No output from silencedetect

humax# ffmpeg -i Derek_20130205_2311.ts -vn -sn -filter:a:0 silencedetect=n=-50dB:d=0.2 -f null -
ffmpeg version 0.10 Copyright (c) 2000-2012 the FFmpeg developers
  built on Feb 29 2012 10:25:07 with gcc 4.2.0 20070124 (prerelease) - BRCM 11ts-20090508
  configuration: --cross-prefix=mipsel-linux- --enable-cross-compile --arch=mipsel --target-os=linux --enable-gpl --enable-libmp3lame --disable-static --enable-shared --disable-asm --prefix=/mod --extra-cflags=-fPIC
  libavutil      51. 34.101 / 51. 34.101
  libavcodec     53. 60.100 / 53. 60.100
  libavformat    53. 31.100 / 53. 31.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 60.100 /  2. 60.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  6.100 /  0.  6.100
  libpostproc    52.  0.100 / 52.  0.100
[mpeg2video @ 0x444270] mpeg_decode_postinit() failure
    Last message repeated 7 times
[mpegts @ 0x42bc00] max_analyze_duration 5000000 reached at 5016000
[mpegts @ 0x42bc00] Could not find codec parameters (Audio: mp3 ([4][0][0][0] / 0x0004), 0 channels, s16)
[mpegts @ 0x42bc00] Could not find codec parameters (Unknown: none ([5][0][0][0] / 0x0005))
[NULL @ 0x446ff0] start time is not set in estimate_timings_from_pts
[NULL @ 0x45fc60] start time is not set in estimate_timings_from_pts
[NULL @ 0x465ed0] start time is not set in estimate_timings_from_pts
[mpegts @ 0x42bc00] PES packet size mismatch
Input #0, mpegts, from 'Derek_20130205_2311.ts':
  Duration: 00:32:54.41, start: 50197.155611, bitrate: 3602 kb/s
  Program 8261
    Metadata:
      service_name    : ITV
      service_provider:
  Program 8325
    Metadata:
      service_name    : ITV2
      service_provider:
  Program 8384
    Metadata:
      service_name    : Channel 4
      service_provider:
    Stream #0:0[0x230]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p, 704x576 [SAR 16:11 DAR 16:9], 15000 kb/s, 26.20 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x231](eng): Audio: mp2 ([4][0][0][0] / 0x0004), 48000 Hz, stereo, s16, 192 kb/s
    Stream #0:2[0x232](eng): Audio: mp3 ([4][0][0][0] / 0x0004), 0 channels, s16 (visual impaired)
    Stream #0:3[0x233](eng): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006)
    Stream #0:4[0xbb9]: Unknown: none ([5][0][0][0] / 0x0005)
  Program 8452
    Metadata:
      service_name    : Channel 4+1
      service_provider:
  Program 8448
    Metadata:
      service_name    : E4
      service_provider:
  Program 8442
    Metadata:
      service_name    : More 4
      service_provider:
  Program 8500
    Metadata:
      service_name    : Channel 5
      service_provider:
  Program 8361
    Metadata:
      service_name    : ITV +1
      service_provider:
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf53.31.100
    Stream #0:0(eng): Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Stream mapping:
  Stream #0:1 -> #0:0 (mp2 -> pcm_s16le)
Press [q] to stop, [?] for help
Junk in packetB time=00:01:39.72 bitrate=   0.0kbits/s
Junk in packetB time=00:08:04.96 bitrate=   0.0kbits/s
Junk in packetB time=00:09:29.40 bitrate=   0.0kbits/s
Junk in packetB time=00:19:05.16 bitrate=   0.0kbits/s
Junk in packetB time=00:24:29.92 bitrate=   0.0kbits/s
PES packet size mismatch32:52.29 bitrate=   0.0kbits/s
[mp2 @ 0x4457d0] incomplete frame
Error while decoding stream #0:1
size=       0kB time=00:32:53.76 bitrate=   0.0kbits/s
video:0kB audio:370080kB global headers:0kB muxing overhead -100.000000%