Built in car DVD player's audio won't work?

I recently bought a used car with built in DVD player. The picture works perfectly fine but the audio doesn't. Does anyone know how I can get the audio to work?

No, you can't just cut up an extension cord and connect it to the battery in place of a power inverter. This is because the vehicle's battery and alternator produce between 12 and 15 volts DC, while your household power outlet provides 230 volts AC. If you want to run a 230VAC device on 12VDC, you need a power inverter.

Update : Approximately what year did car manufacturers start regularly integrating USB capabilities into their cars? For example, would a 2006 model car have a usb port and therefore usb capabilities or is that too early?
At what year would be a reasonable year to think that the car wouldn't have these capabilities.

Approximately what year did car manufacturers start regularly integrating USB capabilities into their cars?

For example, would a 2006 model car have a usb port and therefore usb capabilities or is that too early?

At what year would be a reasonable year to think that the car wouldn't have these capabilities.

I recently tried installing my Pyramid 1000w amp and my Pyle subwoofer into my car. I bought a cheap 10 gauge kit from amazon and installed everything. When I finished I turned on my radio and noticed I couldn't hear anything from my subwoofer but my amp was on. Checked everything but still nothing. Any help thanks in advance.

Side note the car already had wiring for a system, but it looked like a sloppy job so I decided to renew everything.

If you bypass or remove the Bose system, you don't need the adapter for the Bose integration. However, you'll still need a special adapter if you want to keep the retained accessory power feature and the warning chime system working. In this case you'd use a Metra GMRC-01, which should be cheaper than the Bose adapter but still more expensive than a standard wire harness adapter.

Also, your 4-channel amp can drive the front and rear speakers in the vehicle, but you'll lose the factory subwoofer in the center console. To keep that working, you'd need a 5-channel amp.