Media Problems :(

I used to record videos on my phone and it would play well, but now whenever I record a video it refuses to play, it always says: 'this file contains an unsupported media format'. Sometimes also, although it happened at one instance, after taking some pictures like 10, 3 of them refused to open. They would show on gallery grid view of my pictures, but when i click on them, they refuse to show. And finally, I recorded some audio recordings of myself singing, and they played well, but after like 3 days or so, one of them refused to play anymore and started telling me: 'this file contains an unsupported media format'. Help!!! :(

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