ffmpeg: convert audio-only flv to swf

My Flex application records audio-only FLV files using red5--I'd like to convert these to SWF files so I can embed them in other SWF files. (I could also convert to MP3 and then embed them into SWFs myself, but I'd prefer a one step solution.)

Anyone have experience doing this?

What I've tried:

The following naive ffmpeg command fails:

> ffmpeg -i 3139747641.flv -vn movie.swf
FFmpeg version SVN-r21751-snapshot, Copyright (c) 2000-2010 Fabrice Bellard, et al.
  built on Feb 11 2010 09:15:42 with gcc 4.2.1 (SUSE Linux)
  configuration: --enable-gpl --enable-nonfree
  libavutil     50. 9. 0 / 50. 9. 0
  libavcodec    52.5开发者_StackOverflow中文版3. 0 / 52.53. 0
  libavformat   52.52. 0 / 52.52. 0
  libavdevice   52. 2. 0 / 52. 2. 0
  libswscale     0.10. 0 /  0.10. 0
[flv @ 0x8a5e3a0]Could not find codec parameters (Video: 0x0000)
[flv @ 0x8a5e3a0]Estimating duration from bitrate, this may be inaccurate
Input #0, flv, from '3139747641.flv':
  Metadata:
    audiocodecid    : -1
    duration        : 0
    videocodecid    : -1
    canSeekToEnd    : true
  Duration: 00:00:14.88, start: 0.000000, bitrate: N/A
    Stream #0.0: Video: 0x0000, 1k tbr, 1k tbn, 1k tbc
    Stream #0.1: Audio: nellymoser, 8000 Hz, mono, s16
Output #0, swf, to 'movie.swf':
    Stream #0.0: Audio: 0x0000, 8000 Hz, mono, s16, 64 kb/s
Stream mapping:
  Stream #0.1 -> #0.0
Encoder (codec id 86017) not found for output stream #0.0

I've tried adding a dummy video, but this also failed:

> ffmpeg -i dummy.mov -i 3139747641.flv movie.swf
<!-- snip -->    
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'dummy.mov':
  Metadata:
    major_brand     : qt  
    minor_version   : 512
    compatible_brands: qt  
    encoder         : Lavf52.52.0
    encoder-eng     : Lavf52.52.0
  Duration: 00:00:00.10, start: 0.000000, bitrate: 62 kb/s
    Stream #0.0(eng): Video: mpeg4, yuv420p, 10x10 [PAR 1:1 DAR 1:1], 1 kb/s, 10 fps, 10 tbr, 10 tbn, 10 tbc
[flv @ 0x8a67fa0]Could not find codec parameters (Video: 0x0000)
[flv @ 0x8a67fa0]Estimating duration from bitrate, this may be inaccurate
Input #1, flv, from '3139747641.flv':
  Metadata:
    audiocodecid    : -1
    duration        : 0
    videocodecid    : -1
    canSeekToEnd    : true
  Duration: 00:00:14.88, start: 0.000000, bitrate: N/A
    Stream #1.0: Video: 0x0000, 1k tbr, 1k tbn, 1k tbc
    Stream #1.1: Audio: nellymoser, 8000 Hz, mono, s16
picture size invalid (0x0)
Cannot allocate temp picture, check pix fmt

Install the unstripped and extra libraries

sudo apt-get install ffmpeg libavcodec-extra-53

You need to install libmp3lame. Also, you might need to try setting your microphone recording rate to 44.