Textoverlay questions

[Nicolas Dufresne]

Le mercredi 28 juin 2017 à 18:19 +0000, William Salibrici a écrit :
> 
> I tried setting GST_DEBUG="GST_TRACER:7" and
> GST_TRACERS="leaks(GstBuffer)" and running my test app in a command
> window but the tracing didn’t seem to work. I got no trace output. My
> test thread has gst_init at the beginning and gst_deinit at the end.
> My development machine is windows 7 and I’m using GStreamer 1.10.4
> with your windows pre-built binaries.

You would need to be able to dump the allocated object at run-time, but
that's only supported on POSIX system, with unix signals. I think
you'll have to resort at looking into GstMiniObject traces, they
containes ref/unref traces, and find out.

> 
> Any help would be much appreciated.
> 
> Bill
> 
>  
> From: gstreamer-devel [mailto:gstreamer-devel-bounces at lists.freedeskt
> op.org] On Behalf Of Nicolas Dufresne
> Sent: Friday, June 09, 2017 1:59 PM
> To: Discussion of the development of and with GStreamer <gstreamer-de
> vel at lists.freedesktop.org>
> Subject: Re: Textoverlay questions
>  
> Le vendredi 09 juin 2017 à 15:35 +0000, William Salibrici a écrit :
> I am using the following simple pipeline segment to add a text area
> under my compositor video output. In a separate thread, I set the
> “text” property once every second to update the rendered text. For my
> application, the text updates must be real-time.
> 
>  
> 
> videotestsrc pattern=white ! textoverlay ! queue ! comp.sink_2
> 
>  
> 
> My development machine is windows 7 and I’m using GStreamer 1.10.4
> with your windows pre-built binaries.
> 
> My overall pipeline runs without errors but the text updates are not
> always 1 second apart. Sometimes there are pauses between updates
> greater than 1 second. Other times updates come back to back with no
> discernable delay. Sometimes updates appear to be skipped altogether
> [maybe they are just flying by too fast for me to see them]. The
> latency for displaying text seems to vary quite a bit.
> 
> So, here are some questions:
> 
> What is the latency for displaying text [the time between when the
> g_object_set function is called to set the text to be displayed and
> when the text will actually be displayed]?
> Is there any way to achieve a relatively constant latency for
> displaying text?
> Is there any way force the text to be synchronized with the other
> input video streams to my compositor?
>  
> textoverlay has a text pad. You can use this pad to stream text with
> timestamp on it. The simply way it to connect "filesrc
> location=file.srt ! subparse ! ..." Subpase supports most common text
> based sub-title formats, letting you set a timestamp and a duration
> for each text. You can of course replace filesrc with an appsrc or
> fdsrc to stream the data.
>  
> Nicolas
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