DSP - Filter

[DerPicknicker]

Hi @maximmaxim345,

as discussed here is the feature request. It would be great if the DSP would support the following Filters:

• Loudness
• Limiter / Compressor
• High/Low Pass with frequency setting

Best regards & many thanks for your work.

[maximmaxim345]

• Loudness

Can you explain what you exactly expect from such a filter? Could this also be a preset for a Compressor or Limiter, or should this be something separate?

• High/Low Pass with frequency setting

You mentioned this is for use with a subwoofer. How is the sub connected? (I mean, how does it play right now?)

[DerPicknicker]

Hi @maximmaxim345 ,

Thank you for your fast reply.

Regarding loudness:

I don't know if you are aware of it. On normal AVRs / Stereo amps they pushing base and mids this ensures that speakers sounds full even at low volumes. With higher volumes the loudness effect is fading out.

High/Low pass:
It's an esp32 player but the hardware filter on the sub is not great. That's why I would set a specific frequency.

Hope that helps

[maximmaxim345]

About loudness:
So a volume dependant EQ. That should definitely be a separate filter type then.
Another question is if that could be done seamlessly within Music Assistant. The playback would need to be restarted after a change in volume (since the EQ would need to be adjusted for the set volume).

About the sub:
This could be a lot more complicated.
So right now the ESP32 shows up as two channels (left and right) or 3 (2.1)?
So to properly support that use case the DSP of Music Assistant would need to support multiple channels.
Did I understand that correctly?

[DerPicknicker]

I don't know your architecture of that DSP. CamillaDSP uses a buffer and the DSP computation is done sample wise.

If your DSP works like that after a volume change the adjustments should be done only on samples after volume change => no need for restarting playback.

Why are you thinking about stopping and restarting the playback? This would be quite annoying if you change volume and a half seconds it's stopped because of restarting the playback.

The esp32 is a simple snapcast player which is only one element in the player menu. I feed stereo signal into the sub. I guess it's just a hardware bridged channel. So on MA side no need for multichannel support. The DSP should be only capable of setting high or low pass. Nothing complicated (like multichannel).

This leads me to another point - a option for mono mixdown. Because if you use Multiroom it would be better to stream a mono mixdown stream.

[maximmaxim345]

Why are you thinking about stopping and restarting the playback? This would be quite annoying if you change volume and a half seconds it's stopped because of restarting the playback.

Thats just a quirk of the current implementation of MA. We use (mostly) a single ffmpeg CLI to apply the DSP, encode to the speakers format (and I think compress to mp3/flac/alac). Ffmpeg (as a CLI) can not change filters on the fly.
Would need to look into how difficult it is to make that seamless.

The esp32 is a simple snapcast player which is only one element in the player menu. I feed stereo signal into the sub. I guess it's just a hardware bridged channel. So on MA side no need for multichannel support. The DSP should be only capable of setting high or low pass. Nothing complicated (like multichannel).

So multiple esp32 playing together, with one as a sub?

This leads me to another point - a option for mono mixdown. Because if you use Multiroom it would be better to stream a mono mixdown stream.

Sounds usefull.

[DerPicknicker]

Ah well then, you're probably right. Maybe loudness can be done beforehand. But if I read the docs correctly ffmpeg doesn't support on the fly switching.

Esp32: yes they are playing in sync but one is connected to an sub. But the low pass doesn't work as expected. That's why I would like to see that.

But for Multiroom mono mixdown is more important than high / low pass filter ;-)