67 lines
1.5 KiB
Objective-C
67 lines
1.5 KiB
Objective-C
//
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// SubtitleSync.m
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// keyBoard
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//
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// Created by Mac on 2026/1/15.
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//
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#import "SubtitleSync.h"
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@implementation SubtitleSync
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- (NSString *)visibleTextForFullText:(NSString *)fullText
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currentTime:(NSTimeInterval)currentTime
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duration:(NSTimeInterval)duration {
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if (!fullText || fullText.length == 0) {
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return @"";
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}
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NSUInteger visibleCount = [self visibleCountForFullText:fullText
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currentTime:currentTime
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duration:duration];
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if (visibleCount >= fullText.length) {
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return fullText;
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}
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return [fullText substringToIndex:visibleCount];
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}
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- (NSUInteger)visibleCountForFullText:(NSString *)fullText
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currentTime:(NSTimeInterval)currentTime
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duration:(NSTimeInterval)duration {
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if (!fullText || fullText.length == 0) {
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return 0;
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}
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// 边界情况处理
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if (duration <= 0) {
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// 如果没有时长信息，直接返回全部
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return fullText.length;
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}
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if (currentTime <= 0) {
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return 0;
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}
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if (currentTime >= duration) {
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return fullText.length;
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}
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// 计算进度比例
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double progress = currentTime / duration;
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// 计算可见字符数
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// 使用略微超前的策略，确保文字不会落后于语音
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double adjustedProgress = MIN(progress * 1.05, 1.0);
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NSUInteger visibleCount =
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(NSUInteger)round(fullText.length * adjustedProgress);
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return MIN(visibleCount, fullText.length);
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}
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@end
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