I am working with a Colibri iMX6 and iris carrier board, to record audio, with the latest Linux Image.
I managed to record and playback my audio recordings. However, when I checked the signal, I noticed that it was saturating at 0.5 and clipping everything above that.
I am recording via only the left line pin in the iris, and setting ALSA mixer with the following command:
amixer set 'Capture Mux' 'LINE_IN'
Below is an image of the problem – notice the clipping at 0.5 (image taken using Audacity):
But what I expected was as exemplified below (recorded using a Vf61, and only the left line in pin):
Notice that there is no saturation at 0.5 and the signal is close to 1. The voltage limit of both Vf61 and iMX6 boards is 1 Vrms, according to the datasheet of the codec SGTL5000, and the input signal that I used has amplitude 0.9Vrms…
It is worth noting that I used the same command to record in both the Vf61 and iMX6:
arecord -q -r 44100 -f S16_LE -c 1 -t wav -d 30 "recording.wav"
What am I doing wrong?