diff options
Diffstat (limited to 'media/ffvpx/libavutil/mathematics.h')
| -rw-r--r-- | media/ffvpx/libavutil/mathematics.h | 145 |
1 files changed, 111 insertions, 34 deletions
diff --git a/media/ffvpx/libavutil/mathematics.h b/media/ffvpx/libavutil/mathematics.h index 57c44f845..54901800b 100644 --- a/media/ffvpx/libavutil/mathematics.h +++ b/media/ffvpx/libavutil/mathematics.h @@ -18,6 +18,12 @@ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ +/** + * @file + * @addtogroup lavu_math + * Mathematical utilities for working with timestamp and time base. + */ + #ifndef AVUTIL_MATHEMATICS_H #define AVUTIL_MATHEMATICS_H @@ -63,84 +69,155 @@ /** * @addtogroup lavu_math + * * @{ */ - +/** + * Rounding methods. + */ enum AVRounding { AV_ROUND_ZERO = 0, ///< Round toward zero. AV_ROUND_INF = 1, ///< Round away from zero. AV_ROUND_DOWN = 2, ///< Round toward -infinity. AV_ROUND_UP = 3, ///< Round toward +infinity. AV_ROUND_NEAR_INF = 5, ///< Round to nearest and halfway cases away from zero. - AV_ROUND_PASS_MINMAX = 8192, ///< Flag to pass INT64_MIN/MAX through instead of rescaling, this avoids special cases for AV_NOPTS_VALUE + /** + * Flag telling rescaling functions to pass `INT64_MIN`/`MAX` through + * unchanged, avoiding special cases for #AV_NOPTS_VALUE. + * + * Unlike other values of the enumeration AVRounding, this value is a + * bitmask that must be used in conjunction with another value of the + * enumeration through a bitwise OR, in order to set behavior for normal + * cases. + * + * @code{.c} + * av_rescale_rnd(3, 1, 2, AV_ROUND_UP | AV_ROUND_PASS_MINMAX); + * // Rescaling 3: + * // Calculating 3 * 1 / 2 + * // 3 / 2 is rounded up to 2 + * // => 2 + * + * av_rescale_rnd(AV_NOPTS_VALUE, 1, 2, AV_ROUND_UP | AV_ROUND_PASS_MINMAX); + * // Rescaling AV_NOPTS_VALUE: + * // AV_NOPTS_VALUE == INT64_MIN + * // AV_NOPTS_VALUE is passed through + * // => AV_NOPTS_VALUE + * @endcode + */ + AV_ROUND_PASS_MINMAX = 8192, }; /** - * Compute the greatest common divisor of a and b. + * Compute the greatest common divisor of two integer operands. * - * @return gcd of a and b up to sign; if a >= 0 and b >= 0, return value is >= 0; + * @param a,b Operands + * @return GCD of a and b up to sign; if a >= 0 and b >= 0, return value is >= 0; * if a == 0 and b == 0, returns 0. */ int64_t av_const av_gcd(int64_t a, int64_t b); /** * Rescale a 64-bit integer with rounding to nearest. - * A simple a*b/c isn't possible as it can overflow. + * + * The operation is mathematically equivalent to `a * b / c`, but writing that + * directly can overflow. + * + * This function is equivalent to av_rescale_rnd() with #AV_ROUND_NEAR_INF. + * + * @see av_rescale_rnd(), av_rescale_q(), av_rescale_q_rnd() */ int64_t av_rescale(int64_t a, int64_t b, int64_t c) av_const; /** * Rescale a 64-bit integer with specified rounding. - * A simple a*b/c isn't possible as it can overflow. * - * @return rescaled value a, or if AV_ROUND_PASS_MINMAX is set and a is - * INT64_MIN or INT64_MAX then a is passed through unchanged. + * The operation is mathematically equivalent to `a * b / c`, but writing that + * directly can overflow, and does not support different rounding methods. + * + * @see av_rescale(), av_rescale_q(), av_rescale_q_rnd() */ -int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding) av_const; +int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding rnd) av_const; /** * Rescale a 64-bit integer by 2 rational numbers. + * + * The operation is mathematically equivalent to `a * bq / cq`. + * + * This function is equivalent to av_rescale_q_rnd() with #AV_ROUND_NEAR_INF. + * + * @see av_rescale(), av_rescale_rnd(), av_rescale_q_rnd() */ int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const; /** * Rescale a 64-bit integer by 2 rational numbers with specified rounding. * - * @return rescaled value a, or if AV_ROUND_PASS_MINMAX is set and a is - * INT64_MIN or INT64_MAX then a is passed through unchanged. + * The operation is mathematically equivalent to `a * bq / cq`. + * + * @see av_rescale(), av_rescale_rnd(), av_rescale_q() */ int64_t av_rescale_q_rnd(int64_t a, AVRational bq, AVRational cq, - enum AVRounding) av_const; + enum AVRounding rnd) av_const; /** - * Compare 2 timestamps each in its own timebases. - * The result of the function is undefined if one of the timestamps - * is outside the int64_t range when represented in the others timebase. - * @return -1 if ts_a is before ts_b, 1 if ts_a is after ts_b or 0 if they represent the same position + * Compare two timestamps each in its own time base. + * + * @return One of the following values: + * - -1 if `ts_a` is before `ts_b` + * - 1 if `ts_a` is after `ts_b` + * - 0 if they represent the same position + * + * @warning + * The result of the function is undefined if one of the timestamps is outside + * the `int64_t` range when represented in the other's timebase. */ int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b); /** - * Compare 2 integers modulo mod. - * That is we compare integers a and b for which only the least - * significant log2(mod) bits are known. - * - * @param mod must be a power of 2 - * @return a negative value if a is smaller than b - * a positive value if a is greater than b - * 0 if a equals b + * Compare the remainders of two integer operands divided by a common divisor. + * + * In other words, compare the least significant `log2(mod)` bits of integers + * `a` and `b`. + * + * @code{.c} + * av_compare_mod(0x11, 0x02, 0x10) < 0 // since 0x11 % 0x10 (0x1) < 0x02 % 0x10 (0x2) + * av_compare_mod(0x11, 0x02, 0x20) > 0 // since 0x11 % 0x20 (0x11) > 0x02 % 0x20 (0x02) + * @endcode + * + * @param a,b Operands + * @param mod Divisor; must be a power of 2 + * @return + * - a negative value if `a % mod < b % mod` + * - a positive value if `a % mod > b % mod` + * - zero if `a % mod == b % mod` */ int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod); /** * Rescale a timestamp while preserving known durations. * - * @param in_ts Input timestamp - * @param in_tb Input timebase - * @param fs_tb Duration and *last timebase - * @param duration duration till the next call - * @param out_tb Output timebase + * This function is designed to be called per audio packet to scale the input + * timestamp to a different time base. Compared to a simple av_rescale_q() + * call, this function is robust against possible inconsistent frame durations. + * + * The `last` parameter is a state variable that must be preserved for all + * subsequent calls for the same stream. For the first call, `*last` should be + * initialized to #AV_NOPTS_VALUE. + * + * @param[in] in_tb Input time base + * @param[in] in_ts Input timestamp + * @param[in] fs_tb Duration time base; typically this is finer-grained + * (greater) than `in_tb` and `out_tb` + * @param[in] duration Duration till the next call to this function (i.e. + * duration of the current packet/frame) + * @param[in,out] last Pointer to a timestamp expressed in terms of + * `fs_tb`, acting as a state variable + * @param[in] out_tb Output timebase + * @return Timestamp expressed in terms of `out_tb` + * + * @note In the context of this function, "duration" is in term of samples, not + * seconds. */ int64_t av_rescale_delta(AVRational in_tb, int64_t in_ts, AVRational fs_tb, int duration, int64_t *last, AVRational out_tb); @@ -150,15 +227,15 @@ int64_t av_rescale_delta(AVRational in_tb, int64_t in_ts, AVRational fs_tb, int * This function guarantees that when the same value is repeatly added that * no accumulation of rounding errors occurs. * - * @param ts Input timestamp - * @param ts_tb Input timestamp timebase - * @param inc value to add to ts - * @param inc_tb inc timebase + * @param[in] ts Input timestamp + * @param[in] ts_tb Input timestamp time base + * @param[in] inc Value to be added + * @param[in] inc_tb Time base of `inc` */ int64_t av_add_stable(AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t inc); - /** +/** * @} */ |