Losing all the quality converting 720p

[TheDizzle]

Yo!

Bit of a beginner to all this converting stuff because I've never really downloaded 720p files before. Basically, I downloaded a 720p file, 2 GB and found out it was .MKV I then found out my Xbox 360 doesn't like those files when attempting to pass it through connect360, so I set about changing the file type. I know .AVI works well, and after for frickin' ever managed to convert the MKV to AVI.

After doing so, I played the file only to find that it is a very very long way off being 720p and became a 1GB file. I first had problems with the frame rate and changed it to the highest that was available (NTSC 29.97?), hoping that would do the trick but uh uh

I've been using the program FFmpegX, because it's free, and would preferably like to keep using it. All I want to do is turn that file into another file type that the 360 likes without losing any of the quality. Help very much welcome

[TheDizzle]

Ok, I think I have sorted my problem (thanks for the help :P)

I have basically started using another file format (H.264 and changing the file type to .MP4) so far I think it is working. However, one solution always throws up another problem is computing and I need a different sort of help!

When I am converting the files the program FFmpeg always "quits unexpectedly" after about 5 minutes. I've tried using a number of different files, big ones and small ones, and all of them have the same end result. The file ends up being two, one video and one audio. The audio doesn't work and the picture looks perfect, although, it only gets to the point where the program crashed.

Does anyone know what could be going wrong here? Do I have to register in order to unlock this file format or something? I was using the program before, when converting to .AVI but was losing ALL the quality from the 720p file, hence this thread. I just want to watch the film in high quality on my TV through my Xbox, is that so much to ask!!