Security projects typically have requirements of video surveillance. Video surveillance clients are mainly in the form of Native applications in the Web side need to use NPAPI, ActiveX plug-like technology. However, IE decline, Chrome also gave up NPAPI, on the other hand, monitoring equipment hardware vendors gradually standardized video output format. It makes based on open, standardized interfaces of Web video surveillance possible.
Our R & D team has done a lot of attempts, we discuss with HTML5 and its derivative technology-based B / S architecture real-time video surveillance solution. Including two aspects: introductory video coding, basic knowledge of streaming media, and related libraries, frameworks, and introduce HTML5 features can be used for video surveillance, such as media label, MSE, WebRTC, as well as the associated libraries, frameworks.
First, the audio and video coding
Audio, video encoding (Codec, compression) There are many algorithms, there are differences in different browsers support for audio and video encoding algorithm. H264 Such monitoring equipment commonly used in video encoding format, the mainstream browsers have some degree of support. Common audio coding algorithms include: MP3, Vorbis, AAC; common video coding algorithms include: H.264, HEVC, VP8, VP9. The encoded audio and video are typically packaged in a bit stream format container (Container), these formats are common: MP4, FLV, WebM, ASF, ISMA like.
Second, streaming media technology
The so-called streaming media refers to the steady stream generated by the provider, and sustained by the end user to receive, multimedia presentations, just like water. The real world of the media, some inherently streaming, such as television, radio, others are not, such as books, CD. Streaming technology (from the perspective of transmission media) can be used as a substitute for file downloads. Streaming media technology concern is how to pass the media, rather than how to encode the media, is the concrete implementation of various streaming protocols. Media bitstream (container format) encapsulated delivered by streaming server to a streaming client. Streaming protocol may have requirements for the underlying container format, coding format, or may not have any requirements.
Third, live
The key difference between a live stream (Live streaming) and static files to play: when demand usually located on the target file server, has long played a certain file size. Browsers can use progressive download, playback while downloading, there is no live play start and end points. It is expressed as a form of flow, a steady stream of video capture source from the server, the client is transmitted to the live stream is usually adaptive (Adaptive), which is available to the client as the change rate bandwidth may become large, smaller, in order to eliminate possible latency streaming technology not only can be used to monitor the picture preview, you can also improve the user experience of video playback than simple static file playback, streaming playback has the following advantages: relatively low latency, can play adaptive streaming start as soon as possible to avoid Caton.
