MXPA05011875A - Forward trick modes on non-progressive video using special groups of pictures - Google Patents

Abstract

The invention concerns a method (200) and system (100) for encoding a video signal. The method includes the steps of receiving (212) a non-progressive video signal and encoding (214) the non-progressive video signal into at least one group of pictures having at least one prediction source picture and at least one non-prediction source picture. All the non-prediction source pictures are predicted from the at least one prediction source picture such that no non-prediction source picture is predicted from another non-prediction source picture. The method can also include the step of, in response to a forward trick mode command, modifying (217, 218) at least the number of non-prediction source pictures in the group of pictures to convert the non-progressive video signal to a trick mode video signal.

Description

European (AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, Fl, For two-letter codes and other abbreviations, referto tlie "GuidFR, GB, GR, HU, TE, IT, LU, MC, NL, PL, PT, RO, SE, YES, ance Notes on Codes and Abbreviations "appearing at the beginning- SK, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, no ofeach regular issue of the PCT Gazette.GW, ML, MR, NE, SN, TD, TG). Published: - without intemational search report and to be republished upon receipt ofthat repon PROGRESS TRICK MODES IN NON PROGRESSIVE VIDEO USING SPECIAL IMAGE GROUPS BACKGROUND OF THE INVENTION 1. TECHNICAL FIELD The inventive arrangements generally refer to video systems, and more particularly to video systems that record or reproduce digitally encoded video sequences. 2. Description of the Related Art The devices that facilitated the reproduction of video are gaining popularity in the consumer electronics market to date. For example, many consumers have purchased digital video disc players (DVDs) for the purposes of watching pre-recorded programs or recording their favorite programs. A DVD player or recorder typically contains a Motion Picture Expert Group (MPEG) decoder to decode the digitally encoded multimedia data that is stored on the discs that play the recorder or the player. The MPEG video signal to be decoded is comprised of a plurality of groups of images (GOP), each of which typically contains an initial image (I), a plurality of predictive images (P) and a plurality of bidirectional predictive images. (B) During the reproduction of a video signal, some viewers may wish to develop certain trick modes. A trick mode can be any video playback in which playback is not done at a normal speed or in a forward direction. As an example, a fast forward trick mode can be started to allow the specifier to move through the video parts faster. To perform a fast-forward cueing mode on an MPEG video signal, the decoder of the DVD can output a number of images on each GOP of the video signal. The faster the trick mode, the more images in each GOP need to be skipped. Generally, B images are skipped first in successive GOPs until none of them remains, followed by P images until they are also depleted. With respect to the P images, it is necessary to first skip the P image at the end of the GOP (typically the last image in order of display in a GOP) followed by the immediately preceding P image in order of display. This process can continue in such a way that the P image to be skipped is the last P image in the GOP (in order of display) until no P images remain. If desired, the I image can also be skipped, at which point all the GOP is skipped. The principle behind the particular algorithm, in which the B images are skipped first and the P images are skipped after considering their display order, is based on the prediction schemes used in a typical GOP. Specifically, B images are not used to predict other images, and it is useful to jump them for moderate or lower acceleration. In contrast, image I, indirectly and indirectly, is used to predict all the other images in the GOP; if this is the only I image in the GOP, it must be retained if any of the other images in the GOP are not skipped. If the image l were to be skipped without skipping any of the other images, it would be impossible to accurately predict any of the remaining images. Similarly, the P images are used to predict the other P images and the image of a P image differentiating the currently last P image in the GOP would adversely affect the display of any image that follows in the order of display to the figure P salíada. Although acceptable, the algorithm described above requires programming of the additional microprocessor to adjust to the particular order in which the images are skipped. In addition, this jump algorithm does not allow images to be skipped to produce optimal reproduction. For example, if a viewer wanted to play a video at twice the normal playback speed, the most desirable way to skip the images in the video would be to skip all other images. However, in a typical GOP structure, it is not possible to skip the images in this manner due to the limitations described above. Carrying out trick modes may also present other problems, particularly if the video signal contains non-progressive images and a decoder in a remote decoder system is decoding the video signal. In a remote decoder system, the components used to record and reproduce from a storage medium the video signal that contains the non-progressive images do not have direct control over the decoder. That is, the decoder in a remote decoder system is considered a passive decoder. Repeated display of non-progressive images in such an installation may cause a vibration effect to appear in the display if the repeated images contain a moving object. To explain this disadvantage, a brief explanation of the interconnected scan is guaranteed, a process typically used to create non-progressive images. Many televisions employ the technique of intercommunicated exploration. Under this format, the video signal is typically divided into a predefined number of horizontal lines. During each field period, only half of these lines are explored; generally, odd-numbered lines are scanned during the first field period and lines of even numbers are scanned during the next field period. Each scan voltage is referred to as a field and, when combined, the two fields form a complete image or structure. For an NTSC system, sixty fields per second are displayed, resulting in a speed of thirty structures per second. As a moving object moves across the screen on an interconnected scanning television, each field will only display a portion of the moving object. This partial display occurs because one field only exhibits each other horizontal line of the total image. For example, for a particular field n, only the odd-numbered horizontal lines are scanned, and the portion of the moving objection to be displayed in field n is the portion that is scanned during the scan time of the horizontal line. odd number for field n. The next field, field n + 1, is created 1/60 of a second later and will display the even number horizontal lines of the image. Thus, the portion of the moving object shown in the field n + 1 is the portion that is scanned during the even-numbered horizontal line-scan scan for field n + 1. Although each field is temporally dissimilar, the human eye perceives the sequential display of the fields as uniform motion due to the speed at which the fields are exhibited. If an observer activates a trick mode, the trick mode video signal may contain repeated images, images that were recorded under the interconnected scan format. For example, if the observer initiates a trick mode of advancing in a particular image, then that image can be transmitted repeatedly and decoded and displayed on a digital television, for example, containing the remote decoder. However, the display of the repeated images is in accordance with the normal display of non-progressive images, that is, the upper and lower fields that make up the non-progressive image are displayed alternately. These fields are displayed alternately based on a slow forward trick mode playback speed. For example, for a reproduction speed of 1 / 3X (1 X represented normal playback speed), each field will be displayed three times in an alternate way. If a moving object appears in the images recorded under the offline scan format, each field will display the moving object at a specific position. In this way, as the fields of a structure or image are alternately displayed during the slow-motion trick mode, the moving object in the display moves rapidly back and forth from the position in the display towards the ear; in fact, the object in motion seems to vibrate. This vibration is created because the interconnected fields are temporarily distinct and the moving objection appears in a different position for each field.BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a method for encoding a digital video signal. The method may include the steps of receiving a non-progressive video signal and encoding the non-progressive video signal in at least one group of images having at least one prediction source image and at least one non-prediction source image. All non-prediction source images are predicted from the prediction source image in such a way that no non-prediction source image is predicted from another source image of non-prediction. In addition, the method may include the steps of recording the non-progressive video signal in a storage medium and reproducing the non-progressive video signal. The method may also include the step of, in response to a forward trick mode command, modifying at least the number of non-prediction source images in the image group to convert the non-progressive video signal into a signal of trick mode video. In one arrangement, the prediction source image may be an intra image. In addition, at least a part of the non-prediction source images may be predictive images or bidirectional predictive images. As an example, each of the bi-directional predictive images can be unidirectional bidirectional predictive images. In one aspect of the invention, the modification step may include the step of skipping at least one non-prediction source image in the group of images to convert the non-progressive video signal into a trick-mode video signal. Alternatively, the modification step may include the step of inserting in the image group a duplicate of at least one non-prediction source image to convert the non-progressive video signal into a trick-mode video signal. In another aspect, the at least one skipped non-predicted source image may be a predictive image being the last image in order of display in the group of images. In addition, the method may further include the step of converting a previous immediate non-prediction source image, in the order of display in the group of images, to a predictive image unless the previous immediate non-prediction source image is a predictive image In another arrangement, each of the prediction source images and the non-prediction source images may contain a display indicator, and the method may further include the step of modifying the display indicator of at least a portion of the images. of prediction source and non-prediction source images to reflect a projected display order. As an example, the display indicator can be a temporary reference field. It is also understood that the method may include the step of carrying out the steps of receiving and encoding in a remote decoder system. Additionally, the method may include the step of encoding at least a portion of the prediction and non-prediction source images into field images. The present invention also relates to a system for encoding a digital video signal. The system includes a processor for encoding a non-progressive video signal in at least one group of images having at least one prediction source image and at least one non-prediction source image. All non-prediction source images are predicted from the at least one prediction source image such that no non-prediction source image is predicted from another source image of non-prediction. In addition, the system includes a decoder to decode the non-progressive video signal. The system also includes the soffware and electronic circuits convenient to implement the methods described above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a block diagram of a system that can encode a video signal in special GOPs and develop an advanced motion trick mode, in accordance with the inventive provisions in the present. The F1G 1 B is a block diagram of another system that can encode a video signal in special GOPs and develop an advanced motion trick mode, according to the inventive provisions. FIG. 2 is a flow chart illustrating a method for encoding a video signal in special GOPs and developing an advanced motion trick mode used in accordance with the inventive arrangements. FIG. 3 illustrates an example of a special GOP, according to the inventive provisions. Fig. 4A illustrates an example of skipping images in the special GOP of FIG. 3, according to the inventive provisions.

FIG. 4B illustrates an example of inserting duplicate images into the special GOP of FIG. 3, according to the inventive provisions. FIG. 4C illustrates another example of skipping images in the special GOP of FIG. 3, according to the inventive provisions. FIG. 4D illustrates yet another example of skipping images in the special GOP of FIG. 3 and the modification of the display indicators of any of the remaining images, in accordance with the inventive provisions. FIG. 5 is a flow chart illustrating an alternate method for encoding a video signal into special GOPs and carrying out an advanced movement mode of use in accordance with the inventive arrangements. FIG. 6 illustrates a GOP of slow-forward trick mode according to the inventive provisions. FIG. 6B illustrates a GOP containing field images according to the inventive arrangements. FIG. 6C illustrates a GOP in a slow-motion trick mode that contains field images according to the inventive arrangements.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES A system 1 00 is shown in the form of a block diagram in FIG. 1A to implement the different characteristics of advanced operation according to the inventive dispositions. However, the invention is not limited to the particular system illustrated in FIG. 1A, since the invention can be practiced with any other system capable of receiving a video signal, processing the signal and sending the signal to any convenient component, as a display device. In addition, system 1 00 is not limited to reading data from or writing data on any particular type of storage medium, since with system 100 any means of storage capable of storing digitally encoded data can be used. The system 1 00 may include an encoder 1 10 for encoding an incoming video signal, and a microprocessor 1 12 for instructing the encoder 1 10 to encode the video signal according to different techniques, some of which will be explained later. All or parts of the encoder 1 10 and the microprocessor 1 12 can be considered as a processor 1 14 within the perspective of the present invention. The encoder 1 10 can be located in the same apparatus as the microprocessor 1 12 or, alternatively, it can be placed in a device that is remote from the apparatus that houses the microprocessor 1 12. If the encoder 1 10 is remotely located, the encoder 1 10 is not necessarily under the control of the microprocessor 1 12. The system 100 may also include a translator 1 16 for reading data from and writing data to a storage medium 1 18. For example, the data may be a signal of digitally encoded video. The system 100 may also have a decoder 120 for decoding the encoded video signal when it is read from the storage medium 1 1 8 and transferring the decoded video signal to a convenient component, such as a display device. The decoder 120 can be mounted in the same apparatus that contains the microprocessor 1 12 and the controller 1 16 or the decoder 120 can be mounted in a separate device, such as is found in a remote decoder system. Control and data interfaces can also be provided to allow the microprocessor 1 12 to control the operation of the encoder 1 10 (as noted above), the controller 1 16 and the decoder 120. Suitable software or firmware can be provided in the memory for conventional operations performed by the microprocessor 1 12. In addition, program routines can be provided for the microprocessor 1 12, in accordance with the inventive arrangements. In operation, the encoder 1 10 can receive and encode an incoming non-progressive video signal. As is known in the artThis type of video signal is comprised of images that have not been progressively scanned, that is, the images were created through an interconnected scanning technique. In accordance with the inventive arrangements, the microprocessor 1 12 can instruct the encoder 1 10 to encode the forward video signal into one or more GOPs that are particularly useful for developing trick modes. Examples of GOPs will be presented below. The encoder 1 10 can then transfer the encoded video signal to the controller 1 16, which can record the signal in the storage medium 1 18. In the case where the encoder 1 1 0 is located remotely, the encoder 1 1 0 it can encode the incoming non-progressive video signal, but the encoding instructions are not necessarily received from the microprocessor 1 12. If the microprocessor 1 12 receives a playback command, the microprocessor 1 12 can instruct the controller 1 16 to read the encoded video signal of the storage medium 1 18. The controller 1 18 can transfer the signal to the microprocessor 1 12, which can send the signal to the decoder 120. The decoder 120 can decode the video signal and emit the signal for display in a convenient device. If the microprocessor 1 12 receives a trick mode command, the microprocessor 1 12 can skip images in the GOPs or repeat the images of the GOPs. As alluded to above, there may be some examples in which the decoder 120 performing the decoding step is located in a device separate from the apparatus containing the microprocessor 1 12. An example of such an arrangement, or of a remote decoder system, it is illustrated in FIG. 1B, in which the decoder 120 is in a deployment device 122, separated from a multimedia device 124 that can house the microprocessor 1 12. In this case, the decoder 120 may not be under the control of the microprocessor 1 12. However, the trick modes still can be developed in this system 100, in which the microprocessor 1 12 can suppress images or insert duplicates of the images in the video signal before being decoded by the decoder 120 in the display device. 122. It is understood that the encoder 1 10 in this system type may also be remotely located. In another mode, during the encoding step, the images in the non-progressive video signal can be encoded in field images, which can help to avoid the vibration artifact discussed above. The coding of the non-progressive images in field images may allow the microprocessor 1 12 to transmit the field images to a decoder located remotely in a way that can help to control the vibration problem. Such a process will be discussed later. In any of the provisions discussed in relation to FIGS. 1A and 1B, the GOPs created during the coding process will facilitate the effective implementation of a forward trick mode. The total operation of the invention will be discussed in detail below. With reference to FIG. 2, a method 200 is illustrated which shows a way to develop a trick mode in a non-progressive video signal using special GOPs. The method 200 can be practiced in any convenient system capable of encoding and decoding a video signal. The method 200 may begin, as shown in step 210. In step 212, a non-progressive video signal may be received. As noted above, a non-progressive video signal contains images that have been progressively explored, that is, explored through an in-connected exploration technique. As shown in step 214, the non-progressive video signal can be encoded in at least one GOP having at least one prediction source image and at least one non-prediction source image. In an arrangement, all non-prediction source images can be predicted from the prediction source image, such that no non-prediction source image is predicted from another non-prediction source image. With reference to FIG. 3, an example of such a process is shown. In this particular arrangement, the video signal can be encoded in one or more GOPs 300. The GOPs 300 are displayed in order of display. Each of the GOPs 300 may include at least one prediction source image 310 and at least one non-prediction source image 312. These images are non-progressive images having at least one upper field and one lower field. The images are shown in full: the illustration does not show them separately in their respective fields. A prediction source image is an image in a GOP that is not predicted from another image, however, it can be used to predict other images in the GOP. In addition, a non-prediction source image can be any image in a GOP that can be predicted from a prediction source image in that GOP. As an example, the prediction source image 310 can be an I image, and the non-prediction source images 312 can be B and / or P images. Each of the non-prediction source images 312 can be predicted from the prediction source image 31 0, which in this example is correlated with each of the B and P images that are predicted from the I image. Since images P can serve as non-prediction source images 312, it should be evident that a non-prediction source image 312 is not limited to images from which other images can not always be predicted, such as images B However, according to the inventive arrangements, each of the non-prediction source images 312 can be predicted from the prediction source image 31 0 only. In one arrangement, the B images can be unidirectional prediction images, such that the B images prior to, or in front of, the I image (in order of display) can be retro-predicted from the I image, and the images B behind the image I (in order of display) can be predicted in advance of the image I. The numbers subscripts incorporated in the prediction source images 310 and the non-prediction source images 312 can indicate the order in which each of these images will be displayed - in relation to the other images in the GOP - at a normal playback speed. As noted above, the GOP 300 is displayed in order of display. The order of transmission is slightly different in that the prediction source image 31 0, in this example, image l3, can first be transmitted to a decoder followed by the non-prediction source images 312 to be predicted from the source image of prediction 310. It is important to note that the invention is not limited in any way to these particular GOPs 300, since they merely represent an example of a GOP structure in accordance with the inventive provisions. In fact, any GOP in which all source images of non-prediction in the GOP can be predicted from a prediction source image in that GOP is within the perspective of the inventive provisions. In addition, although only two GOPs 300 are shown in FIG. 3 in which each GOP 300 has a prediction source image 310 and six non-prediction source images 312, it is understood that the received video signal can be encoded at any convenient number of GOPs 300 having any convenient number of images of prediction source 310 and non-prediction source images 312. Also, if more than one prediction source image 31 0 is in the GOP 300, any B image in the GOP 300 can be predicted bidirectionally. As an example, more than one prediction source image 310 may be placed in the GOP 300 and some of the non-prediction source images 312 may be predicted from these prediction source images 310. As such, the prediction source images 310 can be transmitted to a decoder before the non-prediction source images 312 that are dependent on these prediction source images 310 for prediction. Referring again to method 200, in step 215, the non-progressive video signal containing the GOPs can be recorded in a convenient storage medium. Once recorded, the non-progressive video signal containing the GOPs can be reproduced, as shown in step 216. In decision block 217 it can be determined whether the number of non-predicted source images in the GOPs are for modify As an example, the modification may be developed in response to a forward trick mode command, such as advanced fast or advanced slow. If no modification occurs, the method 200 may be terminated in step 216. If so, then an id process may be developed in step 218. The operation conducted in step 218 may convert the non-progressive video signal to a signal of trick mode video. Several examples are shown in FIGS. 4A-4D. Again, the images in FIGS. 4A-4D are non-progressive images that are fully illustrated (they have not been separated in their fields). With reference to FIG. 4A, each of the GOPs 300, as illustrated first in FIG. 3, it is displayed with several 312 non-predicted source images removed or skipped. Specifically, the images B0, B2l B4 and P6 in the GOP 300 on the left can be skipped, while images B-i, B and P6 in the GOP 300 on the right can be skipped. Salting such non-prediction source images 312 may cause the reproduction rate to increase. Here, the number of skipped 312 non-predicted source images, half of all the images in the two GOPs 300, is correlated with a playback speed that is twice the normal playback speed, or 2X (1X represents velocity of normal reproduction). According to the inventive arrangements, any one of the non-prediction source images 312 in the GOPs 300 may be skipped to increase the reproduction speed of the video signal without affecting the prediction of any remaining non-prediction source image. 312 in the GOPs 300. This feature is made possible through the coding process described above. One step for placing the 300 GOPs according to the standard MPEG, for example, will be discussed later. Of course, it is understood that the invention is not limited to the example described in relation to FIG. 4A, since the ability to skip all non-prediction source images 312 applies to any other GOP in which the non-prediction source images 312 are predicted from a prediction source image 310. Also, all of the GOP 300 it can be skipped to produce a faster reproduction. Referring again to FIG. 2, modification step 218 may also include the step of inserting into the GOP 300 a duplicate of at least one prediction source image 310 or non-prediction source image 312 to convert the non-progressive video signal into a trick mode video. An example of such an operation is shown in FIG. 4B. Here, a duplicate of each prediction source image 310 and non-prediction source image 312 can be inserted into the GOP 300 (for convenience, only one GOP 300 of FIG 3 is shown). This particular example can produce, a playback speed of YzX. The letter subscript "d" represents the image to which it is associated as a duplicate of the preceding immediate image. Similar to the original non-prediction source images 312, duplicates of such images can be predicted from a prediction source image 310 (according to the MPEG standard, the last image in the GOP 300, the duplicate image P6d, it can be predicted from the image immediately before P, which in this case is the image P6). In addition, the original non-prediction images 312 and their duplicates can be predicted from the duplicate of a prediction source image 310. The example presented in FIG. 4B is explained as follows: all the non-prediction source images 312 and their duplicates opposite (in order of display) of the original prediction source image 310, or image l3, can be predicted from the image l3. Additionally, the original non-prediction source images 312 and their duplicates behind the duplicate (in order of display) of the original prediction source image 31 0, or l3d image, can be predicted from the duplicated image l3d (with the exception of the duplicate image P6d). However, it is understood that this particular arrangement is merely an example, since the non-prediction source images 312 and their duplicates can be predicted from any other convenient prediction source image 310, including any duplicates of a source image. of prediction 310. In another arrangement, one or more of the duplicate images inserted in the GOP 300 may be fictitious B or fictitious P images. A fictitious image B or fictional P is a B or P image, respectively, in which the motion vectors of the fictitious image are set to zero and their residual signal is set to zero or not encoded. For example, the duplicate of the prediction source image 310 (image 13) in the GOP 300 may be a fictitious image P instead of another image I, such as the image l3d. Similarly, the duplicate for the last non-prediction image 312 (image P6) can be a fictitious image P instead of a conventional image P, such as the duplicate image P6d. By using fictional B or P images during a trick mode, the bit rate of the video signal may decrease, which may be necessary in a remote decoder system. It is also understood that fictional B or phantom P images can be inserted into the GOP 300 when images are skipped, particularly in a remote decoder system, since skip images can actually increase the bit rate of a video signal. Referring again to FIG. 2, in decision block 220, it can be determined if the last non-prediction source image in the GOP has been skipped. Otherwise, method 200 may continue in decision block 226 through hop circle A. If so, it may be determined in decision block 222 whether the source image of previous immediate non-prediction in order of display in the GOP, is a P image. If so, method 200 may continue in decision block 226 through jump circle A. If it is not, then the source image of previous immediate non-prediction in the GOP may be convert into a picture P, as shown in step 224. An example of this operation is illustrated in FIG. 4C. The MPEG video specifications require that the last image in a GOP be a P image or an I image. Therefore, if the P6 image in the GOP 300, a non-prediction source image 312, was jumped during a trick mode , the last image in the GOP 300 (if it is not skipped) would be the B5 image, a violation of the MPEG standard. To satisfy the MPEG requirement, the previous immediate non-prediction source image 312, in this case, image B5, can be converted to an image P, or image P5. An image B can be converted to an image P by setting the following parameters for the values of the image P located in the image header of the image B: coding_type_image; vector_to_back_full_plete; and back_code_f. Additionally, the following variable length codes can be set for macroblock type for the values of the image P: cant_macroblock; forward_movement_macroblock; backward_macroblock movement; macroblock pattern; intra_macrobIoque; temporal_temporal_weight_code_flag; and allowed_temporal_people_l classes. This process can instruct a decoder to decode the image as an image P. As such, according to the inventive provisions, the last image in a GOP 300 can be skipped without violating the MPEG requirement that the last image in a GOP be an image P. As another example, referring to FIG. 4A, the B5 image in both GOPs 300, can be converted into a P image to conform to the MPEG standard. Referring again to method 200 of FIG. 2, the prediction source images and the non-prediction source images may contain a display indicator. As determined in decision block 226 of hop circle A, if the display indicators of these images are to be modified, then such a process may be developed in step 228. Remarkably, modifying these display indicators may reflect an order of projected display of prediction source images and non-prediction source images when any of these images is skipped or duplicated. If the display indicators are not to be modified, then method 200 may be stopped at step 230. In one arrangement, the display indicator may be a temporary reference field. A temporary reference field is typically a ten-bit field located in the image header of digitally encoded images. Some decoders depend on the temporal reference field to determine when a particular image in a video signal will be displayed in relation to other images in the video signal. This field normally has an integer value. As an example, referring again to FIG. 3, each GOP 300 contains seven images. The subscript numbers for the non-progressive images in each GOP 300 may correspond to the outer values for each time reference field of the respective image. For example, the time reference field of the first non-prediction source image 312, or image B0, may have an integer value of zero, which indicates that this particular image will be the first in each GOP 300 to be displayed. The temporal reference field of the image B-, the next image to be displayed, may have an integer value of one. Therefore, the integer value of the temporal reference field for each subsequent image to be displayed can be larger by one, up to the image P6, whose temporal reference field can have an integer value of 6. For convenience, the phrase "value whole of the temporal reference field "can also be referred to as" integer value ". When, for example, a source image of non-prediction 312 is skipped, however, the display order according to the original temporary reference fields is no longer valid. Accordingly, the integer value of the temporal reference fields of the prediction source images 310 and the non-prediction source images 312 that follow the skipped image can be modified to indicate an appropriate display order. This feature is also applicable if the duplicates of the prediction source images 310 or the source images. of non-prediction312, are inserted into the GOP 300. As an example, if the image B ^ in the GOP 300 on the right is skipped, then the integer values of the prediction source images 310 and the non-prediction source images 312 that follow this image can be decreased by a value of one. Therefore, the integer value of the temporal reference field of the image B2 can be modified from two to one, the integer value of the temporal reference field of the image l3 can be modified from three to two, and so on. This modification process can continue until the end of the GOP 300 is reached and can ensure that the remaining images in the GOP 300 will be displayed in an appropriate order. Therefore, each time a prediction source image 31 0 or a non-prediction source image 312 in a GOP is displayed, the integer values of the temporal reference fields of the remaining images in that GOP that follow the image jumped, can be decreased by a value of one. The final result is illustrated in FIG. 4D, where the new integer values are shown, the skipped image B1 is represented by a dashed outline and the previous integer values are in parentheses. In a similar manner, whenever a duplicate of a prediction source image 310 or a non-prediction source image 312 is inserted into a GOP 300, the integer values of the images following the inserted duplicates may be increased. for a value of one. It is understood that the invention is not limited to these particular examples, since other forms may be developed, in any other convenient way, to modify the integer values of the relevant temporal reference fields to reflect a projected display order. Furthermore, it should be noted that the invention is not limited to the use of a temporary reference field, since any other convenient display indicator may be modified to reflect a projected display order in any of the modes discussed above. Referring again to the F1G. 2, method 200 can be stopped in step 230. Referring to FIG. 5, a method 500 is illustrated that demonstrates another way of performing a trick mode on a non-progressive video signal by using special GOPs. Similar to method 200 of FIG. 2, the method 500 may begin in step 512. Also, as in step 214 of method 200, the non-progressive video may be encoded in at least one GOP having at least one prediction source image and at least one image of non-prediction source, in which all non-prediction source images can be predicted from the prediction source image, as shown in step 514. In this arrangement, the coded non-progressive video signal can be decoded eventually in a remote decoder system. As noted above, in a remote decoder system, the components used to encode and read from a non-progressive video signal storage medium have no control over the decoder. This lack of control over the decoder can cause problems with the non-progressive video display, particularly during a slow-forward trick mode. For example, FIG. 6A illustrates the GOP 300 of FIG. 3 in which non-progressive images are shown separated in their respective fields. The prediction scheme used in this example is the same as that discussed in relation to FIG. 3 and does not require an additional description here. In this case, each of the non-prediction source images 312 and the prediction source image 31 0 may have an upper field and a lower field. The letter subscript "t" designates the particular field to which it is associated as a superior field; similarly, the letter subscript "b" designates the particular field to which it is associated as a lower field. Here, the GOP 300 represents a GOP of slow-forward trick mode in which a duplicate of each of the images has been added in the GOP 300. The letter subscript "d" represents that a particular field is a duplicate field. As an example, the B0 image can include an upper field B0t and a lower field Bob, while the duplicate of the image B0, image Bod, can have an upper field B0td and a lower field B0bd- As shown, the upper fields and lower are shown in an alternate way. If a moving object appears in these fields, that object will appear to vibrate due to the way in which the fields are displayed. For example, if a moving object appears in one place in the B0t field and another in the B0b field, the object will appear to jump back to the previous place (as shown in the B0t image) when the duplicated B0td field is displayed. . When the next field, the duplicate Bobd field, is shown, the object will appear to jump back to the first place displayed in the B0b-image. Therefore, the moving object seems to vibrate when duplicate images are added to the GOP 300. This vibration effect will continue as long as the duplicate images are inserted into one or more GOPs 300. Referring again to the method 500, another encoding step can be executed to overcome the vibration artifact, which may appear when certain cue modes are initiated in a remote decoder system. . In step 515, the non-prediction source images and the prediction source image can be encoded in field images. As will be explained below, when coding these images in field images, the display of the field images can be carried out in accordance with a way that helps to solve the problem of vibration. An example of this coding step is shown in FIG. 6B. In this example, the GOP 300 described first in FIG. 3 is shown with the original non-progressive images, encoded in field images. For example, image B0, which originally conferred Bot and B0b fields, has been encoded in Bot and Bob field images. Field images that originally comprised non-prediction source images 312 can also be considered as non-prediction source images 312. Similarly, the field images that originally comprised the prediction source image 310 can be considered prediction source images. 310. Therefore, for the purposes of the invention, when reference is made to the terms "source prediction images" or "source images of non-prediction", it is understood that the terms may refer to field images, even though the word "field" is not used expressly as a modifier for the terms. In this particular example, any of the prediction source images 310, i.e., the field images l3t and l3b, can be used to predict any of the non-prediction source images. A suitable example is shown in which the field image 13 (a prediction source image 310) prognosis fodas the non-prediction source images 312 in front (in order of display) of the l3t image. In addition, the field image l3b (also a prediction source image 310) can predict all the non-prediction source images 312 deírás (in order of display) of the image l3. Of course, the invention is not limited to this parficular example, since other suitable prediction schemes may be employed. Referring again to method 500 of FIG. 5, in step 516, the non-progressive video signal containing the GOPs of field images can be recorded on a storage medium. This non-progressive video signal may be reproduced eventually in step 517. In decision block 518, it can be determined if the number of non-prediction source images (field) in the GOP is to be modified. Otherwise, method 500 may terminate in step 517. If yes, such a process may be executed in step 519. Referring to FIG. 6C, the GOP 300 of FIG. 6B is shown with duplicate field images, inserted into the GOP 300. Although this particular example focuses on a trick-forward mode, it is understood that the modification step may include image jumping as well. This GOP 300 in particular, will be illustrated as a GOP in slow-forward trick mode with a playback speed of 1 / 2X. That is, a duplicate of each field image has been inserted into the GOP 300; the duplicates of the field images can also be field images themselves. As reflected in FIG. 6C, the field images are displayed in such a way that a top field image and its duplicate are displayed in succession before the bottom field image below and its duplicate. For example, the field image B.t and its duplicate, field image B0td > are displayed successively and are followed by the display of the field image B0b and its duplicate, field image B.bd- Thus, if a moving object appears in the field images Bot and B0b, the insertion of Duplicate field images will not lead to a vibration artifact because the duplicate, upper field image, B0td, will be displayed next to the original lower field image, B0b. and its duplicate, B0bd. This manner of display in which the groups of field images are displayed before other groups of images have a different parity becomes possible when the prediction source image 310 and the non-prediction source images 312 are encoded in images of field Specifically, when coding the non-progressive field images in field images, the field images can be transmitted to a decoder located remotely in an order that allows them to be displayed in a successive manner, similar to the one illustrated above. For example, a higher field image and its duplicate can be transmitted to a remote decoder for decoding and display, and subsequently, the corresponding lower field image and its duplicate can be transmitted to the remote decoder. To accommodate the display requirement that the field images of different parities must be followed, the parity of these field images, as indicated in the image header, can be modified. For example, if an upper field image is located in a position where a lower field image is normally displayed, the parity of that upper field image may be modified such that the upper field image is actually defined as an image. of lower field. However, changing the parity of an image does not affect the content of the image. As a more specific example, the parity of the duplicate image B0.d, a higher field image, can be modified in such a way that the image is actually defined as a lower field image. In addition, the parity of the BQ field image, a lower field image in a location where a higher field image is typically displayed, can be modified to define the B0 image as a higher field image. This concept can be applied to the remaining field images in the GOP 300. However, the process of modifying the parities of these images does not affect the elimination of the vibration arp. A prediction technique suitable for the GOP trick mode in FIG. 6C is also illustrated. The field image l3. it can also be used to predict any of the 312 non-prediction source images (including duplicate field images) placed in front (in order of display) of the l3t image. As will be appreciated by those skilled in the art, the use of the l3t image to predict these particular images is useful because the l3t image was used to predict the original non-predicted source images 312 in front of the l3t image. In addition, the field image l3bd can be used to predict any of the non-prediction source images 312 behind (in order of display) of the image l3 d- The image l3 d is useful for predicting these images due, in accordance with the In the previous discussion, regarding the parity change of certain images, the l3bd image is defined as a lower field image in this example; a lower field image was the image type used to predict the original non-source prediction images 312 behind image l3. To further improve the prediction scheme of this example, the P6t and Pet images can be converted into B6t and B6td images, showing the previous designations in parentheses. As will be shown for those experiments in maigery, the conversion of these P field images into field B images can prevent the prediction of the last two field images, P6b and P, from being negatively affected. The conversion of an image P into an image B is similar to the process described above in relation to the change of an image B in an image P. That is, the following parameters placed in the image header of the image P can be scaled for values of image B: íipo_codificación_imagen; vecíor_hacia aírás_pel_completo; and back_code_f. Additionally, the following variable length codes can be set for macroblock type for the values of the image B: cant_macroblock; forward_movement_macroblock; towards aírás_movimienío_macrobloque; pafrón_macro block; intra_macroblock; temporal_temporal_weight_code_flag; and permissible temporal_heavy_classes. As an option, one or more of the duplicate images inserted into the GOP 300 can be fictional B or dummy field images P, which can help to decrease the bit rate of the video signal contained in the GOP 300 during a trick mode, including slow and fast forward trick modes. The addition of dummy field images B or P may be particularly useful in a remote decoder system. The remaining steps illustrated in method 500 of the F1G. 5 are similar to the steps presented in method 200 of FIG. 2. Therefore, the steps of the 500 method do not require a deep discussion. In decision block 520, if the last pair of field images was non-predicted in the GOP, they have been skipped, method 500 may continue in decision block 522. If not, the method may end up in the decision block 526 through jump circle A. In decision block 522, it can be determined whether the immediate pair of earlier non-prediction source field images are P-field images. If they are, method 500 may continue in the decision block 526 through jump circle A. If they are not, the immediate pair of non-prediction source field images can be converted into a pair of P field images, as shown in step 524. From of jump circle A, in decision block 526, it can be determined whether the display indicators of the field images in the GOP are to be modified. If not, the method 500 may be stopped in step 530. If the display indicators of the field images are to be modified, such a process may be carried out in step 528. Finally, the method may terminate in step 530. Although The present invention has been described in conjunction with the embodiments described herein, it should be understood that the aforementioned description is intended to illustrate and not limit the scope of the invention as defined by the claims.

Claims (28)

1. CLAIMS 1. A method for encoding a digital video signal, comprising the steps of: receiving a non-progressive video signal; and, encoding the non-progressive video signal in at least one group of images that have at least one prediction source image and at least one non-prediction source image, wherein all non-prediction source images are predicted from at least one prediction source image so no source image of non-prediction is predicted from another source image of non-prediction. The method according to claim 1, further comprising the steps of: recording the non-progressive video signal in a storage medium; and, play the non-progressive video signal. The method according to claim 1, further comprising the step of, in response to an advance cue mode command, modifying at least the number of non-prediction source images in the image group to convert the signal of non-progressive video in a trick mode video signal. 4. The method according to claim 1, characterized in that the prediction source image is an intra image. 5. The method according to claim 1, characterized in that at least one of the non-predicted source images are bidirectional predictive images. 6. The method according to claim 1, characterized in that at least a portion of the non-prediction source images are predictive images. The method according to claim 5, characterized in that each of the bi-directional predictive images is a bidirectional unidirectional predictive image. The method according to claim 3, characterized in that said modification step comprises the step of skipping at least one non-prediction source image in the group of images to convert the non-progressive video signal into a video signal of trick mode. The method according to claim 3, characterized in that said modification step comprises the step of inserting in the image group a duplicate of at least one non-prediction source image to convert the non-progressive video signal into a signal of trick mode video. The method according to claim 8, characterized in that the at least one outdated prediction source image is a predictive image that is the last image in order of display in the group of images, and wherein said method further comprises the step of converting a previous immediate non-prediction source image in order of display in the group of images, into a predictive image unless the previous immediate non-prediction source image is a predictive image. eleven . The method according to claim 3, characterized in that each of the prediction source images and the non-prediction source images contain a display indicator and the method further comprises the step of modifying the display indicator of at least one part of the prediction source images and the non-prediction source images to reflect a projected display order. The method according to claim 1, characterized in that the display indicator is a temporary reference field. The method according to claim 1, further comprising the step of carrying out said reception and coding steps in a remote decoder system. The method according to claim 13, further comprising the step of encoding at least a portion of the prediction and non-prediction source images into field images. 15. A system for encoding a digital video signal, comprising: a processor for encoding a non-progressive video signal in at least one group of images having at least one prediction source image and at least one non-source source image. prediction, wherein all the non-prediction source images are predicted from the at least one prediction source image such that no non-prediction source image is predicted from another non-prediction source image; and, a decoder to decode the group of images. The system according to claim 15, further comprising a controller for recording the non-progressive video signal in a storage medium and reproducing the non-progressive video signal. The system according to claim 1, characterized in that the processor is further programmed to, in response to a forward trick mode command, modify at least the number of non-predicted source images in the video signal. non-progressive to convert the non-progressive video signal into a trick mode video signal. The system according to claim 15, characterized in that the prediction source image is an intra image. 19. The system according to claim 15, characterized in that at least one of the non-prediction source images are bidirectional predictive images. The system according to claim 15, characterized in that at least a portion of the non-prediction source images are predictive images. twenty-one . The system according to claim 19, characterized in that each of the bi-directional predictive images is a bidirectional unidirectional predictive image. 22. The system according to claim 17, characterized in that the processor is further programmed to skip at least one non-prediction source image in the group of images to convert the non-progressive video signal into a video signal so as to trick. The system according to claim 17, characterized in that the processor is furthermore programmed to insert in the group of images a duplicate of at least one non-prediction source image to convert the non-progressive video signal into a video signal. in an ironic way. The system according to claim 23, characterized in that the at least one skipped non-predicted source image is a predictive image which is the last image in order of display in the group of images, and wherein the processor is furthermore programmed to convert an earlier immediate non-prediction source image in order of display in the group of images, into a predictive image unless the previous immediate non-prediction source image is a predictive image. 25. The system according to claim 17, characterized in that each of the prediction source images and the non-prediction source images contain a display indicator and the processor is also programmed to modify the display indicator of at least a portion of the prediction source images and the non-prediction source images to reflect a projected display order. 26. The system according to claim 25, characterized in that the display indicator is a temporary reference field. 27. The system according to claim 15, characterized in that the processor and the decoder are part of a remote decoder system. 28. The system according to claim 27, characterized in that the processor is further programmed to encode at least a portion of the prediction and non-prediction image images in field images.