extrastereo breaks mplayer

[jd1008]

On Fedora 22:
SMPlayer Version: 15.9.0
Using Qt 4.8.6 (compiled with Qt 4.8.6)
Using MPlayer SVN r0

mplayer-1.2-1.fc22.x86_64

I added ExtraStereo to the mini control bar at bottom right.

Now, if I play a song once, all is OK.
But if I come back to that song in the playlist, I get an error banner, which says:

OOOPS! Something wrong happened.

/bin/mplayer -noquiet -slave -identify -nofs -sub-fuzziness 1 -vo xv, -ao alsa -nodr -double -stop-xscreensaver -nomouseinput -input nodefault-bindings:conf=/dev/null -nokeepaspect -wid 69206062 -monitorpixelaspect 1 -subfont-osd-scale 3 -ass -embeddedfonts -ass-line-spacing 0 -ass-font-scale 1 -noflip-hebrew -ass-styles /home/jd/.config/smplayer/styles.ass -subcp ISO-8859-1 -vid 0 -aid 0 -subpos 100 -volume 8 -cache 2048 -osdlevel 0 -vf-add screenshot -noslices -channels 2 -af-add extrastereo -af-add volnorm=1 -af-add scaletempo -af-add equalizer=0:0:0:0:0:0:0:0:0:0 -softvol -softvol-max 999 /sdb3/My_Music/Faun/Faun - Licht - Full Album - 2013-wkvxK630kOQ.mp4

MPlayer 1.2-5.1.1 (C) 2000-2015 MPlayer Team
do_connect: could not connect to socket
connect: No such file or directory
Failed to open LIRC support. You will not be able to use your remote control.

Playing /sdb3/My_Music/Faun/Faun - Licht - Full Album - 2013-wkvxK630kOQ.mp4.

Cache fill: 0.00% (0 bytes)

libavformat version 56.25.101 (external)
libavformat file format detected.
ID_VIDEO_ID=0
[lavf] stream 0: video (h264), -vid 0
ID_AUDIO_ID=0
[lavf] stream 1: audio (aac), -aid 0, -alang und
VIDEO: [H264] 960x720 24bpp 29.970 fps 966.0 kbps (117.9 kbyte/s)
Clip info:
major_brand: mp42
ID_CLIP_INFO_NAME0=major_brand
ID_CLIP_INFO_VALUE0=mp42
minor_version: 0
ID_CLIP_INFO_NAME1=minor_version
ID_CLIP_INFO_VALUE1=0
compatible_brands: isommp42
ID_CLIP_INFO_NAME2=compatible_brands
ID_CLIP_INFO_VALUE2=isommp42
creation_time: 2013-11-29 06:21:45
ID_CLIP_INFO_NAME3=creation_time
ID_CLIP_INFO_VALUE3=2013-11-29 06:21:45
ID_CLIP_INFO_N=4
Load subtitles in /sdb3/My_Music/Faun/
ID_FILENAME=/sdb3/My_Music/Faun/Faun - Licht - Full Album - 2013-wkvxK630kOQ.mp4
ID_DEMUXER=lavfpref
ID_VIDEO_FORMAT=H264
ID_VIDEO_BITRATE=965968
ID_VIDEO_WIDTH=960
ID_VIDEO_HEIGHT=720
ID_VIDEO_FPS=29.970
ID_VIDEO_ASPECT=0.0000
ID_AUDIO_FORMAT=MP4A
ID_AUDIO_BITRATE=192000
ID_AUDIO_RATE=44100
ID_AUDIO_NCH=2
ID_START_TIME=0.00
ID_LENGTH=3087.02
ID_SEEKABLE=1
ID_CHAPTERS=0
Opening video filter: [ass auto=1]
[ass] auto-open
Opening video filter: [screenshot]
[ass] FcConfigAppFontAddDir failed
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
libavcodec version 56.26.100 (external)
Selected video codec: [ffh264] vfm: ffmpeg (FFmpeg H.264)
==========================================================================
ID_VIDEO_CODEC=ffh264
==========================================================================
Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders
AUDIO: 44100 Hz, 2 ch, floatle, 192.0 kbit/6.80% (ratio: 24000->352800)
ID_AUDIO_BITRATE=192000
ID_AUDIO_RATE=44100
ID_AUDIO_NCH=2
Selected audio codec: [ffaac] afm: ffmpeg (FFmpeg AAC (MPEG-2/MPEG-4 Audio))
==========================================================================
[libaf] There can only be one instance of the filter 'extrastereo' in each stream
[libaf] Couldn't create or open audio filter 'extrastereo'
Error at audio filter chain pre-init!

Exiting... (Fatal error)
ID_EXIT=ERROR

So, smplayer code or some library code should simply check to see if sextra stereo
is already enabled for that track, it should simply proceed to play the track instead of
belching an error.

[rvm]