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Topic: AAC file different length than source (Read 2650 times) previous topic - next topic
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AAC file different length than source

Hi, I'm trying to covert all the MJPEG MOV files from my digital still camera into x264/AAC MP4s.  I've tried a few different methods but it always seems to produced an AAC track that is different in length (few milliseconds mostly) than the original.

As example with nice round numbers, I have one MOV that is 3 seconds exactly, the audio stream is RAW 8-bit unsigned 8000Hz data, 24000 samples, 3 seconds in length.  Naturally the same stats if I export it as a PCM WAV file (8KHz PCM WAV file).  Problem is using NeroAACEnc through MeGUI, it produces a file that is 3.328 seconds in length. (using MP4Box -info)

The aac file sounds normal on its own but when MUXed into an MP4 with the video stream (90 frames @ 30fps = 3 seconds exactly), there is a blip at the beginning and a slightly noticeable video freeze at the very end as the audio finishes.

HELP!!  Why don't I get a 3 second AAC out of a 3 second source? 

Eamon