This paper presents a novel fast transcoding framework to efficiently bridge the state-of-art high efficiency video coding (HEVC) standard and its screen content coding (SCC) extension to support the bitstream compatibility over legacy HEVC devices. By exploiting the side information from the SCC bitstream, fast mode and partition decisions are made to accurately translate the novel SCC modes to conventional HEVC modes based on statistical mode mapping techniques. Compared with the full-decoding-full-encoding (FDFE) solution, the proposed framework achieves on average 51% and 82% complexity reductions with 0.57% Bjøntegaard-delta rate (BD-Rate) loss and 9.74% BD-Rate gain under all-intra (AI) and low-delay (LD) configurations, respectively. Compared with the direct transcoding reusing intra mode and inter motion, the proposed mode mapping framework introduces additional 23% and 6% complexity reductions for AI and LD encoding configurations with 0.43% BD-Rate loss and 1.10% BD-Rate saving, respectively. The proposed solution is extended to support the single-input-multiple-output screen content adaptive streaming at the edge clouds, where an SCC bitstream coded in high quality is transcoded into multiple HEVC bitstreams in reduced qualities. Our proposed solution achieves on average 49% and 76% complexity reductions with 0.78% BD-Rate loss and 7.40% BD-Rate gain under AI and LD configurations, respectively.

In this paper, a novel screen content (SC) transcoding framework is presented to efficiently bridge High Efficiency Video Coding (HEVC) and its Screen Content Coding (SCC) extension and support the bitstream backward-compatibility over legacy HEVC devices. Based on the side information analysis of SCC bit-stream, fast mode and partition heuristics are designed to accurately determine the mapping between novel SCC modes and conventional HEVC modes. Compared with the trivial SCC-HEVC transcoding solution, the proposed framework achieves a 42% re-encoding complexity reduction over standard JCT-VC screen content sequences with only 0.52% negligible BD-Rate loss under All-Intra (AI) configuration.

In this paper, a novel screen content transcoding framework is presented to efficiently bridge the state-of-art High Efficiency Video Coding (HEVC) standard and its incoming screen content coding (SCC) extension currently pending finalization. The proposed scheme is implemented as an Intra-coding “pre-processing” module on top of official SCC test model software (SCM). Both Coding Unit (CU) statistical features (such as CU color quantity, CU pixel variance, CU edge directionality distribution, etc.) and decoded video side information (such as CU partitions, modes, residual, etc.) are jointly analyzed. Accordingly, fast CU mode decisions and CU partitions bypass / termination heuristics are designed. Compared with SCM-4.0 official release, the proposed fast transcoding scheme can achieve an average of 48% re-encoding complexity reduction over JCT-VC screen content testing sequences with less than 2.14% marginal BD-Rate increase under SCC common testing conditions for All-Intra (AI) configuration.

This paper presents a novel low-complexity motion estimation and mode decision algorithm for encoding multiple quality layers following the H.264/scalable video coding standard, considering both coarse grain scalability (CGS) and medium grain scalability (MGS). The proposed algorithm conducts motion estimation and mode decision only at the base layer (BL) and enforces the higher layers to inherit the motion and mode decisions of the BL. In order for the decision made at the BL to be nearly optimal for all layers, we use the highest layer reconstructed frame as the reference frame for motion estimation and set the Lagrangian multipliers according to the quantization parameter of the current and higher layers. We also propose a simple early skip/direct decision to further boost the encoding speed. Mode decision and motion estimation is conducted at a higher layer only if the layer below it uses the skip/direct mode for a block. Significant complexity reduction can be achieved because the mode and motion estimation is performed at most once for each macroblock. Because the mode and motion information only needs to be transmitted once, we also achieve a slightly better rate-distortion (R-D) performance for typical videos. Experiments have shown more than 2× (up to 5×) speedup for a three-layer encoder against the conventional R-D optimized reference software JSVM on both CIF and HD sequences, and for both CGS and MGS, with the tradeoff of the coding efficiency measured by the Bjontegaard delta rate.

This paper presents a low-complexity lossless screen content coding method on top of a well structured dictionary based solution DictSCC. Both methods are implemented on the emerging High-Efficiency Video Coding (HEVC) Range Extensions (RExt) to demonstrate the coding efficiency. Compared with the DictSCC our scheme further explores the 2D correlation between neighboring image blocks for performance improvement, and reduces the complexity significantly by constraining the dictionary buffer which will be more favored by the hardware implementation. Results demonstrate averaged 17%, 10% and 8% bit rate reduction over HEVC for screen content compression with respect to All Intra, Random Access and Low-Delay encoder configurations.

This paper presents an advanced screen content coding solution using color table and index map (cTIM) method. This cTIM scheme is implemented in the range extensions of high-efficiency video coding (HEVC-RExt) as an additional tool of intracoding to complement conventional spatial angular prediction to better exploit the screen content redundancy. For each coding unit, a number of major colors will be selected to form the color table, then the original pixel block is translated to the corresponding index map. A 1D or hybrid 1D/2D string match scheme is introduced to derive matched pairs of index map for better compression. Leveraging the color distribution similarity between neighboring image blocks, color table merge is developed to carry it implicitly. For those blocks that color table has to be signaled explicitly, intertable color sharing and intratable color differential predictive coding are applied to reduce the signaling overhead. Extensive experiments have been performed and they have demonstrated the significant coding efficiency improvement over conventional HEVC-RExt, resulting in 26%, 18%, and 15% bit rate reduction at lossless case and 23%, 19%, and 13% Bjontegaard Delta-rate improvement at lossy scenario of typical screen content with text and graphics, for respective all intra, random access, and low-delay using B picture encoder settings. Detailed performance study and complexity analysis (as well as the comparison with other algorithms) have been included as well to evidence the efficiency of proposed algorithm.

This paper first investigates the impact of frame rate and quantization on the bit rate and perceptual quality of compressed video. We propose a rate model and a quality model, both in terms of the quantization stepsize and frame rate. Both models are expressed as the product of separate functions of quantization stepsize and frame rate. The proposed models are analytically tractable, each requiring only a few content-dependent parameters. The rate model is validated over videos coded using both scalable and nonscalable encoders, under a variety of encoder settings. The quality model is validated only for a scalable video, although it is expected to be applicable to a single-layer video as well. We further investigate how to predict the model parameters using the content features extracted from original videos. Results show accurate bit rate and quality prediction (average Pearson correlation >;0.99) can be achieved with model parameters predicted using three features. Finally, we apply rate and quality models for rate-constrained scalable bitstream adaptation and frame rate adaptive rate control. Simulations show that our model-based solutions produce better video quality compared with conventional video adaptation and rate control.

In a prior work, we have developed both rate and perceptual quality models for temporal and amplitude (i.e., SNR) scalable video produced by the H.264/SVC encoder. In this paper, we validate from experimental data that the functional form of the rate model is applicable to H.264/AVC encoded video, which has the same temporal scalability but no SNR scalability, but the model parameter values differ. We further investigate how to predict both rate and quality model parameters using content features computed from the original video. Experimental data show that with proper feature combination, we can estimate the model parameters very accurately, and the estimated bit rate and quality using the predicted model parameters match with the measured bit rate and quality with high Pearson correlation (PC) and small root mean square error (RMSE). We have implemented a simple pre-processor in the H.264/AVC encoder to guide the frame rate adaptive rate control. Results show that our model-based frame rate adaptive rate control outperforms the default rate control algorithm with better quality.