-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Somebody in the thread at some point said: | On Monday 21 July 2008, Cédric Berger wrote: |> Sound quality during calls is indeed not that good. |> |> 1. Volume is usually too low, but I think it can be modified via |> correct settings. |> Seems like people not always hear me at the same level : sometimes |> quite ok, often really too low. I have yet to try more... | | Volume can be adjusted vi a alsamixer, and the mic can be routed via a | compressor and noise gate. Audio routing is far from simple - see the wiki: | http://wiki.openmoko.org/wiki/Neo_1973_audio_subsystem | The route indicated for voice calls on the wiki is via the compressor / noise | gate (ALC) but the state file (2007.2 after opkg upgrade) skips that part. | | Assuming there is sufficient difference in level between voice level and the | level from the earpiece it should be possible to set the noise gate so that | it only triggers when you are actually speaking, stopping the echo. The | compressor should even out the variations in level. | | I don't know yet whether the assumption is true; it maybe that the ALC is | skipped from the state file because it was difficult or impossible to find | settings that reliably blocked echo, but passed voice.
I don't know why we go around it, but when I looked mic -> GSM routing some weeks ago I also found a very direct analogue path. If you're interested to meddle with this, I have some meddling hints. First, the datasheet is open: http://www.wolfsonmicro.com/uploads/documents/en/WM8753.pdf We have fitted 100n in the external ALC path (between ACOP / ACIN) instead of 1uF recommended, I guess it will impact low end, but in telephony the low end as well as the high end are chopped out anyway. Soon, as steve told, you'll be able to see this stuff (and our mistakes) on the schematics for yourself. You can dump the actual codec registers using # cat /sys/devices/platform/soc-audio/codec_reg and you can meddle with them like this # echo "3d 20" > /sys/devices/platform/soc-audio/codec_reg_write first one is the register address in hex, second is value to write in hex. I don't really know what those dozens of alsamixer settings are doing either, I found it easier to read the datasheet and interpret / meddle with the codec registers directly. - -Andy -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iEYEARECAAYFAkiEWNIACgkQOjLpvpq7dMrPUgCeKs86CiONfAJ3tVGwOdWXyib/ TcoAnib9G+BfEEOZxzZsS8vy7Vvr0aw3 =H3+x -----END PGP SIGNATURE----- _______________________________________________ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community