Combining Audio & Video

[Knave]

I have several video files in .mp4 format. One has the visual, the other has the sound. These files are the exact same length.

I looked into combining in VLC through convert/save but I get errors (and I can't select a destination to output to). I can convert the .mp4 audio into audio formats if that helps me.

I do have some ways to combine (for example I have Premiere Elements) but I'm worried that will mess with the visual video quality when all I want to do is convert 2 files into 1. Add audio to video. It seems simple but VLC doesn't seem able to do it. All the VLC guides I found basically ended at "Convert/Save" like it would just work... and it doesn't work for me. My output folder is "Multiple Files Selected." and then if I click to convert anyways, I get the error.

Anyone got any other ideas that don't take too much effort? I'm not good with code or anything but if command prompt can do it or there is a program you know of... I'd appreciate any suggestions.

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[Osprey]

What you want to do is called muxing (short for multiplexing). Demuxing (sometimes called splitting) extracts the raw video and audio streams from a video file (like an MP4) and muxing (sometimes called joining) assembles them again into a new video file. It's completely lossless, so no quality is lost, and it takes only seconds, since no re-encoding is needed. There are many freeware apps that can do one or both. Here are some of the most popular ones, all of which I've used:

MP4Tools / MP4Joiner / MP4Splitter 3.6.1 / 3.7 Beta 2 Free Download - VideoHelp
My MP4Box GUI 0.6.0.6 Free Download - VideoHelp
YAMB 1.6 / 2.1.0.0 beta 2 Free Download - VideoHelp

I believe that each of those will do what you want to do. The first is still being updated, so try that first, but the other two will also work and may have GUIs that you prefer. Basically, they're all just frontends to MP4Box, a command line muxer.

Also, even though it won't quite do what you're looking for now, I highly recommend Avidemux (despite the name, it works with several formats, including MP4). It's a very simple video editor and conversion app that has the rare ability to mux, rather than require re-encoding like most editors and convertors. Simply choose "Copy" as the video and audio formats and those elements will be losslessly saved. I use Avidemux a lot to convert videos to other formats and split and trim videos without losing quality. Also, if you mux your video and audio into the video file that you want, but find that the audio isn't perfectly sync'ed, you can open it in Avidemux and shift it forward (by a positive number of milliseconds) or backward (with a negative number).

AviDemux 2.7.1 / 2.7.1 180929 Nightly Free Download - VideoHelp

 

[Knave]

What you want to do is called muxing (short for multiplexing). Demuxing (sometimes called splitting) extracts the raw video and audio streams from a video file (like an MP4) and muxing (sometimes called joining) assembles them again into a new video file. It's completely lossless, so no quality is lost, and it takes only seconds, since no re-encoding is needed. There are many freeware apps that can do one or both. Here are some of the most popular ones, all of which I've used:

MP4Tools / MP4Joiner / MP4Splitter 3.6.1 / 3.7 Beta 2 Free Download - VideoHelp
My MP4Box GUI 0.6.0.6 Free Download - VideoHelp
YAMB 1.6 / 2.1.0.0 beta 2 Free Download - VideoHelp

I believe that each of those will do what you want to do. The first is still being updated, so try that first, but the other two will also work and may have GUIs that you prefer. Basically, they're all just frontends to MP4Box, a command line muxer.

Also, even though it won't quite do what you're looking for now, I highly recommend Avidemux (despite the name, it works with several formats, including MP4). It's a very simple video editor and conversion app that has the rare ability to mux, rather than require re-encoding like most editors and convertors. Simply choose "Copy" as the video and audio formats and those elements will be losslessly saved. I use Avidemux a lot to convert videos to other formats and split and trim videos without losing quality. Also, if you mux your video and audio into the video file that you want, but find that the audio isn't perfectly sync'ed, you can open it in Avidemux and shift it forward (by a positive number of milliseconds) or backward (with a negative number).

AviDemux 2.7.1 / 2.7.1 180929 Nightly Free Download - VideoHelp

Thanks for the explanation. MP4Box worked perfectly