{"action":"created","issue":{"url":"https://api.github.com/repos/mikebrady/shairport-sync/issues/651","repository_url":"https://api.github.com/repos/mikebrady/shairport-sync","labels_url":"https://api.github.com/repos/mikebrady/shairport-sync/issues/651/labels{/name}","comments_url":"https://api.github.com/repos/mikebrady/shairport-sync/issues/651/comments","events_url":"https://api.github.com/repos/mikebrady/shairport-sync/issues/651/events","html_url":"https://github.com/mikebrady/shairport-sync/issues/651","id":291653512,"number":651,"title":"Differences between shairport-sync's built-in SW volume and ALSA Softvol?","user":{"login":"tuomashamalainen","id":231644,"avatar_url":"https://avatars1.githubusercontent.com/u/231644?v=4","gravatar_id":"","url":"https://api.github.com/users/tuomashamalainen","html_url":"https://github.com/tuomashamalainen","followers_url":"https://api.github.com/users/tuomashamalainen/followers","following_url":"https://api.github.com/users/tuomashamalainen/following{/other_user}","gists_url":"https://api.github.com/users/tuomashamalainen/gists{/gist_id}","starred_url":"https://api.github.com/users/tuomashamalainen/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/tuomashamalainen/subscriptions","organizations_url":"https://api.github.com/users/tuomashamalainen/orgs","repos_url":"https://api.github.com/users/tuomashamalainen/repos","events_url":"https://api.github.com/users/tuomashamalainen/events{/privacy}","received_events_url":"https://api.github.com/users/tuomashamalainen/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":15,"created_at":"2018-01-25T17:32:56Z","updated_at":"2018-02-01T00:37:43Z","closed_at":null,"author_association":"NONE","body":"First of all, my thanks for the incredible work on shairport-sync. I've used it in multiple projects within the last two years and it's been rock-solid so far 👌\r\n\r\n### Background\r\nI'm working on a sound system that features shairport-sync, Spotify Connect and Bluetooth for streaming audio. On the hardware side there is a Pi 3 connected to a [BeoCreate 4-Channel Amplifier](https://www.hifiberry.com/shop/beocreate/beocreate-4-channel-amplifier/), which is a combined I2S DAC/DSP/amplifier and works with the HiFiBerry DAC driver preinstalled in Raspbian (Lite Stretch in this case). The board does not expose hardware mixer controls through ALSA, so Softvol is used to enable volume control with Spotify and Bluetooth.\r\n\r\nPreviously I've used shairport-sync's built-in software volume control, but was hoping to bring shairport-sync also behind Softvol for consistency. Both of these approaches work for volume control, seem to behave very differently from each other.\r\n\r\nIn essence, shairport-sync's built-in SW volume works just the way I want it: it has a good amount of resolution at quiet and normal listening levels where it is needed. With Softvol, however, the volume increases rapidly at the beginning of the scale and then more slowly as volume is turned up, which is rather inconvenient unless the preferred listening level is very high (way too high for pleasant normal listening in a room).\r\n\r\nI plotted the position of iTunes volume slider against the volume level reported by alsamixer to illustrate what I mean:\r\n<img width=\"471\" alt=\"screen shot 2018-01-25 at 18 23 39\" src=\"https://user-images.githubusercontent.com/231644/35401242-a35540ca-0201-11e8-8d7d-36adc38be80e.png\">\r\n\r\nThe ALSA configuration I use can be found [here](https://github.com/hifiberry/beocreate-tools/blob/master/enable-hifiberry), and the shairport-sync configuration [here](https://gist.github.com/tuomashamalainen/9667641007564892c491a8173fa4d11c):\r\n\r\n### The Question\r\nReading the documentation, it looks like shairport-sync does use a nonlinear volume control curve, and I suppose this is what we're looking at on the chart. However, is it by design that the actual volume is so different depending on whether the built-in SW volume control or ALSA Softvol is used? The built-in SW volume control is just about perfect as far as my ears are concerned; is there a way to get the same from Softvol?\r\n\r\n🖖"},"comment":{"url":"https://api.github.com/repos/mikebrady/shairport-sync/issues/comments/362119114","html_url":"https://github.com/mikebrady/shairport-sync/issues/651#issuecomment-362119114","issue_url":"https://api.github.com/repos/mikebrady/shairport-sync/issues/651","id":362119114,"user":{"login":"joerg-krause","id":6870896,"avatar_url":"https://avatars2.githubusercontent.com/u/6870896?v=4","gravatar_id":"","url":"https://api.github.com/users/joerg-krause","html_url":"https://github.com/joerg-krause","followers_url":"https://api.github.com/users/joerg-krause/followers","following_url":"https://api.github.com/users/joerg-krause/following{/other_user}","gists_url":"https://api.github.com/users/joerg-krause/gists{/gist_id}","starred_url":"https://api.github.com/users/joerg-krause/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/joerg-krause/subscriptions","organizations_url":"https://api.github.com/users/joerg-krause/orgs","repos_url":"https://api.github.com/users/joerg-krause/repos","events_url":"https://api.github.com/users/joerg-krause/events{/privacy}","received_events_url":"https://api.github.com/users/joerg-krause/received_events","type":"User","site_admin":false},"created_at":"2018-02-01T00:37:43Z","updated_at":"2018-02-01T00:37:43Z","author_association":"NONE","body":"I've set the min_dB value to -70 dB for comparing with the default value of -51 dB:\r\n\r\n![image](https://user-images.githubusercontent.com/6870896/35654945-c7f5990a-06ef-11e8-96e6-c905e1b69801.png)\r\n\r\nIt is true that with a larger dB range of 70 dB the shairport curve gets closer to the default softvol curve at 51 dB.\r\n\r\n@mikebrady Thanks for the new flat transfer function which I will test tomorrow :smile:"}}
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