MXPA05011879A - Reverse trick modes on 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 progressive video signal and encoding (214) the 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 prediction source picture such that no non-prediction source picture is predicted from another non-prediction source picture. The method also includes the step of, in response to a reverse trick mode command, altering (218) the display order of the group of pictures to permit the group of pictures to be displayed in a reverse order. Additionally, the method can include the step of modifying (220) at least the number of non-prediction source pictures in the group of pictures in response to the reverse trick mode command.

Description

REVERSE TRICK MODES IN PROGRESSIVE VIDEO USING SPECIAL IMAGE GROUPS FIELD OF THE INVENTION Inventive arrangements are generally related to video systems and more particularly to video systems that record or reproduce video sequences encoded in digital form.

BACKGROUND OF THE INVENTION Devices that offer video playback are gaining popularity in the consumable electronic market. For example, many consumers have purchased digital video disc (DVD) recorders or players for the purpose of watching recorded programs or recording their favorite shows. A DVD recorder or player typically contains a decoder from Moving Pictures Experts Group (MPEG) to decode the digitally encoded multimedia data that is stored on the discs that the recorder or player plays. The MPEG video signal to be decoded comprises a plurality of groups of images (GOP), each of which typically contains an intra (I) image and a plurality of predictive images (P) and a plurality of bidirectional predictive images (B) ). When the digital video recorder or player is connected to certain televisions, the digitally encoded signal will be decoded by the MPEG decoder of the digital video recorder or player before being displayed on television. However, it is important that many digital televisions (DTVV) contain their own MPEG decoders. As such, when a digital video recorder or player is connected to a DTV, the video signal read from the disc is decoded remotely by the DTV decoder. This type of decoder is considered a passive decoder since the microprocessor in the digital video recorder or player has no control over the decoder. This configuration can be called as a remote decoder system. During the reproduction of a video signal, some viewers wish to carry out certain trick modes. A trick mode can be any reproduction of a video where the reproduction is not done at a normal speed or in a forward direction. As an example, a reverse trick mode can be started to allow the viewer to locate portions of video that have already been played and the viewer wants to see them again. The reverse trick mode can be at a normal speed or the images in a GOP can be skipped to produce a fast reverse trick mode. In addition, duplicates of the images in a GOP can be inserted into the GOP to generate a slow reverse trick mode. To perform a reverse trick mode on an MPEG video signal, the decoder of the DVD can decode the images in a GOP in a forward direction. Once these images are decoded, the decoder is instructed to display the images in the reverse order, and when necessary, add duplicate images to the GOP or to skip to the GOP. A remote decoder system, however, is not particularly suitable for carrying out reverse trick modes. The reason for this disadvantage is that the microprocessor of the digital video recorder or player can not instruct the decoder to display the images in reverse. As such, the reverse trick mode in such an arrangement, typically, is limited only to send the decoder in reverse order the I images in all or some of the GOPs of the video signal.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a method for encoding a digital video signal. The method may include the steps for receiving a progressive video signal and encoding the 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 so that no non-prediction source image of another non-prediction source image is predicted. further, the method may include the steps of recording the progressive video signal in a storage medium and reproducing the progressive video signal. In response to a reverse trick mode command, the method also includes the step of altering the display group's display order to allow the group of images to be displayed in reverse order. The method may also include the step of modifying at least the number of non-prediction source images in the group of images in response to the inverse trick mode command. In an array, the prediction source image may be an intra image. Also, at least a portion of the source images of non-prediction may be bidirectional predictive images or predictive images. As an example, each of the bi-directional predictive images can be a bidirectional predictive image of a direction. In one aspect of the invention, the step of modifying may include the step of skipping at least one source image of non-prediction in the group of images. Alternatively, the step of modifying may include the step of inserting in the image group a duplicate of at least one source image of non-prediction. In another aspect, the skipped non-predicted source image may be a predictive image that is the last image in the display order in the group of images. In addition, the method may include the step of converting the immediately preceding non-predicted source image in the order of display in the group of images within a predictive image unless the immediately preceding non-predicted source image is a predictive image.

In another arrangement, each of the prediction source image and the non-prediction source images may contain a display indicator and the method may also include the step of modifying the display indicator of at least a portion of the source images of the display. prediction and source images of non-prediction to reflect a proposed deployment order. As an example, the deployment indicator can be a temporary reference field. Such a modification step may occur after altering the display order or the step of modifying at least the number of non-prediction source images in the image group. In another arrangement, after the step of altering, the method may include the step of converting the last non-predicted source image in the altered group of images into a predictive image unless the last non-predicted source image in the altered group of images is a predictive image. In addition, after the alteration step, the method may include the step of selectively converting the non-prediction source images into bidirectional predictive images opposite, in the order of display, of the prediction source image. The method may include the step of carrying out the steps of receiving, encoding and altering in a remote decoder system. The present invention also relates to carrying out a reverse trick mode. The system includes a processor for encoding a 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 a prediction source image so that no non-prediction source image is predicted from another non-prediction source image. The system also includes a decoder to decode the progressive video signal. In addition, in response to a reverse trick mode command, the processor is programmed to alter the order of display of the group of images to allow the group of images to be displayed in an inverted order. The system also includes appropriate software and circuitry to implement the methods described above.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A is a block diagram of a system that can encode a video signal in a special GOP and perform a reverse trick mode in accordance with the inventive arrangements. Figure 1B is a block diagram of another system that can encode a video signal in a special GOP and perform a reverse trick mode in accordance with the inventive arrangements. Figure 2 is a flow chart illustrating a method for encoding a video signal within a special GOP that performs a reverse trick mode with use in accordance with the inventive arrangements. Figure 3 illustrates an example of a special GOP in accordance with the inventive arrangements. Figure 4A illustrates the GOP of Figure 3 in an inverted order in accordance with the inventive arrangements. Figure 4B illustrates the GOP of Figure 4A with deployment indicators modified in accordance with the inventive arrangements.

Figure 4C illustrates the GOP of Figure 4B with an image converted in accordance with the inventive arrangements. Figure 4D illustrates the GOP of Figure 4C with another image converted in accordance with the inventive arrangements. Figure 5A illustrates an example of skipped images in the GOP of Figure 4D in accordance with the inventive arrangements. Figure 5B illustrates an example for inserting duplicate images into the GOP of Figure 4D in accordance with the inventive arrangements. Figure 5C illustrates another example of skipped images in the GOP of Figure 4D in accordance with the inventive arrangements. Figure 5D illustrates another example of images skipped in the GOP of Figure 4D and modifying the display indicators of any remaining image in accordance with the inventive arrangements.

DETAILED DESCRIPTION OF THE INVENTION A system 100 is shown in Figure 1A to implement the different advanced features in accordance with the inventive arrangements, in the form of a block diagram. However, the invention is not limited to the particular system illustrated in Figure 1A, since the invention can be practiced with another system with the ability to receive a video signal, process the signal and emit the signal on any appropriate component, such as a deployment device. In addition, the system 100 is not limited to reading data or writing data of any particular type of storage medium, since any storage medium with the ability to store data encoded in digital form can be used with the system 100. The system 100 it may include an encoder 110 for encoding an incoming video signal, and a microprocessor 112 for instructing the encoder 110 to encode the video signal in accordance with the different techniques, some of which will be explained below. All or some portions of the encoder 110 and the microprocessor 112 can be considered a processor 114 within the scope of the present invention. The encoder 110 can be located in the same apparatus as the microprocessor 112 or, alternatively, can be integrated in the device that is remote from the housing of the microprocessor apparatus 112. When the encoder 110 is remotely located, the encoder 110 it is not necessarily under the control of the microprocessor 112. The system 100 may include a controller 116 for reading data and writing data in a storage medium 118. For example, the data may be a signal encoded in digital form. The system 100 may also have a decoder 120 for decoding the encoded video signal when it is read from the storage medium 118 and transfers the decoded video signal to an appropriate component, such as a display device. The decoder 120 can be mounted in the same apparatus that contains an encoder 110 (when the encoder 110 is not remotely located), the microprocessor 112 and the controller 116 or as will be described later, can be mounted in a separate device. Control and data interfaces can be provided to allow the microprocessor 112 to control the operation of the encoder 110 (as mentioned above), the controller 116 and the decoder 120. Appropriate software or firmware can be provided in the memory for operations conventional ones carried out by the microprocessor 112. In addition, program routines may be provided for the microprocessor 112 in accordance with the inventive arrangements. During operation, the encoder 110 can receive and encode an incoming progressive video signal. As is known in the art, this type of video signal is composed of images that have been scanned in a progressive manner. in accordance with the inventive arrangements, the microprocessor 112 can instruct the encoder 110 to encode the incoming video signal within one or more GOPs that are particularly useful for performing the trick modes. Examples of such GOPs are presented below. The encoder 110 can transfer the encoded video signal to the controller 116, which can record the signal in the storage medium 118. In the case where the encoder 110 is remotely located, the encoder 110 can encode the incoming progressive video signal, but the encoding instructions are not necessarily received from the microprocessor 112. When the microprocessor 112 receives a playback command, the microprocessor 112 can instruct the controller 116 to read the encoded video signal from the storage means 118. The controller 116 can transfer the signal to the microprocessor 112, which can send the signal to the decoder 120. The decoder 120 can decode the video signal and emit the signal for deployment in an appropriate device. When the microprocessor 112 receives a trick mode command, the microprocessor 112 may skip images in the GOP, insert duplicates of the images within the GOP or cause the display of any combination of images in an inverted order. As mentioned before, there are some cases where the decoder 120 performing the decode step is located in a device separate from the apparatus containing the microprocessor 112. An example of such an arrangement is illustrated in Figure 1B, where the decoder 120 is in a deployment device 122, separate from a multimedia device 124 that can host the microprocessor 112. In this case, the decoder 120 may not be under the control of the microprocessor 112. Such a system may be called as a remote decoder system. . However, trick modes can still be carried out in this system 100, where the microprocessor 112 can alter the order of display of the images in the GOP before decoding to allow the images to be displayed in reverse order. . In addition, the microprocessor 112 can delete images or insert duplicates of the images in the GOP before being decoded by the decoder 120 in the display device 122. It should be understood that the encoder 110 in this type of system can also be located remotely. In any of the arrangements described with respect to Figures 1A and 1B, the GOPs created during the coding process will facilitate efficient implementation of the reverse trick mode. The general operation of the invention will be described in detail below. With reference to Figure 2, a method 200 is illustrated which shows a way to perform a reverse trick mode on a progressive video signal with the use of special GOPs. The method 200 can be practiced in any appropriate system with the ability to encode and decode a video signal. The method 200 may begin, as shown in step 210. In step 212, the progressive video signal may be received. As mentioned before, a progressive video signal contains images that have been explored progressively. As shown in step 214, the progressive video signal may be encoded in at least one GOP having at least one prediction source image and at least one non-prediction source image. In an array, all non-prediction source images can be predicted from the prediction source image, so that none of the non-prediction source images is predicted from another non-prediction source image. With reference to Figure 3, an example of such a process is shown. In this particular arrangement, the video signal can be encoded in one or more GOP 300. The GOP 300 are displayed in the order of display. Each of the GOP 300 may include at least one prediction source image 310 and at least one non-prediction source image 312. A prediction source image is an image in a GOP that is not predicted from another image and can still 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 may be an I image, and the non-prediction source images 312 may be B and / or P images. Each of the 312 non-prediction source images may be predicted from the source 310 image. prediction, which in this example correlates with each of images B and P to be predicted from image I. Because P images can function as images 312 non-prediction source, it will be evident that an image 312 source of no prediction is not limited to images from which no other image can be predicted, such as images B. In accordance with the inventive arrangements, however, each of the images 312 source of non-prediction can only be predicted from the image 310 prediction source. In an arrangement, the B images can be prediction images of an address, so that the B images before or in front of the I image (in the order of display) can be predicted regressively from the I image, and the B images behind the Image I (in the order of display) can be predicted in advance of the image I. The suffix numbers incorporated within the images 310 prediction source and the images 312 non-prediction source can indicate the order in which these images will be displayed - in relation to other images in the GOP - at a normal playback speed (forward). As noted before, the GOP 300 is displayed in the order of deployment. The order of transmission is slightly different in that the prediction source image 310, in this example, the image l3, can be transmitted to a decoder first, followed by the images 312 non-prediction source, which will be predicted from the source image 310 of prediction. It is important to mention that the invention is not limited to these particular GOP 300, since it only represents an example of a GOP structure in accordance with the inventive arrangements. In fact, any GOP, in which the source images of non-prediction in the GOP can be predicted, of a source prediction image in that GOP is within the scope of the inventive arrangements. In addition, although only two GOP 300 are shown in Figure 3, where each GOP 300 has a prediction source image 310 and six images 312 non-prediction source, it should be understood that the received video signal can be encoded in any suitable number. of GOP 300 with any number of images 310 source of prediction and images 312 source of non-prediction. Also, when more than one prediction source image 310 is in the GOP 300, any B images in the GOP 300 can be predicted bidirectionally. As an example, more than one image 310 prediction source can be placed in the GOP 300 and some of the 312 non-prediction source images can be predicted from these images 310 prediction source. As such, the prediction source 310 images can be transmitted to a decoder before the images 312 source of non-prediction depend on these images 310 prediction source for prediction. With reference again to method 200, in step 215, the progressive video signal containing the GOPs can be recorded in an appropriate storage medium. Once recorded, the progressive video signal containing the GOPs can be played, as shown in step 216. In step 217, a reverse trick mode command can be received. In response, the order of GOP deployment can be altered to cause the GOP to be displayed in an inverted order, as shown in step 218. An example of such a step is illustrated in Figure 4A. Here, each of the GOP 300, as illustrated first in Figure 3, is shown with the images 310 prediction source and the images 312 non-prediction source in the inverted order. By altering the order of display of the images in the GOP 300 it can be useful to carry out the inverse trick mode, especially in the remote decoder system. The reason that such a process is particularly useful in this type of system is that the decoder in the remote decoder system can not receive instructions that direct the display images in reverse order. However, it should be understood that the method 200 is not limited to the application in a remote decoder system. The prediction source images 310 and the non-prediction source images 312 shown in Figure 3 may contain display indicators. In an array, the deployment indicator can be a temporary reference field. A temporal reference field is typically a ten-bit field located in the image header of the images encoded in digital form. Some decoders rely 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, in general, it has a whole value. With reference again to Figure 3, as an example, each GOP 300 contains seven images. The suffix numbers for the images in each GOP 300 can correspond to an integer values for each time reference field of the respective image. For example, the temporal reference field of the first image 312 non-prediction source or image B0l 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, can have an integer value of one. In this way, the integer value of the temporal reference field for each subsequent image to be displayed can be greater than 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 named as" whole value ". When the order of display of the images in the GOP 300 is altered to allow the GOP to be displayed in the inverted order, as shown in Figure 4A, the indicators of the original display or the integer values will no longer be valid. As such, and with reference again to method 200 of Figure 2, the display indicators of the prediction source images and the non-prediction source images will be modified in order to reflect the proposed order, as shown in step 220 An example of the result of this step is illustrated in Figure 4B. Here, the new integer values reflecting the new deployment order are displayed. The original integer values are shown in parentheses. Although the integer value for the prediction source images 310 in this example did not change, it should be noted that the invention is not limited to this aspect, it may be necessary, based on the structure of the GOP to modify the whole value of the image 310 prediction source. It should be understood that the invention is not limited to this particular example, since other ways can be carried out to modify the integer values of the relevant temporal reference fields to reflect the proposed deployment order. Furthermore, it should be noted that the invention is not limited to the use of temporal reference field, since an appropriate display indicator may be modified to reflect the proposed order of deployment in any of the above-described modes. With reference again to method 200 of Figure 2, decision block 222 can be determined to see if the last source image of non-prediction in the altered GOP is a P-image. For purposes of the invention, the term "altered GOP" "refers to a GOP where the order of display of the images in the GOP has been altered to allow the GOP to be displayed in the inverted order. When it is affirmative, method 200 can be resumed in decision block 226 through a jump circle A. When this is not the case, the last source image of non-prediction in the altered GOP may become a P image, as shown in step 224. An example of this process is shown in Figure 4C.

The last non-prediction source image 312 in the GOP 300, which was originally the image B6, has been converted into a P image or a P6 image. The reason for this conversion is that the specifications for the MPEG video requires that the last image in the GOP is a P image or an I image. As an example, the B image can be converted into a P image by adjusting the values of the P image. in the following parameters located in the image header of image B: type_coding_type; comp! eto_pel_anterior_vector; and previous_f_code. In addition, the following variable length codes can be set for the macroblock_type for the values of the image P: macroblock_quant; macroblock_forward_movement; macroblock_movement_attention; macroblock_pattern; macroblock_intra; spatial_temporal_ponderación_code_label; and allowed space_temporal_ponderación_clases. This step can instruct the decoder to decode the image as an image P. As such, in accordance with the inventive arrangements, the order of deployment of a GOP can be altered to allow the GOP to be displayed in an inverted order without violating the requirement. MPEG that the last image in the GOP is a picture P. With reference again to the method 200 of Figure 2, in the decision block 226 (from the jumping circle A) it can be determined that all the source images of non-prediction in the altered GOP which are opposite (in the order of display) of the prediction source image are images B. When this is the case, method 200 may continue in decision block 230. When this is not the case, then the non-prediction source images can be converted into B images, for example, B-images predicted in a regressive manner, as shown in step 228. For example, with reference to Figure 4D, after the alteration of the display order, the first image 312 non-prediction source was an image P, or an image P0, which is shown in parentheses. In accordance with step 228, the image P0 can be converted into a B0 image. In an arrangement, a P-image can be converted into a B-projected image in a regressive way by adjusting the values of the B-image of the following parameters located in the header of the image of the image P: coding_type_type; complete_pel_anterior_vector; and previous_f_code. In addition, the following variable length codes can be set for the macroblock_type for the values of image B: macroblock_quant; macroblock_front_movement; macroblock_movement_attention; macroblock_pattern; macroblock_ir, tra; spatial_temporal_ponderación_code_label; and allowed space_temporal_weight_ponderation. Because the source 312 images of non-prediction before (in the order of display) of the prediction source image 310 will be the forecasted predicted images, converting such P images into B images improves the prediction scheme of the GOP 300, since P images can not be predicted earlier, then they can only be predicted in advance. The prediction scheme can be used with the altered GOP as shown in Figure 4D. Up to this point, the GOP 300 has been described in relation to a reverse trick mode, where the images in the GOP 300 are displayed in an inverted order at a normal playback speed (normal playback speed is 1X). However, there are certain cases where viewers want to watch the video in reverse at different speeds than 1X, such as a fast reverse or a slow reverse method. Typically, the video speed can be changed by adding images or skipping images in the video. Referring again to Figure 2, it can be determined whether the number of source images of non-prediction in the altered GOP will be modified, as shown in decision block 230. When not, the method 200 may terminate at step 242. When the number of images in the altered GOP is to be modified, such a process may be carried out in step 232. In Figures 5A to Figure 5D, They show several examples. With reference to Figure 5A, each of the altered GOP 300 (as illustrated in Figure 4D), is shown with several images 312 non-predicted source removed or skipped. Specifically, images B0, B2, B4 and P6 on the GOP 300 on the left can be skipped, while images B-, B4 and P6 on the GOP 300 on the right can be skipped. By jumping such images 312 non-prediction source may cause the inverted playback speed to increase. Here, the number of images 312 non-predicted source jumped, half of all images in two GOP 300, is correlated with the playback speed that is twice the speed of normal playback, or 2X. In accordance with the inventive arrangements, any of the 312 non-prediction source images in the GOP 300 can be skipped to increase the inverted playback speed of the video signal without affecting the prediction of any of the images 312 non-prediction source in the GOP 300. This feature is possible by the coding process described here. A step to place the GOP 300 in accordance with the MPEG standard, for example, will be described later. Of course, it should be understood that the invention is not limited to the example described above with respect to Figure 5A, since the ability to skip all images 312 non-prediction source in any order during a fast reverse trick mode applies to any other GOP, wherein the 312 non-prediction source images are predicted from the 310 source prediction image. Also, the full GOP 300 can be skipped to produce faster playback. Referring again to Figure 2, modification step 232 may also include the step of inserting into the altered GOP a duplicate of at least one prediction source image or a non-prediction source image to produce a trick mode of slow reverse. An example of such an operation is shown in Figure 5B. Here, a duplicate of each image 310 prediction source and each image 312 non-prediction source can be inserted into the altered GOP 300 (for convenience), only one GOP 300 is shown). This particular example can produce a reproduction speed of 1 / 2X. The letter subscript "d" represents the image to which it is associated as a duplicate of the immediately preceding image. Like the original source 312 non-prediction images, duplicates of such images can be predicted from a 310 prediction source image (in accordance with the MPEG standard, the last image in the GOP 300, the duplicate of a P6_ image). it can be predicted from the immediately preceding image P, which in this case is 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 Figure 5B is explained as follows: all 312 non-prediction source images and their duplicates opposite (in the order of display) of the original prediction source image 310, or the l3 image, can be predicted from the image l3. In addition, the source 312 images of non-original predictions and their duplicates behind (in the order of display) the duplicate of the image 310 original prediction source, or the image l3d, can be predicted from the duplicated l3d image (with the exception of the image P6d duplicated). However, it should be understood that this particular arrangement is only an example, since the non-prediction source images and their duplicates can be predicted from any appropriate source prediction image 310, which includes any duplicate of a 310 source image. of prediction.

In another arrangement, one or more of the duplicate images inserted in the altered GOP 300 may be a simulated B-image or a simulated P-image. A simulated image B or a simulated image P is a picture B or P, respectively, wherein the motion vectors of the simulated image are set to zero and their residual signal is set to zero or not coded. For example, the duplicate of the prediction source image 310 (the image 13) in the altered GOP 300 may be a simulated P image instead of another I image, such as the l3d image. Similarly, the duplicate for the last non-prediction image 312 (image P6) can be a simulated image P, better than a conventional image P, such as the image P6d. With the use of the simulated B or P images during the trick mode the bit rate of the video signal may decrease, which may be necessary in other circumstances, in particular, when the method 200 is to be carried out in the remote decoder system. Referring again to Figure 2, in the decision block 234 it can be determined whether the last source image of non-prediction in the altered GOP has been skipped. When not, the method 200 may be resumed in step 240. When this is the case, it may be determined in block 236 whether the source image of the immediately preceding non-prediction in the order of display in the altered GOP is a P-image. thus, method 200 may continue to step 240. When it is not, then the immediately preceding non-predicting source image in the altered GOP may be converted to a P image, as shown in step 238.

An example of this operation is illustrated in Figure 5C. As mentioned before, the specifications for MPEG video require that the last image in the GOP be a P-image. Thus, when a P6 image in the altered GOP 300, a 312 non-prediction source image, was jumped during a Quick reverse trick mode, the last image on the GOP 300 (when it was not skipped) will be a B5 image, a violation for the MPEG standard. To satisfy the MPEG requirement, the immediately preceding non-predicting source image 312, in this case, the B5 image, can be converted into an image P, or an image P5. This conversion has already been described, and it is not necessary to describe it again. As such, the last image in an altered GOP 300 can be skipped without violating the MPEG standard that the last image in the GOP must be an image P. Referring again to method 200 of FIG. 2, in step 240 (similar to step 220), the display indicators of the prediction source images and the non-prediction source images can be modified. By modifying the display indicators of these images, it can reflect the proposed order of the altered GOP when any of the source images of non-prediction or prediction are skipped or duplicated. When, for example, a source image of non-prediction is skipped, the previous display order is no longer valid. Accordingly, the display indicators of the prediction source images and the non-predicted source images following the skipped image can be modified to indicate the appropriate deployment order. This feature can also be applied when duplicates of the prediction source images or non-prediction source images are inserted into the altered GOP. As an example, with reference to Figure 5D, when the image B- is skipped, in the altered GOP 300, then the integer values of the prediction source images 310 and of the non-prediction source images 312 that follow this image they can be decreased by a value of one. Thus, 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. In this particular example, the new integer values are shown, the image B-, skipped is represented by a dotted line or the old integer values are in parentheses. This modification process may continue until the end of the altered GOP 300 is reached and can ensure that the remaining images in the altered GOP 300 are displayed in the proper order. Each time a prediction source image 310 or a non-prediction source image 310 is skipped in an altered GOP, the integer values of the temporal reference fields of the remaining images in that GOP following the skipped image can be decreased by a value of one. Also, when the images in the altered GOP are duplicated, the integer values of the images following the added duplicates can be increased by a value of one each time a duplicate is added. With reference to Figure 2, method 200 can be stopped at step 242. Although the present invention has been described along with its modalities, it should be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention. invention, as defined in the appended claims.

Claims (34)

1. A method for carrying out an inverse method, characterized in that it comprises the steps of: receiving a progressive video signal; encoding the progressive video signal into at least one group of images having at least one prediction source image and at least one non-prediction source image, wherein all non-prediction source images are predicted from the image prediction source, so that none of the non-prediction source images is predicted from another non-prediction source image; and in response to a reverse trick mode command, alter the order of display of the group of images to allow the group of images to be displayed in an inverted order. The method according to claim 1, characterized in that it further comprises the step of recording the progressive video signal in a storage medium; and play the progressive video signal. The method according to claim 1, characterized in that it further comprises the step of modifying at least a number of the non-prediction source images in the group of images in response to the inverse trick mode command. 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 a portion of the non-prediction source images are bidirectional predictive images. 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 bidirectional predictive images is a bidirectional predictive image of a direction. The method according to claim 3, characterized in that the step of modifying comprises the step of skipping at least one source image of non-prediction in the group of images.- 9. The method according to claim 3, characterized because the step of modifying comprises the step of inserting in the image group a duplicate of at least one source image of non-prediction. The method according to claim 8, characterized in that the skipped non-predicted source image is a predictive image that is the last image in the display order in the group of images and wherein the method also comprises the step of converting a source image of no immediately preceding prediction in the order of display, in the group of images in a predictive image unless the immediately preceding non-predicting source image is a predictive image. The method according to claim 1, characterized in that each of the prediction source image and the non-prediction source images contains a display indicator and the method also comprises the step of modifying the display indicator of less a portion of the prediction source images and the non-prediction source images to reflect the proposed deployment order. The method according to claim 11, characterized in that the display indicator is a temporary reference field. The method according to claim 3, characterized in that each of the prediction source image and the non-prediction source images contains a display indicator and the method also comprises the step of modifying the display indicator of less a portion of the prediction source images and the non-prediction source images to reflect the proposed deployment order. The method according to claim 13, characterized in that the display indicator is a temporary reference field. 15. The method according to claim 1, characterized in that after the step of altering, also comprises the step of converting the last non-predicted source image in the altered group of images into a predictive image unless the last non-predicted source image in the altered group is a predictive image. The method according to claim 1, characterized in that after the step of altering, it also comprises the step of selectively converting the bidirectional predictive images the source images of non-prediction opposite, in the order of display, of the source image of prediction. 17. The method according to claim 1, characterized in that it further comprises carrying out the steps of receiving, encoding and altering in a remote decoder system. 18. A system for performing a reverse trick mode, characterized in that it comprises: a processor for encoding a progressive video signal into at least one group of images having at least one prediction source image and at least one a non-prediction source image, where all non-prediction source images are predicted from the prediction source image, so that no non-prediction source image is predicted from another source image of non-prediction; and a decoder for decoding the group of images; wherein the processor is also programmed to respond to a reverse trick mode command, altering the order of display of the group of images to allow the group of images to be displayed in reverse order. 19. The system according to claim 18, further comprising a controller for recording the progressive video signal in a storage medium and reproducing the progressive video signal. The system according to claim 18, characterized in that the processor is also programmed to modify at least the number of non-prediction source images in the group of images in response to a reverse trick mode command. 21. The system according to claim 18, characterized in that the prediction source image is an intra image. 2

2. The system according to claim 18, characterized in that at least a portion of the non-prediction source images are bidirectional predictive images. 2

3. The system according to claim 18, characterized in that at least a portion of the non-prediction source images are predictive images. 2

4. The system according to claim 22, characterized in that each bidirectional predictive image is a bidirectional predictive image of a direction. 2

5. The system according to claim 20, characterized in that the processor is also programmed to skip at least one source image of non-prediction in the group of images. 2

6. The system according to claim 20, characterized in that the processor is also programmed to insert in the image group a duplicate of at least one non-predicted source image. The system according to claim 25, characterized in that the skipped non-predicted source image is a predictive image that is the last image in the display order in the image group and where the processor is also programmed to convert a source image of immediately preceding non-prediction in the order of display in the group of images in a predictive image unless the immediately preceding non-predicting source image is a predictive image. The system according to claim 18, characterized in that each of the prediction source image and the non-prediction source images contain a display indicator and the processor is programmed to modify the display indicator of at least a portion. of the prediction source images and the non-prediction source images to reflect the proposed deployment order. 29. The system according to claim 28, characterized in that the display indicator is a temporary reference field. The system according to claim 20, characterized in that each of the prediction source image and the non-prediction source images contains a display indicator and the processor is also programmed to modify the display indicator of at least one portion of the prediction source images and non-prediction source images to reflect the proposed deployment order. 31. The system according to claim 30, characterized in that the display indicator is a temporary reference field. 32. The system according to claim 18, characterized in that the processor is also programmed to, after the alteration of the display order, convert the last source image of non-prediction in the altered group of images into a predictive image unless the last source image of non-prediction in the altered group of images is a predictive image. 33. The system according to claim 18, characterized in that the processor is also programmed to, after altering the order of deployment, selectively convert in bidirectional predictive images the source images of non-prediction opposite, in the order of display, of the source image of prediction. 34. The system according to claim 18, characterized in that the processor and the decoder are part of a remote decoder system.