https://www.comp.nus.edu.sg/~cs4243/projects/TextDetectionSurvey.pdf

Text information extraction in images and video: a survey

Real-time streaming of audiovisual content over the Internet is emerging as an important technology area in multimedia communications. Due to the wide variation of available bandwidth over Internet sessions, there is a need for scalable video coding methods and (corresponding) flexible streaming approaches that are capable of adapting to changing network conditions in real time. In this paper, we describe a new scalable video-coding framework that has been adopted recently by the MPEG-4 video standard. This new MPEG-4 video approach, which is known as Fine-Granular-Scalability (FGS), consists of a rich set of video coding tools that support quality (i.e., SNR), temporal, and hybrid temporal-SNR scalabilities. Moreover, one of the desired features of the MPEG-J FGS method is its simplicity and flexibility in supporting unicast and multicast streaming applications over IF.

/pdf/the-mpeg-4-fine-grained-scalable-video-coding-method-for-44oy5frgp0.pdf

The MPEG-4 fine-grained scalable video coding method for multimedia streaming over IP

Transmission of video over bandwidth varying networks like the Internet requires a highly scalable solution capable of adapting to the network condition in real-time. To address this requirement, scalable video-coding schemes with multiple enhancement layers have been proposed. However, under this multiple-layer paradigm, the transmission bit-rate of each layer has to be predetermined at encoding time. Consequently, the range of bit-rates that can be covered with these compression schemes is limited and often lower than, or different from, the desired range required at transmission time. In this paper, a novel scalable video-coding framework and a corresponding compression method for Internet video streaming are introduced. Building upon the MPEG-4 SNR fine-granular-scalability (FGS) approach, the proposed framework provides a new level of abstraction between the encoding and transmission process by supporting both SNR and temporal scalability through a single enhancement layer. Therefore, our proposed approach enables streaming systems to support full SNR, full temporal, and hybrid temporal-SNR scalability in real-time depending on the available bandwidth, packet-loss patterns, user preferences, and/or receiver complexity. Moreover, our experiments revealed that the presented FGS temporal-SNR scalability has similar or better PSNR performance than the multilayer scalability schemes. Subsequently, an Internet video streaming system employing the proposed hybrid FGS-temporal scalability structure is introduced, together with a very simple, yet effective, rate-control that performs the tradeoffs between individual image quality (SNR) and motion-smoothness in real-time. The hybrid temporal-SNR scalability presented in this paper has been adopted in the MPEG-4 standard to support video-streaming applications.

/pdf/a-hybrid-temporal-snr-fine-granular-scalability-for-internet-2ubj9lp261.pdf

A hybrid temporal-SNR fine-granular scalability for Internet video

This disclosure describes techniques for coding transform coefficients associated with a block of residual video data in a video coding process. Aspects of this disclosure include the selection of a scan order for both significance map coding and level coding, as well as the selection of contexts for entropy coding consistent with the selected scan order. This disclosure proposes a harmonization of the scan order to code both the significance map of the transform coefficients as well as to code the levels of the transform coefficient. It is proposed that the scan order for the significance map should be in the inverse direction (i.e., from the higher frequencies to the lower frequencies). This disclosure also proposes that transform coefficients be scanned in subsets as opposed to fixed subblocks. In particular, transform coefficients are scanned in a subset consisting of a number of consecutive coefficients according to the scan order.

Coding of transform coefficients for video coding

Several embedded video coding schemes have been recently developed for multimedia streaming over IP. In particular, fine-granular-scalability (FGS) video coding has been recently adopted by the MPEG-4 standard as the core video-compression method for streaming applications. From its inception, the FGS scalability structure was designed to be packet-loss resilient especially under unequal packet-loss protection (UPP). However, since the introduction of FGS, there has not been a comprehensive study evaluating its packet-loss resilience under unrecoverable packet losses that are common in Internet streaming applications. In this paper, we evaluate two important aspects of FGS packet-loss resilience. First, we study the impact of applying UPP between the base- and enhancement-layers on FGS-based streams, and we compare equal packet-loss protection (EPP) with UPP scenarios. Second, we introduce the notion of fine-grained loss protection (FGLP), which is suitable for the FGS enhancement-layer, and we develop an analytical framework for evaluating FGLP bounds. Based on these bounds, we show the impact of applying fine-grained protection to the FGS enhancement-layer for different types of video sequences and over a wide range of bit-rates and packet-loss ratios. As illustrated by our extensive simulation results, applying 1) UPP between the base- and enhancement-layers and 2) FGLP for the FGS enhancement-layer can provide significant resilience under moderate-to-high packet-loss ratios (e.g., 5-10%). Furthermore, the merits of this new packet-loss protection technique go beyond the FGS coding scheme, because FGLP can be successfully applied to improve the resilience to packet-losses of other embedded video coding techniques.

/pdf/unequal-packet-loss-resilience-for-fine-granular-scalability-2ttvey1yfs.pdf

Unequal packet loss resilience for fine-granular-scalability video

Advanced digital compression systems, like the MPEG-standard, are entering the consumer market. However, the consumer acceptation of these technologies relies considerably on the possibility of substantial reduction of the implementation costs. In this paper we study a low-cost and high-quality embedded compression system for reducing the memory requirements of an MPEG-2 decoder with a factor of 4 - 6. The proposed embedded codec is based on a low-cost transform coding scheme and employs a modified feedforward coding mechanism to ensure a fixed compression factor. A novel quantization technique is developed, which prevents the error accumulation resulting from multiple encodings of the same pixel data. The decrease in image quality, caused by the embedded compression, is minimal (i.e. less than 1 dB) for MPEG-2 coded sequences at 4 - 9 Mbit/s. The proposed algorithm can also be successfully applied for memory reduction of MPEG- 2 encoders and H.263 codecs.

Novel embedded compression algorithm for memory reduction in MPEG codecs

Video transmission over bandwidth-varying networks is becoming increasingly important due to emerging applications such as streaming of video over the Internet. The fundamental obstacle in designing such systems resides in the varying characteristics of the Internet (i.e. bandwidth variations and packet-loss patterns). In MPEG-4, a new SNR scalability scheme, called Fine-Granular-Scalability (FGS), is currently under standardization, which is able to adapt in real-time (i.e. at transmission time) to Internet bandwidth variations. The FGS framework consists of a non-scalable motion-predicted base-layer and an intra-coded fine-granular scalable enhancement layer. For example, the base layer can be coded using a DCT-based MPEG-4 compliant, highly efficient video compression scheme. Subsequently, the difference between the original and decoded base-layer is computed, and the resulting FGS-residual signal is intra-frame coded with an embedded scalable coder. In order to achieve high coding efficiency when compressing the FGS enhancement layer, it is crucial to analyze the nature and characteristics of residual signals common to the SNR scalability framework (including FGS). In this paper, we present a thorough analysis of SNR residual signals by evaluating its statistical properties, compaction efficiency and frequency characteristics. The signal analysis revealed that the energy compaction of the DCT and wavelet transforms is limited and the frequency characteristic of SNR residual signals decay rather slowly. Moreover, the blockiness artifacts of the low bit-rate coded base-layer result in artificial high frequencies in the residual signal. Subsequently, a variety of wavelet and embedded DCT coding techniques applicable to the FGS framework are evaluated and their results are interpreted based on the identified signal properties. As expected from the theoretical signal analysis, the rate-distortion performances of the embedded wavelet and DCT-based coders are very similar. However, improved results can be obtained for the wavelet coder by deblocking the base- layer prior to the FGS residual computation. Based on the theoretical analysis and our measurements, we can conclude that for an optimal complexity versus coding-efficiency trade- off, only limited wavelet decomposition (e.g. 2 stages) needs to be performed for the FGS-residual signal. Also, it was observed that the good rate-distortion performance of a coding technique for a certain image type (e.g. natural still-images) does not necessarily translate into similarly good performance for signals with different visual characteristics and statistical properties.

Embedded DCT and wavelet methods for fine granular scalable video: analysis and comparison

The diversity in TV images has augmented with the increased application of computer graphics. In this paper we study z coding system that supports both the lossless coding of such graphics data and regular lossy video compression. The lossless coding techniques are based on runlength and arithmetical coding. For video compression, we introduce a simple block predictive coding technique featuring individual pixel access, so that it enables a gradual shift from lossless coding of graphics to the lossy coding of video. An overall bit rate control completes the system. Computer simulations show a very high quality with a compression factor between 2-3.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Compression of mixed video and graphics images for TV systems

Although in the literature comparisons of the effectiveness of MPEG-2 coding on interlaced and progressive sources have been reported, we think some very important aspects are missing in the research sofar. Particularly, the differences in resulting blocking artifacts are neglected, while usually only scenes with abundant vertical detail are evaluated. From our experiments, we conclude that the general opinion concerning the effectiveness of MPEG-2 coding on interlaced picture material is likely biased by the focus on challenging sequences only, while the omission of blockiness metrics in the evaluation significantly increases this bias further.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Toward a fair comparison of the coding efficiency of interlaced and progressive video

The diversity in the nature of TV images is increasing due to the mixing of graphics data with natural scenery. In this paper we study the lossless coding of such graphics data with the objective to come to recommendations for video compression of such images. For this purpose, a comparison has been made between contour coding, template coding and run-length coding of graphical imagery. It is concluded that template coding is suitable for TXT-like images but it is not practical for more generic graphics images. For menus and similar imagery, contour and run-length coding provide interesting options.

Mihaela van der Schaar-Mitrea

Papers

Novel embedded compression algorithm for memory reduction in MPEG codecs

Embedded DCT and wavelet methods for fine granular scalable video: analysis and comparison

Compression of mixed video and graphics images for TV systems

Toward a fair comparison of the coding efficiency of interlaced and progressive video

Evaluation of lossless compression of Teletext and graphics images for TV systems