一、CMTime
Core Media定义的一种时间数据类型
typedef struct
{
CMTimeValue value; //64位有符号整型变量，作为分子
CMTimeScale timescale; //32位有符号整型变量，作为分母
// value/timescale = 对应时间-秒
CMTimeFlags flags; //位掩码，表示时间的指定状态，比如判定诗句是否有效、不确定或是是否出现舍入等
CMTimeEpoch epoch;
} CMTime;
1、创建CMTime
- 1、CMTimeMake()
CMTime CMTimeMake( int64_t value,int32_t timescale)
创建一个代表3秒的CMTime表达式(value/timescale)：
CMTime ts1 = CMTimeMake(3, 1);
CMTime ts2 = CMTimeMake(1800, 600);
CMTime ts3 = CMTimeMake(132300, 44100);
//打印时间结果
CMTimeShow(ts1);
CMTimeShow(ts2);
CMTimeShow(ts3);
//打印结果
{3/1 = 3.000}
{1800/600 = 3.000}
{132300/44100 = 3.000}
在处理视频内容时常见的时间刻度为600，这是大部分常用视频帧率24FPS、25FPS、30FPS的公倍数。音频常见的时间刻度就是采样率，如44.1kHz(44100)、48kHz(48000)。
- 2、CMTimeMakeWithSeconds()
CMTime CMTimeMakeWithSeconds( Float64 seconds, int32_t preferredTimescale)
CMTime t = CMTimeMakeWithSeconds(5, 1); // 5 seconds
CMTimeShow(t);
//{5/1 = 5.000}
- 3、CMTimeMakeFromDictionary
NSDictionary *timeData = @{(id)kCMTimeValueKey : @2,
(id)kCMTimeScaleKey : @1,
(id)kCMTimeFlagsKey : @1,
(id)kCMTimeEpochKey : @0};
CMTime t = CMTimeMakeFromDictionary((__bridge CFDictionaryRef)timeData);
CMTimeShow(t);
//{2/1 = 2.000}
2、CMTime运算
- 1、加减
CMTime ts1 = CMTimeMake(3, 1);
CMTime ts2 = CMTimeMake(5, 2);
CMTime result;
result = CMTimeAdd(ts1, ts2);
CMTimeShow(result);
//{11/2 = 5.500}
result = CMTimeSubtract(ts1, ts2);
CMTimeShow(result);
//{1/2 = 0.500}
- 2、比较
CMTime t1 = CMTimeMake(300, 100); // 3 seconds
CMTime t2 = CMTimeMakeWithSeconds(5, 1); // 5 seconds
CMTimeCompare()
int32_t r = CMTimeCompare(t1, t2);
NSLog(@"compare: %d",r);
//t1 < t2 => -1
//t1 == t2 => 0
//t1 > ts => 1
CMTIME_COMPARE_INLINE()
NSLog(@"t1 > t2 => %@",CMTIME_COMPARE_INLINE(t1, >, t2) ? @"YES":@"NO");
// t1 > t2 => NO
- 3、验证CMTIME_IS_VALID()
NSLog(@"ti is valid :%@",CMTIME_IS_VALID(t1) ? @"YES":@"NO");
// ti is valid :YES
3、CMTime转换为秒
Float64 CMTimeGetSeconds( CMTime time)
CMTime t1 = CMTimeMake(3001, 100);
NSLog(@"second : %f",CMTimeGetSeconds(t1));
//second : 30.010000
4、转换为对象NSValue
+ (NSValue *)valueWithCMTime:(CMTime)time;
CMTime structTime = CMTimeMake(1, 3);
NSValue *valueTime = [NSValue valueWithCMTime:structTime];
NSLog(@"%@", valueTime);
//CMTime: {1/3 = 0.333}
structTime = [valueTime CMTimeValue];
CMTimeShow(structTime);
//{1/3 = 0.333}
5、转换字典NSDictionary
CMTime structTime = CMTimeMake(1, 3);
NSDictionary *timeDict = CFBridgingRelease(CMTimeCopyAsDictionary(structTime, NULL));
NSLog(@"%@", timeDict);
structTime = CMTimeMakeFromDictionary((__bridge CFDictionaryRef)(timeDict));
CMTimeShow(structTime);
/*
{
epoch = 0;
flags = 1;
timescale = 3;
value = 1;
}
{1/3 = 0.333}
*/
二、CMTimeRange
时间范围的数据类型：CMTimeRange，由两个CMTime值组成，第一个定义时间范围的起点，第二个定义时间范围的持续时间。
typedef struct
{
CMTime start;
CMTime duration;
} CMTimeRange;
1、创建
- 1、CMTimeRangeMake()
CMTimeRange CMTimeRangeMake( CMTime start, CMTime duration)
根据开始时间点与持续时间确定时间范围。
//创建一个时间范围，从时间轴的5秒位置开始，持续时长5秒
CMTime duration = CMTimeMake(5, 1);
CMTimeRange range = CMTimeRangeMake(duration, duration);
CMTimeRangeShow(range);
//{{5/1 = 5.000}, {5/1 = 5.000}}
- 2、CMTimeRangeFromTimeToTime()
CMTimeRange CMTimeRangeFromTimeToTime( CMTime start, CMTime end )
根据起始时间点和终止时间点，确定时间范围。
CMTime beginTime = CMTimeMake(5, 1);
CMTime endTime = CMTimeMake(12, 1);
CMTimeRange rangeTime = CMTimeRangeFromTimeToTime(beginTime, endTime);
CMTimeRangeShow(rangeTime);
//{{5/1 = 5.000}, {7/1 = 7.000}}
2、运算
定义变量：
CMTime duration = CMTimeMake(5, 1);
CMTimeRange range = CMTimeRangeMake(duration, duration);
CMTimeRangeShow(range);
//{{5/1 = 5.000}, {5/1 = 5.000}}
CMTime beginTime = CMTimeMake(7, 1);
CMTime endTime = CMTimeMake(12, 1);
CMTimeRange rangeTime = CMTimeRangeFromTimeToTime(beginTime, endTime);
CMTimeRangeShow(rangeTime);
//{{7/1 = 7.000}, {5/1 = 5.000}}
取交叉时间范围
CMTimeRange intersetionRange = CMTimeRangeGetIntersection(range, rangeTime);
CMTimeRangeShow(intersetionRange);
//{{7/1 = 7.000}, {3/1 = 3.000}}
取时间范围总和
CMTimeRange unionRange = CMTimeRangeGetUnion(range, rangeTime);
CMTimeRangeShow(unionRange);
//{{5/1 = 5.000}, {7/1 = 7.000}}
3、转换为对象NSValue
+ (NSValue *)valueWithCMTimeRange:(CMTimeRange)timeRange
CMTimeRange structTimeRange = CMTimeRangeMake(kCMTimeZero, kCMTimePositiveInfinity);
NSValue *valueTimeRange = [NSValue valueWithCMTimeRange:structTimeRange];
NSLog(@"%@", valueTimeRange);
//CMTimeRange: {{0/1 = 0.000}, {+INFINITY}}
structTimeRange = [valueTimeRange CMTimeRangeValue];
CMTimeRangeShow(structTimeRange);
//{{0/1 = 0.000}, {+INFINITY}}
4、转换成字典NSDictionary
NSDictionary *timeRangeDict = CFBridgingRelease(CMTimeRangeCopyAsDictionary(structTimeRange, NULL));
NSLog(@"%@", timeRangeDict);
structTimeRange = CMTimeRangeMakeFromDictionary((__bridge CFDictionaryRef)(timeRangeDict));
CMTimeRangeShow(structTimeRange);
/*
{
duration = {
epoch = 0;
flags = 5;
timescale = 0;
value = 0;
};
start = {
epoch = 0;
flags = 1;
timescale = 1;
value = 0;
};
}
{{0/1 = 0.000}, {+INFINITY}}
*/
