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Making a 2 Channel portable MP3 player for licence paper
quetzalcoatl
post Mar 20 2015, 10:48
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Hello! This is my first post here, so sorry in advance for my noob-ness and I care to mention that I have no audio hardware or coding experience or knowledge.

I was wondering if anyone could give me any suggestions or ideas for the making of the following device:
A portable mp3 player-sized or slightly bigger device with:
- an internal memory (or external, like a microSD f.i.), USB port for uploading tracks, display, basic graphic interface;
- 2 channels, for playing 2 tracks simultaneously, play/pause button, volume buttons for each channel, navigation buttons, select buttons
- jack 3.5mm (for headphones)
- an external remote control (wired or wireless), connected to the player - which is to be handheld - that can crossfade between channels by pressing a button placed on it (like a big red panic button); the crossfade has to stop and return to an inital position when releasing the button, the one that was before pressing it; the crossfade can be liniar, and should be complete (from trackA to trackB) in an interval of 2-4 seconds, after which remaining at full volume until the release of the button, when it will snap back to the inital position.

I want to use this kind of device in a study regarding audioanalgesia.
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probedb
post Mar 20 2015, 11:13
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Is there any reason you can't just use two normal players playing a mono signal?
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quetzalcoatl
post Mar 20 2015, 11:20
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QUOTE (probedb @ Mar 20 2015, 12:13) *
Is there any reason you can't just use two normal players playing a mono signal?


I need stereo sound from both channels to come out through the headphones.
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probedb
post Mar 20 2015, 12:04
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Do you mean both left channels playing at the same time through the left channel? And the same for the right? if so then just have a mixer between the two players?
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quetzalcoatl
post Mar 20 2015, 12:52
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QUOTE (probedb @ Mar 20 2015, 13:04) *
Do you mean both left channels playing at the same time through the left channel? And the same for the right? if so then just have a mixer between the two players?


Yes, something like that, but I can't have a mixer in the clinic, as I will be working with pacients. I need only the 2 channel part and the crossfader from a mixer... I don't really have any use of frequency knobs or other functions. Just volume controll and crossfading.
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saratoga
post Mar 20 2015, 14:21
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If this is for a scientific study, I would write a smartphone app and use an inexpensive smart phone. You can get an adequate device for roughly hundred dollars new or much less used. This will be much cheaper and easier than designing a complete audio player from scratch.
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quetzalcoatl
post Mar 20 2015, 15:29
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QUOTE (saratoga @ Mar 20 2015, 15:21) *
If this is for a scientific study, I would write a smartphone app and use an inexpensive smart phone. You can get an adequate device for roughly hundred dollars new or much less used. This will be much cheaper and easier than designing a complete audio player from scratch.


I've taken this into consideration, and also found it to be more conveniant, but I thought that pacients will find it more difficult to identify and press a non-physical button, like you would find on a smartphone's screen, as they are unable to look at the device, they can only hold it in their hand (this is during dental treatments, so imagine the position of the patient in this situation, he won't be able to look at the device every 2 seconds to see where the button is). Also, accidentally pressing the button by playing around with the phone or by touching the screen by other objects or surfaces is not indicated as it will create the effect when it's not needed.

This is why I wanted a physical button on a remote, so that it can be pressed instantly and consciously, whenever the pain stimulus becomes present.

On the other hand, I've heard that you can program the app so that it uses physical buttons on the phone (such as volume buttons or others). This could partially solve the "non-physical button problem", but usually volume buttons are quite small and close together, giving way for more potential errors in use of the device.

If you have any suggestions to get around these problems, I would be much appreciative!
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saratoga
post Mar 20 2015, 15:43
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QUOTE (quetzalcoatl @ Mar 20 2015, 09:29) *
This is why I wanted a physical button on a remote, so that it can be pressed instantly and consciously, whenever the pain stimulus becomes present.


You could use a bluetooth remote or other controller.

At that point though I suppose you could just use a laptop and have both the headphones and controls be wireless.
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quetzalcoatl
post Mar 20 2015, 15:52
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QUOTE (saratoga @ Mar 20 2015, 16:43) *
QUOTE (quetzalcoatl @ Mar 20 2015, 09:29) *
This is why I wanted a physical button on a remote, so that it can be pressed instantly and consciously, whenever the pain stimulus becomes present.


You could use a bluetooth remote or other controller.

At that point though I suppose you could just use a laptop and have both the headphones and controls be wireless.


Would it be possible to set this all up in a DAW (let's say, Ableton Live) and make a remote controller that connects via wifi or BT that controlls an automation for the crossfading?

What would I need for making this kind of remote and how can I connect it to the DAW?
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klonuo
post Mar 20 2015, 16:00
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QUOTE (quetzalcoatl @ Mar 20 2015, 16:52) *
Would it be possible to set this all up in a DAW (let's say, Ableton Live) and make a remote controller that connects via wifi or BT that controlls an automation for the crossfading?


I'd use Plogue Bidule and control it with OSC messages
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quetzalcoatl
post Mar 20 2015, 16:24
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QUOTE (klonuo @ Mar 20 2015, 17:00) *
QUOTE (quetzalcoatl @ Mar 20 2015, 16:52) *
Would it be possible to set this all up in a DAW (let's say, Ableton Live) and make a remote controller that connects via wifi or BT that controlls an automation for the crossfading?


I'd use Plogue Bidule and control it with OSC messages


Thanks for the suggestion, I'll look into it!
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