What is progressive download? How is video live-streaming live over the internet? All these questions and more are answered in this article.
Corporate internet sites are now embedding helpful ‘how to’ and ‘introductory’ video files in their websites, and are becoming increasingly aware that their visitors are far more likely to watch the 3 minute video than to read through pages of text.
With video streaming over the internet now being taken for granted, we have to ask; How does it function?
Firstly, we have to break video loading down into its 3 most commonly utilized forms.
1) On demand video streaming
2) Progressive download
3) Live video streaming
On requirement video streaming This is where a video articles is streamed over the internet when a web site visitor demands it. An example of this is when you click a play button for a video you want to watch and the video plays. This is very similar to the ‘Progressive download’ that we have mentioned except for one particular main difference. When a video is definitely streamed it is using streaming server technology. Steaming servers are a great way to make sure the video is delivered as it should be. Streaming video with the various streaming server technologies also allows us to get around rather than just stream our video. We can actually have ‘user interaction’ with our loading server allowing us to take a video watcher to a shop to buy some thing they have seen and ‘clicked on’ in the video they are watching for example.
Progressive download: This is where your video clip player downloads the whole video into your computers memory while the video is playing.
Live video streaming: Live video streaming requires a capture device, like a video camera, encoding software that transcodes or converts the video transmission from the camera into a web compliant movie format and a streaming server.
It camera will pass on the video information to the encoder, which will send the transcoded video up to the streaming server (usually over the internet) using One of the various streaming protocols. The streaming server will then broadcast the encoded video over the internet to your viewers that will see your video live, generally having a short delay, commonly about seven to 20 seconds of what is going on in real time.
What is MPEG4? MPEG4 has been designed to allow video playpack on the wide variety of platforms. It can be used on computer systems, HD TV, PDA’s and mobile phones.
Although there are many different video platforms on the internet, the basis for all streaming, whether live, on demand or modern download, all work using comparable coding schemes derived from work finished MPEG2, the prior format to MPEG4.
MPEG4 is made up of ‘data channels’ used to send the video stream and the sound stream. The number of data channels is not really explicit. Generally we have a video transport channel that is used to stream the video data, we have up to 8 stations for audio, usually MP3 or AAC (Advance Audio Codec), we now have a channel for subtitles and we have a data channel that allows details to be passed to and from the loading server.
The reason video can be live-streaming successfully over the web is the delivery method. Video, especially in films, is delivered frame by frame. This really is carried over from traditional recording methods where each frame provides the full picture presented to the viewer. These frames are played back one after the other so quickly that, to the human eye, creates the result of continuous movement.
Compressed MPEG4 video is made up of ‘I-Frames’ and ‘P-Frames. I-Frames are effectively frames that contain all the information needed to display a body, where a P-Frame is an update of the I-Frame. So what the decoder will is show an I-frame and then show a series of P-Frames that update changes in movement etc . Due to this, the video size is massively reduced. This particular explains why, when watching a video over the internet you sometimes see empty squares in the picture. This is because the particular P-Frames were not received in time as well as the decoder cannot update those areas in the video.
What is a Codec The Codec is a way of coding and decoding information. So all the different video formats on the internet work in an identical way, using an encoder to reduce movie and audio data whilst protecting as much quality as possible. This movie is then transmitted over the internet so when it reaches the clients participant it gets decoded into, or even as near to, its original format.