Question

我要求从特定时间播放mp3 [以毫秒为单位]。经过一些研究，我的赌注是AVPlayer，这似乎是每个有类似要求的人的选择。不幸的是，它不起作用[代码包括在最后]。我想知道是否有其他任何我可以用来播放任何iOS支持的文件格式的东西，包括start＆amp;使用毫秒时间刻度指定停止？

这是我使用AVPlayer的代码。我创建了一个mp3，它在4.3秒内静音约600ms，然后噪音大约一秒钟。我有3个选项来创建CMTime以与seekToTime一起使用：

4300值，1000时刻度
4.3 * 60000,60000时标
4.3 * mp3文件的时间刻度，带有mp3文件的时间刻度。

不幸的是，没有一个选项适合我，它总是设置在噪音内的某个地方。

我试图使用较低的值，仅仅是为了它。我得到3.7秒，在设定之后，在沉默之前开始一点点。有趣的是：如果我使用3.75，它将在噪音中间开始播放。

代码的关键部分：

CMTime声明：

mediaAudioStart = CMTimeMake((int64_t) (floatValue * 60000), 60000);

或

int32_t timeScale = _mediaAudioPlayer.currentItem.asset.duration.timescale;
mediaAudioStart = CMTimeMake((int64_t) (floatValue * timeScale), timeScale);

或

mediaAudioStart = CMTimeMake(4300, 1000);

完整代码

seekToTime的用法：

[_mediaAudioPlayer seekToTime:mediaAudioStart toleranceBefore:kCMTimeZero toleranceAfter:kCMTimeZero completionHandler:^(BOOL finished) {
        if (finished) {
            [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(mediaAudioPlaybackFinished) name:AVPlayerItemDidPlayToEndTimeNotification object:nil];
            NSLog(@"CURRENT TIME: %lld", _mediaAudioPlayer.currentTime.value);
            [_mediaAudioPlayer play];

        } else {
            NSLog(@"Could not seek media overlay file.");
        }
    }];

ViewController.m

- (void)prepareMediaAudio {
    NSLog(@"prepareMediaAudio");
    NSString *mediaAudioPath = [[NSBundle mainBundle] pathForResource:@"boostmiddle" ofType:@"mp3"];
    NSURL *mediaAudioURL = [[NSURL alloc] initFileURLWithPath:mediaAudioPath];
    if (!_mediaAudioPlayer) {
        AVPlayer *player = [AVPlayer playerWithURL:mediaAudioURL];
        [self setMediaAudioPlayer:player];
        [_mediaAudioPlayer addObserver:self forKeyPath:@"status" options:0 context:nil];
    } else {
        [self mediaAudioSeek];
    }
}

- (void)stopMediaAudio {
    NSLog(@"stopMediaAudio");
    if (_mediaAudioPlayer) {
        [_mediaAudioPlayer removeObserver:self forKeyPath:@"status"];
        [_mediaAudioPlayer pause];
        _mediaAudioPlayer = nil;
    }
}

- (void)mediaAudioSeek {
    NSLog(@"mediaAudioSeek %lld %d", mediaAudioStart.value, mediaAudioStart.timescale);

    [_mediaAudioPlayer seekToTime:mediaAudioStart toleranceBefore:kCMTimeZero toleranceAfter:kCMTimeZero completionHandler:^(BOOL finished) {
        if (finished) {
            [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(mediaAudioPlaybackFinished) name:AVPlayerItemDidPlayToEndTimeNotification object:nil];
            NSLog(@"CURRENT TIME: %lld", _mediaAudioPlayer.currentTime.value);
            [_mediaAudioPlayer play];

        } else {
            NSLog(@"Could not seek media overlay file.");
        }
    }];
}

- (void)mediaAudioPlaybackFinished {
    NSLog(@"mediaAudioPlaybackFinished");
    [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:nil];
    [self stopMediaAudio];
}


- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
                        change:(NSDictionary *)change context:(void *)context {
    NSLog(@"observeValueForKeyPath");
    if (object == _mediaAudioPlayer && [keyPath isEqualToString:@"status"]) {
        if (_mediaAudioPlayer.status == AVPlayerStatusReadyToPlay) {
            NSLog(@"READY TO PLAY");
        } else if (_mediaAudioPlayer.status == AVPlayerStatusFailed) {
            NSLog(@"Could not load Media Overlay audio");
        }
    }
}

- (IBAction)button1Action:(id)sender {
    NSString *value = valueText.text;
    float floatValue = [value floatValue];
    NSLog(@"button1Action %f", floatValue);
    mediaAudioStart = CMTimeMake((int64_t) (floatValue * 60000), 60000);
    [self mediaAudioSeek];
}

- (IBAction)button2Action:(id)sender {
    NSString *value = valueText.text;
    float floatValue = [value floatValue];
    NSLog(@"button2Action %f", floatValue);
    int32_t timeScale = _mediaAudioPlayer.currentItem.asset.duration.timescale;
    mediaAudioStart = CMTimeMake((int64_t) (floatValue * timeScale), timeScale);
    [self prepareMediaAudio];
}

- (IBAction)button3Action:(id)sender {
    NSLog(@"button3Action [4300, 1000]");
    mediaAudioStart = CMTimeMake(4300, 1000);
    [self prepareMediaAudio];
}

- (IBAction)stopAction:(id)sender {
    [self stopMediaAudio];
}

- (IBAction)prepareAction:(id)sender {
    [self prepareMediaAudio];
}

示例项目

您可以从这里获取我的项目，包括我用于测试的mp3文件。只需在文本字段中输入4.3。

https://www.dropbox.com/s/7q2xmuhdu1xih75/iosAudioTest.zip?dl=0

修改

更新mp3文件后 - 缩短 - 用于到达同一地点的值发生了变化。现在4.3点到其他地方：/现在我对seekToTime方法的操作完全无能为力。

Answer 1

https://warrenmoore.net/understanding-cmtime

以上帖子对我遇到的CMTime有最清晰的描述。你在解释它是错的我害怕。如果你想要跳4.3秒，你需要CMTime为（4.3,60000），其中4.3是秒数，60000是你每秒所需的精度。

[av_player seekToTime:CMTimeMakeWithSeconds(4.3, 60000) toleranceBefore:kCMTimeZero toleranceAfter:kCMTimeZero];

会将CMTime设置为4.3秒，精度为60000 - 这意味着您可以在每秒之间跳转到60000个不同位置中的任何一个。

如何从＆amp;在iOS上以毫秒为单位的特定时间？

1 个答案: