![]() (I say generally because occasionally events have a short form based on the content.) Interleaving repeats for the remainder of the DataSizeĮvent data is stored after the standard header in time-delta format.Įach event is represented by an 8bit code, and generally followed by 16bits worth of delta offset values, and zero or more data fields of varying byte lengths, determined by the event code. Note: Interleaved data is stored in the opposite order to the list data defined in the waveform header component.Įxample, Two multiplexed waveforms, one with an interleave of 5, sample type 0, and the other has an interleave of 5, sample type 1Ġx00 44 1 (Starting from the first byte in the data block) Different sample types can be interleaved together, and may therefore be different sizes. Only 8 bit samples have been observed, but I feel it's safe to assume the interleave counts samples and not bytes. If more than one waveform is present, the data is multiplexed together in small groups of samples, the size of which is determined by the interleave value and sample type stored in the header. If only one waveform is present (indicated by number of signals = 1), this simply contains DataSize/SampleSize samples for this block in order. Important: For some reason, this list is stored in reverse order.įollowed by the 8bit sum of all header information, stored at 0x16+(nsig*3)Ĭalculating just the size of a blocks data areaĭataSize = BlockLength – HeaderLength – Extra Header stuff – 1 byte header checksum – 2 byte block checksumįor summary & event data, this translates to DataSize = BlockLength-18įor waveform data, this translates to DataSize = BlockLength-18-(nsig*3) Waveform Data Header (.005 files) Idxĝata Type DetailsĠx0f 16bit integer Number of secondsĠx12 16bit integer Number of signals (nsig)įollowed by a list containing (nsig * 24bits) of data describing how each waveform data is stored:Ġx14 16bit integer Sample interleave The standard header is just followed by the 8bit checksum at position 0x0f, which is additive sum of all header values up to this byte. Standard PRS1 Header Example Ġ1 16bit integerělockLength (in bytes, including header & checksum values)Ġ3 8bit integerğileType (Defining additional header information)Ġ7 32bit integer Session Sequence NumberĠb ē2bit integer TimeStamp (UNIX Epoch)Ġ0 indicates no additional header data is needed. In most cases it would be better to use the internal values instead, but the are handy for quick lookup. The filename component minus the extension gives session sequence number. The file's extension provides an extra indication of the type of data contained: The cycle repeats for each subsequence block, although only waveform data has been observed to contain multiple blocks. Each block begins with a 15 byte header, any additional header data, an 8 bit header checksum, the data stream itself (in a not-so-well-defined structure), followed by a 16bit data integrity checksum. Plus accidentally leaving out the SD card doesn't suck anywhere near as much as when it's done on others machines.Įach PR System One data file has a well defined structure containing a sequence of one or more data blocks. This is probably the best of the bunch as far as CPAP storage systems go - I say this mainly because they bothered to design it around a decent per-session model, and the machine doesn't unnecessarily wipe out data while it has a mostly empty SD card. Keeps all flow waveform data, unless the card is left out, in which case it retains Event, general graphs & Summary data.Summary data contains settings info for each session, like humidifier, flex settings, etc. ![]() A little stingy with the flow waveform resolution, only 5hz.Manufacturer failed to openly document this relatively complex data format.2.1.3 Calculating just the size of a blocks data area.2.1.2 Waveform Data Header (.005 files).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |