Method of redundant picture coding using polyphase downsampling and the codec using the method

Provided are a method for redundant slice coding by polyphase down-sampling (PD) and a codec using the method. An encoder for redundant slice coding by PD includes a PD coding unit rearranging a residual block that is a difference between a current block and a prediction block into four sections by performing PD on the residual block, a quantization transform unit transforming and quantizing at least one of the sections of the residual block, and a reference block generation unit generating a reference block based on a value obtained by performing inverse transform and inverse quantization, and then inverse PD on the at least one transformed and quantized section by the quantization transform unit.

TECHNICAL FIELD

The present invention relates to an encoder and a decoder for redundant slice coding by polyphase down-sampling (PD) in a Joint Scalable Video Model (JSVM).

BACKGROUND ART

Redundant slices effectively improve the robustness of Advanced Video Coding (AVC) (Text of ISO/IEC FDIS 14496-10; Advanced Video Coding; N5555, March 2003) from packet loss.

The redundant slices can be coded by simply repeating primary slices, which results in significantly decreasing the coding efficiency.

DETAILED DESCRIPTION OF THE INVENTION

Technical Problem

To solve the problem, a redundant picture is presented using the smallest number of bits by being coded with a changed parameter, e.g., a changed quantization coefficient. However, the display quality of a reconstructed picture of the redundant picture coded with a larger quantization coefficient decreases resulting in a loss of detailed information.

Technical Solution

The present invention provides a redundant slice coding method by polyphase down-sampling (PD) in a Joint Scalable Video Model (JSVM), in which error resilience of a switched virtual circuit (SVC) and coding efficiency increase by changing the number of discrete cosine transform (DCT) coefficients that are to be transmitted.

The present invention also provides a redundant slice coding method by PD, wherein if some of the DCT coefficients in a single redundant slice are transmitted, reconstruction is performed using spatial redundancy between neighboring pixels, thereby improving reconstruction quality.

Advantageous Effects

As described above, according to the present invention, by using redundant slice coding by PD in JSVM, the amount of DCT coefficients to be transmitted is adaptively changed, thereby improving error resilience of SVC and coding efficiency.

Furthermore, when some of the DCT coefficients in a single redundant slice are transmitted, reconstruction is performed using spatial redundancy between neighboring pixels, thereby improving reconstruction quality.

In addition, the present invention can also be applied to a codec that does not perform DCT. In other words, by removing the DCT and an inverse transform from the codec of the present invention, the present invention is applied to a pixel level having residual information of brightness or color values, thereby improving error resilience.

Moreover, according to the present invention, since a redundant slice of the same quality can be coded using a lesser amount of bits, the bandwidth of a network can be more efficiently used.

Also, reconstruction using spatial redundancy between neighboring pixels for a case where some of the DCT coefficients are transmitted can be applied to error concealment for a primary coded picture having an error as well as decoding of a redundant slice.

BEST MODE

According to an aspect of the present invention, there is provided an encoder for redundant slice coding by polyphase down-sampling (PD), the encoder comprising: a PD coding unit rearranging a residual block that is a difference between a current block and a prediction block into four sections by performing PD on the residual block;

a quantization transform unit transforming and quantizing at least one of the sections of the residual block; and a reference block generation unit generating a reference block based on a value obtained by performing inverse transform and inverse quantization, and then inverse PD on the at least one transformed and quantized section by the quantization transform unit.

According to another aspect of the present invention, there is provided a decoder for redundant slice coding by polyphase down-sampling (PD), the decoder comprising: a receiving unit receiving a bitstream including a coefficient that is obtained by rearranging a residual block into four sections by PD coding and performing transform and quantization, and then entropy encoding on at least one of the sections of the residual block from an encoder; a PD inverse coding unit performing entropy-decoding, inverse quantization, and inverse transform on the bitstream and performing inverse PD on the at least one section of the residual block for reconstruction; and a decoding unit reconstructing sections of the residual block which are not received from the encoder based on the at least one section reconstructed by the PD inverse coding unit and a previously decoded frame.

According to another aspect of the present invention, there is provided a codec for redundant slice coding by polyphase down-sampling (PD), the codec comprising: a PD coding unit rearranging a residual block into four sections by performing PD coding on the residual block; a coding unit performing coding by sequentially performing a transform, quantization, and entropy-coding on at least one of the sections; a PD inverse coding unit performing entropy-decoding, inverse quantization, and inverse transform, and then inverse PD on the at least one encoded section; and

a decoding unit reconstructing sections of the residual block that are not encoded based on the at least one section that is reconstructed by the PD inverse coding unit and a previously decoded frame.

According to another aspect of the present invention, there is provided a method for redundant slice coding by polyphase down-sampling (PD), the method comprising: rearranging a residual block that is a difference between a current block and a prediction block into four sections by performing PD on the residual block; transforming at least one of the sections; quantizing the at least one transformed section; and generating a reference block based on a value obtained by performing inverse transform and inverse quantization, and then inverse PD on the at least one transformed and quantized section.

According to another aspect of the present invention, there is provided a method for redundant slice decoding by polyphase down-sampling (PD), the method comprising: receiving a bitstream including a coefficient that is obtained by rearranging a residual block into four sections by PD and performing transform and quantization, and then entropy encoding on at least one of the sections from an encoder; performing inverse PD on the at least one section after performing entropy-decoding and inverse quantization, and inverse transform on the bitstream; and reconstructing sections of the residual block which are not received based on the at least one section on which the transform and quantization and the entropy encoding have been performed and a previously decoded frame.

According to another aspect of the present invention, there is provided a method for redundant slice coding by polyphase down-sampling (PD), the method comprising: rearranging a residual block into four sections by performing PD on the residual block; performing encoding by sequentially performing transform, quantization, and entropy-coding on at least one of the sections; performing inverse PD after performing the entropy-decoding, inverse quantization, and inverse transform on the at least one encoded section; and reconstructing sections of the residual block which are not encoded based on at least one reconstructed section and a previously decoded frame.

MODE OF THE INVENTION

Hereinafter, the present invention will be described in detail by explaining embodiments with reference to the accompanying drawings. In the drawings, like reference numerals denote elements performing like functions.

FIG. 1is a block diagram illustrating an encoder100for redundant slice coding by polyphase down-sampling (PD) according to an embodiment of the present invention.

Redundant slice coding is effective for video communications that is resilient to packet loss and can be implemented by repeating slices or coding slices with different coding parameters. In the present embodiment, error resilience of a switched virtual circuit (SVC) and coding efficiency increase by performing redundant slice coding by PD.

The encoder100includes a PD coding unit110, a quantization transform unit120, a reference block generation unit130, and an entropy encoding unit140.

The PD coding unit110performs PD on a residual block through a difference between the current block and a prediction block in order to rearrange the residual block with four sections.

If a 4×4 transform block is used, a redundant slice coding method by PD applies PD on an 8×8 inter residual block that has not yet been processed by a discrete cosine transform (DCT).

Note that in the present embodiment, a redundant slice can be encoded using other redundant slice coding methods that follow the AVC standards.

For example, a picture can be encoded by both a PD-based method and a high quantization parameter (QP)-based method. In the latter case, a transformed coefficient is encoded with a high QP after undergoing PD and DCT.

PD will be described in more detail with reference toFIG. 3.FIG. 3illustrates an example of PD.

The quantization transform unit120includes a transform unit121for transforming at least one of the four sections of the rearranged residual block and a quantization unit122for quantizing the transformed sections.

The quantization transform unit120may selectively transform and quantize some of the sections of the residual block (seeFIG. 3(b)) that are rearranged after PD of the PD coding unit110according to an available bandwidth.

More specifically, N/4 of the residual block is adaptively coded. Here, N is a natural number between 1 and 4. For example, the quantization transform unit120transforms and quantizes at least one of the four sections (310,311,312, and313as illustrated inFIG. 3) of the residual block that is rearranged after PD. In this way, the encoder100generates different bitstreams corresponding to different bitrates.

The reference block generation unit130generates a reference block based on a value obtained by performing inverse quantization (Q−1) and inverse transform (T−1) on one section that has been transformed and quantized by the quantization transform unit120and then performs inverse polyphase down-sampling (PD−1) on the result.

The reference block generation unit130sets the values of the pixels of the sections of the residual block that were not transformed and quantized by the quantization transform unit120to 0 and the pixels of the sections transformed and quantized by the quantization transform unit120to the values obtained by performing inverse quantization (Q−1) and inverse transform (T−1) and then inverse polyphase down-sampling (PD−1). The reference block generation unit130then adds the residual block to a prediction block obtained from previously decoded images, thereby generate a reference block.

For example, the reference block generation unit130sets the values of the pixels (e.g., 0, 2, 4, 6, 8, 10, 12, and 14 as illustrated inFIG. 5A) of the sections of the residual block that were transformed and quantized by the quantization transform unit120to the values obtained by performing inverse quantization (Q−1), inverse transform (T−1) and then inverse polyphase down-sampling (PD−1) and adds the residual block to a prediction block, thereby generate a reference block. Inverse polyphase down-sampling (PD−1) will be described in more detail with reference toFIG. 4.FIGS. 4A and 4Billustrate examples of inverse PD.

The reference block generation unit130sets the values of the pixels (e.g., 1, 3, 5, 7, 9, 11, 13, and 15 as illustrated inFIG. 5A) of the sections of the residual block that were not transformed and quantized by the quantization transform unit120to0and adds the residual block to a prediction block, thereby generate a reference block.

The entropy encoding unit140performs entropy encoding based on the already transformed and quantized pixels from among the pixels of at least one section.

For example, if some (310and312ofFIG. 3) of the sections of the residual block that is rearranged by the PD coding unit110are transformed and quantized by the quantization transform unit120, the entropy encoding unit140performs entropy encoding based on the temporally previously transformed and quantized pixels within the sections (310and312ofFIG. 3) that were transformed and quantized by the quantization transform unit120. Entropy encoding will be described in more detail with reference toFIG. 5.

FIG. 2is a block diagram illustrating an encoder for redundant slice coding by PD according to an embodiment of the present invention.

To facilitate understanding of PD that is used in the present invention, examples for explaining PD and inverse PD are shown inFIGS. 3,4A, and4B.

In the present invention, PD is applied to redundant slice coding. In redundant slice coding by PD of the present invention, lost samples can reasonably conceal an error occurrence from information of their neighboring samples and thus, error resilience can improve.

As shown inFIG. 3, PD rearranges the residual block into the four sections310,311,312, and313. The pixels (r0, c0) of the original residual block (a) are rearranged to the pixels (rp, cp) by PD.

InFIG. 4A, when the quantization transform unit120transforms and quantizes only one section410of four sections410,420,430, and440of a residual block, inverse PD is performed on the section410.

InFIG. 4B, when the quantization transform unit120transforms and quantizes two sections410and440of the four sections410,420,430, and440of the residual block, inverse PD is performed on section410.

As shown inFIGS. 4A and 4B, when inverse PD is performed on at least one section that is transformed and quantized by the quantization transform unit120, pixels (ra, ca) in the transformed and quantized section are returned to the original positions (r0, c0).

A relationship between the pixels (r0, c0) and (ra, ca) is defined as follows.
r0=2*[ra−(ra/4)*4]+(ra/4)
c0=2*[ca−(ca/4)*4]+(ca/4)  (2)

FIG. 5illustrates a view for explaining entropy encoding in an encoder for redundant slice coding by PD according to an embodiment of the present invention.

To maintain coding efficiency while providing error resilience, some of the four sections of a residual block that undergoes PD are transformed and quantized and then, encoded by the entropy encoding unit140.

InFIG. 5, two of the four sections of the residual block are selectively transformed and quantized, and then encoded.

FIG. 5(a) illustrates encoding for a case where a second quadrant section410and a third quadrant section430ofFIG. 4Aare transformed and quantized by the quantization transform unit120.

In this case, a neighboring block available to the entropy encoding unit140is only a top neighboring block. In other words, the number of non-zero transform coefficient levels is predicted from the top neighboring block.

FIG. 5(b) illustrates encoding for a case where a first quadrant section420and a second quadrant section410are transformed and quantized by the quantization transform unit120.

In this case, a neighboring block that is available to the entropy encoding unit140is only a left neighboring block. In other words, the number of non-zero transform coefficient levels is predicted from the left neighboring block.

FIG. 5(c) illustrates encoding for a case where the second quadrant section410and a fourth quadrant section440are transformed and quantized by the quantization transform unit120.

In this case, a neighboring block that is available to the entropy encoding unit140is only a top-left neighboring block. In other words, the number of non-zero transform coefficient levels is predicted from the top-left neighboring block.

FIG. 5(d) illustrates encoding for a case where the first quadrant section?420and the fourth quadrant section440are transformed and quantized by the quantization transform unit120.

In this case, a neighboring block available to the entropy encoding unit140is only a top-right neighboring block. In other words, the number of non-zero transform coefficient levels is predicted from the top-right neighboring block.

FIG. 6illustrates the reconstruction concept of a pixel in redundant slice coding by PD, according to an embodiment of the present invention. The reference block generation unit performs pixel reconstruction in redundant slice coding by PD.

In the current frame illustrated inFIG. 6, a gray pixel indicates a pixel that is reconstructed after being coded, a white pixel indicates a pixel that is not coded, and a dotted pixel630indicates a pixel reconstructed by a prediction based on a previous frame and a spatially neighboring pixel.

Since all the sections of the residual block are not coded, if reconstruction is not easy due to an error or a loss during reconstruction of a redundant slice that is not coded or transmission of a sequence, the value of a pixel that is not coded is predicted to be a first preliminary reconstruction value620based on previously predicted coded pixels610.

A second preliminary reconstruction value is estimated based on the average of the values of the coded pixels631,632,633, and634adjacent to the pixel630that is not coded.

A difference between the first preliminary reconstruction value620and the second preliminary reconstruction value is obtained. If the difference is less than a predetermined threshold, the first preliminary reconstruction value620is used as a reconstruction value. Otherwise, the second preliminary reconstruction value is used as a reconstruction value.

FIG. 7illustrates a change in a picture parameter set RBSP syntax according to an embodiment of the present invention.

In the encoder using PD according to an embodiment of the present invention, a new syntax redundant_pic_type is immediately added after the redundant_pict_cnt_present_flag syntax of a picture parameter set RBSP syntax (S.7.3.2.2) as illustrated in710ofFIG. 7.

A change in semantics is made as follows. Redundant_pic_type specifies a redundant slice coding method. The value of redundant_pic_type is an integer ranging between 0 and 1. When a new redundant slice coding method is used, the range of the value of redundant_pic_type may increase.

If redundant_pic_type is 0, it means that a redundant picture is coded by simply repeating a primary picture. If redundant_pic_type is 1, it means that the redundant picture is coded by PD according to the present invention.

FIG. 8illustrates an indication of redundant_pic_type in a JSVM encoder configuration file. As shown inFIG. 8, to indicate a redundant slice coding method, a new entry is added at the end of the JSVM encoder configuration file.

FIGS. 9A and 9Bare block diagrams illustrating decoders for redundant slice coding by PD according to an embodiment of the present invention.

FIG. 9Ais a conceptual view of a decoder900for redundant slice coding by PD according to an embodiment of the present invention. The decoder900includes a receiving unit910, a PD inverse coding unit920, and a decoding unit930.

The receiving unit910receives a bitstream including a coefficient that is obtained by rearranging a residual block into four sections by PD and performing transform and quantization and then, entropy encoding on at least one of the sections of an encoder. More specifically, the receiving unit910receives the bitstream transmitted from the entropy encoding unit140illustrated inFIG. 1and transmits the bitstream to the PD inverse coding unit920.

The PD inverse coding unit920of the decoder900performs entropy decoding, inverse quantization, and inverse transform on the bitstream and then, reconstructs the at least one section by inverse PD.

A conventional decoder performs reconstruction with all encoded blocks transmitted from an encoder, but in the present invention, an encoder performs PD and transmits only a block that is selectively transformed and quantized according to the state of a bandwidth and then, entropy-encoded to the decoder900and the PD inverse coding unit920of the decoder900reconstructs the transmitted block.

The decoding unit930reconstructs the sections of the residual block that are not received from the encoder based on the at least one section reconstructed by the PD inverse coding unit920and a previously decoded frame (or field).

FIG. 9Bis a block diagram of an example of a decoder for redundant slice coding by PD according to an embodiment of the present invention.

FIG. 10is a block diagram of a codec for redundant slice coding by PD according to an embodiment of the present invention.

The codec roughly includes an encoder and a decoder.

The encoder rearranges a residual block into four sections by performing PD, transforms, quantizes, and entropy-encodes some of the sections, and transmits the result to the decoder.

The decoder reconstructs the sections that are not coded based on a bitstream including the at least one section that is encoded, which is received from the encoder.

The encoder includes a PD coding unit1010, an encoding unit1020, and a reference block generation unit1030, and the decoder includes a PD inverse coding unit1040and a decoding unit1050.

The PD coding unit1010rearranges the residual block into four sections by performing PD on the residual block. The encoding unit1020sequentially transforms, quantizes, and entropy-encodes at least one of the four sections for encoding.

The reference block generation unit1030generates a reference block based on a value obtained by performing inverse quantization and inverse transform and then, inverse PD on the at least one section that is transformed and quantized.

The PD inverse coding unit1040of the decoder performs entropy-decoding, inverse quantization, inverse transform, and then inverse PD on the at least one section that is coded. The decoding unit1050reconstructs the sections that are not encoded based on the at least one section that is reconstructed by the PD inverse coding unit1040and a previously decoded frame (or field).

More specifically, the decoding unit1050includes a reconstruction estimation unit1051and a reconstruction unit1052.

The reconstruction estimation unit1051estimates a first preliminary reconstruction value of the pixels of the sections that are not encoded using a previously decoded frame (or field) and a second preliminary reconstruction value based on the average of the values of the pixels of the encoded section, which are adjacent to the pixels of the sections that are not encoded.

If a difference between the first preliminary reconstruction value and the second preliminary reconstruction value is greater than a predetermined threshold, the reconstruction unit1052sets the second preliminary reconstruction value as the values of the pixels of the sections that are not encoded. Otherwise, the reconstruction unit1052sets the first preliminary reconstruction value as the values of the pixels of the sections that are not encoded.

FIG. 11is a flowchart illustrating a redundant slice coding method by PD of an encoder according to an embodiment of the present invention.

Referring toFIG. 11, after PD is performed on a residual block that is a difference between the current block and a prediction block, the residual block is rearranged into four sections in operation S1110. A discrete cosine transform (DCT) is performed on at least one of the sections in operation S1120. In this case, one to four sections can be selected for DCT based on the state of a bandwidth.

The at least one section that undergoes DCT is quantized in operation S1130.

In a reconstruction path of the encoder, a reference block is generated based on a value obtained by performing inverse transform, inverse quantization, and then inverse PD on the at least one section in operation S1140.

In this case, the values of the pixels of the sections that are not transformed and quantized in operation S1120are set to 0, the values of the pixels of the at least one transformed and quantized section to the value obtained by performing inverse transform, inverse quantization, and then inverse PD on the at least one section, and the resulting residual block is added to a motion-compensated prediction block to generate a reference block in operation S1140.

Entropy encoding is performed based on the already transformed and quantized pixels from among the pixels of the at least one section in operation S1141.

FIG. 12is a flowchart illustrating a redundant slice coding method by PD of a decoder according to an embodiment of the present invention.

A bitstream including a coefficient obtained by rearranging a residual block into four sections by PD and performing transform and quantization, and then entropy encoding on at least one of the sections is received from an encoder in operation S1210.

Entropy decoding is performed on the received bitstream in operation S1220and inverse quantization and inverse transform are performed on the entropy-decoded bitstream in operation S1230. Inverse PD is performed on at least one section that under goes PD at the encoder in operation S1240.

After inverse PD, the sections of the residual block that are not transmitted from the encoder are reconstructed based on the at least one section reconstructed in operation S1240and a previously decoded frame in operations S1250-S1272.

Reconstruction is performed as follows.

A first preliminary reconstruction value of the values of the pixels of the sections that are not received from the encoder is estimated using the previously decoded frame in operation S1250and a second preliminary reconstruction value is estimated based on the average of the values of the pixels of the at least one reconstructed section, which are adjacent to the pixels of the sections that are not received from the encoder in operation S1260.

It is determined whether a difference between the first preliminary reconstruction value and the second preliminary reconstruction value is greater than a predetermined threshold in operation S1270. If the difference between the first preliminary reconstruction value and the second preliminary reconstruction value is greater than the predetermined threshold, the second preliminary reconstruction value is set as the values of the pixels of the sections that are not received from the encoder in operation S1271.

Unless the difference between the first preliminary reconstruction value and the second preliminary reconstruction value is greater than the predetermined threshold, the first preliminary reconstruction value is set as the values of the pixels of the sections that are not received from the encoder in operation S1272.

FIG. 13is a flowchart illustrating a redundant slice coding method by PD of an encoder and a decoder according to an embodiment of the present invention.

Referring toFIG. 13, PD is performed on a residual block by rearranging the residual block into four sections at the encoder in operation S1310. Then, transform, quantization, and entropy coding are sequentially performed on at least one of the four sections for encoding in operation S1320.

The at least one encoded section is transmitted to the decoder and the decoder performs entropy-decoding, inverse quantization and inverse transform, and then inverse PD based on a received bitstream in operation S1330.

The sections that are not encoded by the encoder are reconstructed based on the at least one section that is reconstructed by PD and a previously decoded frame in operation S1340.

FIGS. 14A through 19illustrate experiment results on the improved performance of redundant slice coding by PD according to an embodiment of the present invention.

To compare the performances of an error-free case, a case where a redundant picture is generated using a QP value, and by redundant slice coding by PD according to the present invention is compared by carrying out a simulation based on reference software of H.264, i.e., JM10.1. The Foreman and New images have a Quarter Common Intermediate Format (QCIF) size and a Stefan image has a Common Intermediate Form at (CIF) size. All experimental images are encoded by inserting a redundant picture between every 2 sheets for an IPPP structure. An intra period is 1 second, the number of reference frames is 5, context adaptive variable length coding (CAVLC) is used as an arithmetic coding method, and rate-distortion optimization is an ON state. Packet loss rates (PLRs) of 3%, 5%, 10%, and 20% are applied to an encoded bitstream at random and corresponding peak signal to noise ratios (PSNRs) are measured.

InFIGS. 14A and 14B, the performance of redundant slice coding by PD according to the present invention and the RD performance of QP-based coding are compared for a case having an error.

InFIGS. 14A and 14B, the RD performances of redundant slice coding1410and1411by PD according to the present invention and QP-based coding1420and1421are compared for a case having an error in a Foreman sequence.

When a PLR is low (as inFIG. 14A), for example 3%, redundant slice coding1410by PD according to the present invention exhibits slightly improved performance. However, when the PLR is high (as inFIG. 14B), for example 5%, redundant slice coding1411by PD according to the present invention exhibits an improved peak signal to noise ratio (PSNR) between 1.1 dB and 2 dB as compared to QP-based coding1421. In other words, as a PLR increases, a gap between coding according to the present invention and conventional coding is widened.

InFIGS. 15A through 15D, in an environment having an error (Foreman, QCIF, and 10 fps) the performance of redundant slice coding by PD according to the present invention and the performance of QP-based coding are compared, according to an embodiment of the present invention.

InFIGS. 15A through 15D, simulation results according to different bitrates are shown in a Foreman sequence. In this case,FIGS. 15A through 15Dshow experiment results for bitrates of 64 kbps, 128 kbps, 192 kbps, and 320 kbps.

It can be seen fromFIGS. 15A through 15Dthat redundant slice coding1510,1511,1512, and1513by PD have a better reconstruction quality than QP-based coding1520,1521,1522, and1523in terms of PSNR.

In each case, as the PLR increases, redundant slice coding by PD according to the present invention can still achieve better performing results than QP-based coding.

InFIG. 16, in an environment having an error (Stefan, CIF, 30 fps, 10 Mbps), the performance of redundant slice coding by PD and the performance of QP-based coding are compared, according to an embodiment of the present invention.

Improvement in performance, as illustrated inFIGS. 14A through 15D, can also be seen in a Stefan sequence. In other words, as illustrated inFIG. 16, if a transmission environment deteriorates, redundant slice coding by PD according to the present invention provides a gradually decreasing curve with respect to the quality of a reconstructed picture as compared to QP-based coding.

InFIG. 16, when PLR is 3%, QP-based coding shows better performing results than the present invention by about 0.1 dB. However, this is a rare case for decoding of redundant slice coding by PD when the PLR is low. In general, redundant slice coding by PD exhibits better performance when compared to QP-based coding.

InFIG. 17, in an environment having an error (News, QCIF, 10 fps, 64 Mbps), the performance of redundant slice coding by PD and the performance of QP-based coding are compared, according to an embodiment of the present invention.

As illustrated inFIG. 17, the error resilience of H.264 in a packet loss environment can obtain a PSNR improvement of 1.6 dB through redundant slice coding by PD according to the present invention as compared to QP-based coding.

InFIGS. 18A and 18B, in an environment having an error, the performance of redundant slice coding by PD and the PSNR performance of QP-based coding are compared, according to an embodiment of the present invention.

In order to illustrate improved error resilience of H.264,FIG. 11illustrates in detail PSNR performing results of redundant slice coding by PD and QP-based coding in frame units.

It can be seen from experiment results that redundant slice coding by PD according to the present invention exhibits better performance than QP-based coding for all the time.

FIGS. 19A through 19Cillustrates the qualities of reconstructed pictures in a Foreman sequence in the case of PLR=10%, according to an embodiment of the present invention.

FIG. 19Aillustrates the display quality of a reconstructed picture in an error-free environment,FIG. 19Bshows the display quality of a reconstructed picture using QP-based coding, andFIG. 19Cillustrates the display quality of a reconstructed picture using redundant slice coding by PD.

It can be noticed from a decoded picture that redundant slice coding by PD according to the present invention provides improved display quality as compared to QP-based coding.

The present invention can also be embodied as computer readable code on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system.

Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.