JMF introduction of the time based media

1. Time-based media (time-based)

Any change in data over time can be defined as a time based medium. Audio clips, midi sequences, video clips, and animations are all time based media forms.

The following figure illustrates the main characteristics and the use process of the time based media from the basic data processing process patterns:

2. Streaming (streaming media)

One of the main features of the time based media is that it must be transmitted and processed in real time. Once the media data stream is turned on, its receive (receiving) and display (presenting) data must be based on time. Because of this, time based media is often defined as streaming media (streaming).

2.1 Content Type

The format of the media store is called its content type. QuickTime, MPEG, WAV are all types of content.

2.2 Media streaming (streams)

Media streaming refers to the media data obtained from a local file, network or camera. Media flow often contains multiple data channels, which are called tracks. For example, a QuickTime file might contain a sound channel and a video path. Multi-channel media flows are often referred to as composite (multiplexed) or synthetic (complex) media streams. Separation (demultiplexing) refers to the process of extracting a single channel from a synthesized media stream.

The type of a path identifies the type of data it contains, such as audio or video. The format of a path defines the data structure it contains.

A media stream can be identified by its storage location and the protocol used to access it. For example, you can use a URL to locate a local or non-local QuickTime file. If it is local, it can be accessed through the File Protocol (protocol). If it is on a Web server, it can be accessed through the HTTP protocol (HTTP protocol). When you cannot use a URL to locate a media stream, you can use a media locator (medium locator) to identify the location of the media stream.

The following is a media stream classification based on transmission mode:

lpull-data transmission that is initiated and controlled by the client. Hypertext Transfer Protocol and File Transfer Protocol are all pull protocols.

lpush-data transfer initiated and controlled by the server side. Real-time Transfer Protocol (RTP) is a push protocol for streaming media.

2.3 Common media formats (formats)

The following table lists the commonly used audio (TABLE2) and video (TABLE1) formats. When choosing a format, we should consider the requirements for media quality, CPU requirements, and bandwidth requirements for network transmission.

TD style= "BORDER:0;PADDING:0;" >jpeg

content Type	quality	cpu Requirements	bandwidth Requirements
avi QuickTime	medium	low	high
mpeg	high	high
h.261	avi RTP	low	medium	medium
h.263	quicktime AVI RTP	medi Um	medium	low
high	high
indeo	quicktime AVI	medium	medium	medium

Table 1: Common video formats

Format	Content Type	Quality	CPU Requirements	Bandwidth Requirements
Pcm	Avi QuickTime Wav	High	Low	High
Mu-law	Avi QuickTime Wav Rtp	Low	Low	High
ADPCM (DVI, IMA4)	Avi QuickTime Wav Rtp	Medium	Medium	Medium
MPEG-1	MPEG	High	High	High
MPEG Layer3	MPEG	High	High	Medium
Gsm	Wav Rtp	Low	Low	Low
g.723.1	Wav Rtp	Medium	Medium	Low

Table 2: Commonly used audio formats.