I read the article: Modding a CD ROM drive to read DVDs. In my car trunk I have a 6-CD changer. However, it can read only audio CDs. Would it be possible to change the laser head (or adjust it) to add support for MP3 discs? Or is reading MP3 discs not related to the laser head? After some research, it looks like decoding MP3 audio is not related to laser head but hardware.

I know that a new player with DVD and USB support is not expensive. I have a built in audio system (SC-816). Its a '99 Volvo C70. Original system sound is good and I am happy with it. I also are seen some adapters to plug into a changer input.

I already have this mod, but I need to switch songs in the MP3 player. Also, when I switch off the radio, the MP3 stays on.


The short answer is no.

The long answer is probably, but you'd need to entirely replace most of the control logic for the CD player.

It's true that the actual mechanical assembly used for reading a plain-old audio CD should be entirely capable of reading a CD with MP3s burned onto it.

The decoding logic is another story. Simple audio CDs basially have sequential DAC vaules encoded on them. The "decoding" basically involves reading the sequential values, and sticking them on the output DAC (there is a bit more to it, generally related to buffering so if you hit a bump, it doesn't interrupt the playback, but that's the gist).

Decoding MP3s is significantly more involved. There is very little likelyhood that the electronics in a CD player could be adapted to do MP3 decoding. Even if they were capable (it actually takes a pretty significant amount of processing power to decode an MP3. You couldn't do it on an arduino, for example), you would need to be extremely familiar with the embedded device they use to run the CD player.

This is all assuming that the device used to play back audio CDs isn't a specialty chip designed just for CD playback, and is instead a reprogrammable microcontroller. If the CD player uses a purpose-specific controller, the only way to make it play MP3s would be to entirely replace the control electronics with your own.

Realistically, if the problem is that when you turn off the car, your MP3 player keeps playing, there is probably a simpler solution. You just need a mechanism that automatically stops your MP3 player when the car is shut off.

Many MP3 players have line-out outputs, that are only active when they are connected to a charger. If you have a charger that only outputs power when the car is on, that would solve the problem quite easily.

Realistically, any further solution is probably going to be specific to your MP3 player, and would probably warrant another question.

  • \$\begingroup\$ I figured out in my mind, that maybe i can add raspberry pi to all this. CD charger has 8 pin input (in radio unit). The idea is that links some pins to raspberry pi input pins and then handle that on Linux (next/prev songs etc.). But i need figure out what signals are going from pins in radio unit. If i can detect next / prev / seek signals, then, i think, that raspberry pi can help. \$\endgroup\$ – Guntis Apr 25 '13 at 6:20
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    \$\begingroup\$ @Guntis - the only way adding a raspberry pi would work would be if you had a USB-CDROM drive attached to it. Basically, there is no realistic way you will be able to make the existing CD mechanism work with other hardware. \$\endgroup\$ – Connor Wolf Apr 25 '13 at 6:45
  • \$\begingroup\$ if i add raspberry, then i can store MP3 on USB flash drive and attach it to raspberry. So - i no need anymore compact discs. \$\endgroup\$ – Guntis Apr 25 '13 at 7:47

I'll keep it short and simple.

You could do it, assuming you can redesign the whole thing.

The problem is not related to the read laser, though. It is the electronics/hardware behind it. The electronics is probably hardwired to play back only audio CDs. MP3 is a form of encoding for audio, which means you will have to decode it while playing back. Since you have an audio CD player, there is a 99.99999% chance that it does not contain the support circuitry to decode MP3 encoded audio.

You could do it if you routed the CD drive control circuitry to a microcontroller (that has enough computing power necessary), decode it, then send the decoded signals back to the audio system.

Then again, it's way more trouble than what it's worth. I'd just suggest that you burn audio CDs instead of MP3.


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