Dynamic bit allocation in video combining for multipoint conferencing

Sun, Ming–Ting; Wu, Tzong-Der; Hwang, Jenq‐Neng

doi:10.1109/82.673649

Cited by 19 publications

(20 citation statements)

References 8 publications

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“…A simple technique to transcode a video to lower bit rate is to increase the quantization step at the encoder part in the transcoder [35], [43]. Spatial resolution can be done in a number of ways (see Fig.…”

Section: Requirements and Functionalitiesmentioning

confidence: 99%

Video transcoding: an overview of various techniques and research issues

Ahmad

Wei

Sun

et al. 2005

IEEE Trans. Multimedia

282

154

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Abstract-One of the fundamental challenges in deploying multimedia systems, such as telemedicine, education, space endeavors, marketing, crisis management, transportation, and military, is to deliver smooth and uninterruptible flow of audio-visual information, anytime and anywhere. A multimedia system may consist of various devices (PCs, laptops, PDAs, smart phones, etc.) interconnected via heterogeneous wireline and wireless networks. In such systems, multimedia content originally authored and compressed with a certain format may need bit rate adjustment and format conversion in order to allow access by receiving devices with diverse capabilities (display, memory, processing, decoder). Thus, a transcoding mechanism is required to make the content adaptive to the capabilities of diverse networks and client devices. A video transcoder can perform several additional functions. For example, if the bandwidth required for a particular video is fluctuating due to congestion or other causes, a transcoder can provide fine and dynamic adjustments in the bit rate of the video bitstream in the compressed domain without imposing additional functional requirements in the decoder. In addition, a video transcoder can change the coding parameters of the compressed video, adjust spatial and temporal resolution, and modify the video content and/or the coding standard used. This paper provides an overview of several video transcoding techniques and some of the related research issues. We introduce some of the basic concepts of video transcoding, and then review and contrast various approaches while highlighting critical research issues. We propose solutions to some of these research issues, and identify possible research directions.Index Terms-Frequency domain, heterogeneous video systems, H.26X, MPEG-X, motion vector refinement, spatial domain, video transcoding.

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Section: Requirements and Functionalitiesmentioning

confidence: 99%

Video transcoding: an overview of various techniques and research issues

Ahmad

Wei

Sun

et al. 2005

IEEE Trans. Multimedia

282

154

View full text Add to dashboard Cite

show abstract

“…In a multipoint video conferencing system, usually only one or two participants are active at any given time [3]. The active conferees need higher frame rates to produce a better video quality as well as to present a smoother motion.…”

Section: Dynamic Frame Allocation For Video Combining In Multipoimentioning

confidence: 99%

“…Thus, it is necessary to regulate the frame rate of each transcoder according to the motion activity in the current frame of the subsequence. To obtain a quantitative measure for , we use the accumulated magnitudes of all of the motion vectors estimated for the macroblocks in the current frame [3], [27], i.e., (27) where is the total number of macroblocks in the current frame, and and are the horizontal and vertical components of the motion vector of the th macroblock, which uses the previous nonskipped frame as a reference.…”

Section: Dynamic Frame Allocation For Video Combining In Multipoimentioning

confidence: 99%

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

Fung

Chan

Siu

2004

IEEE Trans. Multimedia

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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.

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“…In [7], a joint rate-control scheme taking into account the various spatiotemporal tradeoffs among all objects in a scene for MPEG-4 object-based transcoding is proposed. Dynamic rate-control algorithms tailored for multipoint video conferencing are discussed in [84]- [86].…”

Section: B Rate Controlmentioning

confidence: 99%