GStreamer multi pipeline time sync

Tue Dec 1 22:19:33 UTC 2020

You could try using audiotestsrc (there's a "silence pattern") and mix it
with your alsasrc ... this way "something" is always going down that path.

> ------------------------------
>
> Message: 5
> Date: Tue, 1 Dec 2020 21:31:57 +0100
> From: Peter Biro <pettair at gmail.com>
> To: Discussion of the development of and with GStreamer
>         <gstreamer-devel at lists.freedesktop.org>
> Subject: Re: GStreamer multi pipeline time sync
> Message-ID: <FB10063C-7F0D-4946-BE24-AA6EB388D764 at gmail.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Thanks! That can work!
>
>  Is there a way how I can 'send silence' from an audio source (or anything
> in the middle)?
>
> Currently this is my audio pipeline:
> alsasrc ! queue ! audioconvert ! appsink name=app_sink
>
> Also  I tried to play around with the 'max-size-time' property on a queue,
> but I cut that solution since I had issues with disabling only the filesink
> output. The way I tried it is to redirect the filesink output to the
> /dev/null and reconfigure it to a proper place when a recording event
> arrives but for that I had to set the file sink state to GST_STATE_NULL (or
> GST_STATE_READY it was a while ago) which caused issues with the other
> parts of he pipeline. But it would be great if this part could also be
> covered by plain pipeline on the gst side.
>
> > On 2020. Dec 1., at 11:38, Thornton, Keith <keith.thornton at zeiss.com>
> wrote:
> >
> > Hi,
> > the buffering can be done with a standard gstreamer queue by dynamically
> manipulating the threshold and queue size parameters. Have you considered
> the possibility of recording silence when no audio is present.
> > Gruesse
> >
> > Von: gstreamer-devel <gstreamer-devel-bounces at lists.freedesktop.org> Im
> Auftrag von Peter Biro
> > Gesendet: Dienstag, 1. Dezember 2020 10:21
> > An: Discussion of the development of and with GStreamer <
> gstreamer-devel at lists.freedesktop.org>
> > Betreff: Re: GStreamer multi pipeline time sync
> >
> > Sure, I can describe it more in detail.
> >
> > You are right about that the streaming / displaying is mandatory and the
> recording is optional (it can be triggered).
> >
> > Unfortunately the actual use case is a bit more complex: when the user
> hits record the recording also should include the video(and maybe audio
> too) for the previous 30 seconds(actual time is also configurable) as well.
> So there should be a live stream and this 'buffered' recording. Also I
> cannot 'pre-mux' the audio with the video since audio is completely
> optional and it could be configured to be recorded only when the recording
> is started (so there would be video for like 30 seconds from the buffer and
> then audio would join in later). The hard requirement is this (to have X
> seconds of video before the user hits the record and optional audio
> attached to it) but I wanted to implement it in a general way so the other
> part of the application should not be aware if the 'buffered' data is audio
> or video.
> >
> > This is why I started with separate pipelines and transferring the data
> between them with appsinks and appsrcs, and do the buffering and other
> logic on the application side, I guess this is a naive way of implementing
> it so if there is any suggestion it is more than welcomed :D
> >
> > Thanks!
> >
> >
> > On 2020. Dec 1., at 5:06, gotsring <gotsring at live.com <mailto:
> gotsring at live.com>> wrote:
> >
> > Can you describe what you are trying to achieve? It sounds like you want
> to
> > grab video and audio (e.g. webcam and mic), combine/mux those streams,
> then
> > be able to view the stream it and optionally record it. Something like:
> >
> > View/Record pipeline (gst-launch-1.0)
> > videotestsrc ! timeoverlay ! tee name=videotee ! queue ! autovideosink \
> > audiotestsrc wave=8 ! tee name=audiotee ! queue ! autoaudiosink \
> > videotee. ! queue ! x264enc ! matroskamux name=muxer ! filesink
> > location=save_location.mkv async=false \
> > audiotee. ! queue ! muxer.
> >
> >
> > Playback (just to test)
> > gst-play-1.0 save_location.mkv
> >
> > This should probably not be used exactly, but that's the gist. You can
> just
> > google how to mux streams using GStreamer. I also think that queue has a
> > property that allows you to effectively add a delay to a stream
> > (min-threshold-time), is this what you wanted?
> >
> >
> >
> > --
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