4. Frame formats

JANE file formats are an adaptation of the beautiful PPM format. They consist of an ASCII header and a binary data section. The header consists of:

1. A magic word on a line by itself
2. Lines each containing a key and a value, separated by whitespace

The last line of the header must have as a key either data or datafile. The value is the data length in ASCII for data, or a filename for datafile.

Keys and values cannot contain whitespace. A data line must have exactly one newline after the length number. The frame data begins immediately thereafter.

Times are specified in seconds, in order to be agnostic about the source format (30000/1001 is evil!).

The start_time key is followed by the start time (from the perspective of the sending plugin) as a floating-point number (in ASCII. If start_time is negative, it refers to a negative time with respect to the end of the clip.

The duration key is followed by the duration of the data, also as a floating-point number.

Plugins that have no concept of start or end time (such as live feeds or computer-genreated data) should set start_time and duration to whatever was requested.

Calculating the frame rate from the above information is left as an exercise for the reader.

The header may contain any other key-value pairs that the creator finds useful or thought-provoking. Plugins must gracefully preserve unknown key-value pairs.

4.1 JANE Video Formats
4.2 JANE Audio Format

4.1 JANE Video Formats

JANE video frame files start with the magic line JaneVideoFormat\n

Required keys are height, width, and format. For now, there are two defined formats: RBGA-uint8-packed and YUVA-uint8-packed. Since this is byte-oriented format, endianness should not be an issue (though X11 seems to worry about it neurotically, to the point of specifying bit order in a byte, while bytes are supposed to be atomic... WTF? Anyway, I digress.)

Both formats are a list of pixels in English reading order (left to right, top to bottom). Each pixel consits of four one-byte integers - three for color, one for opacity.

Frames may be interlaced. If so, they should have a header with key interlace and value top-first or bottom-first. Interlace of none may be specified as well.

4.2 JANE Audio Format

JANE audio files represent a single (mono) audio channel.

JANE audio files start with the line JaneAudioFormat\n.

The only defined format so far is pcm-float32. The data payload consists of IEEE 754 floating-point numbers in the range -1.0 to 1.0.

The frames key specifies the number of frames contained in the data payload. A frame in a discrete sample, so for audio frames, this is what would normally be called the sample count.