Apparatus and method for recording digital image data

0001The present invention relates to a media recording device and associated method for storing data comprising means operable to compress data at a first compression rate and to store the compressed data.

0002With the launch of digital satellite and terrestrial broadcasting systems, high quality videos can be transmitted with very little or no perceptible loss of picture quality. Unlike analogue broadcasting systems, with digital broadcasting systems, further information can be transmitted alongside the picture and sound information. This allows a viewer to access a variety of additional features. For example, a viewer can access a variety of different entertainment platforms using digital broadcasting. Due to these advantages, there has been growing interest in recording and playback devices (sometimes referred to as an image recording and reproducing apparatus) utilising high quality video such as those used in digital broadcasting.

0003In general, a recording and playback device may be a video cassette recorder (VCR), a digital video disc player/recorder (DVDP), or a digital video recorder (DVR).

0004The DVR is in increasing demand because it can record and playback videos (and sound) from terrestrial broadcasting, satellite broadcasting, cable broadcasting and network broadcasting over the Internet. Since the DVR records the videos (and sounds) as files containing video data in a hard disc drive (HDD), performing a file search for playback is simple, and degradation of the image quality seldom occurs even if the video is repeatedly played back.

0005However, the HDD has limited storage capacity. Therefore, the DVR compresses the video data for more space-effective storage, usually employing a moving picture experts group (MPEG) format which is an efficient compression method.

0006Previously, audio was the main source of public entertainment. However, the use of videos for entertainment is increasing. Therefore, there is a desire to increase the number of video files recorded on the HDD. Moreover, due to the amount of data required to represent high quality video, the DVR may reach its storage capacity limit quickly even if provided with a high capacity HDD.

0007When the size of the stored videos reaches the capacity of the HDD (or any recording medium), some stored videos should be deleted. Alternatively, the HDD can be replaced with one having a larger capacity, or an extra HDD (or other recording medium) can be added. However, the stored videos are sometimes reluctantly deleted, and additional expense is incurred for a replacement or additional HDD.

0008An aspect of the present invention is to address the above problems and to provide at least the advantages described below.

0009The present invention relates to a media recording device operable to compress data representative of media at a first compression rate and to store the compressed data. A media recording device according to the present invention is characterised in that, in response to a control signal, the device is operable to decode the stored compressed data, to recompress the decoded data at a second compression rate, and to store the recompressed data.

0010The present invention also relates to a method of recording data, comprising compressing data representative of media at a first compression rate and storing the compressed data.

0011A method according to the present invention is characterised by, in response to a control signal, decoding the stored compressed data, recompressing the decoded data at a second compression rate, and storing the recompressed data This is advantageous because a user has the opportunity to reduce the amount of storage space taken up by a video without actually deleting the video. This gives the user flexibility to keep videos they may previously would have had to delete or buy a new storage medium to keep.

0012The term "compression rate" refers to the amount of compression that is effected, for example in terms of the reduction in data quantity, perhaps expressed as a fraction or percentage.

0013Preferably, the device is operable to store the recompressed data in replacement of the compressed data. By "replacement", this does not necessarily mean that the recompressed version will physically overwrite the compressed version. However, instead of the recording device accessing the compressed version of the video, it will access the recompressed version of the video when playing back the stored video.

0014Also, the device may also be operable to store said recompressed data after the device experiences a power down event. In other words, the recompression of the data may occur when the recorder is put into "standby".

0015An embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: <ul id="ul0001" list-style="none" compact="compact"><li>Figure 1 is a view of a display system connected to a recording/playback device according to an embodiment of the present invention;</li><li>Figure 2 is a block diagram of the recording/playback device of Figure 1 according to an embodiment of the present invention;</li><li>Figures 3A to 3D are images illustrating example screen shots of a menu screen used for re-compressing and re-recording data; and</li><li>Figure 4 is a flowchart illustrating a method for re-compressing and re-recording data according to an embodiment of the present invention.</li></ul> Referring to Figure 1, a recording/playback device 100 is connected to a television (TV) 300, which is used as a display, by a transmission cable 350. The recording/playback device 100 is operated using a remote controller 200, which is an external device, and passes appropriate signals to the TV 300 to display videos and produce sounds.

0016Referring to Figure 2, the recording/playback device 100 comprises an input/output terminal part 110, a switching part 123, a first switch part 140, a second switch part 150, a moving picture experts group (MPEG) encoder 161, a hard disc drive (HDD) 171, and a main controller 180.

0017The input/output terminal part 110 receives signals from different sources, and outputs the received signals and a signal reproduced from the HDD 171 and a disc player 175.

0018The input/output terminal part 110 includes a super-video input terminal (S-V IN) 111, a super-video output terminal (S-V OUT) 112, a radio frequency input terminal (RF IN) 113, a radio frequency output terminal (RF OUT) 114, a line video and audio input terminal (LINE V_IN, LINE A_IN) 115, a line video and audio output terminal (LINE V_OUT, LINE A_OUT) 116, and a serial parallel digital interface (SPDIF) 117.

0019A tuner 121 tunes to a channel so that the appropriate signal can be received through the RF input terminal 113. The tuner 121 tunes to a channel requested by an input/output control part 125. The input/output control part 125 is controlled by the main controller 180. The switching part 123, which is controlled by the input/output control part 125, selectively controls the input/output terminals connected to the switching part 123 so that different combinations of the input/output terminals can be connected with one another.

0020A video decoder 131, controlled by the main controller 180, decodes and converts the analogue signal received through the super video input terminal or the switching part 123, into a digital video signal. The digital video signal is output from the video decoder 131 to an MPEG encoder 161 through a first video path switch 140a of the first switch part 140. The first video path switch 140a is controlled by the main controller 180.

0021An audio analogue-to-digital converter 133 converts the analogue audio signal input through the switching part 123 to a digital audio signal. The digital audio signal is input to the MPEG encoder 161 through a first audio path switch 140b of the first switch part 140. The first audio path switch 140b is controlled by the main controller 180.

0022The MPEG encoder 161, receives the digital video signal from the video decoder 131 and the digital audio signal from the audio analogue-to-digital converter 133 through the first switch part 140. The MPEG encoder 161 encodes the signals using a compression format and rate set by the main controller 180. The encoded signals are stored in the HDD 171. Preferably, the MPEG encoder 161 uses the MPEG-2 format, although the invention is not so limited. As an example, if the digital video and audio signals are recorded using MPEG-2 at a standard definition (SD) bitrate of 6Mbps, 3 Giga byte (GB) of storage is required for a one-hour recording.

0023Although the HDD 171 is used as an example in this embodiment, it will be appreciated that other recording media such as an optical recording medium or a semiconductor memory could equally be used.

0024A synchronous dynamic random-access memory (SDRAM) 163 is used as a buffer to temporarily store the data encoded by the MPEG encoder 161.

0025A data management part 177 manages recording and playback of the data onto and from the HDD 171 or the disc player 175. A light receiving part 191 receives operation signals from the remote controller 200 and outputs the operation signal to the main controller 180.

0026The main controller 180 may be a single-chip integrated circuit (IC) comprising a central processing unit (CPU) 181, an MPEG decoder 183 for decoding data compressed in the MPEG format, and an on screen display (OSD) part 185 for generating data corresponding to a menu. The MPEG decoder 183 and the OSD part 185 may equally be separate chips respectively connected to the main controller 180.

0027The MPEG decoder 183 decodes the MPEG compressed data so as to restore and output the original digital video and audio signals, respectively. The digital video signal output from the MPEG decoder 183 is input to a video encoder 137 through a second video path switch 150a of the second switch part 150. The second video path switch 150a is controlled by the main controller 180. The digital audio signal output from the MPEG decoder 183 is input to a digital-to analogue converter 135 via a second audio path switch 150b of the second switch part 150. The second audio path switch 150b is controlled by the main controller 180.

0028The video encoder 137, receives the digital video signal output by the MPEG decoder 183 via the second video path switch 150a. The digital video signal is converted to an analogue video signal which is output to the switching part 123. The digital-to-analogue converter 135, receives the digital audio signal output from the MPEG decoder 183 via the second audio path switch 150b. The digital-to-analogue converter 135 converts the digital audio signal to an analogue audio signal which is output to the switching part 123.

0029Hereinbelow, there will be explained processes for re-compressing using high compression rates and re-recording in the HDD 171 the data which was previously compressed by the MPEG-2 format and recorded in the HDD 171.

0030When the user instructs the main controller 180 to commence operating the image recording and reproducing apparatus in an 'edit' mode, the OSD part 185 is instructed by the main controller 180 to output an edit menu. The user may instruct the main controller 180 using operation buttons provided on the remote controller 200 or a key input part 193. The light receiving part 191 or the key input part 193 then transmits the user's command to the main controller 180. The output 'edit' menu is transmitted to the TV 300 through the second video path switch 150a, the video encoder 137, the switching part 123, and the line video and audio output terminal 116, and as a result, the 'edit' menu screen is displayed on the TV 300. The user then moves a cursor on the 'edit' screen displayed on the TV 300 using direction keys on the remote controller 200 or the key input part 193, and selects menus highlighted by the cursor using a 'confirmation' key. The main controller 180 controls the OSD part 185 to display or change the menu screens, characters, symbols, and pictures according to a user's command.

0031Figures 3A to 3D are images illustrating examples of re-compressed and re-stored data, using the 'edit' menu screen displayed on the TV 300. Since the image recording and reproducing apparatus is set in the edit mode, the TV 300 displays the menu screen in the 'edit' mode, as shown in Figure 3A. The word 'Edit' is displayed on top of the menu screen, indicating the menu item 410 currently displayed on the menu screen. Additionally, 'Instructions' is displayed on the bottom 440 of the menu screen providing a link for guidance around the screen using the keys.

0032Information about the keys of the remote controller 200 and the functions of the keys is also displayed at the bottom 440 of the menu screen.

0033Sub-menus 420 for the current menu item 410 are displayed under the current menu item 410. In Figure 3A, items of 'Combine', 'Divide', 'Delete', 'Partial Delete', and 'Recomp(ression)' are illustrative of sub-menus of the 'Edit' menu. When a user places the cursor on the 'Recomp' menu using the direction keys of the key input part 193 or the remote controller 200, the main controller 180 controls the data management part 177 to read information about the video data stored in the HDD 171. The information about the video data may comprise the first (or representative key) frame of the video data, the title, the date of storage, running time and video quality. The main controller 180 controls the OSD part 185 to output a signal corresponding to the information, and the output signal is transmitted to the TV 300 via the second video path switch 150a, the video encoder 137, the switching part 123, and the line video and audio output terminal 116.

0034The data information is displayed on a 'Recomp' window 430 as shown in Figure 3A. The 'Recomp' window 430 displays a video data list 431 currently stored in the HDD 171 by horizontally showing the first (or representative key) frame 431 a to 431f of respective video data. If the user moves the cursor downward on the 'Recomp' window using direction keys, the cursor is placed on the video data list 431, and video data information 433. The video item highlighted by the cursor is displayed at the bottom of the data list 431. More specifically, the cursor is placed on the first image 431a of the first video data such that the title, the date of storage, the running time and the image quality of the first video data are displayed as the video data information 433 shown in Figure 3A.

0035The user can move the cursor in a horizontal direction to highlight different video data. The user then presses the confirmation key to select the video data file for re-compression. The first (or representativekey) frame of the selected video data is displayed in a re-compression video data list 435. Figure 3B illustrates a resultant re-compression list displaying the first image 431 a and 431e from the first and fifth video data file as selected from the data list 431.

0036In order to re-compress the selected data, a user moves the cursor down using the direction key and places the cursor on the 'Execute' icon 437, and presses the confirmation key. As shown in Figure 3C, a re-compression rate-setting window 450 appears in the centre of the screen. For example, a high-quality (HQ) method records the digital video and audio signals using 4Mbps bitrate, and a standard-quality (SQ) method records the signals using 2Mbps bitrate.

0037When either one of the two compression rates displayed on the re-compression rate setting window 450 is selected by the user using the direction keys and the 'confirmation' key, a re-compression time setting window 460 is displayed in the center of the screen. The re-compression time setting window 460 is shown in Figure 3D and allows the user to determine when the re-compression should take place. If the user selects 'Now', re-compression of the selected data begins immediately. If the user selects 'Automatic', the selected video data will be re-compressed after the main switch of the image recording and reproducing apparatus is turned off by the user. This means that the video data re-compression is performed when the image recording and reproducing apparatus is not in use since a large amount of time will be taken for the data re-compression. Therefore, the inconvenience of not being able to use the image recording and reproducing apparatus during data re-compression can be prevented.

0038After the user selects video data from amongst the video data stored in the HDD 171 for re-compression, and sets the re-compression rate and time, the process of which was previously described, the image recording and reproducing apparatus performs re-compression with respect to the selected video data according to the selected re-compression rate and time. Hereinbelow, the processes for re-compression of the image recording and reproducing apparatus will be described in greater detail.

0039If the user sets 'Now' as the re-compression time, the image recording and reproducing apparatus performs re-compression of the selected data at once. Accordingly, the main controller 180 controls the selected data stored in the HDD 171 so that it is transmitted to the MPEG decoder 183 via the data management part 177. The MPEG decoder 183 decodes the received MPEG-2 data to restore the digital video and audio signals. The digital video and audio signals are then output. The digital video signal output from the MPEG decoder 183 is fed into the MPEG encoder 161 via the second video path switch 150a and the first video path switch 140a. The digital audio signal output from the MPEG decoder 183 is input to the MPEG encoder 161 via through the second audio path switch 150b and the first audio path switch 140b. The main controller 180 controls the first and the second switch parts 140 and 150 so that a data transmission path is provided for the digital video and audio signals output from the MPEG decoder 183. The digital video and audio signals are then fed to the MPEG encoder 161.

0040The MPEG encoder 161 re-compresses and re-stores the input digital video and audio signals according to the re-compression rate to the HDD 171. If the digital video and audio signals are recorded using 4Mbps or 2Mbps bitrate, 2GB or 1GB is required for 1-hour recording, respectively. When recording using MPEG-4 with 1Mbps bitrate, 0.5GB is required for 1-hour recording. Accordingly, if certain data previously recorded using 6Mbps bitrate is re-compressed using 4Mbps or 2Mbps or 1Mbps, the required storage capacity of the recording medium decreases to 2/3, 1/3 or 1/6, of the previously required amount respectively. Although image quality deteriorates when the compression rate is high, because video which has been previously watched is rarely watched again, the image quality is not so important, and thus re-compressing and re-storing a previously watched video using a high compression rate is a very effective way of utilizing the storage medium.

0041If the user selects 'Automatic' for the re-compression time, the main controller 180 stores the list of the selected data to the SDRAM 187. Such selected data is re-compressed when the user turns off the main switch of the image recording and reproducing apparatus. The re-compression is performed in the same manner as the re-compression according to the 'Now' re-compression time.

0042Referring to Figure 4, when the user sets the 'Edit' mode using the operation buttons provided on the remote controller 200 or the key input part 193, a menu screen showing the edit mode is displayed on the TV 300. When the 'Recomp' item, from amongst the sub-menus of the displayed edit menu, is selected by the user, the re-compression mode begins in step S611.

0043In the re-compression mode, the main controller 180 controls the data management part 177 to read information about MPEG data stored to the HDD 171. The main controller 180 controls the OSD part 185 to output a signal corresponding to the read information. The output signal is transmitted to the TV 300 via the second video path switch 150a, the video encoder 137, the switching part 123, and the line video and audio output terminal 116. The data information may comprise the first (or representative) image of the video, the title, the date of storage, running time and image quality. These are displayed in the 'Recomp' window 430. The 'Recomp' window 430 displays the list of videos 431 currently stored in the HDD 171 and the data information about the video highlighted by the cursor, such as the title, the date of stroage, the running time and the image quality in step S613. The user moves the cursor around the video data list, highlighting the video data to be re-compressed, and presses the confirmation key, thereby selecting the data that will be re-compressed in step S615.

0044In order to re-compress the data selected in step S615, the user has to move the cursor down using the direction key and place the cursor on the 'Execute' icon 437, and press the confirmation key to execute the command. The main controller 180 detects whether there is an execution command from the user in step S621. When there is an execution command input by the user, the re-compression rate setting window 450 is displayed in the centre of the screen. The user can select one of the two compression rates, e.g., the HQ method using the 4Mbps bitrate or the SQ method using 2Mbps bitrate, displayed on the re-compression rate setting window 450. This selection is made using the direction keys and the confirmation key in step S623.

0045When the user selects the compression rate, the re-compression time setting window 460 is displayed in the centre of the screen. The user selects between the 'Now' and 'Automatic' schedule for compressing the data in step S625. If the user selects 'Now', re-compression of the selected data begins immediately in step S631. Therefore, the main controller 180 controls the selected video stored in the HDD 171 to be fed to the MPEG decoder 183 via the data management part 177 in step S633.

0046The MPEG decoder 183 decodes the received MPEG-2 data so as to restore the digital video and audio signals. The restored signals are then output from the MPEG decoder 183. The digital video signal output from the MPEG decoder 183 is input to the MPEG encoder 161 via the second video path switch 150a and the first video path switch 140a. The digital audio signal output from the MPEG decoder 183 is input to the MPEG encoder 161 via the second audio path switch 150b and the first audio path switch 140b. The main controller 180 controls the first and the second switch parts 140 and 150 to generate a video data transmission path such that the digital video and audio signals output from the MPEG decoder 183 can be input to the MPEG encoder 161 in step S635.

0047The MPEG encoder 161 re-compresses the input digital video and audio signals according to the compression rate set by the user in step S637, and re-stores the signals to the HDD 171 in step S639. If the digital video and audio signals are recorded using the 4Mbps, 2Mbps or 1Mbps bitrate, 2GB, 1GB or 0.5GB storage space is required, respectively for a 1-hour recording. If certain video recorded using the 6Mbps bitrate and requiring 3GB for 1-hour recording, is re-compressed using 4Mbps, 2Mbps or 1Mbps, requirements for the storage capacity of the recording medium decrease respectively to 2/3, 1/3 or 1/6 of that originally required, thereby enabling effective use of the storage capacity of the recording medium.

0048In step 631, if the user selects 'Automatic' for the re-compression time, the main controller 180 stores the list of the selected data to the SDRAM 187 in step S641. After this, when the user turns off the main switch of the image recording and reproducing apparatus, the selected data start to be re-compressed in step S643. The re-compression is performed as in steps S633 to S639.

0049As can be appreciated from the above, in certain embodiments of the present invention, video previously compressed and recorded in the recording medium can be re-compressed and re-recorded at higher compression rates. Accordingly, many inconveniences of having to delete pre-stored data for additional storage, replace the storage medium with the one of larger capacity, or add an extra storage medium when video data exceeds the capacity of the storage medium in use, can be prevented, and therefore, storage capacity of the storage medium of the present invention can be very efficiently used.