Song Synchronization

// Call the NTP time synchronization interface when entering the room.
[TXLiveBase updateNetworkTime];

// In the TXLiveBaseDelegate callback, determine whether the time synchronization is successful.
- (void)onUpdateNetworkTime:(int)errCode message:(NSString *)errMsg {
    // errCode 0: 0: Time synchronization is successful and the deviation is within 30ms; 
    // 1: Time synchronization is successful, but the deviation may be over 30ms; 
    // -1: Time synchronization failed.
    if (errCode == 0) {
        // Call TXLiveBase's getNetworkTimestamp to obtain the NTP timestamp.
        NSInteger ntpTime = [TXLiveBase getNetworkTimestamp];
    } else {
        // Call updateNetworkTime again to initiate a time synchronization.
        [TXLiveBase updateNetworkTime];
    }
}

NSDictionary *json = @{
                        @"cmd": @"startChorus",
                        // Scheduled time for a tutti.
                        @"startPlayMusicTS": @(startTs),
                        @"musicId": @"musicId",
                        @"musicDuration": @(musicDuration),
                      };
NSString *jsonString = [self jsonStringFrom:json];
[trtcCloud sendCustomMessage:jsonString reliable:NO];

- (void)onRecvCustomCmdMsgUserId:(NSString *)userId cmdID:(NSInteger)cmdId seq:(UInt32)seq message:(NSData *)message {

    NSString *msg = [[NSString alloc] initWithData:message encoding:NSUTF8StringEncoding];
    NSError *error;
    NSDictionary *json = [NSJSONSerialization JSONObjectWithData:[msg dataUsingEncoding:NSUTF8StringEncoding]
                                                         options:NSJSONReadingMutableContainers
                                                           error:&error];

    NSObject *cmdObj = [json objectForKey:@"cmd"];

    NSInteger musicDuration = [[json objectForKey:@"musicDuration"] integerValue];

    NSString *cmd = (NSString *)cmdObj;

    // tutti command
    if ([cmd isEqualToString:@"startChorus"]) {
        // tutti start time
        NSObject *startPlayMusicTsObj = [json objectForKey:@"startPlayMusicTS"];
        NSString *musicId = [json objectForKey:@"musicId"];

        NSInteger startPlayMusicTs = ((NSNumber *)startPlayMusicTsObj).longLongValue;
        // The difference between the scheduled tutti time and the current time.
        NSInteger startDelayMS = labs(startPlayMusicTs - [TXLiveBase getNetworkTimestamp]);
        // Start preloading, and jump the song progress according to the difference 
        // between the scheduled duet time and the current NTP time.
        NSDictionary *jsonDict = @{
            @"api": @"preloadMusic",
            @"params": @{
                    @"musicId": @(musicId),
                    @"path": path,
                    @"startTimeMS": @(startDelayMS),
            }
        };
        NSData *jsonData = [NSJSONSerialization dataWithJSONObject:jsonDict options:0 error:NULL];
        NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
        [subCloud callExperimentalAPI:jsonString];

        // play music
        TXAudioMusicParam *param = [[TXAudioMusicParam alloc] init];
        param.ID = musicId;
        param.path = url;
        param.loopCount = 0;
        param.publish = NO;

        [[subCloud getAudioEffectManager] startPlayMusic:param onStart:^(NSInteger errCode) {
            // star play callback
        } onProgress:^(NSInteger progressMs, NSInteger durationMs) {
            // lyric progress callback
        } onComplete:^(NSInteger errCode) {
            // play completely callback
        }];

    }
}

self.startPlayChorusMusicTs; // The originally scheduled tutti time.
// Current playback progress
NSInteger currentProgress = [[self audioEffecManager] getMusicCurrentPosInMS:self.currentPlayMusicID];
// The ideal playback time progress of the current song.
NSInteger estimatedProgress = [TXLiveBase getNetworkTimestamp] - self.startPlayChorusMusicTs;
if (estimatedProgress >= 0 && labs(currentProgress - estimatedProgress) > 50) {
    // When the playback progress exceeds 50ms, make adjustments.
    [[subCloud getAudioEffectManager] seekMusicToPosInMS:self.currentPlayMusicID pts:estimatedProgress];
}