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Feedback-based error-resilient video coding relies on efficient transmission of feedback messages. The Audio-Visual Profile with Feedback (AVPF) for Real-time Transport Control Protocol (RTCP), i.e. RTP/AVPF, supports low-latency feedbacks. In this paper, a reference picture selection (RPS) method using RTP/AVPF-compliant feedback is proposed. A restriction period is first derived in the codec layer based on the previously transmitted back-channel message, the RTCP reporting interval, the round-trip time, and the processing delay of the encoder. Then, a feedback message is transmitted when the restriction period is passed and an incorrectly reconstructed picture is detected. At the encoder, the decoded picture buffer (DPB) is adaptively controlled to combat feedback delay fluctuation in RTP/AVPF. Simulation results show that the proposed entire solution outperforms traditional RPS, wherein a back-channel message is transmitted for every lost picture and the DPB is managed by sliding window. ©2009 IEEE.

Depth-Image-Based Rendering (DIBR) is widely used for view synthesis in 3D video applications. Compared with traditional 2D video applications, both the texture video and its associated depth map are required for transmission in a communication system that supports DIBR. To efficiently utilize limited bandwidth, coding algorithms, e.g. the Advanced Video Coding (H.264/AVC) standard, can be adopted to compress the depth map using the 4:0:0 chroma sampling format. However, when the correlation between texture video and depth map is exploited, the compression efficiency may be improved compared with encoding them independently using H.264/AVC. A new encoder algorithm which employs Scalable Video Coding (SVC), the scalable extension of H.264/AVC, to compress the texture video and its associated depth map is proposed in this paper. Experimental results show that the proposed algorithm can provide up to 0.97 dB gain for the coded depth maps, compared with the simulcast scheme, wherein texture video and depth map are coded independently by H.264/AVC. ©2009 IEEE.

Bi-predictive (B) slices are not supported in the Baseline profile of the Advanced Video Coding (H.264/AVC) standard, which results in a decreased coding efficiency compared with other profiles supporting B slices. However, many application standards, such as the mobile multimedia services specified by the Third Generation Partnership Project (3GPP), use only the Baseline profile for H.264/AVC. Therefore, it is worth investigating H.264/AVC coding when only intra (I) and inter (P) slices are supported. In this paper, a content-adaptive Quantization Parameter (QP) cascading scheme for the hierarchical P coding method compatible with Baseline profile of H.264/AVC is proposed. The proposed method is based on a picture-level QP optimization. The proposed method has a significantly better rate-distortion performance than the traditional IPPP coding structure and outperforms hierarchical P coding methods using fixed delta QP settings between temporal levels noticeably with up to 0.53 dB gain in average luminance Peak Signal-to-Noise Ratio (PSNR).

The Multiview Video Coding (MVC) standard is currently under development by the Joint Video Team as an extension of the Advanced Video Coding (H.264/AVC) standard. An MVC encoder compresses more than one viewpoint of a scene captured by different cameras. Redundancies between views can be used for inter-view prediction in encoding as well as error concealment in decoding. In this paper, a new algorithm utilizing motion information of pictures from other views to conceal a lost picture is proposed. The algorithm first derives motion information for a lost picture based on motion fields of pictures in adjacent views. Then, traditional motion compensation is invoked within the view containing the lost picture to derive a concealed frame. Experimental results show that the proposed algorithm can improve video quality with a negligible computational complexity overhead compared to simple temporal error concealment algorithms. ©2008 IEEE.

Random access is a desirable feature in many video communication systems. Intra pictures have been conventionally used as random access points, but correct picture content can also be recovered gradually within a range of pictures starting from a non-intra random access point. This paper proposes the use of the isolated regions technique for gradual decoder refresh and presents how the proposed method can be used in the upcoming ITU-T Recommendation H.264, also known as MPEG-4 Part 10 or Advanced Video Coding. The presented simulations reveal that the proposed method outperforms intra-picture-based random access points in error-prone network conditions. It is also shown that the proposed method is more flexible and suits packet-based transmission better compared to progressively located intra-coded slices.

This paper presents the error concealment (EC) feature implemented by the authors in the test model of the draft ITU-T video coding standard H.26L. The selected EC algorithms are based on weighted pixel value averaging for INTRA pictures and boundary-matching-based motion vector recovery for INTER pictures. The specific concealment strategy and some special methods, including handling of B-pictures, multiple reference frames and entire frame losses, are described. Both subjective and objective results are given based on simulations under Internet conditions. The feature was adopted and is now included in the latest H.26L reference software TML-9.0.

Region-of-interest coding and unequal error protection are two important tools in video communication systems to improve received visual quality. One common property of the two techniques is that unequal coding or transmission is applied to improve the quality of the most important parts of images. The proposed sub-picture coding technique facilitates both region-of-interest coding and unequal error protection by partitioning images to regions of interest and separating the corresponding coded data units from each other. Simulation results show that the overall subjective quality is considerably improved compared to the conventional coding schemes.

Coding of a scene transition is often a challenging problem, from compression efficiency point of view, because motion compensation may not be a powerful enough method to represent changes between pictures in the transition. This paper proposes a overlay coding technique for coding faded scene transitions. As shown by extensive simulations, over 50% bit-rate savings in both cross-fades and through-black fades compared to earlier techniques can be achieved. Overlay coding suits situations where video is edited manually or automatically.