[vdr] Re: Linear volume response in VDR

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Emil Naepflein wrote:
> 
> Hi,
> 
> the volume control in vdr is not linear. The following patch makes the
> volume control better:
> 
> --- dvbdevice.c.org     2004-09-25 14:15:45.000000000 +0200
> +++ dvbdevice.c 2004-09-25 14:18:33.000000000 +0200
> @@ -786,7 +820,12 @@
>  {
>    if (HasDecoder()) {
>       audio_mixer_t am;
> -     am.volume_left = am.volume_right = Volume;
> +     int i, Vol;
> +
> +     for (i = 1, Vol = 0; i < Volume; i++)
> +        Vol += (256 - i) * (256 - i);
> +
> +     am.volume_left = am.volume_right = Vol / 21718;
>       CHECK(ioctl(fd_audio, AUDIO_SET_MIXER, &am));
>       }
>  }

Seems to improve the volume control.

Can you elaborate a little on the theory behind this?
An incoming Volume of 220 already leads to a result of
255.

Klaus