> ## Documentation Index
> Fetch the complete documentation index at: https://docs.useharmonia.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# ffmpeg

> How Harmonia deterministically renders clips, reels, captions, and local media fixtures.

ffmpeg performs deterministic media transformation after cognitive stages have proposed grounded source moments. It is application tooling, not a model-accessible effect tool.

## How Harmonia uses it

* Cut authorized source media to validated Nimi time ranges.
* Reframe output for vertical social formats.
* Burn captions when the installed build supports the subtitles filter.
* Concatenate selected moments into reels.
* Produce internal clip assets before any external publishing proposal.
* Render deterministic local PNG fixtures in explicit mock development mode.

Commands are constructed as argument arrays without a shell. Inputs, output paths, durations, and supported filters are checked before execution.

## Security and authority

ffmpeg reads only authorized local or staged media and writes internal artifacts. Rendering does not approve publishing, choose copy, or prove that an external post exists.

## Failure behavior

Missing binaries, invalid media, non-zero exits, absent outputs, and unsupported caption filters remain explicit. Captions may be skipped with a recorded note when the local build lacks the filter; the system does not claim captioned output in that case.

## Evidence status

Real local ffmpeg invocations and artifact checks have automated coverage. External publication of a rendered asset requires a separate approved effect and verification receipt.

## Relevant files

* `agent/harmonia_agent/clipper.py`
* `agent/harmonia_agent/generative_media.py`
* `agent/harmonia_agent/stages.py`
* `agent/tests/test_generative_media.py`