Output Pitch Definition

IF09 buffers may have a pitch (also referred to as a stride), which includes byte padding, on a per-scan line basis. Pitch is defined as the distance, in bytes, from one pixel to the pixel directly below it in the buffer. In other words, the offset in a buffer to the point (x, y) will be exactly pitch bytes less than the offset in the buffer to the point (x, y + 1). It is a requirement of the IF09 that any pitch defined by graphics hardware be a multiple of four bytes, to prevent unaligned memory accesses. An IF09 buffer in which the pitch is equal to the width of the source image, in bytes, will automatically meet this requirement, since the format is only defined for images whose width is a multiple of four pixels.

The pitch in an IF09 buffer is required to be proportional to the width of the plane being written. For example, if an image is 160 pixels and the pitch is given as 200, Indeo will write 160 bytes of data and skip 40 in the Y plane, and write 40 bytes of data and skip 10 in the V and U planes.