Setting volume from C++ on the audio cape (Rev B1)

[Charles Kerr]

I have the following code which I think should set the volume on the audio cape to 100%

int32_t mixer_fd=0;

mixer_fd=open("/dev/mixer", O_WRONLY);

if (mixer_fd>0)

{

        int vol=0x6464;

                                                                if (ioctl(mixer_fd, SOUND_MIXER_WRITE_VOLUME, &vol)==-1)

       {

          std::cout <<"Error setting volume"<<std::endl;

      }

      close(mixer_fd);

}

However, the volume is still barely audible.  Is there something else that needs to be done?

[John Syn]

From: Charles Kerr <charle...@gmail.com>
Reply-To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Date: Friday, June 20, 2014 at 6:36 PM
To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Subject: [beagleboard] Setting volume from C++ on the audio cape (Rev B1)

I have the following code which I think should set the volume on the audio cape to 100%

Use alsamixer to experiment with the various settings. After that, it will be easier to work out how to do this programatically. 

Regards,

John

int32_t mixer_fd=0;

mixer_fd=open("/dev/mixer", O_WRONLY);

if (mixer_fd>0)

{

        int vol=0x6464;

                                                                if (ioctl(mixer_fd, SOUND_MIXER_WRITE_VOLUME, &vol)==-1)

       {

          std::cout <<"Error setting volume"<<std::endl;

      }

      close(mixer_fd);

}

However, the volume is still barely audible.  Is there something else that needs to be done?

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[Charles Kerr]

I found the answer, for those trying to do this.

Change this line

ioctl(mixer_fd, SOUND_MIXER_WRITE_VOLUME, &vol)

to 

ioctl(mixer_fd, SOUND_MIXER_WRITE_PCM, &vol)

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