M = video rtp port number RTP/AVP 97 a = rtpmap:97 H.264/90000 Sequence Number H.264 is a dynamic payload type, and the clock rate is 90 kHz, which is specified in the SDP as follows: For example, G.711|>Law uses a static payload type of 0, and the clock rate is defined in RFC 3551. When using SIP signaling with dynamic payload types, the clock rate should be defined in the appropriate attribute line of the Session Description Protocol ( SDP) offer. There is one important distinction: For the static payload types, the clock rate is specified in the payload format. The numeric value of the payload type may be predefined (called static payload types in the range of 0 to 96) or can be dynamically assigned during the capability negotiation between the conference server and the endpoint.
#Ast rtp read rtp codec 96 received from how to#
When the endpoint or conference server receives an RTP packet, it uses the payload type to determine how to interpret the payload. RFC 3550 defines payload type as a 7-bit field that identifies the codec type and sample rate of media carried in the packet. Without the M bit, the receiver would need to wait for one additional packet to detect a change to a new frame number.
#Ast rtp read rtp codec 96 received from full#
The M bit is helpful in video streams because it allows the endpoint to know that it has received the last packet of the frame so that it may display the full image. The M bit is intended to allow significant events such as frame boundaries to be marked in the packet stream. ■ Marker (M): 1 bit-The interpretation of the marker is defined by the RTP profile in use. CSRC is explained in much more detail later in this chapter in the section "Contributing Source Identifiers." ■ Contributing Source (CSRC) count (CC): 4 bits-The CSRC count contains the number of CSRC identifiers that follow the fixed header. ■ Extension (X): 1 bit-If the extension bit is set, exactly one header extension must follow the fixed header. Some encryption algorithms with fixed block sizes might need padding to carry several RTP packets in a lower-layer protocol data unit. The last octet of the padding contains a count of how many padding octets should be ignored, including itself. ■ Padding (P): 1 bit-If the padding bit is set, the packet contains one or more additional padding octets at the end, which are not part of the payload. The Version field is set to a value of 2 in most RTP implementations to denote the RTP profile defined in RFC 3551. ■ Version (V): 2 bits-This field identifies the version of RTP. The fields in this first octet of the RTP header are described as follows: The following sections describe the octets in the RTP header shown in Figure 4-2. Payload Header (Optional Depending on the Codec) Payload The header has the format illustrated in Figure 4-2. We list applications of some common types of payload.As stated in RFC 3550, the RTP header has a 12-octet mandatory part followed by an optional header extension. This field is of length 7-bit to indicate type of payload. The length of this field is 1-bit and it is used as end marker by application to indicate end of its data. Here maximum possible number of contributor is 15 as a 4-bit field can allows number form 0 to 15. This 4-bit field indicates number of contributors. If value of this field is set to 1, then its indicates an extra extension header between data and basic header and if value is 0 then, there is no extra extension. If value is 1, then it denotes presence of padding at end of packet and if value is 0, then there is no padding. The explanation of each field of header format is given below: The header format of RTP is very simple and it covers all real-time applications. The diagram of header format of RTP packet is shown below:
%2C445%2C286%2C400%2C400%2Carial%2C12%2C4%2C0%2C0%2C5_SCLZZZZZZZ_.jpg "ast rtp read rtp codec 96 received from")
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