EP1299796A1

EP1299796A1 - Enhanced resolution display

Info

Publication number: EP1299796A1
Application number: EP01949428A
Authority: EP
Inventors: Johan Janssen
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 2000-06-29
Filing date: 2001-06-20
Publication date: 2003-04-09
Also published as: KR100746845B1; CN1383504A; WO2002001341A1; CN1255719C; KR20020032560A

Abstract

A method and system for providing an enhanced video display is provided. The video signal can be displayed (960i) with twice the resolution as the standard format (480p), in an interlaced format, which can be displayed at the high resolution level in a device (337) constructed to display the high resolution level and still be displayed properly in a displayed device constructed to receive and display the standard format of one-half the resolution. Thus, a signal can be provided in an interlaced 960i format and be displayed in a display device constructed to receive, process and display video in the 960i format. However, if a device (340) is only constructed to receive, process and display a video signal in a progressive format (480p), the device will process (345) and display (347) it as if the signal were in the progressive format (480p).

Description

Enhanced resolution display

BACKGROUND OF THE INVENTION

The invention relates generally to displaying video images and more particularly to methods and systems for displaying video images with high resolution.

Video signals can be transmitted in progressive or interlaced video format. In the progressive format, the lines of an image are generally displayed horizontally, one after the other, from the top of the screen to the bottom. The next frame is then displayed, one line at a time, from top to bottom. In an interlaced video signal, the frame is the assembly of alternate lines comprising two sequential fields, e.g., lines 1, 3, 5, 7 . . . and then lines 2, 4, 6, 8 . . . . The lines of each field are displayed every 1/60 of a second. Because this occurs so quickly, it appears as one complete picture.

Transmitting a video signal in an interlaced format is helpful to conserve bandwidth. FIG. 1 shows the vertical spatial differences between a 480p signal, in the progressive format, and a 480i signal in the interlaced format. As shown in FIG. 1, successive frames of the 480p signal have identical vertical alignment with the 480 lines of resolution in the vertical direction of successive frames. The 480i signal comprises two fields of a 480 line frame in the interlaced format, in which each field has 240 lines of resolution. However, they are offset and when viewed sequentially, provide the same 480 lines of resolution as the 480p signal.

480p is a known standard picture format. The 704 X 480 pixel progressive (60 frame) version is one of the Digital Television formats. 480i is the NTSC resolution and is also one of the ATSC resolutions. However, 480 lines of resolution may not be fully satisfactory for certain applications. Although it is possible to increase resolution by increasing the line content of the video signal, such a signal would not be displayed properly with televisions which are constructed to operate with signals in the 48 Op format. It is also desirable to provide video signals in a standard format. 480p is one such standard format.

Various video formats and standards are described in the ATSC Digital Television Standard, dated September 16, 1995, Doc. A/53, and October 4, 1995, Doc. A/54. DE 196 41 517 Al, US-A 4,907,069, and US-A 5,128,791 describe signal processors and display systems that can be used to display video in either progressive or interlaced modes. However, problems can arise when information is provided, such as in a disk, at a high resolution intended to be displayed in a high resolution television, but the viewer has a lower resolution television not capable of processing or displaying the high resolution video content.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments.

Accordingly, it is desirable to provide a method and system for displaying video with enhanced resolution while still providing a video signal which could be displayed properly in a conventional lower resolution device.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with preferred embodiments of the invention, a method and system for providing an enhanced video display is provided. The system and method provide a signal that can be displayed in both a high resolution interlaced format in a high resolution display device and a lower resolution progressive format with a low resolution display device. Thus, a signal can be provided in an interlaced 9601 format and be displayed in a display device constructed to receive, process and display video in the 960i format. However, if a display device is only constructed to receive, process and display a video signal in the 480p format, the device will receive the signal at 960i and process and display it as if the signal were in the 48 Op format.

Accordingly, it is desirable to provide an improved system for displaying video signals with high resolution. Another embodiment of the invention provides an improved method for displaying video signals with high resolution.

Another embodiment of the invention provides an improved method and signal for displaying video images which can operate with conventional and enhanced video display devices. Another embodiment of the invention provides an improved system which can operate with conventional and enhanced video signals.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the system and signal adapted to effect such steps, or as exemplified in the following detailed description and drawings and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For an enhanced understanding of the invention, reference is had to the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 shows the vertical spatial differences between a 480p and a 480i video signal;

FIG. 2 shows the vertical spatial differences between a 480p signal and a 960i signal;

FIG. 3 is a block diagram showing a system in accordance with the invention; FIG. 4 is a block diagram of a video signed being transmitted and encoded in accordance with an embodiment of the invention; and

FIG. 5 is a block diagram of a signal being decoded and displayed in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Video signals can be transmitted, received, processed and displayed in the progressive or interlaced format. In a progressive scan, also called a non-interlaced format, the video images are displayed as successive frames. In each frame, the horizontal lines of pixels are displayed sequentially. Thus, in the 480p format, lines 1-480 will be displayed in sequence for one frame and then again for the next frame. In an interlaced format, two half pictures (fields), which together comprise a single frame are displayed sequentially. For example, when a frame is in the interlaced format, the frame can be divided into an odd line (lines 1, 3, 5 . . .) field, followed by an even line (lines 2, 4, 6 . . .) field. Together the odd horizontal lines of pixels of one field and the even horizontal lines of pixels of the second field comprise a single image frame. Thus, in a 480i display, odd lines 1, 3, 5 . . . 479 will be displayed, followed by even lines 2, 4, 6 . . .480. However, a viewer only perceives a single frame with 960 horizontal lines of resolution. Interlaced signals are known in the art. However, they are known to have drawbacks. For example, interlacing a signal can be considered a handicap, because it complicates the image processing techniques. An interlaced signal is nevertheless advantageous because it can preserve the vertical resolution of a progressive signal of the same resolution, while requiring only one-half of the bandwidth. Therefore, a signal which is transmitted in 480i, can have the same resolution as a signal transmitted in the 480p format, but requires only one-half of the bandwidth. On the other hand, if the bandwidth of a 48 Op signal is used, the vertical resolution of a 960i signal can be provided for the same amount of bandwidth. Referring to FIG. 2, it can be seen that because two fields of a 960i signal each have 480 lines of resolution, twice the resolution can be achieved when the signals are interlaced to form a 960i display in a single frame.

Digital television signals are conventionally transmitted in compressed form in accordance with MPEG standards, such as MPEG-2 standards. The signal is then decoded and displayed. An MPEG encoder and/or decoder can still process the signal properly whether it encodes the 480p or 960i format from a spatial resolution point of view. Thus, if a 960i format video signal is input to an MPEG encoder which is set up with instructions to process the signal as if it were a 480p signal, a signal with enhanced resolution can be provided which will be displayed on a device capable of displaying 960 interlaced lines of resolution as well as one capable of displaying only 480 lines of resolution.

Referring generally to FIG. 3, for purposes of illustration only, a video source 300, which might originate from a broadcaster in a high resolution format, such as 1088i or 720p which are US ATSC standard formats, creates a signal 301 which is transmitted to a signal processor 310 for creating a source video signal 311 in the 960i format. This can be done by de-interlacing, scaling to 960 lines of resolution and then re-interlacing, all in one algorithm. Signal 311 is transmitted to an encoder 320 and can be subjected to various known pre-processing procedures. Encoder 320 codes and compresses signal 311 for transmission, such as in accordance with MPEG-2 as a compressed coded signal 321. In the case where signal 311 was in the 960i format, the coder can be set to code the signal as if it were in the 480p format. Coded signal 321 can be displayed by a high resolution system 330 which can be constructed to display in the 960i format or to a low resolution system 340 which can be constructed to display video in the 480p format.

System 330 includes a decoder 335 which provides a video signal 336 in the 960i format, for example. System 330 can also subject signal 336 to various known postprocessing signal enhancement procedures. System 330 also includes a display 337 which is constructed to receive signal 336 and display signal 336 in the 960i format, for example.

Coded signal 321 is also compatible with system 340 which can be constructed to display video in the 480p format. System 340 includes a decoder 345 which receives and decodes signal 321 and transmits a signal 346 to a display 347 in the 480p format, for example. Display 347 can be constructed to display video signal 346 in the 480p format.

As non-limiting embodiments of the invention, an add-on, such as a Digital Video Recorder (DVR) which incorporates transcoding (going from a high picture resolution bit rate to another) can be coupled to a high resolution television. The television or DVR can be constructed to recognize the 480p signal as actually containing sufficient vertical resolution information to be capable of display in the 960i format and can adjust post processing to yield twice the vertical resolution as the 480p format. This can be done by embedding instructions in portions of the coded signal or with mechanical or electrical switches which, for example, can recognize a DVD as a type coded as 480p, but with 960i resolution display capabilities. The invention can also be directed to MPEG and other decoders with specialized pre and post processing units to insure that the high resolution interlaced signal transmitted as a progressive signal at half the resolution is displayed with high resolution.

In one embodiment of the invention, as illustrated in FIGS. 4 and 5, a signal 410, which in this example is a 1080i or 720p signal generated by a broadcaster, is to be stored in a storage device with a fixed capacity with high definition (HD) recording capabilities, such as a DVD, as a 480p signal. In what can be referred to as the transparent mode, the device can record 2 hours of HD (1080i or 720p) information. If the Long Play (LP) mode is desired, this mode of recording the transmission permits twice the record time (4 hours) of the transparent mode. However, for this Long Play mode, it is desirable to maintain the original high picture quality. Alternatively, a DVD which can function in both 960i capable systems or 480p systems may be desired. In order to double the recording capacity of the DVD, it is necessary to reduce the bit rate of the MPEG encoded incoming signal. This is referred to as transcoding. It is also desirable to change the format. However, the resulting format should be compliant with a standard, such as ATSC. A standard 480p format permits encoding at a slower bit rate, but can lead to reduced picture quality. Nevertheless, it is desirable to make the DVD compatible with 480p systems because not all users will have 960i systems.

A recording system 400 can be used to record signal 410 in a storage device such as a DVD which can be played back with either a high resolution display or a low resolution display. First, signal 410 is decoded with an MPEG decoder 420, which generates a decoded signal 421. Signal 421 is then scaled to be displayed as a series of 720 X 960i frame images, with each frame comprising two 720 X 480 fields. Thereafter, the signal is packed 440 and encoded 441 in accordance with an MPEG standard as if the signal was a 720 X 480p signal. The signal processor can be constructed to code in this manner. As part of this coding, it can embed meta level data to indicate that this is a signal that can be displayed as 720 X 960i frames, composed of interlaced 720 X 480 fields. This code can be incorporated into the header or in other known manners. Thus, in encoder 441, the signal is encoded at the lower bit rate. Accordingly, a signal 499 can be output and sent to a display device or stored in a storage medium, such as a DVD. This signal can be decoded and displayed at either 480p or 960i. A display system 500, shown in FIG. 5, can be used to display a signal transmitted as a 480p signal in the 960i format, in accordance with preferred embodiments of the invention, as long as the signal contains sufficient vertical resolution data to be displayed in the 9601 format. A signal 499' can come from a storage medium such as a DVD that was encoded as set forth above with reference to FIG 4. Display system 500 will know (as . discussed herein) that the signal can be displayed in the 960i format. First, in decoder 510, the signal is MPEG decoded. Decoding at this stage is the same decoding as if the signal were an ordinary 480p signal. Next, in a repacker 520, the signal is repacked as a series of 720 X 960i frames. This will only occur if system 500 receives instructions to do so or is constructed to do so. A 720 X 960i signal 530 can then be subjected to various post processing techniques, such as signal peaking, in a postprocessor 540 and then sent to a display 550. System 500 can be incorporated into a TV or can be an add on, such as a DVD player.

System 500 can be "told" that MPEG stream 499' is in fact a 960i signal and not a 480p signal, as the signal header states. This can be accomplished in various known ways. For example, meta data can be incorporated in reserved portions of the MPEG stream, such as the header. VCRs and TVs, such as those currently sold by Philips Electronics, can be "told" that the 480p stream is really a 960i stream when connected with a scart cable which permits the transmitter and display to identify and communicate with each other through an additional data transmission line. DVDs or other media which store data encoded as in FIG. 4 can be provided with physical structures, such as holes or tabs or optical or magnetically readable information to instruct the display to convert the "480p" signal to a 960i signal. If the devices cannot communicate, or if the display system cannot process a 960i signal, the display system will not know the true nature of the signal it is receiving and will assume that it is a 480p signal as indicated by the signal header and display the signal in the 480p format at reduced resolution.

As can be seen, by providing a signal in the interlaced format and encoding the signal as if it were of one-half the vertical resolution in the progressive format, a signal with enhanced resolution can be provided which is also compatible with display devices constructed to display at the lower resolution progressive format.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above methods and constructions and systems without departing from the scope of the invention, is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. A method of processing a video signal, comprising: providing a video signal (301); formatting the video signal into an interlaced format (960i) of a first high resolution (310); encoding the video signal for transmission as if the signal (480p) were of one- half the resolution and in the progressive format (320); and transmitting the encoded signal (321).

2. The method of claim 1 , wherein after encoding as if the signal was at one half resolution, the signal is stored in a storage medium (499) and then read from the storage medium (499') prior to decoding.

3. A system (400) for processing video signals, comprising: a decoder (510) constructed to receive a video signal (499') coded in a progressive format (480p) which has sufficient information to be displayed at twice the resolution in an interlaced format (960i), decode (510) the video signal and prepare (520, 530) the signal to be displayed (550) at twice the resolution of the received signal, in the interlaced format.

4. The system of claim 3, wherein the system is constructed to receive a video signal coded in the progressive format (480p) and convert the signal (520) into the interlaced format (960i) at twice the resolution.

5. The system of claim 4, comprising a digital video recorder for reading a video signal (499') from a DVD in the progressive format (480p) and transmitting the signal (530) in the interlaced format (960i) at twice the resolution.

6. The system of claim 5, including a television which receives the signal from a DVR (499') and displays the signal (550) in the interlaced format (960i) at twice the resolution.

7. A video display device, comprising: a receiver (500) constructed to receive a video signal (499') of a first low resolution (480p), a signal processor (510) constructed to determine whether the received signal should be displayed at twice (960i) the resolution of the first low resolution (480p) and a display for displaying the signal (550) in either the first resolution or twice the resolution.

8. The display device of claim 7, comprising a signal processor which decodes the low resolution signal (510), doubles the resolution of the received signal, creates two fields representing a video frame and interlaces the fields to provide a frame of doubled resolution (520).

9. A method of encoding a video signal, comprising: providing an interlaced signal (301) at a first high resolution and encoding the signal (320) as if it were a progressive signal of one half the first resolution.

10. A storage medium, having stored therein, a signal (499) of a first high resolution, encoded in a progressive format at a low resolution of one half the first resolution, the medium being constructed to instruct a signal receiver (500) to convert the signal read from the media (499') from the low resolution into the first resolution, in the interlaced format.

11. The storage medium of claim 10, comprising a physical structure which identifies the storage medium as a storage medium having stored therein a signal of a first high resolution, encoded in a progressive format at a low resolution of one half the first resolution, the physical structure capable of being identified by a signal receiver to convert the signal read from the media from the low resolution into the first resolution, in the interlaced format.