I tested a 3gp file in Nokia 2720 fold (Series 40 5th Edition, Feature Pack 1 Lite)
If the sound is AMR-NB everything is fine.
If the sound is AMR-WB the video is played, but there is no sound. (The file plays fine on N900)
If I extract the AMR-WB stream and put it into an AMR file the same device can play the sound.
So is this really a feature that the video player supports less audio formats than the music player?
What would be a video format with sound that could be recommend for such low end devices? Small size but still somewhat better sound quality than AMR-NB.