llMulDiv function

[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The llMulDiv function implements the formula ((a*b)+rnd)/c where each term is a 64-bit value.

Time stamps and seek times are 64-bit values, so this function is useful for performing conversions on 32-bit systems. For example, the formula for bytes-per-second is

(Number of Bytes * Reference Time) / 10,000,000

which can be calculated as llMulDiv(nBytes, rtTime, 10000000, 0). Use the rnd parameter as a rounding factor.

Syntax

LONGLONG WINAPI Int64x32Div32(
   LONGLONG a,
   LONGLONG b,
   LONGLONG c,
   LONGLONG rnd
);

Parameters

a

Multiplicand.

b

Multiplier.

c

Divisor.

rnd

Rounding factor.

Return value

Returns either the (a * b + rnd)/c calculation or one of the following values.

Remarks

Rounding on the division is toward zero. Division by zero is counted as an overflow condition.

Requirements

See also

Miscellaneous Helper Functions

Int64x32Div32