newish vlc user, urgent help wanted on 4 questions

[pzz020165]

please note, i use windows 8 but i don't think that this is relevant to the issues and confusion i am having so i have used this section of the forum to post it.

i have been a vlc user for a while but only used it as a simple video player for playing videos from my hard drive, dvds and music on loop. but i've had a few issues and i also want to understand how to perform several potentially difficult operations with vlc.

question 1. cutting up and rejoining video. lets say i have a video which we shall call A and i want to change it's last few minutess to another video B. what i will need to do is cut the last few minutes off video A and then somehow connect that chopped down version with video B so that where those few minutes were chopped off video B will play instead. ideally this would be done in such a way that the end result of "videoA(-it's chopped bit) followed by video B" is all in one avi/mp4/mpg/other format file. how is this done, i have heard vlc can do that but cannot easily find how. if it is not possible to rejpin is it atleast possible to trim donw the end/start of a given video file to make a new video file which is shorter and of fewer megabytes? thanks

question 2. weird behaviour of mpg files. i have many videos on my computer ad post play perfectly except a few of them which are mpg format files. these particular files will play but soemthing really weird happens to the time bar on the right. the right bar usually displays the full length of video(i know it can display the time left but i don't use it on that setting) but on a few files it displays some ridiculously long time when started and this "full length time" then drops and then randomly varies up and down. in an example of a 55 second video clip suffering this problem it first opens and shows the length as 14 minutes, then after maybe 5 seconds of playing it reads 1 minute 20 seconds, then later it reads 50 seconds, then it goes back up to say 59 seconds, then down again randomly. what on earth is going on here? thanks

question 3. understanding what codecs actually are. in the past i found the only thing that defined a file type was the extension (a .doc file was always a word document, a .skp was always a sketchup model, a .png was always an image,etc) yet it seems video files come in an absurd array of forms where the extension merely becomes a "container" and then something called a codec is involved, the same i assume with audio files but i haven't used pure audio files in vlc. sometimes this means avi, a format which usually plays in windows media player is not the same sort of .avi and will not play in other software that will successfully play most avi files. please explain how video formats are defined, what codecs are and how it all "works". i understand this question may have a ong and complex answer so i won't say that question 3 is urgent. thanks.

question 4. conversions, how. i know vlc can convert files between formats and codecs etc but it always seems to crash when i try, i assume i am doing something wrong. when i try and convert i cannot find a simple "raw avi"(i think every video program ever plays this) output format anywhere on the list nor can i seem to manage to specify where i want the video to be saved to (what folder, the output destination box won't select folders, only files to overwrite). then when i try and perform the conversion the program crashes, even for tiny 1 minute low res videos. vlc starts displaying a very rapidly flashing title in the "top bar"(where the minimize and red X close butttons are found) which alternates from vlc to the file name and back almost to fast to see vlc freezes but seems to be using lots of memory and such (according to windows task manager). please explain how to convert video formats in such a way that it works and vlc does not crash. i would also like to know how to specify the output format, i don't understand all those codec options and such. finally i would like to know how to take existing raw avi files (i make them in blender) and make them into less megabyte heavy videos without significant quality loss, raw avi sometimes gives me things like 120 megabytes for a 10 second video of aspect ratio 500 pixels by 500 pixels (which is far to large for convenient youtube upload). thanks

if anyone could answer any of those 4 questions, expecially the first and second, i would be very grateful. thank you.

to clarify my OS is windows 8 (not 8.1) and my vlc version is 2.1.3 "rincewind". it was preinstalled on this computer when i first got it and the version has been updated a few times since. and 1 more thing. i'm using the civilised desktop part of windows 8 not the nasty metro interface, my type of vlc is run from an exe file buried away under "program files" on my c drive.

[pzz020165]

excuse me but i could really use some info on these questions please.
thank you
for extra info i've now updated to vlc version 2.1.5 (still "rincewind").