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How to Fix MythTV Analog Volume Too Loud

Summary

This tutorial describes how to reduce the recording volume of an analog tuner for MythTV.

These steps were documented using Mythbuntu 14.04.1 with MythTV 0.27, but should also work with other MythTV installations.

Contents

Problem: MythTV Analog Tuner Recording Volume Too Loud

The normal procedure for adjusting the recording volume of an analog tuner is to modify the Volume (%) in the MythTV Backend Recording Profile for MPEG-2 encoders. Unfortunately this does not always work as I discovered with a Hauppauge WinTV HVR-2250 MC Dual TV Tuner / Encoder card.

This problem is evident with the recorded volume being too loud, and audio is distorted or clipped. It is especially noticeable when both digital and analog tuners are being used because the analog volume is significantly louder. For instance when switching from viewing a digital broadcast to an analog broadcast, the viewer is jolted by the jarringly loud sound of the analog recording.

Solution: Reduce Analog Tuner Recording Volume with v4l2-ctl Command

The following steps indicate how to list the settings for a tuner card, how to adjust the recording volume for an analog tuner, and how to make these volume settings more permanent.

For reference, on my Hauppauge HVR-2250 dual tuner card (2 analog and 2 digital tuners), the device names are in the following form:

    Analog device name:  /dev/video#
   Digital device name:  /dev/dvb/adapter#/frontend0
Where the "#" (hash mark or number sign) represents a whole number starting at zero "0".

List Tuner Settings

To list the tuner settings of the first analog tuner, use the following command:

v4l2-ctl --list-ctrls -d /dev/video0

Output:


        brightness (int)    : min=0 max=255 step=1 default=127 value=127 flags=slider
          contrast (int)    : min=0 max=255 step=1 default=66 value=66 flags=slider
        saturation (int)    : min=0 max=255 step=1 default=62 value=62 flags=slider
               hue (int)    : min=0 max=255 step=1 default=128 value=128 flags=slider
            volume (int)    : min=-83 max=24 step=1 default=20 value=0 flags=slider
         sharpness (int)    : min=0 max=15 step=1 default=8 value=8 flags=slider
       stream_type (menu)   : min=0 max=1 default=0 value=0 flags=update
      video_aspect (menu)   : min=0 max=3 default=1 value=1
    video_b_frames (int)    : min=1 max=3 step=1 default=1 value=1 flags=update
    video_gop_size (int)    : min=1 max=255 step=1 default=15 value=15
video_bitrate_mode (menu)   : min=0 max=1 default=0 value=1 flags=update
     video_bitrate (int)    : min=1000000 max=6500000 step=100000 default=5000000 value=5000000
video_peak_bitrate (int)    : min=1000000 max=6500000 step=100000 default=5000000 value=5000000

From this output we can see that the range of volume values is from -83 to 24, and that the default value is 20.

TIP:   v4l2-ctl not installed?

You can install the v4l2-ctl command on Debian/Ubuntu based GNU/Linux distributions with:

sudo apt-get install v4l-utils

Set Tuner Volume

The recording volume of the first analog tuner can be set with the following command:

v4l2-ctl --set-ctrl volume=# -d /dev/video0

Where the "#" (hash mark or number sign) represents a number in the range -83 to 24.

Through a process of trial and error of setting the recording volume, recording a TV show and then listening to the TV show, I determined that an analog tuner recording volume of 4 was about the same loudness as the recording volume on the digital tuner.

Apply Tuner Settings on MythTV Backend Start / Reboot

To ensure this change takes effect every time the MythTV Backend starts, use the following steps:

  1. In a terminal window, start a text editor (we'll use leafpad) to create a file named mythtv-set-volume.sh in directory /usr/bin.

    sudo leafpad /usr/bin/mythtv-set-volume.sh

  2. Copy and paste the following content into the file to set the recording volume of each analog tuner.

    ---------- begin file mythtv-set-volume.sh ----------
    #!/bin/sh
    #    Purpose:  To set the recording volume of each analog tuner
    #  Called by:  MythTV Backend Setup -> System Events -> Master backend started
    # Parameters:  none
    #
    #
    # Set the recording volume of each analog tuner to 4
    #
    for k in /dev/video*; do
      v4l2-ctl --set-ctrl volume=4 -d $k
    done
    
    ---------- end file mythtv-set-volume.sh ----------
  3. Save the file and exit the text editor.
  4. Make the /usr/bin/mythtv-set-volume.sh file executable.

    sudo chmod a+x /usr/bin/mythtv-set-volume.sh

  5. Start Applications -> System -> MythTV Backend Setup.

    Note that this step is best performed when no recordings are taking place so that recordings in progress are not affected.

  6. Click Yes to close any currently running mythbackend processes.
  7. Enter your "pvr" account password.
  8. Select 8. System Events
  9. Scroll down to event Master backend started and set the event to:

    /usr/bin/mythtv-set-volume.sh

    and Save the setting.

  10. Press ESC until you exit the MythTV Backend.
  11. Enter your "pvr" account password to start mythtv-backend.
  12. Click Yes to run mythfilldatabase.

Congratulations. Your MythTV PVR should now automatically set the analog tuner recording volume on each reboot of the PVR. :-)

References

While learning how to address is the issue of recording volume from an analog tuner being too loud, I found the following references useful:

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