iphone - Add sound to AVMutableVideoComposition multiple times -

i'm using avmutablevideocomposition add video , audio.

i have multiple video , audio files stitch together, works fine.

i'm using code add audio:

avurlasset *audioasset = [[avurlasset alloc] initwithurl:[nsurl fileurlwithpath:path] options:nil];              [compositionaudiotrack inserttimerange:titlerange                                oftrack:[audioasset trackswithmediatype:avmediatypeaudio][0]                                 attime:partzerotime                                  error:&err]; 

the path correct (used nslog check) , partzerotime insertion point every audio track (the audio played @ beginning of video only). audio file same (some m4a file).

this works first audio, though. every subsequent audio isn't played. not receive error adding audio asset.

i tried create separate track music, same result.

any ideas?

[edit]

i might not entirely clear want do, here's more information: have video composition of several clips stitch avmutablecomposition. contains intro (where try add music), followed 1 or 2 clips, intro (with music) followed more video. added separate track music --music--silence--music--silence.

i tried adding silence insertemptytimerange messes everything. used inserttimerange:tr oftrack:nil... gives me same result before: first music clip played, every following clip won't...

i'm pulling hair out on this...

ok, dumb... :)

the problem was, defined timerange wrong. instead of using cmtimerangemake(kcmtimezero, introduration) defined cmtimerangemake(introstart, introduration) introstart starting time of music...