TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

H.261 is called video codec for audiovisual services at p * 64 kbit/s (know also as p64
algorithm) [14]. This ITU-T recommendation was developed to target a constant bit rate
videophone, videoconference and other audiovisual services over ISDN. The H.261 model consists
of five stages: a motion compensation stage, a transformation stage, a lossy quantization stage, and
two lossless coding stages.
The coding algorithm is a hybrid of inter-picture prediction, transform coding, and motion
compensation. The H.261 specification is already implemented in several telecommunications
devices and is integrated onto custom chips by several manufacturers. The difference between
H.261 and MPEG-1 algorithm is in the bit-rate. MPEG-1 was not designed for packet video
streaming. It has a bit rates–0.9 Mbps to 1.5 Mbps and consequently achieves higher quality than
H.261.
3.2.1.1.3 H.263 and H.263+
H.263 is a recommendation that specifies a coded representation that can be used for
compressing moving picture at low bit rates [16]. The basic configuration of the video source
coding algorithm is based on ITU-T recommendation H.261. H.263 differs from H.261
recommendation in the flowing. Half pixel precision is used for the motion compensation
compared to full pixel precision. In addition to the core H.263 coding algorithm, four negotiable
coding options are included to improve performance. All these options can be used together or
separately. These options are: Unrestricted Motion Vector mode, Syntax-based Arithmetic Coding
mode, and Advanced Prediction mode and PB-frames mode. H.263 supports five resolutions. In
addition to CIF (352 x 288) and QCIF (176 x 144) that were supported by H.261, there is sub-
QCIF (128 x 96), 4CIF (704 x 576), and 16CIF (1408 x 1152). H.263+ was formally known as
H.263v2 [17]. This codec enhances H.263 codec by adding new types of options which are
scalability pictures, improved PB frames, custom source formats, and nine new coding modes.
3.2.1.1.4 MPEG-1, MPEG-2(H.262) and MPEG-4
Moving Picture Experts Group (MPEG) was created to develop video packing standards. At
the moment there are three MPEG-standards available and two on the process: MPEG-1 (ISO-
11172) [18], MPEG-2 (ISO-13818) [15] and MPEG-4 (ISO-14496) [19]. The ISO/ IEC IEC13818
namely MPEG-2 is known also as ITU-T recommendation H.262, This recommendation is
designed for high definition video quality [15]. Also multimedia document description interface
MPEG-7 (ISO-15938) [20] and frame of reference standard MPEG-21 (ISO-18034) [21] is under
development. MPEG-1, 2 and 4 are currently the wide well known codec in the word. Thanks to
MPEG standards that Digital Television is now possible.
The first standard developed by MPEG committee is MPEG-1 codec. This codec targets a bit
storage rate of 0.9 - 1.5 Mbps offering VHS quality at CIF resolution and 30 frames per second.
MPEG-1 is not adapted for transmission over loosely packet switching environment such as IP,
due to the dependencies present in the P (Predicted) and B (bi-directional predicted) frames. For
this reason, MPEG-1 does not offer resolution scalability and the video quality is highly vulnerable
to packet losses.
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