I wrote this for newbies, skip the formalities and go to Opening Your File.
Guide to extract a clip from an MPG, VOB, or DVD with MPEG StreamClip
Testing Conditions
-The version of MPEG StreamClip used in this guide was Windows 1.2.1b5
-The procedure was tested with a vob and an mpg file
Conventions
-The symbol "->" is used to indicate a sequence of actions in a menu. For example, File->Open means to click the file menu, then click the Open submenu.
-The "*" symbol is being used as a placeholder for a name prefix. For example "*.vob" refers to any file, of which the filetype is VOB. This part of the filename is referred to an the Filename Extension. It may not display in Windows, but instead only the main filename is shown, with an icon. You must change your view settings to see the full name, or else realize how a certain filetype looks. Looking at the properties of a file should also show the real name.
-The "+" is used to show the simultaneous pressing of keys. For example, "ctrl+o" means to press and hold CTRL, then press O, then release both.
What is lossless cutting?
-MPEG and some other video formats are internally stored as groups of pictures, called
GOPs. If you try to trim a scene from within a GOP boundary, the editor has to re-encode part of your clip. The re-encoding causes a loss in quality.
-There is a way to cut out a part of a video with perfect quality. It requires a program which supports lossless editing on GOP boundaries. StreamClip has this ability.
-GOP stands for Group of Pictures
-Video formats which are stored iin this way are known as inter-frame formats.
Opening an mpg or vob file
-If opening from a DVD, please see below.
-Use File->Open Files. Find a *.vob or *.mpg
-The file display in the main window, initially showing the first frame
Opening a DVD
---This section is untested---
-You can directly open the *.vob files as found under the folder VIDEO_TS. They will be named like "VTS_01_1.VOB". However, it's not obvious in which file your desired clip lies, therefore it is better to use Open->DVD.
-Try playing the DVD first and finding your scene with the normal menus. Then use the information display function of your DVD player to read the Title and Chapter that's currently playing.
-You can use this information to open the correct spot in StreamClip.
Trimming to Keyframes
-Move the slider under the video to the start of the scene you would like to keep. Note the position.
-Use Edit->Go to Keyframe, or use it's
shortcut, by pressing ctrl+k. Note if the position moves ahead (further to the right) or left (previous to your cut). If the slider moved to the right, back it up. Try with ctrl+k again, until you've backed up far enough, that using ctrl+k goes to a point before your desired spot. This is called going to the keyframe. They could make this more convenient!
-Click the Edit->Select In, or use the shortcut I, by typing I.
-Use the same technique to move to a keyframe just beyond the end of your desired section.
-Click the Edit->Select Out, or use the shortcut O.
Saving Your Clip
-If you have opened a *.vob or DVD, do File->Convert to MPEG.
Note: There is a simple check to indicate that your clip is untouched. View your CPU Activity Graph and ensure that there's no spike in computing power used. The CPU will peak only if there's an encoding operation, which you are trying to avoid.
-If you have opened an *.mpg, you can use File->Save As.
-Name the file with a reminder of the scene it contains.
Congratulations! You have just made a perfect copy of your scene.
Cutting From Other Formats
-StreamClip supports cutting from other video formats, but it's ability to losslessly cut in these cases is unconfirmed.
Similar Programs
MPEG2CUT2 is another program which supports lossless cutting of mpeg files, known as a GOP-level editor.
Links
MPEG StreamClip
http://www.squared5.com/
MPEG2CUT2
http://rocketjet4.tripod.com/Mpg2Cut2.htm