08-11-2019, 10:50 AM
Hi Kent
I believe that cava is working fine on Moode 6. The behaviour you saw may be related to pipes and blocking.
When I looked at writing a spectrum analyser my first thought was to write my own, using an FFT library. I then came across Cava, and thought I would hack the code. However, when I looked closer I found that Cava provides all that is need for working with external programs, and using pipes doesn't add much overhead, and so I used it as-is.
I consider the main difficulty in providing a spectrum analyser is getting a copy of the audio that is playing, as it may not come from MPD. It could be in the form of a stereo ALSA stream, and could possibly be supoorted by the music player software by providing an ALSA plugin in the chain that just passes on the audio forwards, but that could be overidden in a configuration file to duplicate the audio and pass one copy forwards as before and the other copy would be available to be read by Cava (see https://github.com/antiprism/mpd_oled/issues/4 ).
The situation is complicated by the fact that other software, e.g. equalisers, might also want to modify the ALSA configuration, which is why it would be useful if the music player software was able to provide some hooks into the ALSA configuration for player plugins and external programs. However, I need to look into this some more before suggesting it as a feature.
Adrian.
I believe that cava is working fine on Moode 6. The behaviour you saw may be related to pipes and blocking.
When I looked at writing a spectrum analyser my first thought was to write my own, using an FFT library. I then came across Cava, and thought I would hack the code. However, when I looked closer I found that Cava provides all that is need for working with external programs, and using pipes doesn't add much overhead, and so I used it as-is.
I consider the main difficulty in providing a spectrum analyser is getting a copy of the audio that is playing, as it may not come from MPD. It could be in the form of a stereo ALSA stream, and could possibly be supoorted by the music player software by providing an ALSA plugin in the chain that just passes on the audio forwards, but that could be overidden in a configuration file to duplicate the audio and pass one copy forwards as before and the other copy would be available to be read by Cava (see https://github.com/antiprism/mpd_oled/issues/4 ).
The situation is complicated by the fact that other software, e.g. equalisers, might also want to modify the ALSA configuration, which is why it would be useful if the music player software was able to provide some hooks into the ALSA configuration for player plugins and external programs. However, I need to look into this some more before suggesting it as a feature.
Adrian.
