#summary How to use the video recorder

= Video-recorder =

== How to use it ==

Options can be set in special page, you can access it using button left to 'game settings' button. Currently, it contains only options, but later it will also contain list of recorded videos. To record video you must press ‘R’ during playing a game or watching a demo; then press ‘R’ again to stop recording. Recorded videos are saved to `<user data path>/Videos` (`~/.hedgewars/Videos` or `%USERPROFILE%\Hedgewars\Videos`). Note that video encoding does not happen in real-time; actually, it will occur after you have closed game engine; it takes some time so you must not close frontend after you have closed game engine or you may get damaged video files.

== How it works ==

Video recording does not happen in not real-time. Instead it works as follows:

When you play game or watch a demo press ‘R’, game then will start to record camera positions to `VideoTemp/?.txtout` and sound to `VideoTemp/?.sw`. Press ‘R’ again to stop recording. After you will close game engine, `QTfrontend` will rename `?.txtout` to `?.txtin` and run an invisible instance of game engine which will actually encode video using prerecorded camera positions and sound; during encoding video file will be in `VideoTemp` and after encoding, it finishes it and moves it to `Videos/` and the files `?.txtin` and `?.sw` will be automatically removed.

== Notes ==

 * If you press ‘R’ multiple times during one game, you will get several videos. They all will be encoded simultaneously, and each instance of game engine will use hundreds of megabytes so be careful.

 * It is supposed to use H.264 (MPEG-4 AVC) video codec. Binaries of `ffmpeg` for Windows include it. However, on GNU/Linux you may have stripped `libavcodec` without `libx264`, then different codec will be used which will generate several times larger files. For Ubuntu, this may help: http://ubuntuforums.org/showthread.php?t=1117283

 * Logs from ffmpeg/libav are written to game log (`Logs/game0.txt`).

 * Tested only on Windows and GNU/Linux.

 * For offscreen-rendering, the OpenGL FAQ (http://www.opengl.org/wiki/FAQ#Offscreen_Rendering) suggests the following:

  “_Some people want to do offscreen rendering and they don't want to show a window to the user. The only solution is to create a window and make it invisible, select a pixelformat, create a GL context, make the context current. Now you can make GL function calls. You should make a FBO and render to that. If you chose to not create a FBO and you prefer to use the backbuffer, there is a risk that it won't work._”

 SDL 1.2 does not allow to create invisible window, that’s why glut library is used. (SDL 1.3 allows it)

 * Video recorder relays on framebuffer extension or auxiliary buffer for offscreen rendering. If your OpenGL implementation has none of these, then video recording may not work for you. Although, framebuffer extension must be common nowadays.

 * Setting large resolutions for video may not work due to limitations in your OpenGL implementation. At least resolutions not exceeding your screen resolution should work.