VS1063 - Talk-Back (decoding) while encoding Ogg/Vorbis

[ottinger]

Hi everyone,

i am currently working on an OpenSource/OpenHardware project called OggStreamer http://oggstreamer.wordpress.com/

I read the VS1063 datasheet and i found the feature called the "Sidestream Sigma-Delta Modulator"
I was wondering whether this feature would allow to playback some ISDN-quality Mono-Audiosignal, while encoding Ogg/Vorbis at the same time. (using the SDM in the pcmmixer path)

I think that this would mean to implement some tiny vsdsp-plugin which hooks up to the SDM-Interrupt and feeds samples from a small buffer, which gets filled from an external uC.
I am curious if this Idea could work?

If this is possible, this would allow to implement a talk-back channel for this Streaming Device.

best wishes, Georg

[pasi]

I read the VS1063 datasheet and i found the feature called the "Sidestream Sigma-Delta Modulator"
I was wondering whether this feature would allow to playback some ISDN-quality Mono-Audiosignal, while encoding Ogg/Vorbis at the same time. (using the SDM in the pcmmixer path)

There is actually very little preventing the PCMMixer to work in codec and encoding modes. The memory areas do not overlap (PCMMixer FIFO is at the end of Y memory), and SDM sidepath is not used by anything else (ADMixer can not be used in encoding/codec mode). Also, AICTRL0 is only used by the encoding/codec modes to set the samplerate during startup. After that is available for PCMMixer.

The biggest hindrance is that the encoding/codec mode does not call the PcmMixerCheck() function, which turns PcmMixer on/off. It should not be a lot of effort to enable the use of PCMMixer in encoding modes with the next vs1063a patches release.

We're touching a lot of interrupt stuff (to support very high interrupt loads), so the patch needs to be tested quite thoroughly. I can send a beta version, if you don't mind possible bugs (and promise to send useful bug reports if you do find any).

[ottinger]

Hi Pasi,

thanks for your reply.
May I ask you a further question? (Because i am not so familiar with the VS1063 yet) - Are you saying with the right patch this would be possible to implement without a special vs1063-plugin. Just configuring the pcmmixer and feeding its FIFO - Is this correct?

About the beta patch - i am quite busy in getting the first batch of OggStreamers produced so this Idea will be an Issue for me only in Jan/Feb 2012.

thanks, Georg

[pasi]

with the right patch this would be possible to implement without a special vs1063-plugin. Just configuring the pcmmixer and feeding its FIFO - Is this correct?

Almost. The encoding mode just needs to check if you want PCMMixer activated (which is does not currently do). At least it should work just like that.

After that it is "just" a question of CPU cycles.

[ottinger]

Hi Pasi,

i would like to try out the pcmmixer, while encoding. I would have time for this in the Beginning of March ...

best wishes, georg

[ottinger]

its been a while (four years - crazy how time is flying) - but I am still interested in using the pcmMixer of the VS1063 while encoding.

Is your offer to provide a beta patch for this feature still valid?

kind regards,
Georg

[pasi]

I don't remember if I have tested it, but the source code says the following:
20130620: PcmMixer should work with encoder and codec modes.
Using PcmMixer with AEC will not be the best of ideas,
although playback through it will just be considered
double-talk by AEC.

So get the latest vs1063a patches package and give it a try.

Yeah, time flies.