Using the Editor
Now we're ready for the fun stuff, making a movie!
Locate the clip you want to edit and drag it into the Video Timeline. Once you have it placed, simply double-clip the clip in the timeline and it will load the editing interface.
First Things First
Before you get to work, you should first view the entire clip by hitting the play button. This is recommended to ensure the clip captured what you were hoping for. If it didn't, then you just saved yourself a lot of time. At this point, you might as well head back the game and try to recapture the magic.
The Magic Marker
The Marker is the backbone of the Video Editor. Think of it as a cue. When a marker is placed you are telling the editor that you want something to happen at this very instance, whether it be a camera-angle change, slow-motion, filter change, etc.
You can place a marker by pressing the "M" key or by mouse-clicking the appropriate button on the interface.
After you've placed a marker, a menu will appear that displays many options. All of the listed options will influence the selected marker, though a few options, like slow-motion, will carry to the next marker unless reset, so be mindful of what you have active from one marker to the next.
Ready to Save
You've placed a bunch of markers and now have a masterpiece ready to share with the world. All you need to do is click the Save Clip button, which saves all of your edits and effects, and you can safely return to the main Video Editor interface. Your edited clip will still be in the timeline, though now it has all of your directorial orders attached.
Name That Clip!
If you've visted the Rockstar Games Social Club with the intent of viewing video clips created by your fellow gamers, you've no doubt seen a lot of movies called "Video1". This is the default name GTA IV gives a clip unless it has been renamed. Rockstar didn't make the naming of a clip very intuitive and a lot of people are confused, so let me clear this up right now. From the Editor section that includes your video timeline, you'll see a yellow font next to a big "Play" icon (an arrow pointing right). Double-click on the letters and you'll see a cursor appear, which allows you to type in a title.
Warning! Name your clip before rendering the final output from the Gallery Section, or the default title "Video1" will be embedded in your video as the title.