Problema com RA streaming com o mplayer

Question

Estou tentando reproduzir um streaming de .ra com o mplayer deste URL:

rtsp://mm6.rai.it/radiofonia/radio3/napoli/battiti/2012/battiti2012_10_04.ra

Eu uso para executar o comando mplayer rtsp://url.ra , mas agora isso parece não funcionar

MPlayer2 UNKNOWN (C) 2000-2011 MPlayer Team
mplayer: could not connect to socket
mplayer: No such file or directory
Failed to open LIRC support. You will not be able to use your remote control.

Playing rtsp://mm6.rai.it/radiofonia/radio3/napoli/battiti/2012/battiti2012_10_04.ra.
Resolving mm6.rai.it for AF_INET6...

Couldn't resolve name for AF_INET6: mm6.rai.it
Resolving mm6.rai.it for AF_INET...
Connecting to server mm6.rai.it[212.162.85.53]: 554...

librtsp: server responds: ''
librtsp: server responds: ''
rtsp: read error.
librtsp: server responds: ''
Cache size set to 640 KBytes
Cache fill:  0.00% (0 bytes)   

Cache not filling, consider increasing -cache and/or -cache-min!
Detected file format: REAL
Stream description: Audio Stream
Stream mimetype: audio/x-pn-realaudio
[real] Audio stream found, -aid 0
RM: No audio stream found -> no sound.
No stream found.


Exiting... (End of file)

Depois de um pouco de googleing eu descobri que o problema é libav, então eu testei o comando mplayer --demuxer=lav rtsp://url.ra

MPlayer2 UNKNOWN (C) 2000-2011 MPlayer Team
mplayer: could not connect to socket
mplayer: No such file or directory
Failed to open LIRC support. You will not be able to use your remote control.

Playing rtsp://mm6.rai.it/radiofonia/radio3/napoli/battiti/2012/battiti2012_10_04.ra.
Resolving mm6.rai.it for AF_INET6...

Couldn't resolve name for AF_INET6: mm6.rai.it
Resolving mm6.rai.it for AF_INET...
Connecting to server mm6.rai.it[212.162.85.53]: 554...

librtsp: server responds: ''
librtsp: server responds: ''
rtsp: read error.
librtsp: server responds: ''
Cache size set to 640 KBytes
Cache fill:  0.00% (0 bytes)   

Detected file format: RealMedia format (libavformat)
Cache not filling, consider increasing -cache and/or -cache-min!
[lavf] stream 0: audio (cook), -aid 0
Clip info:
title: BATTITI DEL 04.10.2012
author: BATTITI
copyright: Copyright © 1997 2000 Netia Digital Audi
comment: 
==========================================================================
Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders
ad_ffmpeg: initial decode failed
ADecoder init failed :(
Could not open audio decoder ffmpeg.
Opening audio decoder: [realaud] RealAudio decoder
Error: /usr/lib/codecs/cook.so: cannot open shared object file: No such file    or directory
Win32 LoadLibrary failed to load: /usr/lib/codecs/cook.so
Error loading dll
ERROR: Could not open required DirectShow codec cook.so.
Read the RealAudio section of the DOCS!
ADecoder preinit failed :(
Could not open audio decoder realaud.
Opening audio decoder: [realaud] RealAudio decoder
AUDIO: 22050 Hz, 1 ch, s16le, 20.7 kbit/inf% (ratio: 2583->0)
Selected audio codec: [racook] afm: realaud (RealAudio COOK)
==========================================================================
[AO OSS] audio_setup: Can't open audio device /dev/dsp: No such file or  directory
AO: [alsa] 22050Hz 1ch s16le (2 bytes per sample)
Video: no video
Starting playback...


MPlayer interrupted by signal 8 in module: decode_audio

O comando mplayer -ac help me diz que o codec cook.so está presente

...
...
ra10cook    realaud   working   RealPlayer 10 COOK audio  [cook.so]
racook      realaud   working   RealAudio COOK  [cook.so.6.0]
...

Estou usando a versão mais recente do linux mint com o kernel 3.2.0.

EDITAR: Se eu baixar o streaming antes e eventualmente reproduzi-lo com o mplayer, tudo funciona bem.

Onde está o problema?