voaacenc produces stereo when IMHO it should produce mono

[Sebastian Dröge]

On Sa, 2016-03-05 at 12:19 +0000, Andy Robinson wrote:
> Hello,
> 
> This pipeline produces a mono mp4 as I would expect:
> 
> gst-launch audiotestsrc num-buffers=100 ! audio/x-raw, channels=1 ! 
> lamemp3enc ! mp4mux ! filesink location=test.mp4
> 
> However both of the next two produce stereo, which seems wrong to me:
> 
> gst-launch audiotestsrc num-buffers=100 ! audio/x-raw, channels=1 ! 
> voaacenc ! mp4mux ! filesink location=test.mp4
> 
> gst-launch audiotestsrc num-buffers=100 ! audio/x-raw, channels=1 ! 
> voaacenc ! audio/mpeg, channels=1 ! mp4mux ! filesink
> location=test.mp4
> 
> So, how can I get voaacenc to encode a mono input to a mono output?
> (or should I be using a different encoder to produce aac?)

How do you know that it creates stereo streams? Looks all ok here.
Which version of GStreamer are you using?

$ gst-launch-1.0  audiotestsrc num-buffers=100 ! \
    audio/x-raw, channels=1 ! voaacenc ! fakesink -v

$ gst-launch-1.0  audiotestsrc num-buffers=100 ! \
    audio/x-raw, channels=1 ! voaacenc ! decodebin ! fakesink -v

$ gst-launch-1.0  audiotestsrc num-buffers=100 ! \
    audio/x-raw, channels=1 ! voaacenc ! mp4mux ! \
    filesink location=test.mp4

$ gst-discoverer-1.0 test.mp4
[...]
Channels: 1
[...]

-- 
Sebastian Dröge, Centricular Ltd · http://www.centricular.com

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