H120 24 bit optical in

[Snowman]

I've been searching for a while but can't find a definite answer... so could anybody tell me if rockbox supports 24bit via digital input on the iriver h120?

I read somewhere that it doesn't work because the cpu can't handle that amount of data, but that post is about 2 years old and I don't understand why the cpu shouldn't be able to handle e.g. a 24bit/48kHz stream if it can handle a 16bit/96kHz stream.

[petur]

as far as I know, this is because we can only do 16bit with DMA, and 24bit would then have to be done in PIO mode (ie the CPU has to read every sample manually from the bus) which would be very heavy for the cpu

ask amiconn in IRC for the nasty details

[LinusN]

Besides, the Coldfire audio bus can only handle 20-bit audio.

[Snowman]

Besides, the Coldfire audio bus can only handle 20-bit audio.

Is this documented anywhere? I searched all coldfire documentation and the sourcecode but can't find any hints.

Btw, since the hardware design of the h120 and h320 is almost identical, am I right that it would be possible to install a optical interface on the h320?

[LinusN]

Besides, the Coldfire audio bus can only handle 20-bit audio.

Is this documented anywhere? I searched all coldfire documentation and the sourcecode but can't find any hints.

Yes it is. Check the MCF5249 User's Manual, http://www.rockbox.org/twiki/pub/Main/DataSheets/MCF5249UM.pdf

Page 17.3: "Five audio interface receivers (IIS1, IIS3, IIS4, and two EBU receivers) send their received data on an internal 40-bit wide bus, the Internal Audio Data Bus." (That is 40 bytes for two channels, i.e 20-bit samples.)

Page 17.13: "The IEC958 receive block (19) extracts the audio data from the stream and puts this in 20-bit format on Internal Audio Data bus. The format is exactly the same as the format produced by the serial data interfaces."

Page 17.18: "The IEC958 interface provides the necessary features to allow transmitting of digital data according to the IEC958 specification with the exception that only 20-bit data is supported."

Btw, since the hardware design of the h120 and h320 is almost identical, am I right that it would be possible to install a optical interface on the h320?

In theory yes, but unfortunately the Coldfire chip is a BGA package, so you won't be able to reach the I/O pins for the EBU audio...

[Snowman]

My bad, I must've been blind... I searched the whole manual (and mcf5250's) a few times. Now that's a good starting point to dig through the sources...

Thanks for answering my noobish questions!