Add Soundtrack

Here's how to losslessly add a soundtrack to a video,

• Open CsDownloadVid, click Start, click "Separate audio and video"

• Click the button that says "Combine Audio+Video Channel (lossless)"

• Choose an audio file (typically .m4a, .mp4, or .mp3)

• Choose a video file (typically .mp4, .m4v, or .mkv)

• That's it! You'll now see an output file alongside the video file.

(There are a few common audio types that aren't supported in a mp4 video, like flac. The mkv format seems to support many more audio and video encodings.)