> ## Documentation Index > Fetch the complete documentation index at: https://docs.decktalk.app/llms.txt > Use this file to discover all available pages before exploring further. # Requirements and costs > The Python version DeckTalk needs, what decktalk setup downloads and where it puts each download, the ffmpeg license, the accounts a build needs, and which commands spend ElevenLabs credits. ## Python DeckTalk needs Python 3.12 or later. Its two Python dependencies are Playwright and static-ffmpeg, and you do not need Node. The [quickstart](/quickstart) installs it with uv, pipx, or pip. ## What setup downloads `decktalk setup` makes three downloads, once per machine, and `decktalk doctor` reports on each of them afterwards. | Download | Where it goes | | ------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Chromium | The command runs `playwright install chromium`, which puts the browser in Playwright's cache. The cache is `~/.cache/ms-playwright` on Linux, `~/Library/Caches/ms-playwright` on macOS, and `%LOCALAPPDATA%\ms-playwright` on Windows. | | ffmpeg and ffprobe | The static-ffmpeg package downloads a static build for your platform into its own directory, inside the Python environment that DeckTalk is installed in. | | KaTeX | The command downloads the KaTeX release from GitHub into DeckTalk's per-user cache, under `katex/`. The cache is `~/.cache/decktalk` on Linux, or `$XDG_CACHE_HOME/decktalk` when that variable is set, `~/Library/Caches/decktalk` on macOS, and `%LOCALAPPDATA%\decktalk` on Windows. The `DECKTALK_CACHE_DIR` variable moves it. | On Linux, `setup` passes `--with-deps` to Playwright, which also installs Chromium's system libraries with apt-get. Playwright runs apt-get through sudo, or through `su root -c` when sudo is missing, and it uses neither when `setup` runs as root. On a distribution without apt-get this step fails, and `setup` stops before it downloads ffmpeg and KaTeX. `decktalk init` copies the cached KaTeX into the project's `deck/katex/`, so equations render with no network. When the KaTeX download fails, `setup` warns and continues, and a project created before KaTeX is cached loads it from a CDN instead. When `setup` has not run, static-ffmpeg downloads ffmpeg the first time DeckTalk asks for it. An ffmpeg on your PATH is used only when static-ffmpeg cannot provide one, and `DECKTALK_FFMPEG` and `DECKTALK_FFPROBE` override both. ## The ffmpeg license DeckTalk is licensed under Apache-2.0. ffmpeg's own source is licensed under LGPL-2.1-or-later, and the builds that static-ffmpeg downloads are GPL builds that include libx264. The Linux, Windows, and Intel macOS builds are configured with `--enable-gpl`, `--enable-version3`, and `--enable-libx264`, so they are licensed under GPL-3.0-or-later. The Apple silicon macOS build is configured with `--enable-gpl` and `--enable-libx264`, so it is licensed under GPL-2.0-or-later. DeckTalk runs ffmpeg as a separate process and does not link against it. To use a build of your own, set `DECKTALK_FFMPEG` and `DECKTALK_FFPROBE` to its two executables. [THIRD\_PARTY\_NOTICES.md](https://github.com/jacobcbeaudin/decktalk/blob/main/THIRD_PARTY_NOTICES.md) lists every third-party component and its license. ## Accounts A silent build needs no account and no API key. A voiced build needs an ElevenLabs API key in `ELEVENLABS_API_KEY` and a voice id in `ELEVENLABS_VOICE_ID`. Every ElevenLabs plan, including the free plan, can call the API. `decktalk soundscape` needs the API key and no voice id. The quickstart's [Add your voice](/quickstart) step shows where both values go, and the [FAQ](/help/faq#what-does-it-cost) compares the plans. ## What spends credits Only two parts of DeckTalk call ElevenLabs. The `narrate` stage calls the text to speech endpoint, and `decktalk soundscape` calls the sound effects and music endpoints. | Command or change | When it spends credits | | -------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------ | | `decktalk build` without `--silent` | The build voices every section whose text, title, or voice changed since the last voiced build, and every section when the cache is empty. | | `decktalk narrate` without `--silent` | The command voices the same sections that a build would. The `--only` flag limits it to the sections named. | | `--force` on `build` or `narrate` | The run voices every section again, whether or not it changed. | | A changed voice id, model, output format, or `[voice]` setting | The next voiced build voices every section again, because the cache key includes all of them. | | `decktalk soundscape` | The command generates every ambience, effect, and music part whose request changed or whose file is missing, and `--force` generates every item again. | Each voiced section costs the characters of its whole text, so an edit costs the characters of every section whose text changed, not only those of the changed sentences. `decktalk narrate --dry-run` prints the text that a run would send, section by section, and `decktalk soundscape --dry-run` prints every request. Neither makes an API call. A silent build spends nothing, and so do `setup`, `init`, `doctor`, `beats`, `record`, `measure`, `check`, `assemble`, `verify`, `shots`, `status`, and `runtime`. A silent build after a voiced one empties the narration cache. It writes its placeholder tracks over the voiced mp3 files, so the next voiced build voices every section again and spends credits on all of them. [Rebuild one section](/guides/rebuild-one-section#a-silent-build-and-a-voiced-build) explains the cache. ## Time Recording runs in real time, one section after another, so a first silent build of the scaffold takes a few minutes. [Rebuild one section](/guides/rebuild-one-section) shows how `--only` records only the sections that changed. ## Next [Your first deck](/guides/first-deck) writes one section from scratch in the script, the cues, the project file, and the page, and builds it.