[FFmpeg-user] audio-only flv over rtmp

Christian Ebert blacktrash at gmx.net
Mon Aug 5 12:50:09 CEST 2013

* Leo Currie on Monday, August 05, 2013 at 11:30:52 +0100
> I'm trying to generate an RTMP live stream for Flash clients that contains
> audio only.

Why don't you stream just MP3?

> 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://
> I'm trying this:
> ffmpeg -re -i (my input stream) -acodec aac -strict experimental -ab 96k
> -ar 44100 -vn -f flv rtmp://
> ..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?

FLV is Flash Video, so a missing video track does not make sense
imho. Furthermore I don't think you need this contortion for RTMP
(see above). I packed audio into a FLV container for
*pseudo*streaming, but again then you need a _minimal_ video
track to be able to inject metadata.

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