NGN
Multimedia Services Control Protocol

MPEG is a standard for "the generic coding of moving pictures and associated audio information. The function of MPEG is to take analogue or digital video signals and convert them into packets of digital information that are more efficiently transported on modern networks This process of converting audio and video signal to digital form is called compression (or coding). Opposite process is called decompression (or decoding) when digital audio and video signal is converted to analog form. MPEG is a system for compression and encoding of digital multimedia content. MPEG standard compresses the video and audio into much less information as it needed before, consuming less transmission bandwidth. Level of compression depends on bandwidth requirements and also on level of quality.

MPEG 1

The default size for an MPEG-1 video is 352x240 at 30 fps for NTSC (352x288 at 25 fps for PAL sources). These were designed to give the correct 4:3 aspect ratio when displayed on the rectangular pixels of TV screens. For a computer-based viewing audience, 320x240 square pixels give the same aspect ratio. MPEG-1 delivers roughly VHS quality at 30 frames per second at 1.5 Mbps. It can be scaled up or down in size or bit rate, but range between 1.2 – 1.5 Mbps is the optimal bit rate.

MPEG 2

MPEG-2 needs about 6 Mbps to provide the quality movie on DVDs, although data rates up to 15 Mbps are supported. 720x480 is the typical 4:3 default resolution, while 1920x1080 provides support for 16:9 high-definition television. MPEG-2 is now arguably the most successful new consumer standard ever relative to its acceptance in the marketplace. Presently it is the predominant standard for existing digital video equipment worldwide. Based on MPEG-2, digital television (both standard definition, SD, and high definition, HD) has become the norm for broadcasting, replacing analog broadcast in all but standard terrestrial and cable television.

MPEG 4

MPEG-4 and H.264 have a common heritage within the ISO and ITU standards committees. As a result the overall coding approach is quite similar. Both algorithms are based on a common heritage of DCT based, hybrid image coding, first used in H.261 and MPEG-1. A number of comparison tests have been performed between H.264 and MPEG-2/MPEG-4 on standard MPEG test material. For standard resolution (704x480, 60 Hz interlaced) video sequences to achieve a PSNR level of 28, NBA must be coded at a rate of 5 Mbps using MPEG-2, but only 1.8 Mbps using H.264.

MPEG Audio Compression

MP3 is actually part of the MPEG-1 standard. The audio portion of the MPEG-1 specification contains three different compression schemes called layers. Of the three, Layer 3 provides the greatest audio quality and the greatest compression. At 8 kbps, MP3 will sound like a phone call – intelligible, but nothing that would ever be called high-fidelity. Good-quality music starts at about 96 kbps, but generally 128 or 160 kbps to would be closer to "CD quality".

RTSP

RTSP (Real-Time Streaming Protocol) is an application-level protocol for control over the delivery of data with real-time properties and its goal is streaming of multimedia over multicast and unicast in "one to many" applications. RTSP provides an extensible framework to enable controlled, on-demand delivery of real-time data, such as audio and video.

Sources of data can include both live data feeds (e.g. Live TV channels) and stored clips (e.g. Video On Demand). RTSP establishes and controls single or several data delivery time synchronized media sessions, provide a means for choosing delivery channels such as UDP, multicast UDP and TCP, and provide a means for choosing delivery mechanisms based upon RTP and control mechanism of streams upon RTCP. RTSP is not tied to RTP and RTCP. There is no notion of an RTSP connection – instead, a server maintains a session labeled by an identifier. An RTSP session is in no way tied to a transport level connection such as a TCP connection.

During an RTSP session, an RTSP client may open and close many reliable transport connections to the server to issue RTSP requests. Alternatively, it may use a connectionless transport protocol such as UDP. The streams controlled by RTSP may use RTP, but the operation of RTSP does not depend on the transport mechanism used to carry continuous media. The protocol is intentionally similar in syntax and operation to HTTP/1.1 so that extension mechanisms to http can in most cases also be added to RTSP.

IGMP

Internet Group Management Protocol (IGMP), allows Internet hosts to participate in multicasting. IGMP allows users to announce their intention to join particular multicast groups. These groups are identified by their unique Class-D IP addresses.

When a workstation wants to participate in a multicast group, it sends an IGMP “join” message to its local router. If multiple routers exist on a single segment, they can mutually elect a “Designated Router (DR)” to manage all of the IGMP messages for that segment. After a router receives one or more “joins” for a specific group, the router will forward any packets destined for that group to the appropriate interface. The router should only forward one copy of the data packet per interface.

If multiple receivers exist on a single interface they will all receive the same information by monitoring common multicast MAC and IP addresses. If the multicast group has receivers spread over several router interfaces, the router must replicate the packet and deliver a copy to each interface that contains registered users. This type of transmission activity can be immense, which is why IGMP is highly useful as a stateful protocol. The designated router regularly verifies that the attached workstations want to continue to participate in their respective multicast groups. The designated router sends periodic “queries” to the receivers. These queries are transmitted to a well-known multicast address (224.0.0.1) that is monitored by all systems. If the receivers are still interested in that particular multicast group, they will respond with a “membership report” message. When the router stops seeing responses to queries, it will delete the appropriate group from its forwarding table.

MLDv2

MLD (Multicast Listener Discovery) is de facto derivate of IGMP used in IPv6 networks. It is control layer protocol used to control multicast stream flow in IPv6 network. MLD and MLDv2 protocols are designed for use only in IPv6 network. This protocol is follower of IGMP in IPv4 networks used for joining some network node to multicast group. Multicast groups are separated by IP addresses. Procedure of joining some multicast group on network is to announce next routing point, which must be directly attached to some of the requester interfaces.

Node asks it need packets provided for some particular group. If router point have not access to some multicast group data, it must also join it on other interface(s) and forward this data to requester. Router point is sending request to next router point. This process must recursively continue to router point, where source of multicast group data is connected. Note that a multicast router may itself be a listener of one or more multicast addresses; in this case it performs both the "multicast router part" and the "multicast address listener part" of the protocol, to collect the multicast listener information needed by its multicast routing protocol on the one hand, and to inform itself and other neighboring multicast routers of its listening state on the other hand.