БЕСШОВНОЕ ВОСПРОИЗВЕДЕНИЕ ЖИВОЙ ПОТОКОВОЙ TCP-ТРАНСЛЯЦИИ МЕТОДОМ ОПЕРЕЖАЮЩЕЙ ЗАГРУЗКИ С НИЗКОЙ ЗАДЕРЖКОЙ

Abstract

The article discusses the client-server technology for organizing seamless live TCP-streaming with the use of progressive download method. Main factors which have a major impact on the overall playback latency have been identified. A study on the most important factor – the size of the client’s receiving buffer Lbuf – was carried out. It was found that the hypothetical display time of the last frame taken consists of two components: 1) the general instability, which has the character of a pronounced “band of instability”, and 2) episodic “drawdowns” associated with spontaneous media flow retentions in data transmission channel.The result of these drawdowns is an increase in Lbuf, resulting in increased playback delay. The article proposes a method to reduce the client’s receive buffer latency downto acceptable level (100-300 ms), allowing two-way communication between clients – an algorithm for smooth correction of client receiving buffer size. The article includes the results of the smooth correction algorithm in the implementation of TCP-Streaming by means of progressive downloading method. The implementation is a distributed software package consisting of one or more encoding processes, retransmitting process, client-side software. The media-flow Encoders converts data from the media-data sources (camera, computer screen, microphone) and transmits them to the clients via Retransmitter. The client-side software is a set of web pages (HTML + JS) where the receive buffer smooth correction algorithm is implemented. It was concluded that live TCP-streaming by means of progressive download method is quite suited to organize the communication with low latency between clients.