mp4 file not playing in an application that supports mp4 files

[mindstormer]

I recently transferred my media library from iTunes to MediaMonkey. MediaMonkey supports mp4 files, but I am not able to play mp4 files on it, though it can be played on iTunes. I know this is a codec problem, but I want to know exactly what is going on. If a file is an mp4 file and an application claims to support it, why doesn't it work? How do I go about solving this--is installing a codec pack the only way? I've heard bad things about codec packs, some claim that it hurts more than it helps. Rather than installing a codec pack, how can I find out exactly what codec I need and download it?

Also, I will be doing video conversions. Will converting an mp4 file of one codec to another mp4 file of another decrease its quality at all? I want to use SUPER Converter to accomplish this task because it can "convert videos without transcoding," which I find is a very strong feature that's not in many of the top video converters.

I want to learn how to manage all these codecs in order to preserve the quality of all my videos and have it all be compatible with the application I am using.

Thanks.

[aedipuss]

mediamonkey is mainly an mp3 audio player. i've used it for years and didn't know it played video at all until you just said it did. try playing the videos with vlc. if they still don't play then a good start to identifying the problem would be to use mediainfo on a video. put it in test mode and copy/paste the results here. also it is possible to upload a sample problem video here if it's under 100mb.

[mindstormer]

Oh... I just looked up and read that: *mp4 files * Certain formats may depend on installation of codecs separately. This is strange as mp4 is quite popular and iTunes natively supports it.

Anyway, I know I can install K-Lite Codec Pack and the problem is solved, but I only want to install what I need (I only know that codec packs can often create as much problems as it can solve). I want to learn how to manage and convert codecs and what encoders and decoders are.

I've attached the information provided by MediaInfo. There is so much information provided--I don't know what to Google for and what to download.

Thanks.