Low-Complexity and High-Quality Frame-Skipping Transcoder for Continuous Presence Multipoint Video Conferencing

Abstract

Abstract-This paper presents a new frame-skipping transcoding approach for video combiners in multipoint video conferencing. Transcoding is regarded as a process of converting a previously compressed video bitstream into a lower bitrate bitstream. A high transcoding ratio may result in an unacceptable picture quality when the incoming video bitstream is transcoded with the full frame rate. Frame skipping is often used as an efficient scheme to allocate more bits to representative frames, so that an acceptable quality for each frame can be maintained. However, the skipped frame must be decompressed completely, and should act as the reference frame to the nonskipped frame for reconstruction. The newly quantized DCT coefficients of prediction error need to be recomputed for the nonskipped frame with reference to the previous nonskipped frame; this can create an undesirable complexity in the real time application as well as introduce re-encoding error. A new frame-skipping transcoding architecture for improved picture quality and reduced complexity is proposed. The proposed architecture is mainly performed on the discrete cosine transform (DCT) domain to achieve a low complexity transcoder. It is observed that the re-encoding error is avoided at the frame-skipping transcoder when the strategy of direct summation of DCT coefficients is employed. By using the proposed frame-skipping transcoder and dynamically allocating more frames to the active participants in video combining, we are able to make more uniform peak signal-to-noise ratio (PSNR) performance of the subsequences and the video qualities of the active subsequences can be improved significantly.Index Terms-Compressed-domain processing, frame skipping, video compression, video conferencing, video transcoding.

Software-based serverless endpoint video combiner architecture for high-definition multiparty video conferencing

“…In particular, the pixel domain combiner at the video bridge requires a complete re-encoding of the combined frames, which further reduces video quality when the combined frames are finally decoded and reconstructed at client endpoints ). An analysis on these drawbacks by Fung et al, (2004) shows that the peak signal to noise ratio (PSNR) video quality as a result of the re-encoding process exhibited an average drop of 3.5 dB per combined video frame.…”

“…H.263) due to constrained quantization parameters settings in this standard. Hence transcoding of H.263 video was carried out in (Fung et al, 2004;Lin et al, 2003) where macroblocks and discrete cosine transformed (DCT) coefficients of source video frames were manipulated to generate a combined frame. However, with the standardization of the H.264 codec, it became increasingly complicated to perform coded domain video combining as these methods amplifies requantization error and drift between source and combined video streams (Banerji et al, 2006).…”

“…Recent work by Le and Nguyen (2010), Cycon et al (2011) and Akkus -et al (2011) described centralized and peer-to-peer MCU video architectures, based on the H.264 Scalable Video Coding (SVC). Other related methods can be found at Le and Nguyen (2010), Cycon et al (2011), Akkus -et al (2011, Liu et al (2005), Fung et al (2004), Lei et al (1994), Sun et al (1998), Sun et al (1997), Zhu et al (1999), Lin et al (2003), Banerji et al (2006), Zhang and Lei (2010).…”

A Frame-Activity-Based Dynamic Frame-Skipping Transcoder

“…Fung et al [12] mentioned a two-frame-skipping scheme in DCT-domain, and Zhang et al [9] illustrated a two-frame-skipping algorithm as well, but both of them use a traditional solution to multi-frame skipping, which is shown in Fig. 5.…”

Robust Distributed Multi-Point Video Conferencing Over Error-Prone Channels

“…Multi-point video conferencing, which involves multiples conferees and realizes a virtual conference room, is one of the potential applications. Conventional multi-point video conferencing systems often consider a centralized scheme and assume error-free communication channel [1,2]. When we consider holding a conference over a large-scale network with time-varying error-prone channels, centralized schemes require long round-trip delays for resource allocation and cannot react to fast changing conditions in both communication channel and video content.…”