And use whichever method works for you.
But why can't anyone tell you this will be in sync? Because the source audio rate can be anything so loss of sync is possible and a recurring issue in video edit apps. It's not an exclusive problem to Freemake.
However, one nifty feature is the ability to add audio tracks to video files, which can be done by adding a video file and audio file and then selecting the “Join into one file” checkbox.
I quote the above re Freemake video converter. I would like to see a full tutorial re this operation, since there is nothing else online about it. I believe this operation is sometimes called "Muxing", whereby a new audio track is added to an old video picture.
I have an mp4 video with loud audio hiss. I converted the file to WAV audio. I then pushed this audio file through Audacity free software to clean away the hiss and rendered the result as a WAV file.
Now comes the interesting bit: I am wondering if I can load the video, (picture), onto Freemake video converter; load the WAV, (audio); select "No audio" on the video tab and "Join Files" and convert to mp4. Will picture and sound be matched perfectly in sync? How long will it take to convert the joined files - I am using a 1 hour video??
Would I be better off converting the audio file to MP3 instead of WAV, before muxing the two files together?

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