VMusic2 volume fadeout

[jssherrard]

Could someone please show a functional volume fadeout (from max to mute) subroutine for a VMusic2 on P0 for the Prop-1???

Thanks!

[edited to correct fumbly-fingers!]

[JonnyMac]

That's probably not going to happen.  Here's why: To do a volume change on the VMUSIC player you have to send a serial command; when you send a serial command the VMUSIC processor stops sending audio data to the MP3 decoder -- what usually happens then is that MP3 decoder buffer runs out and you get an audio glitch (this was confirmed by an e-mail discussion with VMUSIC engineers).  This is especially true with the Prop-1 at 2400 baud; the bit timing at 2400 is very long.  I've seen this same problem with the Prop-2 at 9600 baud as well.

I use the Prop-SX with the VMUSIC player so that I can have 38.4K baud (16x the Prop-1 speed) comms; this lets me send commands on the fly that are quick enough not to have a negative impact on the MP3 buffer.

Sorry to be the bearer of disappointing news.  The VMUSIC player is really cheap... but doesn't do everything we'd all like it to do.  If possible, open your file in Audacity and modify it with a fade out (I like the Cross Fade Out effect best).

[jssherrard]

...Sorry to be the bearer of disappointing news.

No worries!

;D

I am quite new to all this and still wrapping my brain around which controllers are capable of what. I will simply have to adjust my prop to facilitate the abilities of the Prop-1 or upgrade to the Prop-SX. The Audacity option will not work in this situation due to the fact that the fadeout may be initiated by a PIR trigger at any possible point during the audio playback.

I am also noticing some audio glitch while playing back higher bps MP3 files. Anything over 192kbps sounds occasionally glitchy. Is this normal?

[JonnyMac]

I have not noticed any audio glitches associated with bit rate, but then, I normally encode at 192 kbps.   Another factor that could come into play is the access time of the thumb drive you're using.  The Vinculum chip has to pull data from this, buffer it, then transfer to the MP3 decoder -- lots of stuff going on.

This is why I am beginning to doubt that smooth fades using the MP3 decoder's volume control is ever going to be possible; the Vinculum chip has to stop streaming MP3 data to the decoder when it's processing extenal commands.  One possibility perhaps worth exploring is the use of an external digital potentiometer.

After MHC I'm going to spend more time with the device, perhaps using the SPI interface to see if that helps at all -- again, I'll be using the Prop-SX as it has the horsepower for me to get the most from the VMUSIC player.