[FFmpeg-user] audio-only flv over rtmp

[Leo Currie]

Hi -

I'm trying to generate an RTMP live stream for Flash clients that contains
audio only.
Is there a special option to prevent the flv muxer generating a video
stream?

Here's an example of the kind of stream I'd like to generate:
rtmp://87.117.250.4/radiosix3/

I'm trying this:
ffmpeg -re -i (my input stream) -acodec aac -strict experimental -ab 96k
-ar 44100 -vn -f flv rtmp://127.0.0.1/live/test
..which connects to my local nginx instance running the rtmp module.

When I try to play the stream in VLC, it complains about an 'undf' video
format, but audio plays fine. Looking at the stream properties in VLC I can
see there is indeed an 'undf' video stream 0, with the audio being stream 1.

Is there an option for the flv muxer to prevent this video stream being
generated? I tried -vn but this doesn't do what I expect.

Or am I going about this the wrong way?

Thanks.

Leo