SuperFrameHandle is an internal method of sdrdab which is responsible for synchronization, correction and creating super-frame with data received from energy dispersal function during MSC decoding.
Structure of super-frame is simple: it is composed of frames. Each one has 56-bits header and an AU (Access Unit).
Firstly, the receiver concatenates five consecutive DAB frames to build the audio super frame. The receiver checks which five consecutive DAB frames within a sub channel constitute an audio super frame. This means that audio super frame buffer has to store least 5 DAB frames.
When the receiver detects i.e. too many consecutive audio super frames with uncorrectable errors in the audio super frame header, synchronization process is launched. Even in the presence of reception errors, the receiver should be able to synchronize to the audio super frame structure.
A first test is used to check whether the first DAB frame in the audio super frame buffer might be the beginning of an audio super frame. If that is not the case, then the first DAB frame is removed and the next received DAB frame is added to the end of the audio super frame buffer.
If the first five DAB frames are a valid audio super frame, the receiver corrects all errors (if there were any) with use of the Reed Solomon algorithm and then checks the header checksum. For this test, the Fire code is used for error detection only. If valid audio super frame was received, synchronization is completed.
To ensure that the synchronization process is able to synchronize to the first occurrence of an audio super frame, every received DAB frame is checked whether it could be the beginning of an audio super frame. If the Fire code detects too many errors, then the first DAB frame probably does not contain the beginning of an audio super frame.
- ETSI TS 102 563
- ETSI EN 300 401
- ETSI TR 101 496-2