how 2 startmovie

Make a folder in your csgo folder and title it tga or whatever you want (steamapps\common\Counter-Strike Global Offensive\csgo\tga)

MAKE SURE THAT IF YOU ARE RECORDING A GOTV DEMO YOU TYPE host_timescale 0 INTO CONSOLE

When you're in your demo, exec the movie config and go to where you want to record your clip.  Once you are at the clip set the framerate you want to record at (host_framerate ___) and than type startmovie tga/clipname. (this takes a LONG TIME, make sure you have your steam set to offline or do not disturb so you dont get notifications and need to re record)

Once you've finished recording the frames there is no way to stop it other than closing the game, so type quit in console.

All of the frames will be saved as TGA image files in your new folder.  Open VirtualDub and drag the first frame into it, than hit Cntrl+R and set the framerate to whichever host_framerate you recorded at (you can also get to this screen by opening the video tab on the top bar of VDub and clicking Frame Rate..).  After its set hit F7, or click file on the top bar and click Save as AVI...

Once it finishes compiling the frames into a video file, you can delete all of the tga files in the folder, make sure VDub is closed when you delete them or the frame you dragged into it wont get deleted.

Now put the video file into vegas and sync it with the audio. (startmovie will record a .wav audio file with the tgas but it will not work as audio for the clip if you recorded with host_timescale 0 because the audio breaks when the value is lower than 1, however POVdemos where you do not need to change the host_timescale will record audio at the correct speed.)