音频与渲染的AVMutableComposition中的视频不同步

AVMutableComposition

video:
    empty: Y, {{0/1 = 0.000}, {48/100 = 0.480}}
    empty: N, {{48/100 = 0.480}, {600/600 = 1.000}}
    empty: Y, {{888/600 = 1.480}, {900/600 = 1.500}}
    empty: N, {{894/300 = 2.980}, {1040/600 = 1.733}}
audio:
    empty: Y, {{0/1 = 0.000}, {48/100 = 0.480}}
    empty: N, {{48/100 = 0.480}, {45056/44100 = 1.022}}
    empty: Y, {{66224/44100 = 1.502}, {65194/44100 = 1.478}}
    empty: N, {{894/300 = 2.980}, {77824/44100 = 1.765}}

CMTimeRange

CMTime