Files made of Digital Television broadcast can be very large. One hour of program can easily be over two gigabytes. I had one recording from which I wanted to take a part and convert it to another format. So I needed tools to edit the file I had and convert it. The Digital Television broadcast was in MPEG Transport Stream format that the video editing software already on my PC could not handle. Option of first converting the whole program to another file format for editing did not seem to be a good idea (conversion artifacts, conversion time). I think that the best idea would be to directly edit the MPEG Transport Stream in a way I could extract the part I wanted.
Edit/cut MPEG2 TS thread gave some links to some interesting looking editing software. From the list I selected Mpg2Cut2. It is a free and simple MPEG editor program for Windows to join/append/merge and cut/split MPG/MPEG2/MPEG1, VOB/DVD, TS/HDTV and DAT/VCD/SVCD files. It is a GOP level binary editor for basic cutting of MPEG Program Stream files. Just what I needed. With this program I could pretty easily select the parts of video I am interested in and save that part of video to a new MPEG transport stream file. The program gave some error messages that the transport stream has some things it did not understand, telling the program to continue anyway gave the results I wanted.
Now I have the the video material I need as a new file (exactly same quality as original video). I checked that everything was right by viewing the video with VLC media player. Then I converted the material to a format I wanted with SUPER converting tool. That was easier than trying to do the conversion with VLC because the software user interface for that operation was not very easy to use and had changed quite much since I used the program last time for video format conversion.