From: Mike Brady Date: Mon, 9 Apr 2018 18:58:24 +0000 (+0100) Subject: Clarify setting for Raspberry Pi X-Git-Tag: 3.2RC2~3 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7e69739bd2036df21bfd019acacee794808c9ea0;p=thirdparty%2Fshairport-sync.git Clarify setting for Raspberry Pi --- diff --git a/README.md b/README.md index 48c9d19b..ec34beea 100644 --- a/README.md +++ b/README.md @@ -354,11 +354,20 @@ Note: Shairport Sync can take configuration settings from command line options. **Raspberry Pi** -The Raspberry Pi has a built-in audio DAC that is connected to the device's headphone jack. An updated audio driver has greatly improved the quality of the output – see [#525](https://github.com/mikebrady/shairport-sync/issues/525) for details. To activate the updated driver, add the line: +The Raspberry Pi Models A and B have a built-in audio DAC that is connected to the device's headphone jack. An updated audio driver has greatly improved the quality of the output – see [#525](https://github.com/mikebrady/shairport-sync/issues/525) for details. To activate the updated driver, add the line: ``` audio_pwm_mode=2 ``` -to `/boot/config.txt` and reboot. +to `/boot/config.txt`. To make Shairport Sync output to the built-in audio DAC and use its hardware mixer, in the `alsa` section of the configuration file, set the output device and mixer as follows: +``` +alsa = +{ + output_device = "hw:0"; // the name of the alsa output device. Use "alsamixer" or "aplay" to find out the names of devices, mixers, etc. + mixer_control_name = "PCM"; // the name of the mixer to use to adjust output volume. If not specified, volume in adjusted in software. + // ... other alsa settings +``` +(Remember to uncomment the lines by removing the `//` at the start of each.) When these changes have been made, reboot the machine. + Apart from a loud click when used for the first time after power-up, it is quite adequate for casual listening. A problem is that it declares itself to have a very large mixer volume control range – all the way from -102.38dB up to +4dB, a range of 106.38 dB. In reality, only the top 50 dB of it is in any way usable. To help get the most from the DAC, consider using the `volume_range_db` setting in the `general` group to instruct Shairport Sync to use the top of the DAC mixer's declared range. For example, if you set the `volume_range_db` figure to 50, the top 50 dB of the range will the used. With this setting on the Raspberry Pi, maximum volume will be +4dB and minimum volume will be -46dB, below which muting will occur. From a user's point of view, the effect of using this setting is to move the minimum usable volume all the way down to the bottom of the user's volume control, rather than have the minimum usable volume concentrated very close to the maximum volume.