# Add a Silent Audio Track to a Video Give an audio-less video a silent audio track so uploaders and editors that require an audio stream accept it. The picture is copied untouched, in your browser. ## Run it - **CLI:** `gizza tool video-add-silent-audio 'url=https://example.com/input' 'channels=stereo' 'sample_rate=48000' 'bitrate=128' 'existing_audio=replace'` - **Web:** https://gizza.ai/tools/video-add-silent-audio/ - **Agents:** machine-readable descriptor (parameters JSON Schema) at https://gizza.ai/tools/video-add-silent-audio/tool.json ## Inputs - `file` — Video _(file; accept: video/*)_ - `channels` — Channels _(field)_ - `sample_rate` — Sample rate _(field)_ - `bitrate` — Audio bitrate _(field)_ - `existing_audio` — If the video already has audio _(field)_ ## Output - Video with a silent audio track (video) ## Query parameters Open the tool pre-filled and auto-run via URL: - `channels` — Channels - `sample_rate` — Sample rate - `bitrate` — Audio bitrate - `existing_audio` — If the video already has audio - `url` — fetch the input file from a public URL (CORS-permitting) Example: `https://gizza.ai/tools/video-add-silent-audio/?url=https://example.com/input&channels=stereo&sample_rate=48000&bitrate=128&existing_audio=replace` --- ## Give a silent video the audio stream other tools insist on Plenty of files have a picture but no sound at all: screen captures, exported renders, timelapses, GIF conversions, drone clips. That is perfectly valid video — but a lot of uploaders, editors, ad platforms and playback pipelines assume every file has an audio stream, and reject or mangle the ones that don't. The standard fix is to add a track of pure digital silence. This tool does exactly that. Load a video, and it comes back with a silent audio track attached. The **picture is stream-copied** (`-c:v copy`) — not re-encoded — so it stays byte-for-byte identical, the file processes in seconds, and nothing is uploaded: ffmpeg runs inside your browser tab. ### What it does under the hood The silence isn't a file you have to supply — it is generated on the fly by ffmpeg's `anullsrc` source at the channel layout and sample rate you pick, then muxed alongside your untouched video and bounded to the video's exact length. **Worked example:** `screencast.mp4` is a 12 MB, 3-minute H.264 recording with no audio stream, and an upload check keeps failing it. Load it here with the defaults (stereo, 48 kHz, 128 kbps) and you get `screencast-silent-audio.mp4`: the same 3-minute H.264 picture, unchanged, now carrying one AAC audio track of silence — and the upload goes through. ### The options - **Channels** — `stereo` (default) is what most validators expect; `mono` is half the size and still a perfectly valid audio stream. - **Sample rate** — `48000` Hz (default) is the video-world standard, `44100` Hz matches CD/editor conventions, `22050` Hz keeps the added bytes smallest. - **Audio bitrate** — `128` kbps is the universally accepted default. Silence sounds the same at every setting, so `32`–`64` kbps is a good choice on a long clip; `192` kbps is there for checks that demand a higher rate. - **If the video already has audio** — `replace` (default) leaves exactly one track in the output, the silence, so the clip ends up muted. `keep` preserves the original track and adds the silence as a second track. On a video with no audio the two behave identically. ### Notes and limits - The video stream is copied losslessly — the picture, resolution, frame rate and duration are untouched. - The output keeps the input container (mp4 → mp4, mov → mov, mkv → mkv, webm → webm). Any other container falls back to mp4. - WebM output uses **Opus at 48 kHz** — that is the only rate Opus encodes, so a 22.05/44.1 kHz choice is pinned to 48 kHz there. Every other container uses **AAC** at the rate you picked. - `keep` re-encodes the existing audio track at the chosen bitrate (it can't be copied while a filter-generated track is being added in the same pass). - Input and output are each capped at 25 MB — the file is processed in your browser's memory. - This adds an audio stream; it does not add sound. If you want to attach real music or narration, that needs a second media file and a different tool. ## FAQ
My video already plays fine — why would I add silent audio? Because something downstream requires an audio stream. Upload validators, ad platforms, some NLE timelines, hardware players and automated encoding pipelines routinely error out, drop the file, or produce a broken result when a video carries no audio track at all. A silent track satisfies the requirement without changing anything you can see or hear.
Does this re-encode or degrade my video? No. The picture is stream-copied with `-c:v copy`, so the video stream in the output is bit-identical to the input. Only the new audio track is encoded, and it contains nothing but silence.
What's the difference between "no audio track" and "a muted audio track"? A video with **no audio track** has zero audio streams — that's what trips up strict tools. A **muted** video has an audio stream whose samples are all zero. This tool turns the first into the second. If your file already has an audio stream and you simply want it silenced, choose `replace`: the existing track is dropped and a silent one takes its place.
How much bigger does the file get? Very little. Silence compresses extremely well, and the added track is roughly the bitrate you choose times the clip length as an upper bound — at 32 kbps that's about 240 KB per minute at worst, usually far less. The video stream, which is the bulk of the file, is copied unchanged.
Which formats work, and how large can the file be? Anything ffmpeg can read; mp4, mov, mkv and webm are the common cases and each keeps its own container. The output is named after the original with a `-silent-audio` suffix (e.g. `clip.mp4` → `clip-silent-audio.mp4`). WebM gets an Opus track at 48 kHz, everything else an AAC track. Input and output are each capped at 25 MB.
Is my video uploaded anywhere? No. ffmpeg runs as WebAssembly inside your browser tab, so the file never leaves your device.
## Related tools - [Fit Audio to an Exact Length](https://gizza.ai/tools/audio-fit-to-length/): Make any audio file an exact number of seconds — pad it with silence when it's short or trim it when it's long. Runs in your browser, nothing uploaded. - [Shorten Long Audio Pauses](https://gizza.ai/tools/audio-pause-shortener/): Tighten speech pacing by shortening long silent gaps to a natural pause length in your browser. Nothing is uploaded, free. - [Resample an Audio File](https://gizza.ai/tools/audio-resampler/): Change any audio file's sample rate — 8 kHz voice to 192 kHz studio — with high-quality ffmpeg resampling, right in your browser. Runs locally, nothing is uploaded, free. - [Bitcrush an Audio File](https://gizza.ai/tools/bitcrush/): Crush audio into lo-fi, retro and 8-bit textures by reducing bit depth, lowering the effective sample rate and blending the result in your browser. - [Add Chorus to Audio](https://gizza.ai/tools/chorus/): Add a configurable chorus effect to an audio file in your browser with ffmpeg: voices, delay, depth, rate, decay, and output format controls.