WO2005029857A1

WO2005029857A1 - System and method for lossless reduction of bandwidth of a data stream transmitted via a digital multimedia link

Info

Publication number: WO2005029857A1
Application number: PCT/EP2003/010523
Authority: WO
Inventors: Michael Riedel; Roland Neumann
Original assignee: Inova Semiconductors Gmbh
Priority date: 2003-09-22
Filing date: 2003-09-22
Publication date: 2005-03-31
Also published as: AU2003273916A1; EP1665790A1

Abstract

There is provided a system for lossless reduction of bandwidth of a data stream transmitted via a digital multimedia link, comprising coding means for coding at least one control signal such that at least one control word is generated each time said at least one control signal changes, multiplexer means for multiplexing payload data and said at least control word such that there is provided said data stream comprising said payload data if no blanking period of said payload data is present and said at least one control word if said blanking period of said payload data is present, data transmission means for transmitting said data stream, demultiplexer means for receiving said data stream transmitted by said data transmission means for demultiplexing said payload data and said at least one control word from said data stream such that said payload data and said control word are separated from each other, and decoding means for decoding said at least one control word such that said at least one control signal is recovered. Furthermore, there is provided a method which uses such system.

Description

SYSTEM AND METHOD FOR LOSSLESS REDUCTION OF BANDWIDTH OF A DATA STREAM TRANSMITTED VIA A DIGITAL MULTIMEDIA LINK TECHNICAL FIELD

The present invention relates to a system and method for lossless reduction of bandwidth of a data stream transmitted via a digital multimedia link. BACKGROUND ART

Digital satellite systems, DVD players, digital cameras and HDTV, combined with PC graphics, games and the Internet offer a huge amount of digital video and audio data. This multimedia data is processed digitally, and to complete the digital infrastructure the data should be transmitted and displayed digitally without any loss known from analog transmission and display technologies.

One method for transmission of multimedia data such as video data, audio data and so on, is a method which uses the format MPEG to transmit data using a data compression method in order to minimize the required bandwidth.

However, such method is not lossless which means that information contained in originally compressed data is lost and cannot be recovered on a receiver side.

On the one hand it is important to transmit data having in mind that each detail of the transmitted data can be recovered on the receiver side depending on the respective application and on the other side it is important to reduce bandwidth of the transmitted data in order to save bandwidth of the transmission channel.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a system and method for lossless reduction of bandwidth of a data stream transmitted via a digital multimedia link.

As to the system this object is solved by the subject matter of claim 1 and as to the method this object is solved by the subject matter of claim 6.

In more detail, according to a first aspect of the present invention there is provided a system for lossless reduction of bandwidth of a data stream transmitted via a digital multimedia link, comprising coding means for coding at least one control signal such that at least one control word is generated each time said at least one control signal changes, multiplexer means for multiplexing payload data and said at least control word such that there is provided said data stream comprising said payload data if no blanking period of said payload data is present and said at least one control word if said blanking period of said payload data is present, data transmission means for transmitting said data stream, demultiplexer means for receiving said data stream transmitted by said data transmission means for demultiplexing said payload data and said at least one control word from said data stream such that said payload data and said control word are separated from each other, and decoding means for decoding said at least one control word such that said at least one control signal is recovered.

According to a preferred embodiment of the present invention there is provided a system, wherein said transmission means comprises a transmit FIFO and a receive FIFO, said data stream being input to said transmit FIFO before being transmitted and said transmitted data stream being input to said receive

FIFO before being input to the demultiplexer means.

According to a further preferred embodiment of the present invention there is provided a system, wherein said payload data and said at least one control signal are provided synchronous to a system clock of an payload data input interface.

According to a further preferred embodiment of the present invention there is provided a system, wherein said payload data is at least one of pixel data and audio data.

According to a further preferred embodiment of the present invention there is provided a system, wherein said coding means is a run-length coding means and said decoding means is a run-length decoding means.

According to a second aspect of the present invention there is provided a method for lossless reduction of bandwidth of a data stream transmitted via a digital multimedia link, comprising the steps of coding at least one control signal such that at least one control word is generated each time said at least one control signal changes, multiplexing payload data and said at least control word such that there is provided said data stream comprising said payload data if no blanking period of said payload data is present and said at least one control word if said blanking period of said payload data is present, transmitting said data stream, receiving said data stream for demultiplexing said payload data and said at least one control word from said data stream such that said payload data and said control word are separated from each other, and decoding said at least one control word such that said at least one control signal is recovered.

According to a preferred embodiment of the present invention there is provided a method, wherein said data stream being is FIFO processed before being transmitted and said transmitted data stream being FIFO processed before being demultiplexed.

According to a further preferred embodiment of the present invention there is provided a method, wherein said payload data and said at least one control signal are provided synchronous to a system clock of an payload data input interface.

According to a further preferred embodiment of the present invention there is provided a method, wherein said payload data is at least one of pixel data and audio data. According to a further preferred embodiment of the present invention there is provided a method, wherein said coding is a run-length coding and said decoding is a run-length decoding.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects of the present invention will be apparent from and elucidated with reference to the embodiments described hereinafter and considered in connection with the accompanying drawings, in which:

Fig. 1 is a block diagram of a system for lossless bandwidth reduction of a pixel data stream according to an embodiment of the present invention; Fig. 2 is a time chart of states of various signals used in the system according to the embodiment of the present invention; and

Fig. 3 is a time chart of fill levels of FIFOs used in the system according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

First of all it should be noted that the present invention can be advantageously used in combination with a system and a method disclosed in the application "SYSTEM AND METHOD FOR FORMING A BIDIRECTIONAL

MULTIMEDIA LINK" from the assignee of the present application, simultaneously filed herewith, representative's file number IN0424. However, the present invention is not limited to such application and, therefore, there is merely given a short abstract of the technology described in the aforementioned application in order to enhance intelligibility of the background of the present invention. In the aforementioned application there is disclosed a reliable, long distance, serial Gigabit/s and digital multimedia link which is due its serial nature highly scalable. One the one hand bandwidth can be increased by adding additional links or decreased by reducing links and on the other hand the bandwidth of different types of multimedia data such as video data, audio data and sideband data and so on can be amended in a respective link to change the bandwidth for such data in the respective link.

Such multimedia link is a high-speed serial and long-distance link for video data, audio data and other digital data as sideband data which supports video formats ranging from VGA with 18 bit color depth up to SXGA with 24 bit color depth and even UXGA with 18 bit color depth.

A pixel stream as it is output from a graphic controller or the like or as it is input at a LCD display or the like comprises predetermined number of n bits for pixel color data and up to three pixel control signals which are used for horizontal and vertical synchronization. Pixel color data bits and pixel control signals are valid at each pixel clock edge. When the pixel control signals indicate a so-called blanking period the pixel color data bits carry no meaningful information.

A bandwidth of such a pixel stream is a product of pixel clock frequency and a sum of the pixel color data bits and the pixel control signals.

The following table 1 shows an overview of different video formats from VGA to UXGA according to VESA and the required bandwidth.

Table 1

X Y V Color H Pixel H H V V BW BW Freq. Freq. Clock Total Visible Total Visible total \ΛOHBH< pixel pixel Hz Bit kHz MHz pixel pixel line line GBit/s GBit/s

640 480 60 18 29.82 23,86 800 651 497 480 0,429 0,349 VGA 640 480 60 24 29,82 23,86 800 648 497 480 0,573 0,464

800 600 60 18 37.32 38.22 1024 811 622 600 0,688 0,545 SVGA 800 600 60 24 37,32 38,22 1024 808 622 600 0,917 0,724

1024 768 60 18 47,7 64,11 1344 1035 795 768 1 ,154 0,889 XGA 1024 768 60 24 47,7 64,11 1344 1032 795 768 1 ,539 1 ,181

1280 1024 60 18 63,6 108,9 1712 1291 1060 1024 1 ,960 1 ,478 SXGA 1280 1024 60 24 63,6 108,9 1712 1288 1060 1024 2,613 1 ,966

1600 1200 60 18 74,52 161 2160 1611 1242 1200 2,897 2,161 UXGA

1600 1200 60 24 74,52 161 2160 168 1242 1200 3,863 2,876

The serial data transmission system disclosed in the aforementioned application from the assignee of the present application advantageously provides up to two serial links and a net link bandwidth slightly above 1 GBit/s per serial link. Especially the formats SXGA and UXGA require a bandwidth which exceeds the available net link bandwidth even for a two link setup as is obvious from table 1.

Any bandwidth reduction has to guarantee the an compression algorithm does not change the pixel data as the pixel data might be automatically processed by an image processing system after transmission.

The basic concept of the present invention is to replace the pixel control signals by control words which just indicate a change of status of the control signals and to suppress any pixel color data during a blanking period. The resulting pixel data stream now comprises pixel color data during a period of no blanking followed by a sequence of few control words when the blanking period occurs. This saves for VESA pixel formats approximately 20 % of the required bandwidth for the native pixel stream as shown in Fig. 1.

Fig. 1 is a block diagram of a system for lossless bandwidth reduction of a pixel data stream according to an embodiment of the present invention. In Fig. 1 reference sign 1 denotes a pixel data input interface, reference sign

2 denotes a run-length coding means, reference sign 3 denotes a multiplexer means, reference sign 4 denotes a transmit FIFO (first-in first-out memory), reference sign 5 denotes a serial data transmission means, reference sign 6 denotes a receive FIFO, reference sign 7 denotes a demultiplexer means, reference sign 8 denotes a run-length decoding means and reference sign 9 denotes a pixel data output interface.

The pixel data input interface 1 is connected to the run-length coding means 2 and drives one input of the multiplexer means 3. The run-length coding means drives another of the multiplexer means 3. The output of the multiplexer means 3 is connected to an input of the transmit FIFO 4. An output of the transmit FIFO 4 is connected to an input of the given serial data transmission means 5. An output of the serial data transmission means 5 is connected to an input of the receive FIFO 6. An output of the receive FIFO 6 is connected to an input of the demultiplexer means. One output of the demultiplexer means 7 is directly connected to the pixel data output interface 9 and another output of the demultiplexer means 7 is connected with an input of the run-length decoding means 8. An output of the run- length decoding means 8 is also connected to the pixel data output interface 9. Pixel color data and pixel control signals are provided synchronous to a pixel clock at the pixel data input interface 1. The run-length coding means 2 generates pixel control words each time one of the pixel control signals changes. The multiplexer means 3 merges pixel color data provided directly from the pixel data input interface 1 and pixel control words generated by the run-length coding means 2. The resulting serial data stream shows a variable bandwidth with maximum bandwidth when the pixel color data is transmitted and a bandwidth close to zero when the pixel control words are transmitted. To leverage the bandwidth for a constant serial data transmission the transmit FIFO 4 is used.

As is obvious from Fig. 3 at a receiver side a receive FIFO 6 stores a certain offset level of the pixel color data and the pixel control words. After demultiplexing by the demultiplexer means 7 the pixel color data is forwarded directly to the pixel data output interface 9 and the pixel control words are decoded within the run- length decoding means 8. This run-length decoding means 8 drives the pixel control signals according to the control words generated at a transmitter side by the run-length coding means 2. This pixel control signals are then forwarded to the pixel data output interface 9. Due to the fact that changes of pixel control signals do not occur very often, for example there could be four changes of the pixel control signals during 200 intervals of the pixel clock, there are transmitted merely few pixel control words because a different pixel control word is merely generated and transmitted if the pixel control signals change. In the example given above merely four pixel control words would be transmitted. Therefore, effective lossless reduction of bandwidth is achieved.

The embodiment of the present invention has been described with respect to pixel data and pixel control signals. However, it is also possible to apply the present invention to any types of data having payload data and control signals as mentioned above with respect to the pixel data. The present invention can advantageously applied on different multimedia data such as at least one of pixel data and audio data and so on. Furthermore, although there has been described an embodiment using a serial data transmission means the present invention is also applicable to another data transmission means such as a parallel data transmission means or the like because the manner of bandwidth reduction is independent from the data transmission means used in an respective application of the present invention.

Although the present invention has been described by way of a specific embodiment of the present invention it is not intended to delimit the present invention the specific embodiment described above. Rather, the present invention is intended to include all modifications and amendments which fall within the scope of the present invention as defined in the appended claims.

Claims

1. System for lossless reduction of bandwidth of a data stream transmitted via a digital multimedia link, comprising: coding means for coding at least one control signal such that at least one control word is generated each time said at least one control signal changes; multiplexer means for multiplexing payload data and said at least control word such that there is provided said data stream comprising said payload data if no blanking period of said payload data is present and said at least one control word if said blanking period of said payload data is present; data transmission means for transmitting said data stream; demultiplexer means for receiving said data stream transmitted by said data transmission means for demultiplexing said payload data and said at least one control word from said data stream such that said payload data and said control word are separated from each other; and decoding means for decoding said at least one control word such that said at least one control signal is recovered.

2. System according to claim 1 , wherein said transmission means comprises a transmit FIFO and a receive FIFO, said data stream being input to said transmit FIFO before being transmitted and said transmitted data stream being input to said receive FIFO before being input to the demultiplexer means.

3. System according to one of the claims 1 or 2, wherein said payload data and said at least one control signal are provided synchronous to a system clock of an payload data input interface.

4. System according to one of the claims 1 to 3, wherein said payload data is at least one of pixel data and audio data.

5. System according to one of the claims 1 to 4, wherein said coding means is a run-length coding means and said decoding means is a run-length decoding means.

6. Method for lossless reduction of bandwidth of a data stream transmitted via a digital multimedia link, comprising the steps of: coding at least one control signal such that at least one control word is generated each time said at least one control signal changes, multiplexing payload data and said at least control word such that there is provided said data stream comprising said payload data if no blanking period of said payload data is present and said at least one control word if said blanking period of said payload data is present, transmitting said data stream, receiving said data stream for demultiplexing said payload data and said at least one control word from said data stream such that said payload data and said control word are separated from each other, and decoding said at least one control word such that said at least one control signal is recovered.

7. Method according to claim 6, wherein said data stream being is FIFO processed before being transmitted and said transmitted data stream being FIFO processed before being demultiplexed.

8. System according to one of the claims 6 or 7, wherein said payload data and said at least one control signal are provided synchronous to a system clock of an payload data input interface.

9. System according to one of the claims 6 to 8, wherein said payload data is at least one of pixel data and audio data.

10. System according to one of the claims 6 to 9, wherein said coding is a run-length coding and said decoding is a run-length decoding.