Caching of MPEG-4 Streams

Komssys is an Open-Source RTSP/RTP implementation which consists of a server, a proxy and a client. The current implementation of komssys supports onyl a limited set of media formats, such as MPEG-1-Systems. One partly missing format is the newest multimedia standard of the Moving Pictures Experts Group (MPEG), i.e. MPEG-4. At the moment the proxy is able to forward MPEG-4 streams from a server (e.g. Darwin Streaming Server from Apple) to a client but not to save them into a file for caching purpose.

In the scope of this work these missing capabilities have to be implemented for komssys. Therefore, a MPEG-4 stream, which arrives at the proxy needs to be saved together with additional information about the stream and from the RTP-packets into a file. If somehow later a second request for the same stream arrives at the proxy the saved stream needs to be read from the file and the RTP-packets needs to be reconstructed and send to the client.

Based on the existing caching capabilities of the komssys proxy an appropriate solution to support caching of MPEG-4 streams needs to be designed and implemented. The existing class LCRTPCachingReflectorGM should be a good starting point. This class is the implementation of the so called Graph Manager (GM) which controlls the datapath consisting of several Stream Handlers through which the data units of the stream will be pipelined. SHs are small data processing units which can be connected by a GM into an acyclic directed data path. A SH can either consume or generate data units or transmit data units from its input to its output. Additionally, each SH can manipulate the data units and, when connected to a data path, a stream which is pipelined through these SHs can be processed or manipulated in a certain manner. The GM is responsible for the configuration of each SH when the data path is built as well as for its control and reconfiguration during transmission of the stream.

• Komssys - KOM(S) Streaming System