Sound but no picture!!

[herethere]

Hi all I have encountered another problem that I can't seem to find a answer for from googling ,the problem is that I downloaded a video to my phone and although its there the the video starts I can hear the sound and everything but there is no picuture with it...
The video is in mpeg 4 format so what do you all think I should try to do so as I can get the picture with the sound....? Thanks.

 

[sitlet]

What phone? What resolution? What codec? What is the source? What program did you use?

 

[herethere]

Hi my phone is the HTC Desire the format of the video is mp4...I have a video format converter but I don't know which format to convert it to...

 

[sitlet]

Again: What codec? and what is the source?

mp4 is a container, NOT a codec. use MediaInfo if you dont know the codec.