Combine Audio with Video
Merge any video's picture with a different audio track. Used to finish vocal separation results (silent video + voice = music-removed video; silent video + instrumental = karaoke video), or to swap audio on any clip.
Processing your video merge
Please wait — combining picture with new audio (~1-3 seconds CPU per minute of video)
All VocalDock tools
Free online audio tools for music, video and podcasting.
Vocal Remover
Split vocals and instrumental from any song.
Remove Music from Video
Remove background music from vlogs, podcasts, and lecture videos while keeping the voice clean.
Noise Remover
AI noise removal for podcasts, meetings, and field recordings.
Text to Speech
Generate speech from text using a saved or uploaded voice sample.
Stem Splitter
Separate a song into 6 stems: vocals, drums, bass, guitar, piano, other.
Karaoke Maker
Sing over an instrumental track and auto-mix the result.
BPM & Key
Detect tempo (BPM) and musical key of any audio.
Audio Cutter
Trim audio clips with millisecond precision.
Audio Joiner
Merge multiple audio files into one seamless track.
Pitch Changer
Shift pitch up or down without changing tempo.
Voice Changer
Change your voice with 8 free presets — robot, deep, chipmunk, echo and more.
Ringtone Maker
Create custom 30-second ringtones for iPhone and Android.
Voice Recorder
Record audio from your microphone right in the browser.
Vocal Range Test
Find your vocal range and voice type by singing your lowest and highest notes.
Audio Converter
Convert audio between MP3, WAV, FLAC, M4A, AAC, OGG, Opus, and AIFF.
Video to MP3
Extract audio from MP4, MOV, WebM and more.
Acapella Extractor
Extract isolated acapella vocals from any song for remixes and covers.
Karaoke Video Maker
Make karaoke videos by removing vocals from any music video — keep the picture and instrumental.
Drum Isolator
Extract clean drum tracks from any song for sampling, remixing, and practice.
Bass Isolator
Pull bass lines out of any song for transcription and learning.
Guitar Isolator
Isolate guitar tracks from any song for tab transcription and solo analysis.
Piano Extractor
Extract piano parts from any song for sheet music and practice.
Combine video with new audio in seconds
Stream-copy mux — no re-encoding, no quality loss.
Stream Copy Mux
Video stream is copied as-is without re-encoding. Quality is identical to the source video, just with a new audio track.
AAC Audio Output
Output audio is encoded as AAC inside the MP4 container — the most compatible format for sharing, browsers, and editing software.
Trimmed to Shortest
Output length matches whichever input is shorter (video or audio). Avoids dangling silent video or audio that doesn't fit.
Fast Processing
Most 4-minute videos finish in 1-3 seconds plus upload time. Cost: 2 credits per minute of video.
How it works
Two inputs, one merged output.
Source video
MP4 / MOV / WebM / MKV / AVI. Only the picture stream is kept — original audio is discarded.
New audio
MP3 / WAV / M4A / AAC / OGG / FLAC. This becomes the audio track of the merged video.
Merged MP4
Output: original picture + new audio, packaged as a downloadable MP4. Length matches the shorter input.
Frequently asked questions
Will the video quality stay the same?
Yes. We use ffmpeg stream copy on the video stream — no re-encoding means zero quality loss. The output video is bit-for-bit identical to the source picture, only the audio is replaced.
What if the video and audio are different lengths?
The output is trimmed to the shorter of the two. If your video is 60 seconds and audio is 45 seconds, the output is 45 seconds. This prevents dangling silent video or audio after the picture ends.
Can I use this for any video + audio combination?
Yes. Common uses: (a) replacing the music in a video with your own narration, (b) putting vocal-only audio over a music-removed video to get a clean talking-head clip, (c) creating karaoke videos by adding instrumental audio to the original picture.
How does it work with Remove Music from Video?
The Remove Music from Video tool gives you three files: silent video (picture only), vocals.mp3, and instrumental.mp3. Click 'Get Voice-Only Video' to mux the silent video with vocals (background music removed). Click 'Get Karaoke Video' to mux with instrumental (vocals removed). Each merge runs through this video mux task type.
What does it cost?
2 credits per minute of source video. A 4-minute video costs about 8 credits. Free starter credits on sign-up cover several merges.