problems creating a live stream with AAC using rtp to quicktime player

Marco Ballesio gibrovacco at
Sat May 28 10:42:56 PDT 2011


On Fri, May 20, 2011 at 10:33 PM, Eric Shoquist
<eshoquist at>wrote:

> Audio however seems to be a different beast. I’ve found even when piping
> AAC to a filesink, in order for quicktime to play the audio, I have to use
> qtmux or mp4mux after the encoding phase.

it's understandable as long as it's about playing local files.. streaming is
a different beast and usually the muxer role is played from the payloader
(see below).

>   When I attempt to mimic my video pipeline for audio like the following:
> gst-launch -v alsasrc device=hw:0,0 num-buffers=$((30*60*5)) ! \
>         audio/x-raw-int, endianness=1234 ! \
>         queue ! \
>         TIAudenc1 engineName=codecServer codecName=aacheenc ! \
>         qtmux  ! \
>         rtpmp4vpay pt=96 ! \
>         udpsink host= port=9010 auto-multicast=true
> The pipeline doesn’t play – I get errors linking mp4mux to rtpmp4apay (caps
> don’t match). Using gst-inspect I see that qtmux has only 1 src -
> video/quicktime, and when looking at the rtpmp4 plugins none of them take
> that as a sink. So I’m unclear how I can stream the audio with rtp. Is there
> a different mux I can use that doesn’t put out video/quicktime, but still
> works with quicktime player? Or is there some other plugins to use between
> qtmux and one of the rtpmp4[a,v,g]pay plugins that will convert the caps to
> video/mpeg?

you should use NO muxers if yoiu're already payloading, that is, try
connecting the encoder directly to the payloader. It should just work (r).

Besides, you should make sure that in the rtpsp negotiation (I didn't
understand how it's done prior using these pipelines, but I'll assume some
magic happens under the hood) the audio format is specified as something
like MP4A-LATM (as for rfc3016). Indeed, RealMedia has its own payloading
format and it might happen that the negotiation assumes that one to be used.

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