PL192033B1 - Bit stream processing for replay - Google Patents

Abstract

An apparatus reproduces a bit stream signal from a disk and the bit stream is controlled to ensure that only requested bit stream data is coupled for MPEG decoding. A transducer is repositioned to obtain requested bit stream data prior to completion of preceding MPEG picture decoding. The bit stream data is read prior to buffer storage to select wanted data for storage and to reject unwanted data. Buffer storage is reallocated for trick play operation and is random accessed to facilitate trick play picture selection. MPEG picture decoding and storage are controlled to facilitate frame decoding within one field period. Decoded pictures are stored and read out substantially concurrently within a field period.

Description

Description of the invention

The present invention relates to a method and apparatus for reproducing a digitally encoded signal from a medium, in particular for identifying repetition data in a multiplex format.

The introduction of discs recorded by digitally compressed audio and visual signals, for example using MPEG compression protocols, offers consumers an audio and video quality that is virtually indistinguishable from that of the original material. However, users expect performance characteristics from digital DVD video discs similar to those of an analog VCR cassette recorder. For example, a cassette recorder plays forward or reverse at speeds other than write speed. These non-standard speed playback features are also known as trick modes. Trick modes are more difficult to implement with MPEG encoded video signals due to the hierarchical nature of this compression, which forms groups of images having varying degrees of compression. These groups are referred to as GOP picture groups and require sequential decoding. The detailed MPEG 2 standard is the ISO / IEC 13818-2 standard. The MPEG 2 signal stream may contain three types of pictures having different degrees of content compression. The Type I Internally Encoded frame has the least compression of the three types and is decoded without reference to any other frame. The P predicted frame is compressed with respect to the preceding I or P frame and achieves a higher compression rate than the internally coded frame. The third type of MPEG frame, referred to as bidirectional coded, B-frame, is compressed based on the prediction of the preceding and / or following frames. Bidirectional coded frames have the highest degree of compression. These three types of MPEG frames are arranged into groups of GOP pictures that include, for example, 12 frames arranged as in Fig. 1A. Since only the intrinsically coded frame is decoded without reference to any other frame, each group of pictures can only be decoded following the decoding of the I-frame. The first predicted frame P is decoded and stored based on the stored modification of the preceding I frame. successively P-frames are predicted from the stored preceding P-frames. The prediction of P-frames is shown in Fig. 1A by curved solid arrows.

From the European patent specification No. EP 696 798, a method and device for data recording, a data carrier and a method and device for data reproduction are known, where an MPEG signal is recorded on various types of disc media. The description discloses a logging format containing additional information recorded separately from data as subcodes in each sector of the recorded medium. These subcodes provide information, e.g., image type, related to data in each sector, used during recovery to control the data recovery process.

It is known from US Pat. No. 5,535,008 to jump-through mode for reproducing data recorded in MPEG format, for example using CD-ROM, as well as playing back a plurality of data at predetermined intervals. The data to be restored next is located by subtracting the first determined value from the value corresponding to the total number of predetermined intervals. Average Type I frame spacing is used to address the transducer for fast track or reverse playback.

A method of recording in MPEG format on an optical disk is known from the European patent description No. EP 737 975. The format to be recorded includes a management area and a program area where the program data has a hierarchical structure. This format has some similarities to that of a universal DVD video disc.

A digital reproduction device for reproducing digitally processed photographic images is known from US Patent No. 5,543,925. The images are recorded on an optical compact disc for display on the screen according to stored data representing a pre-recorded sequence or a user-defined sequence. For each digital image stored, that image files contain a number of lower-order files, sub-files that define the same scanned image with different resolutions. These versions with different resolutions of the same image advantageously shorten the waiting time for the image presentation.

It is known from European Patent No. EP 651 391 to reproduce digitally encoded images at high speed using both two- and three-frame memories which store multiple groups of images for use in frame reverse playback. The selection of the output signal alternates between the decoded image memories. The memory selection and output image retention times are sensitive to the availability of the decoded images and the time required to obtain the next desired image.

The hierarchical nature of the encoded frames, including the groups of MPEG pictures, requires that the I and P-frames of each group be forward-decoded. In this way, the reverse mode functions are realized by performing efficient backward jumps to an earlier or preceding I-frame and then forward decoding the given group of pictures. The decoded frames are stored in the frame buffer memory for subsequent reads in the reverse direction to obtain the desired reverse program sequence.

Figure 1B shows forward normal speed playback up to time t0, after which the triple speed reverse trick play mode is selected. The trick mode of operation is initiated at time t0 when the I-frame (25) is decoded and displayed. The next frame requested for decryption is the I-frame (13), therefore the position of the transducer is repositioned to reach the I-frame (13) as indicated by the arrow J1. After reading and decoding the I-frame (13), the transducer is shifted to reach and decode the P-frame (16) as indicated by the arrow J2. This process is repeated as indicated by arrows J3, J4. Following the acquisition and decoding of the P-frame (22), the transducer is moved, as indicated by the arrow Jn, to read the I-frame (1). Smooth representation of the motion of images requires decoding and displaying of I- and P-frames as well as B-frames. The jump and playback process is repeated for the preceding group of images, thus moving backwards through the recorded data, while smoothly playing back the material in reverse order on the video output.

Performing a visually smooth playback in trick play mode requires a timely disc search and access to selected images in memory. Although each digital disk is encoded with a data navigation system to provide image access points in each unit of the visual object, these points are limited in number and may naturally contribute to the time-escalated motion of images. In order to achieve temporarily smooth play back in trick mode, with multiple speeds forwards and backwards, it is required to access and decode all encoded pictures. Although such an operation is possible at the expense of memory capacity, bitstream analysis and selection for cached storage make it possible to improve trick mode reproduction through efficient memory utilization.

The method according to the invention consists in searching the data stream for the location of the second type-specific sector in multiple sectors, searching the second sector of a specific type for the location of the second start code for this type of start code from a plurality of start codes, determining the second start code as a residual incomplete boot image, the incomplete boot image value and the remaining boot image value are combined to form the complete boot image.

Preferably, the type is read from the complete start code, the type read from the complete start code is stored, the byte address for the complete start code is calculated and the byte address for the complete start code is stored.

Preferably, when searching the data stream, the sector address for a specific type sector is remembered.

Preferably, when determining a code as incomplete, the value of the specific incomplete startup code is remembered.

Preferably, a flag is specified when determining the code as incomplete.

Preferably, when determining the code as incomplete, the byte address for the start code determined to be complete is remembered.

Preferably, when determining the second start code, the residual value of a start code of a given type is remembered.

Preferably, when specifying the second start code, the flag is reset.

The apparatus according to the invention is characterized in that a synchronization and demodulation channel processor connected to the buffers is connected to the converter connected to the analog preamplifier by means of a processor block for controlled bitstream processing, comprising a driver for identifying a specific type sector in the bitstream stored in the buffer memory.

PL 192 033 B1

Preferably the controller is connected to the processor to identify the undesirable sector and connected to buffers for writing to clear the identified undesirable sector.

Preferably, the device is adapted to operate in trick mode.

Preferably the controller is adapted to store a sector address of an identified specific sector.

Preferably, a first bitstream storage memory and a second data storage memory are connected to the transducer connected to the analog preamplifier, which is controllable with the first memory and a controller for controlling the identification of the information in the bitstream is connected to the first and second memories, the controller being connected to the first and second memories. a first memory for outputting a bit stream from a sector specific address having first and second portions, and a controller is connected to the second memory to store the first portion and to erase the second portion of the bit stream.

Preferably, a processor block for processing the stored bit stream is coupled to the buffers and comprising an algorithm for identifying the MPEG start code distributed across data sectors, and the processor is adapted to search the stored bit stream in response to the algorithm to identify the MPEG striped start code and store the identified sector address. Striped MPEG start code, and the algorithm reconstructs the striped MPEG start code to form a complete MPEG start code.

An advantage of the invention is the efficient use of the memory in a method and apparatus for reproducing a digitally encoded signal.

Fig. 1A shows a group of MPEG pictures 2, Fig. 1B - recorded groups of pictures during playback and triple speed backward trick play, Fig. 2 - block diagram of a digital disc player with a device according to of the invention, fig. 3, a part of the block diagram of fig. Fig. 2, Fig. 4 - digital disc player of Fig. 2 with another device according to the invention, Fig. 5A and Fig. 5B - exemplary bitstream before buffering, Figs. 5C-5D - example data in the buffer memory, and Fig. 6 - network activities to obtain boot codes that are spread across sector boundaries.

Figure 2 shows an exemplary block diagram of a digital video disc player. Drive system 10 receives digitally recorded disks 14 to be rotated by a motor 12. A digital signal is recorded on disk 14 as a helical track containing holes of length defined by 8/16 modulation coding, bit sensitive to the data signal. The record on disk 14 is read by a transducer 15 which receives the reflected laser beam, and the reflected laser light is received by a photo detector or photoelectric transducer. An imaging device such as a lens or mirror that forms part of the transducer 15 is servo-operated and driven by a motor 11 to follow the recorded track. Different parts of the video are available thanks to the sudden repositioning of the imaging device. The servo-driven motors 11 and 12 are driven by a servo controller 20. The converter 15 is coupled to an optical analog preamplifier 30 that includes drive circuits for a laser source and a preamplifier that provides amplification and correction of the reflected photo output from the photoelectric converter. The amplified and corrected reproduction signal from analog preamplifier 30 is fed to the sync and demodulation channel processor 40 where the reproduction signal is used to synchronize the phase locked loop which is used for the 8:16 modulation demodulation used in recording.

The MPEG-encoded bitstream is detectably and error-corrected encoded using the Reed-Solomon encoding which is applied in blocks of 16 sectors where each sector contains 2048 bytes of data loaded. Thus, as a result of the 8:16 demodulation, the reproduced data stream is deinterleaved and reshuffled, and the error is corrected by the Reed-Solomon correction performed in the ECC buffers 45 and 46 in Fig. 4. Each buffer stores 16 sectors of the reproduced data stream, arranged as an array to facilitate deinterlacing and to allow product processing of row and column. Cascaded ECC buffers introduce a delay of approximately (2 * 16 * 1.4) milliseconds to the serial bit stream being played, where the number 2 represents a pair of ECC buffers, 16 represents sectors where correction is made and 1.4 milliseconds represents sector period at one rotational speed. Thus, the reproduced serial bit stream is delayed by at least about 45 milliseconds.

PL 192 033 B1

The error corrected signal bit stream 41 is fed via a call processor to a bitstream or mechanical / track buffer 60A. The buffer 60A contains a DRAM memory and is used to store an amount of reconstructed data such that data loss when repositioning the transducer 15 does not result in any visible loss during decoding. The final output image stream will be perceived by the viewer as smooth and continuous. The bitstream buffer 60A is part of an exemplary 16 megabit DRAM, which is partitioned further to form buffers 60C and 60D frames for storing at least two decoded image frames to store the compressed video bit stream in buffer 60B prior to the decoding process, creating a stream buffer 60E audio signal bits and other 60F, 60G, 60H buffers. The sync and demodulation channel processor 40 also includes timing control circuits that control writing via link 505 to the bitstream buffer 60A. Data is recorded discontinuously due to changes in the addresses of the playback tracks, resulting for example from user-defined video playback content such as director cuts, overarching guidelines or even user-selectable alternate angles. In order to facilitate faster access and obtain the recorded signal, the disk 14 is rotated at an increased speed, resulting in a higher bit rate and possibly discontinuous delivery.

The recorded data stream is grouped into ECC blocks of 16 sectors. Each sector has a unique sector identification address which is protected with error correction bits which are processed by the ECC 47 in Fig. 4. However, since the sector address is short and sector specific, there is no signal delay of the sector address 42. resulting from the error correction processing block ECC 47, is not significant. The sector address signal 42 is coupled to provide position information to the servo controller chip 50, which provides drive and control signals for motors 11 and 12. Motor 12 spins disk 14 and performs servo rotation at different speeds. The transducer 15 is set and serviced by the motor 11 responsive to the sector address signal 42 and is additionally controlled to suddenly reposition or jump to another sector address or location on the disk surface in response to a sector address request sent by the control bus I ² C 514 , and coupled via element 54 of Fig. 4.

The digital video disc player is controlled by the CPU 510 of block 500, which receives the reconstructed bitstream and error marks from the timing and demodulation channel 40 and issues control instructions to the servo controller 50. In addition, the CPU 510 receives user control commands from user interface 90 and functions. control from the MPEG decoder 530 of block 500. The system buffer 80 is addressed and provides data to the CPU 510. The buffer 80 includes, for example, RAM and a PROM. RAM is used to store various data obtained from bitstream 41 by CPU 510, such data including, for example, decryption data, bitstream management data and frame buffer data, and navigation data. The PROM memory, for example, includes transducer travel algorithms that improve trick mode at a given speed forwards and backwards.

In Figure 3, MPEG-encoded bitstream is fed to connection processor 505 of Figure 3, which serves as a demultiplexer to separate MPEG-encoded audio and video and control DVD bitstream data. Alternatively, the bitstream demultiplexing is performed under the software control of the DMA buffer 60A direct memory access circuitry from the CPU 510 of FIG. 3, which is hereinafter microprocessor 510. The encoded bitstream before or in the path buffer 60A is searched by microprocessor 510 to locate it. and reading headers and extracting navigation data. Bitstream searching will be discussed with reference to FIG. 6.

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The microprocessor 510 is coupled to circuit 514 by the signal leading a control bus I ² C to control or to require the transmitter to adopt a new position in order to achieve a new sector required by the trick play sequence. The transducer setup is controlled by the stored sequence or reproduction jump pattern that is indexed with respect to the reconstructed sector addresses and the GOP addresses read from the beacon packet data contained in each video object block unit of a VOBU. Exemplary sector addresses and a VOBU Beacon Pack are shown in Fig. 5A. However, as a result of presenting the transducer, sectors that have been pre-searched from the headend are identified by

Microprocessor 510 as not those required by the jump instruction. In this case, the microprocessor 510 clears the unwanted data in the track buffer 60A and ensures that only the requested data is present in that buffer.

After identifying the sector or header addresses, the microprocessor 510 controls the direct access path to the track buffer 60A which effectively separates MPEG data from other data stored in the DVD format in the buffer. In this way, the DMA video chip 515 separates the compressed video bits that are destined to be stored in a 60B video buffer. Similarly, compressed audio bits are read from the buffer 60A and stored in the audio signal buffer 60E. Sub-picture data is also read from the buffer 60A by the DMA chip and stored in the buffer 60F.

The compressed video bit stream in the video bit buffer 60B is searched for a higher level image or start codes by a start code detector 520. The detected start code signal 512 is provided to microprocessor 510, which then communicates with the MPEG decoder 530 via signal 511 to indicate the next picture type, quantizer settings, and initiate the decoding process. The decoder status signal 513 is fed back to the microprocessor 510 to communicate the completion of the decoding process and that the picture data is available for display or storage. Compressed video bit buffer 60B acts as a first in, first out or circular buffer where a stored bitstream is available and downloaded sequentially for MPEG decoding. However, trick mode operation is improved by freely accessing the buffer 60B as will be described below.

In the MPEG decoder 530, the video bit stream is processed by a variable length decoder 531 which searches the bit stream for slice and block start codes. Some of the decoded pictures from each picture group are written to the frame buffer 60C and 60D to be used thereafter as prognostics when obtaining or constructing other pictures, for example P or B pictures in the picture group. The 60C and 60D frame buffers have a capacity of at least two video frames. The separated audio packets are stored in an audio bit buffer 60E, which is read during the audio decoding process at block 110. Following MPEG or AC3 audio decoding, a digital audio signal is generated and fed to the audio post processor 130 to convert the digital signal. to analog and generate output acoustic signals with different base bands. The output digital video signal is transformed into a raster image format by the display processing buffer 580 from the decoded blocks read from the reference frame buffer 60C / D. However, in trick mode, the output source is a field memory reconfigured from memory not used in trick mode. Such block to raster conversion in display buffer 580 is supervised in response to trick mode operation. The display buffer 580 is coupled to an encoder 590 that performs the digital-to-analog conversion and generates video components of the baseband and encoded video signals.

The operation of the exemplary video player of Fig. 2 may be considered with reference to Fig. 1B which illustrates the forward play and backward trick play sequences. The coded relationship existing in each group of pictures requires that each group of pictures be decoded in the forward direction starting with an I-frame or picture. In this way, the reverse mode functions are performed by efficiently jumping backwards to read an earlier or preceding I-frame and then forward decoding on that group of pictures. The decoded images are stored in the frame buffers for subsequent reading in reverse order. However, sequences that contain B pictures use further properties described later. In Fig. 1B, it is assumed at some time preceding the time t0, for example at a point in the I-type picture (1), that the video player forward reproduces conditions in response to a user command. Each group of pictures is forward-decoded as shown in Fig. 1A by arrows joining frames I, B, and P. At a time preceding moment t0, a triple-speed trick play mode is selected which is initiated at time t0, where a type II image is decoded and displayed (25). The next image required for decoding in reverse trick mode is the I image (13), whereby the transducer is displaced as indicated by the arrow J1 to obtain the I image (13). Signal reading and decoding follow the reproduction sequence indicated in Fig. 1B by

J1 arrow to reach I-frame (13), J2 arrow to reach P-frame (16), P-frame J3 arrow (19), J4 arrow - P frames (22) ... J (n). Disturbing B-frames, shown in Fig. 1B, are read but may be discarded, e.g., in a buffer by erase write or by decoder abandonment as required by the specificities of each trick play mode. In order to avoid the previously described need for additional reverse mode video buffering, various methods of MPEG decoder operation, buffer memory control and allocation are used.

The computation of data is performed in units of sectors referenced in bitstream 41 or path buffer 60A. However, since the MPEG image start code is hidden in the DVD data formatting method and does not have to start at the sector boundary, the resulting positioning of the image start codes in sector units may inevitably include portions of the preceding sectors that do not contain the video data. .

Figure 5A shows a portion of exemplary bitstream 41 including a video object unit including audiovisual data and sub-picture data sectors. Each sector contains 2048 load bytes with sector addresses shown shaded at the sector boundaries.

In Figure 5B, video A ends in sector 54 and is immediately followed by video B. However, the remainder of the start code of video B appears in sector 65, with interfering sectors 55-64 containing sub-picture and audio data.

Figure 5C shows the designation or the location of the image data / video sectors in the sector units where the start code for image A is shown in vector 2 with the start code of the next B image appearing in sector 9. Equation 1 shows the location of the image data by the sector count - image A starts in sector 2 and ends in vector 9, so the image A lasts across 8 sectors.

In Figure 5C, the unwanted data fragments are shown where the video data is imaged with respect to the video sector numbers. However, such video sector numbering is directly related to the sector number or address in the played bitstream. In Figure 5C, the video bitstream is shown together with a picture A marked by a picture start code starting byte 1000 of video sector 2.

The preceding 999 bytes of sector 2 correspond to the data in the previous picture. It is possible to apply more detailed processing in which the image data is located in units of bytes. Accurate byte processing requires more complex memory control than required for sector-level accuracy. However, when using precise byte processing, only the complete image data is stored in the video bit buffer, thus eliminating fragments and avoiding the MPEG 530 decoder hang-up. The exact determination of the bytes of the pictures is shown in Fig. 5C for an A picture, where the picture start code starts with a byte 500 of sector 9. On this basis, the size of the A picture is calculated from Equation 2, which is 13,835 bytes. Thus, the exact byte addresses of the pictures enable the microprocessor 510 to indicate a specific byte in the video bit buffer 60B from which the variable length VLD decoder 531 of Fig. 3 will start the decoding process.

If the picture data is specified in units of sectors, the MPEG decoder reading the video bitbuffer pictures must be protected against hangup resulting from fragments of discarded pictures appearing before or after the desired picture is decoded.

Figure 5D shows such image fragments in a video bit buffer for different sectors containing P- and B-frames, where unwanted data from the previous or next image is indicated by diagonal hatching. Each VOBU Video Object Block Unit includes navigation data that identifies the end sector address of the first I picture and the last sector addresses of the two following references or P pictures of the first group of VOBU pictures. The navigation data additionally includes type I picture sector addresses in the preceding or following VOBUs, and hence, only a trick mode based on Type I frames is implemented without difficulty. However, problems with picture fragments are avoided if the final byte of the desired picture is identified. The microprocessor 510 / A, for example of the ST20 type, is configured as a search engine that searches the data stored in the track buffer for the end I-frame byte within the end sector stored in the buffer 60A. In this way, by identifying the I picture, it can be loaded by itself into the video bit buffer 60B, thus avoiding the storage of partial pictures which presents decoder blocking problems. The 510 / A microprocessor is

The PL 192 033 B1 is used for example to find the start codes only in the I picture mode because the stopping sector is known from the navigation data. However, in the case of P-frames, B-frames, or different I-pictures, a microprocessor may not be a practical solution as a test must be performed for each data byte in the bitstream, which means heavy use of the microprocessor 510.

The localization and determination of start codes before starting the decoding process are facilitated by the circuit which uses connection interface block 505 in Fig. 3 to search for start codes in the bitstream before the path buffer 60A. Such use of connection interface 505 introduces image preprocessing or analysis and / or audio headers that are signaled to microprocessor 510. Thus, having identified headers in the incoming bitstream ahead of the path buffer, images and audio required by a particular trick mode can be stored in the path buffer 60A. wherein unwanted images and other data are cleared in the buffer by an erase write.

In the first arrangement, the start codes are located by using a start code detector 520 which searches the bitstream either in the track buffer 60A or the video bit buffer 60B. Although this method has the advantage that MPEG start code detector design is known, the detector nevertheless requires compact data. Hence, only data in the video bit buffer can be searched, without DVD and transport data structures. Thus, searching MPEG data in the mechanical / track buffer is difficult to improve, does not optimally use memory, and microprocessor 510 is overloaded with interrupts, thus requiring a second microprocessor, e.g. microprocessor 510A, to detect the start code.

In the apparatus according to the invention, start code detection is improved by a start code detector which searches the bitstream exclusively for MPEG start codes before or in the track buffer 60A. Thus, by advantageously applying the early parsing of the MPEG video headers to the bitstream, trick picture reproduction requirements are met and the memory work specified for trick play is performed. The stream of video packets before the video bit buffer is processed in trick mode. For example, in the reverse playback mode, preprocessing allows a specific selection of images to be buffered for decoding during trick work and to remove unwanted images prior to storage. Such picture selection, for example B-frame rejection, approximately doubles the number of I and P pictures stored in a video bit buffer 60B during trick play. Thus, by this selection and deletion, the video bit buffer 60B will initialize only the pictures desired or determined by trick play, thus it is possible to store more video object units determined by trick mode, thus improving the reproduction operation.

In the first device of the invention, the memory capacity of the track buffer 60A and the video bit buffer 60B are increased during trick mode playback by selecting only the data to be used sequentially to store. For example, in trick play mode, B-frames are not decoded and thus need not be stored in track or video bit buffers. In this way, only the desired images are stored and unwanted or other data is discarded. In order to facilitate this selection between wanted and undesired pictures, it is required that the bitstream or video packet stream be preprocessed, analyzed or searched to locate a sequence header, picture group header or picture header before being loaded into memory. Such analysis or preprocessing of the compressed bitstream enables MPEG parameters such as time_code, closed_gop and broken_link data to be determined for each group of GOP pictures. In addition, by preprocessing the packet stream, the picture_start_code picture start code is localized, enabling the picture_header picture header processing, which in turn allows for the determination of e.g. a temporal_reference reference, picture_coding_type picture coding type (I, P and B). However, such MPEG analysis is difficult due to the DVD breakdown of MPEG data into sectors of 2048 bytes. In addition, since the 4 byte MPEG start codes are not aligned with sectors, the picture start code may be distributed across the sector boundary. Figure 5B illustrates the bitstream before path buffer 60A where picture A ends in sector 54 and immediately follows the picture start code B. However, the remainder of the B picture start code appears in sector 65, with interfering sectors 55-64 occurring. containing sub-picture and audio data.

PL 192 033 B1

Figure 5C illustrates a demultiplexed video sector bitstream before a video bit buffer 60B where the picture start code is shown in sector 2 with the next B picture start code appearing in sector 9. The decomposed start code exists for a C picture where it is initialized by byte 2046 sector 12 and continues in sector 13. Hence, part of the boot code resides in one video sector with the rest in the next video sector.

FIG. 6 shows the inventive method for analyzing a bit stream with a distributed start code. This method identifies and records sector types and addresses, and additionally identifies and stores desired start codes. Striped or partial start codes are identified and stored by using a start code tag that indicates the occurrence of such a situation. The boot code residue present in the next video sector is identified and read to complete the boot code. The method of FIG. 6 illustrates the MPEG searching and parsing processes applied to the bitstream 41 before being loaded into the paths buffer. The bitstream is searched for desired sectors, e.g. video sector, which is then searched for distributed start codes. The decomposed start code is separated by other non-video sectors containing e.g. sounds, sub-pictures, navigation data, etc. In this way, the bitstream is searched and the next video sector is identified and processed until disturbing non-video sectors are processed. undesirable at any given time, for example during a particular trick mode, and which may be cleared before being written to memory or cleared in exemplary track buffer 60A. Thus, having the next video sector identified, the data packet is searched for the next start code. However, since the fragment code flag is set, the remainder of the fragment startup code is searched for, and with its occurrence, the remainder is folded with the portion from the previous video sector to complete the startup code.

The diagram in Fig. 6 shows the inventive method used to search a bit stream to identify the desired sector addresses, picture types and their addresses, and to detect and reassemble the distributed start codes. The method starts in step 10 in which the error-corrected bit stream is searched for the desired sectors from among a plurality of sectors, including navigation data, audio, video, and sub-picture sectors. In step 100, the video sector is detected and the response NO creates a loop that leads to a further bitstream search. The audio sector is similarly detected in step 105 and its address properly stored. If the result of the test in step 100 is YES, it means a video sector has been detected and that sector address is stored in step 101. The detected video sector initiates another test in step 200 to detect a start code within that video sector. Step 200 represents a picture start code, however, different start codes, for example sequence headers, GOP picture group headers, or picture headers, all exist within this video sector and hence may each be decomposed beyond sector boundaries, may be present. The answer of NO in step 200 creates a loop that continues searching for the boot code in that video sector. YES in step 200 indicates detection of start code, which initiates another test for detecting partial start code in step 250. Determining the start code as partial or complete, depicted in steps 200 and 250, occurs simultaneously or in series as each start code becomes partial or incomplete when interrupted by the appearance of a sector boundary and sector address as illustrated in Figures 5B and 5C. The answer of NO in step 250 creates a loop waiting for the fragment startup code to appear. Additionally, NO in step 250 also indicates detection of the complete startup code which is tested in step 255 to determine if it is the desired type. The desired start codes return YES to the test in step 255, which results in keeping the location of the type and byte in the given sector address in step 260.

Detection of the partial start code results in a YES response in step 250 which causes the bitstream search sequence to restart to find the next video sector by looping back to step 100. YES in step 250 also initiates a test in step 300 to determine if it is. partial startup code marker set. A fragment start code flag is not set until the first broken or partial start code is detected. NO in step 300 sets a marker of the fragment start code in step 350, and additionally stores the value of the fragment code in step 400. YES in step 300 indicates detecting the rest or residual of the decomposed start code and resets the sub-tag.

The start code in step 500 is YES, and in step 300 the detected start code is also stored in step 450. In step 550, the values of the partial start code of step 400 and the remainder of step 450 are assembled together to recover the decomposed start code. Finally, in step 575, type of recovered start code, byte and sector address are stored. Hence, the described method of the invention identifies and stores specific types and addresses of sectors, identifies and stores the types of start code and addresses of bytes in sectors, and identifies and assembles fragments of the decomposed start code. The DVD bitstream is analyzed to determine, for example, specific types of MPEG-encoded pictures, before being stored in the buffer memory.

It is preferable to control the order of the MPEG picture decoding process based on where individual pictures start and end in the video bit buffer. Hence, knowledge of the image location in the video bit buffer 60B, for example, as shown in Fig. 5C or as determined by bitstream search in Fig. 6, allows the start memory pointers in the start code detector 520 and the variable-length detector 531 are routed to directly accessible images as requested, for example when running in trick mode. Working in reverse at a given frame rate and / or with slow reverse playback motion requires B-frame playback. Reverse operating mode is simplified in terms of buffer memory requirements by reversing the order in which adjacent B-frames are decoded. This reversal of the decoding order is achieved by setting memory boot indicators to decode the image requested by trick mode. In addition, size and cache control are simplified when running in trick mode by skipping or not reading images in the video bit buffer, as required by trick playback algorithms. The memory size and its control are further optimized during trick play by allowing multiple decoding of pictures either immediately or according to a specific request of the trick play algorithm. The implementation of the above functions requires careful control of the read / write functions and the synchronization between them.

The block diagram of Fig. 4 shows the same functions and numbering of elements as in Fig. 2, however, Fig. 4 contains additional circuits according to the invention which will be explained. The digital video disc player shown in Figs. 2, 3 and 4 includes two parts: a front part and a rear part. The front part controls the disk and the converter, and the rear part carries out the MPEG decoding process and general control. This functional separation provides a solution to consistent MPEG decoding. However, with this split into back end processing and control, the microprocessor can become overloaded, for example when running in trick mode, and particularly during reverse play. As described, the microprocessor 510 is to manage the incoming bitstream 41 received from the head end and identify desired and undesired data. Preferably, the repetitive bitstream is searched for, for example, for the location of a specific MPEG encoded image in order to store and / or determine a specific byte address for that specific MPEG encoded image in the repeating bitstream or storage medium.

Claims (14)

Patent claims A method of reproducing a digitally encoded signal, in particular obtaining a start code from a start code in a data stream located in a plurality of sectors processed during playback by a digital disk device, in which a data stream is searched for a specific type sector location in a plurality of sectors, a sector of a specific type is searched for a start code location from a plurality start code, a start code is defined as incomplete, characterized in that a data stream is searched for the location of the second sector specific type in multiple sectors, the second sector specific type is searched for the location of the second start code for this type of start code from the start code multiplicity, the second start code is defined as the remainder of the incomplete code boot image, the incomplete boot image value and the remaining boot image value are combined to form the complete boot image. PL 192 033 B1 2. The method according to p. The method of claim 1, wherein the type is read from the complete start code, the type read from the complete start code is stored, the byte address for the complete start code is calculated, and the byte address for the complete start code is stored. 3. The method according to p. The method of claim 1, characterized in that when searching the data stream, the sector address for a specific type sector is memorized. 4. The method according to p. The method of claim 1, wherein the value of the specified incomplete startup code is memorized when determining the code as incomplete. 5. The method according to p. The method of claim 1, wherein a flag is determined when determining the code as incomplete. 6. The method according to p. The method of claim 1, characterized in that when the code is determined to be incomplete, the byte address for the start code determined to be complete is stored. The method according to claim 1, characterized in that when determining the second start code, the residual value of a start code of a given type is memorized. 8. The method according to p. The flag of claim 1, wherein the flag is reset when determining the second start code. 9. Apparatus for reproducing the digitally encoded signal from a medium, comprising a converter for processing the digitally encoded signal and generating a bitstream connected to a memory for storing the bitstream information, characterized in that the converter (15) connected to the analog preamplifier (30) is connected to the converter (15) connected to the analog preamplifier (30). a synchronization and demodulation channel processor (40) coupled to the buffers (80, 60) via a processor block (500) for controlled bitstream processing, including a driver (510) for identifying a specific type sector in the bitstream stored in the buffer (80, 60). 10. The device according to claim 1 The method of claim 9, characterized in that the controller (510) is coupled to the processor (500) to identify the undesirable sector and coupled to buffers (80, 60) to write to clear the identified undesirable sector. 11. The device according to claim 1 The apparatus of claim 9, wherein it is adapted to operate in trick mode. 12. The device according to claim 1, The method of claim 9, characterized in that the controller (510) is adapted to store a sector address of the identified specific sector. 13. The device according to claim 1, The method of claim 9, characterized in that a first memory (45) for storing the bitstream and a second memory (46) for storing data is connected to the transducer (15) connected to the analog preamplifier (30), which is controlled to the first memory (45) and to the first memory (45). and the second memory (45, 46), a controller (510) is attached to control the identification of information in the bitstream, the controller (510) is coupled to the first memory (45) to output a bitstream from a specific sector address having first and second portions. and a controller (510) is coupled to the second memory (46) to store the first portion and clear the second portion of the bit stream. 14. The device according to claim 1 The method of claim 13, characterized in that a processor block (500) for processing the stored bit stream is connected to the buffers (80, 60) and comprising an algorithm for identifying the MPEG start code distributed across data sectors, and the processor (500) is adapted to search the stored bit stream. in response to this algorithm to identify the MPEG striped start code and store the sector address of the identified MPEG striped start code, and the algorithm recreates the striped MPEG start code to form a complete MPEG start code.