After a lot of research i found the answer that everyone in the group was looking for, for playing a file's including audio and video which you have downloaded from your mobile as .mp4 extension can be played through Quick time player. There is no need to go for Quick Time pro and converting your .mp4 to .mov extension. You just have to follow few simple steps in order to see and listen the movie clearly.
Steps to Follow:-
1. First you have to find your audio and video codec, in my case the video was mp4v and the audio was "samr".
The audio codec, which is samr is not supported by VLC. So, you have to convert the "samr" (i.e AMR) codec to another codec, which could be mp3, wav etc. You will find the converter for your operating system at the following location:-
it's free of cost. But before that the second step is -->
2. Rename the files from mp4 to 3gp.
3. Download the convertor from the website mentioned above.
4. Open the convertor--> select the input file as one of your video file and the output file as a new file.
5. Start the converter, it will take less than a second for the file to convert.
6. Run the file using Quick time and now you can hear the sound. You don't have to use the converter for each and every file. You just have to do the conversion once and the solution will work for the rest.
Hope it helps................
Thanks and Regards,