Issue "Skip frame Extraction" on Automatic1111 "v1.0.0-pre" Version

[threeforces]

Had the "Skip frame Extraction" everytime on Step 1 because ffmpeg.exe was not found.

However when you installed Automatic1111 via [v1.0.0-pre](https://github.com/AUTOMATIC1111/stable-diffusion-webui/releases/tag/v1.0.0-pre installation method you have to add Path to ffmpeg also into the enviroment.bat.

`@echo off

set DIR=%~dp0system

set PATH=C:\Windows\system32;C:\Windows;%DIR%\git\bin;%DIR%\python;%DIR%\python\Scripts;C:\ffmpeg\bin
set PY_LIBS=%DIR%\python\Scripts\Lib;%DIR%\python\Scripts\Lib\site-packages
set PY_PIP=%DIR%\python\Scripts
set SKIP_VENV=1
set PIP_INSTALLER_LOCATION=%DIR%\python\get-pip.py
set TRANSFORMERS_CACHE=%DIR%\transformers-cache`

This solves the issue!