Ming Liou, "Overview of the px64 kbit/s Video Coding Standard, " Communications of the ACM, vol. 34, no. 4, pp. 59--63, April 1991.  Home/Search   Document Not in Database   Summary   ACM   TOC   Related Articles   Check

....to finding a metric that will guarantee a good coding performance. Two of such metrics are the mean square error (MSE) and the mean absolute difference (MAD) Considering that block based motion estimation is most commonly used in multimedia standards such as MPEG1 [13] MPEG 2[14] and px64[15], we briefly highlight the block based forms of the MSE and the MAD metrics. The most commonly used blocksize is and it is usually referred to as the macroblock. The MSE is calculated as follows: # ( 0 132 465 7 8 9; 465 # = BADC 8 E F C K LADC)M ....

Ming Liou, "Overview of the px64 kbit/s Video Coding Standard, " Communications of the ACM, vol. 34, no. 4, pp. 59--63, April 1991.

....is possible to reduce Vdd to 4:0V and still meet the 200ns constraint. The extent of the slack that is available depends on the constraints imposed by the environment, as illustrated by the next example. Example 2 : Let us consider an image that has 288 Theta 360 pixels as per the CIF standard [8]. Consider the task of performing a discrete cosine transform (DCT) on the luminance information of each pixel. A commonly used approach is to divide up the image into blocks, say of 8 Theta 8 pixels, and perform a DCT on each block separately. Each 8 Theta 8 block thus obtained now requires a ....

M. Liou, "Overview of the px64 kbit/s video coding standard," Communications ACM, vol. 34, Apr. 1991.

.... for video transmission using p 64 Kb s channels (p = 1, 30) For p = 1 or 2, the available bit rate is severely limited and only videophone quality is possible [Sutherland92] If p is greater than or equal to 6, higher quality video can be transmitted, e.g. suitable for video conferencing [Liou91]. The CCITT encoder is a hybrid coder, as it uses both DCT based coding and predictive coding, in which a block in the current frame is predicted from a block in the previous frame using a feedback loop. The standard also has an optional specification for motion compensation. The video formats ....

M. Liou, "Overview of the px64 kbit/s Video Coding Standard," Communications of the ACM, Vol. 34, No. 4, pp. 59-63 (April 1991).

....proposed by [13] when these techniques for search window adjustment are applied for full search(FS) threestep search(TSS) new three step search(NTSS) 1. Introduction Motion compensated prediction plays a very important role in the efficient coding of video sequences. MPEG1, 2[1] ITU T H. 261[2] and H.263[3] adopted the motion compensated prediction to reduce temporal redundancy which resides in successive frames. Most of the algorithms developed for motion estimation are block based techniques called block matching algorithm(BMA) The most general approach for BMA is to use full search ....

M. Liou, "Overview of the Px64 kbit/s Video Coding Standard," Communication of the ACM, 34(4) 59-- 63, (Apr. 1991).

....that have changed their position from image i to image i 1. Thus, before image i 1 is sent, the receiver already has most of the information about the blocks in i 1, only some small differences to image i are missing. The two video compression standards currently used over the Internet (H. 261 (Liou, 1991) and MPEG ( Le Gall, 1991) Anonymous, 1993a) employ two techniques to make use of temporal redundancy in video: motion detection followed by differential encoding of blocks. For a given block bi 1 in image i 1, motion detection determines which blocks in image i 1 are sufficiently different ....

Liou, M. (1991). Overview of the px64 kbit/s Video Coding Standard. Communications of the ACM, 34(4), 60-63.

....to which the human eye is relatively insensitive, may be removed without degrading the perceptual quality of the decoded image. H. 261 is a popular coding standard, which makes use of DCT (Discrete Cosine Transform) and other techniques to compress video spatial units (frames or subframes) [15]. Since such coded units have random (but highly autocorrelated) transmission requirements (say, in bits) the corresponding coding schemes are referred to as VBR (Variable Bit Rate) Figure 1 displays a TEStool screen showing the results of the algorithmic TES modeling for an empirical sample ....

Liou, M. "Overview of the px64 kbit/s Video Coding Standard", Communications of the ACM, Vol. 34, No. 4, 59--63, 1991.

....of N 2 compared to N 4 for BMA ME) and is robust even in a very noisy environment. This algorithm can also take 2D DCT coefficients of images as input to estimate motions and therefore can be incorporated in encoders of most current video compression standards such as MPEG and CCITT H261 [1][2]. In other words, DXT ME can combine both DCT encoders and motion estimation into a single component to achieve further saving of operations and hardware complexity. Furthermore, the transmitter and receiver structures are symmetric for this combined DCT based motion estimation scheme. 2. ....

M. Liou, "Overview of the px64 kbit/s Video Coding Standard," Communications of the ACM, Vol34, No4, April 1991.

....similarly. The dashed lines are the motion vectors used by the other subbands. For subbands Y blh and Y bhl, the ECVQ coders may be replaced with ECTCQ coders. For detail see Section 6.2 3 Modifications to H.261 Coder The coding of the lowest frequency subband uses a variant of the H. 261 coder [10]. A few changes, mainly regarding the size of the block used for motion compensation, had to be made so that the coder could be used in the subband structure. H.261 computes motion vectors for each 16 Theta 16 macroblock. If this were to be done on the LFS, it would be equivalent to using 64 ....

M. Liou, "Overview of the px64 kbits/s Video Coding Standard," Communications of the ACM, vol. 34, pp. 59-63, Apr. 1991.

....Note that a closed mouth shape is rendered for the sound m , which would not be possible without speech information. Figure 7: Result of speech assisted interpolation. 5 Speech Assisted Video Coding We combine speech assisted interpolation with existing video coding algorithms (e.g. px64 [Liou, 1991]) to improve the image quality. These coders typically drop a number of frames without coding them (frame skipping) to satisfy the bit rate constraint, at the expense of loss of lip synchronization. To minimize motion jerkiness and maintain lip synchronization, they normally put a constraint on ....

Liou, M., "Overview of the px64 kbit/s video coding standard," Communications of the ACM, April 1991.

....proposed by [12] when these techniques for search window adjustment are applied for full search(FS) three step search(TSS) new three step search(NTSS) 1 Introduction Motion compensated prediction plays a very important role in the efficient coding of video sequences. MPEG 1,2[1] ITU T H. 261[2] and H.263[3] adopted the motion compensated prediction to reduce temporal redundancy which resides in successive frames. Most of the algorithms developed for motion estimation are block based techniques called block matching algorithm(BMA) The most general approach for BMA is to use full search ....

M. Liou, "Overview of the Px64 kbit/s Video Coding Standard," Communication of the ACM, 34(4) 59--63, (Apr. 1991).

....and commonalty in the characteristics of these compression standards. This will help in the discussion of the proposed filtering mechanisms and the implications these have on other topics covered in this paper. However, for the interested reader, we have found the following literature [33] 16] [17] and [2] of great value in our own understanding of these compression standards. A. Commonality and Differences Across the Standards The different standards have been brought about to address different application areas: JPEG is intended for still image compression, H.261 has been developed to ....

M. Liou, "An Overview of the px64 kbit/s Video Coding Standard", Communications of the ACM, Vol. 34, No. 4, April 1991, pp. 59-63.

....Although the KLT is considered as the optimal transform (in terms of the ability to pack most of the energy into the fewest coefficients, de correlation of the inputs and minimization of the mean square error) most standard compression techniques such as JPEG [16, 23] MPEG [7] and H. 261 [11] are based on the DCT. This is primarily due to the asymptotic equivalence between the DCT and the KLT, and the existence of fast transforms for the DCT [18] We thus concentrate on DCT based compressed video, though the proposed techniques can be applied to any linear orthogonal transform. The ....

M. Liou, "Overview of the px64 kbits/s video coding standard", Communications of the ACM, 34, 4, 59-63, 1991.

....Thus, the knowledge of motion helps in removing significant interimage redundancy, as is the case in predictive or hybrid (predictive transform or predictive subband) coding compensated for motion. In fact, these techniques include most algorithms currently used in videoconferencing [41] [42] and proposed for High Definition Television (HDTV) 21] 60] Sampling structure conversion and noise reduction are two examples of image sequence processing that can benefit greatly from the knowledge of motion. In the case of conversion, two scenarios are possible. In one situation a missing ....

....conversion (e.g. NTSC PAL, or NTSC HDTV) 3.3. 1 Motion compensated prediction Predictive coding is the most widely used technique for temporal redundancy reduction, and is incorporated in some way in most existing or proposed image coding standards, from low resolution teleconferencing [42] to HDTV [21] 60] Motion trajectory estimates are used to predict an image field from previous fields using samples along the same estimated trajectory. The prediction error is then encoded and transmitted. Motion compensated predictive coding is normally accomplished using the DPCM structure ....

M. Liou, "Overview of the p x 64 kbits/s video coding standard," Communications ACM, vol. 34, pp. 59--63, Apr. 1991.

....these problems. 3. Video Delivery Properties Problems associated with data collection, storage, transmission and delivery must be addressed in the process of video delivery. To address the huge data volume problem, different compression and encoding standards have been proposed and utilized[17, 18, 27]. For example, the first specification from the Moving Picture Experts Group, MPEG 1, uses interframe compression to achieve compression ratios of about 50:1 by applying lossy methods. The MPEG specification utilizes differential coding techniques based on temporal reduction, also known as ....

M. Liou, "Overview of the PX64 Kbit/s Video Coding Standard", Communications of the ACM, April 1991, pp. 59-63. 302 C. ORJI, D. ADJEROH, P. BOBBIE AND K. NWOSU

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Liou, M., "Overview of the px64 kbit/s Video Coding Standard," Comm. of the ACM, Vol. 34, No. 4, p. 59-63, 1991.

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Liou M., "Overview of the px64 kbit/s video coding standard", Commun. ACM, vol. 34, no. 4, pp. 59-63, April 1991.

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Liou, M., "Overview of the Px64 Kbit/s Video Coding Standard," Communications of the ACM, vol. 34, no. 4, April 1991, pp. 59-63.

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M. Liou, "Overview of the px64 kbit/s video coding standard," Communi. of the ACM, vol. 34, pp. 59--63, April 1991.

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M. Liou, "Overview of the px64 kbit/s Video Coding Standard", In Communications of the ACM, Vol. 32, No. 4, 1991.

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M. Liou, "Overview of the px64 kbit/s video coding standard," Communication of the ACM, vol. 34, no. 4, pp. 59--63, Apr. 1991. (a) (b) (c) (d)

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Liou, M. [1991] "Overview of the px64 kbit/s Video Coding Standard", Com. of the ACM, vol. 34, no. 4, pp. 59-63, April 1991.

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Ming Liou, "Overview of the px64 kbit/s Video Coding Standard", CACM, vol. 34, no. 4, pp.

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M. Liou, "Overview of the px64 kbit/s video coding standard," Commun. ACM, Vol. 34, pp. 59-63, Apr. 91.

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Liou M., 1991. Overview of the px64 kbit/s Video Coding Standard, Comm. of the ACM, Vol. 34, No. 4, (April), pp. 59-63.

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M. Liou, "Overview of the px64 kbit/s video coding standard," Commun. ACM, Vol. 34, pp. 59-63, Apr. 91.

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