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I have two files, one is MP4 file with video only and another is M4A audio file. What is the best and simpliest method of merging these two tracks in a single MP4 container? Is it possible to do this without transcoding (loosing quality)? Thanks!

Open source and free software is my preference.

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Do they actually line up correctly or do you also need to synchronize them? If it is synced, this is effectively a duplicate of video.stackexchange.com/questions/10730/…. Different source for the streams, but same solution should work. –  AJ Henderson Jun 9 at 13:28
I wouldn't say its a 100% duplicate. While the answer works, there are also other tools specifically for MP4. The question might help people that search specifically for MP4 merging. –  Professor Sparkles Jun 9 at 13:48
Scratch that, tsMuxer only allows MP4 as input not as output. –  Professor Sparkles Jun 9 at 14:25

1 Answer 1

MP4muxer will do the job, it even takes raw h264 streams.

This process is usually called "muxing" and can be done with virtually any container format. Of course audio and video has to have the exact same length to have synchronized audio and video.

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Thanks! I will give it a try! –  Slava Fomin II Jun 10 at 6:51

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