT INVENTION
It is an object of the present invention to provide a novel device for encoding an audio-visual signal, which overcomes the disadvantages of the prior art.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a video encoding system which includes a video source providing a multiple frame vid

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