[FFmpeg-user] audio-only flv over rtmp

[Leo Currie]

On 5 August 2013 11:50, Christian Ebert <blacktrash at gmx.net> wrote:

> * 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?
>

My source is actually a 32kbps AAC+ stream coming from an Icecast server,
so I should really be doing '-acodec copy'.


>
> > 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?
>
> 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.
>


Indeed, and MPEG is Moving Picture Experts Group, but we can have MP3
audio. So perhaps none of these formats have very good names!

I didn't know that a video track was needed for metadata, so perhaps all I
need to do is be able to generate the "right kind" of dummy video track for
my FLV.

Or is there another way to stream aac audio over rtmp in a way that Flash
player (e.g. JWPlayer) will understand?
Perhaps a different mux? Is this what you meant by streaming in MP3 - can I
stream without a container?

Thanks -

Leo