Stream audio to USB port and use external USB DAC

[diditaldude]

Unfortunately audio quality of 90% of portable MP3 players leaves much to be desired.
Finding an MP3 player that matches both the desired feature set and the desired quality is seldom possible.
Few players have good audio quality and fewer yet provide optical out (like the famous iRiver H120) that audiophiles use to connect external DAC's.
If it were possible to use RockBox to stream digital audio to USB instead of streaming it to low quality internal DAC; it would then be possible to connect an MP3 player to any portable USB DAC (such as iBasso D10, RSA Predator, Headroom, D2 Viper, Pico, Nuforce Icon and many many others).
This is exactly like plugging a USB external audio card into a PC - it streams digital audio to that device (that is how the USB DAC's mentioned above work).
This would finally allow music lovers to choose an MP3 player based on features other than audio quality and leave digital-to-analog convertion and amplification to a dedicated device of their choice.

Does anyone know how complicated this is?

Thanks!

[saratoga]

Does anyone know how complicated this is?

Very complicated.  And search, this has been asked many times before.

[diditaldude]

saratoga, thank you for the reply.

I apologize for double posting - I failed to find threads on this prior to posting (I did search...)

Anyway - "Very complicated" is good, because it means it's possible.

Maybe if enough developers (including me) join in on this we could tackle this?
There must be lots of other dev's who want this feature and can help...

 

[saratoga]

Anyway - "Very complicated" is good, because it means it's possible.

On some targets its probably possible, though you'll likely need to find a way to provide power to a DAC, so it may not be very portable unless they make battery powered USB DACs.

Maybe if enough developers (including me) join in on this we could tackle this?
There must be lots of other dev's who want this feature and can help...

I think you're the only person to ever express interest on actually working on it, but I'm sure if you asked about USB in the IRC channel, some of the people who have worked on it could point you to the right sections of code and perhaps the relevant specifications to read (assuming there are specifications for this sort of thing).

[froggyman]

doesnt the iPod have support for USB out? or is that different that what he is talking about?

[GodEater]

It depends what you mean by "USB out". USB covers a whole range of things. Currently Rockbox only implements Mass Storage over USB - nothing else.

[gevaerts]

As far as I know the ipods don't have the necesary wiring for USB host (which is what you need for this). The portalplayer PP502x SoCs are supposed to have host support, but I'm not aware of any PP502x player that actually can do it.

The only players  where I'm confident about being able to get this working are the European H300, the Gigabeat S, and the Gigabeat F with dock. It may also be possible on some of the iAudios, but we have no documentation about the USB host controller in them.

[Multiplex]

Another way of using an external DAC woul dbe to get one of the very few players that can output digitally - the iRiver H100 series has optical output and I think one other has a digital but i can't remember which.

44.1kHz and 16bit still though.