Why just sound is played for some mp4 files?

Question

I have some mp4 files that just sound is played not video with jw player and f4 player. But all other mp4 files are playing correctly. what can be wrong?

Answer 1

Pump the video through Handbrake with the default options, plus check "Web optimized." I'll wager that it plays just fine in JW Player after that.

It's a freebie: http://handbrake.fr/

Answer 2

MP4, like any other format, requires specific CODECs for playback. No matter what player you are using, if you do not have the required CODEC for THAT specific clip, you will not play it back correctly. To make matters worse, audio and video are seperate CODECs. This is why you may hear audio, but see no video. It's also why some clips play, and others don't. Different CODECs.

A CODEC is a "COder/DECocer" for audio and video streams. Unless you can view the properties of a particular clip, you really don't know what CODEC the author used.