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Have a look at the insides of the Racer file formats.

The RTD file format is used for storing telemetry data (since v0.8.18). It has stabilized quite a bit throughout the years.

The endianness is based on Intel CPU's. An 'int' is 32 bits and a float is also 32 bits.
Strings are written as 'short len; char data[len]' - without the trailing zero. For example, the string "hello" would be written as a 16-bit short (value 5) and 5 chars. In total it would take 7 bytes.

RTD files can be converted to ASCII text files using the RTD2ASCII tool, which is provided with every Racer version, starting from v0.9.0RC6. From there on, it should be simple to convert to any type of telemetry tool.

Header

The file header is as follows:

• RTD0 - a 4-byte identifier (char[4])
• int32 signals - the number of signals in the file (7 for example)
• float dx - the timestep in seconds (expect 0.01 for example)

Properties

After the header a number of generic properties are written:

• PROP - a 4-byte identifier (char[4])
• int properties - the number of properties in the file
• for each property (so 0..properties-1), a string 'key' and a 'string value'. See the introduction for the specific storage of strings.

Properties are used to pass things like 'car' and 'track' in a flexible way. More properties may be stored in the future.

Meta-properties

Next, a number of meta-properties are written. These are properties that are less global, such as laptime information. This chunk may not be present in old RTD files.

• MPRP - a 4-byte identifier (char[4])
• int metaproperties - the number of meta-properties in the file
• for each property (so 0..properties-1), a string 'key' and a 'string value'. See the introduction for the specific storage of strings.

Signal data

Next is the the signal data.

• SGNL - a 4-byte identifier (char[4]) that indicates a signal is coming up (some telemetry programs call this a 'channel').
• int signalType - this used to be a signal type indicator, but is now obsolete. You can read it, but the number has no meaning.
• int sampleCount - the number of samples (each sample is stored as a float).
• char name[32] - 32 characters with the signal name. Ends with a zero, so effectively a signal name can only be 31 characters long.
• float samples[sampleCount] - the sampled data.

That's all there is to it, really.

(last updated March 29, 2013 )