This problem was reported on Ubuntu stations, which use PulseAudio.
We recommend using the PulseAudio backend to SDL or removing PulseAudio and using only Alsa drivers.
Kdenlive uses SDL for audio and video output. However, there appears to be a problem somewhere between SDL, ALSA, and PulseAudio. One possible remedy is to install the PulseAudio backend for SDL, if it is available on your distribution. For Debian and Ubunutu based distributions, try this:
sudo apt-get install libsdl1.2debian-pulseaudio
If that does not help, make sure you have set the Audio Driver to Auto in Kdenlive settings. Also, try restarting Kdenlive and possibly reboot your computer to reset everything. If that does not work, then consider removing PulseAudio per the directions below.
Remove the added lines to /etc/asound.conf.
If /etc/asound.conf did not exist when you installed PulseAudio, you may remove /etc/asound.conf entirely.
After this, you may remove all of the installed PulseAudio packages:
sudo apt-get install esound
will remove PulseAudio packages.
To disable pulseaudio you may need to select alsa for for all options in /system/preferences/sound
Log-out and start a new session.
Then test Alsa drivers using this command:
speaker-test -Dplug:surround51 -c6 -l1 -twav to test if
Select Alsa as an audio driver.