VLC media player lagging video

[Obamargarine]

Whenever I play a 720p MKV file in VLC there are horizontal lines because a section of the picture changes faster than another section. In Windows Media Player classic the video is fine but the surround sound never works, it just plays in stereo, even though the AC3 filter is configured to 5.1.

Does anyone know what can be done about either one of these problems, or is there a better program for playing MKV files?

thanks..

[Dv8ted2]

Are you sure that the video has 5.1 sound?

If it plays fine in media player classic, then use media player classic.

[Obamargarine]

yes it has 5.1 sound because it plays 5.1 sound in VLC player. I don't want to use media player classic because that doesn't play the surround.

[Dv8ted2]

Make sure the setting for accelerated output is selected in VLC.

[redwudz]

yes it has 5.1 sound because it plays 5.1 sound in VLC player. I don't want to use media player classic because that doesn't play the surround.

MPC HC plays my surround sound fine out through a coaxial audio connection to my surround sound amp. It even plays MKVs with DTS 6 channel surround sound with 1536 Kbps audio bitrate.