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Fade on stop/pause - via Line-out

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JdGordon:
so someone just needs to come up with a really fast DSP so we can do this stuff at the last possible moment before it goes out to the DAC

Multiplex:

--- Quote from: JdGordon on January 12, 2010, 08:03:50 PM ---so someone just needs to come up with a really fast DSP so we can do this stuff at the last possible moment before it goes out to the DAC

--- End quote ---
I'm assuming that comment is for the fade on pause - L/R balance would be OK using the same mechanism as the other interactive DSP operations - or even the ones that have no special treatment (Replay Gain Pre-Amp for example)

I remember reading some of the code that deals with that and being HUGELY impressed - I've worked on 'professional' projects where the quality of the code was nowhere near as good as Rockbox!

Blue Dude:
The problem with moving instantaneous user interface effects such as fade-on-pause, key clicks, volume changes, balance, etc. to the DSP is that the DSP is not at all instantaneous.  Depending on the size and mode of the PCM buffer, it can lag by several seconds.  Even setting low latency means an unacceptable 1/4 second or more delay.

Crossfade sounds smooth because it is uses a less granular fade interval than the volume control, but its fade effect is mixed directly into the output buffer, usually with a several second delay.  Quite a lot of trouble goes into making a fade happen in real time.  It's possible to do a real time pause fade in the same fashion, but it would be destructive, requiring a rebuffer every time it's done (effectively equivalent to stop/resume).  This isn't prohibitive, but it's one reason why it's not a trivial change.  It's just plain easier to step the volume down, pause the DMA in hardware, then step up than it is to operate directly on the output buffer, stop everything, and then resume.

Sounds like an interesting project, though...

Falco98:
I have checked the changelog (major changes, anyway) and there is no mention of this, but the issue seems to have been fixed in 3.5 -- i am running a 5.5g 80gb ipod, and now when playing thru its line-out in my girlfriend's car, it does fade out and in on stop and pause / resume.  I wish it were mentioned in a changelog somewhere, I'm curious as to what was done.

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