dynamic stream recording

[Milian Wolff]

On Mittwoch, 27. November 2019 08:55:12 CET Tim Müller wrote:
> On Tue, 2019-11-26 at 17:39 +0100, Milian Wolff wrote:
> 
> Hi Milian,

Hey Tim!

> > Is this still the recommended way of doing things? For a novice, it
> > is extremely difficult to follow - the code is complex and apparently
> > requires  manual setup of the pipeline, which is unfortunate - the
> > flexibility of `gst_parse_launch` has helped me a lot so far.
> 
> I think by and large this is still correct, but it depends a bit on
> what exactly you want to do.
> 
> Can you describe your goals/requirements? There are many types of
> 'dynamic' stream recording.

Will do, see below.

> gst_parse_launch() just doesn't work very well for dynamic things.
> Having
> said that, you can still use helpers like
> gst_parse_bin_from_description(),
> which are like gst_parse_launch() but  give you a bin / pipeline part
> instead of a full top-level pipeline. So you can use it for branches
> for example.

Great, that's exactly the kind of method I was looking for. May I suggest that 
a link to gst_parse_bin_from_description is added to gst_parse_launch?

> If you provide more specific info we might be able to point you to more
> specific examples.

I have an X shaped pipeline: two sources a) and b) , a video mixer in the 
center, and then two outputs c) and d):

Center:

```
    glvideomixer name=m ! tee name=t
```

Source a) is essentially the video camera:

```
    rpicamsrc preview=false ! \
        video/x-raw,format=RGBA,width=320,height=240,framerate=25/1 ! \
        glupload ! m.
```

Source b) is a dynamic overlay image from another sensor source:

```
    appsrc name=overlaysrc blocksize=307200 stream-type=0 ! \
        rawvideoparse format=rgba width=320 height=240 frame-size=307200 
framerate=25/1 ! \
        video/x-raw,format=RGBA,width=320,height=240,framerate=25/1 ! \
        glupload ! m.
```

Sink c) is the live preview:

```
    t. ! queue name=display_queue ! qmlglsink name=sink
```

Sink d) is the record branch:

```
    t. ! queue name=record_queue ! glcolorconvert ! gldownload ! \
        video/x-raw,format=ARGB ! videoconvert ! \
        omxh264enc control-rate=1 target-bitrate=1145000 ! \
        video/x-h264,profile=baseline ! h264parse ! avimux ! \
        filesink location=test.avi
```

Initially I was hoping I could create this pipeline just once and then 
selectively enable/disable the record branch.

What I'll try next is to only create the record branch once but connect/
disconnect it dynamically to the tee as needed. Afaik while the record branch 
is disconnected and thus not PLAYING, I should be able to change the 
filesink's location property too - right?

Thanks

-- 
Milian Wolff | milian.wolff at kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt, C++ and OpenGL Experts
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