MP3 players

[funfairEE]

I am wanting to build a simple MP3 player that plays different MP3s with different switches, each switch plays a different mp3. I am thinking that the way it wold probably work is have a micro controller with some form of memory chip, the micro to find the mp3s in the storage, move them into the built in ram on the micro then output it on one of the pins.

is there a simpler way?
Is there any of the shelf chips that are dedicated to this sort of thing?

any information on this subject is much appreciated.

thanks a lot funfairEE

[harnon]

There are probably a billion mp3 player schematics on the web..... E.g. http://www.opencircuits.com/Music_Player? You may be able to adapt one of these.

Most devices use a Chip from http://www.vlsi.fi. These are relatively expensive in small quantities because of the mp3 licensing costs, however Sparkfun sell some of the chips and mp3 shields for Arduino as well, just do a search there.

[funfairEE]

are there any similar chips to the vlsi ones that decode a few different formats like mp3 and wav, not having any look finding a UK suppler.

[amyk]

It might be easier and cheaper to modify an existing MP3 player to do this for you.

[SoftwareSamurai]

What about... THIS?

(Yeah, okay, not out yet, but still...pretty exciting!)

[funfairEE]

It might be easier and cheaper to modify an existing MP3 player to do this for you.

If i was to do that wold probably have to desolder all the components and use them but its a possibility I guess.

[TerminalJack505]

Are you needing to play MP3s?  Or do you just want to play music/sound?  If you avoid the whole MP3 patent issue you'll have a lot more options.  You can decode the MP3s on your PC into your own format and use that, perhaps?  Nice thing about this option is that you might be able to get away with using an 8-bit MCU if you keep the encoding simple.

If you really need to decode MP3s then you'll need at least a low end 32-bit MCU for the decoding.  Then check into projects such as this one:

MAD: MPEG Audio Decoder

It's Open Source but there is still the whole MP3 license issue so you're probably expected to pay a fee to someone.

Atmel has an application note about using this decoder with their UC3 MCUs:

Atmel AVR32840: AVR UC3 Audio Player MAD MP3 Decoder

I haven't used the decoder.  I just found it doing a little Googling.

[T4P]

There are codes out there meant for ARM used for MP3 decoding . STM32F4 ... w/e
But STM32F4 being ARM Cortex-M4 means you don't need to deal with a extra DSP if you do need , because it's there already , and a high performance one on top of that .

[amyk]

Actually you don't need that much CPU power to decode MP3.

The old common s1mp3 designs (ATJ208x/9x series) mostly had a Z80 and 24-bit DSP running at 72MHz, and that was enough to decode MJPEG too (128x160, 15FPS). If I remember correctly ALi had a design with an 8051 running at ~120MHz and that could do video too

[T4P]

Actually you don't need that much CPU power to decode MP3.

The old common s1mp3 designs (ATJ208x/9x series) mostly had a Z80 and 24-bit DSP running at 72MHz, and that was enough to decode MJPEG too (128x160, 15FPS). If I remember correctly ALi had a design with an 8051 running at ~120MHz and that could do video too

Because it's cheap and available , it isn't a outdated design and it reduces part counts .

[slateraptor]

Because it's cheap and available , it isn't a outdated design and it reduces part counts .

What does that have to do with anything??

is there a simpler way?
Is there any of the shelf chips that are dedicated to this sort of thing?

As harnon has already suggested, the simplest way would to integrate an off-the-shelf mp3 decode ASIC into your design. It's expensive, but without a doubt the simplest.

[T4P]

Because it's cheap and available , it isn't a outdated design and it reduces part counts .

What does that have to do with anything??

If he was referring to my post , then it's true . Because off the shelf 8051's cost the same as a STM32F4 ...

[codeboy2k]

If you need MP3 because its a design to be used by others, beyond your control, and it's a design need, then you would
probably need to use an off-the-shelf mp3 decoder. 

However, if you have control over the source files, and are planning to pre-load the device with various sound files
to play at the flip of a switch, then why not use OGG as your source format.  It's open source, no royalties, and if you
do have original source material in MP3, you can use a PC to convert it to OGG format for storage on your device.

Again, this is only a solution if you have control over the source audio. If you expect others to load clips, and play them,
then you probably need to use MP3, unless you can train your uses to first convert files to OGG format.

OGG is considered superior to MP3, and is free and open source.

[amyk]

If you're going to convert then why not convert to uncompressed PCM format like WAV. NAND flash is cheap enough these days and if all your device is going to have to handle only several short songs. A 2GB (16Gb) chip can hold more than 6 hours of 16-bit 44.1KHz stereo PCM. That greatly simplifies the hardware and software because all it has to do is read data from the flash and stream it to a DAC.

[slateraptor]

If you're going to convert then why not convert to uncompressed PCM format like WAV.

I'd argue that half the fun is in decoding the MP3.