Hamed Amor

Technical issues in low rate transform coding

The transmission of video information through a narrowband channel requires a significant degree of image compression. In addition to the actual coding procedure, the frame rate is reduced, the spatial sample rate is lowered, and the color components are further filtered. Through a review of a practical and flexible image compression configuration, the important technical aspects of video coding are presented. The complexity of the currently developed system is discussed for operation over a 64 kbit/s communication channel. The specific and primary considerations include the following: After a reduction of temporal and spatial resolution, the luminance and color difference signals are divided in pixel blocks of 16 x 16 and 8 x 8, respectively. Then they are passed on to a motion-compensated differential pulse-code modulation coding system with a subsequent discrete cosine transform of the prediction error. The appropriate quantization in performed by means of several Huffman tables.

Technical Issues In Low Rate Transform Coding

The transmission of video information through a narrow band channel requires a significant degree of image compression. In addition to the actual coding procedure, the frame rate is reduced, the spatial sample rate is lowered and the color components are further filtered. Via the review of a practical and flexible image compression configuration, the important technical aspects of videocoding is presented. The complexity of the currently developed system is discussed for the operation over a 64 kbit/sec communication channel. The specific and primary considerations include the following: After a reduction of temporal and spatial resolution, the luminance and color difference signals are divided in pixel blocks of 16 x 16 and 8 x 8, respectively. Then, they are passed on to a motion compensated DPCM coding system with a subsequent discrete cosine transform of the prediction error. The appropriate quantization is performed via several Huffman tables.

High-definition video codec for broad band applications

The video codec presented here will aim at transmitting HIgh Definition Video (HDV) over wide band transmission channels, such as B-ISDN. Primarily, the HDV codec is adapted to the switched broad band network, VBN (Vermitteltes Breitband Netz), of the German Bundespost Telekom with a gross bit rate of 139,264 Mbit/s. To cope with noise effects, appearing in most transmission channels, and especially in satellite links, a robust Forward Error Correction (FEC) unit has been included in the codec.

140-Mbit/s HDTV coding using subband and hybrid techniques

To realize the complex algorithms of encoding and decoding HDTV signals at the required pixel rate, it is advisable to split the image into several data channels. These channels have to be processed in parallel. As an alternative to splitting the image into horizontal or vertical stripes, the image can be split into different frequency bands. In this paper, a coding scheme for HDV signals, based on band splitting and band interpolation, is presented (the abbreviation HDV is used for high-definition video, symbolizing the use of the presented codec for more than television purposes). The concept of subband coding in combination with motion compensated prediction and transform coding is described.

Enhanced 64 Kbit/s Video Phone-System

In several papers, the basic concept of a 64 kbit/s video-codec was presented with different points of emphasis. Based on the system presented in [1], several methods are investigated to enhance the reconstructed picture quality of this codec. The basic coding concept consists of a reduction of the temporal and the spatial resolution, a block oriented motion compensated DPCM, and a DCT-coding. The investigations include time-filtering, dual spatial resolution, an improved motion estimation, and a modified coder and buffer control.