Dynamic text-overlay on live-stream using gst-launch-1.0

Tue Feb 28 06:30:17 UTC 2017

Thanks again Nicolas.  I feel like I’m getting very close.  Here’s what I have right now, and this basically kinda sorta works:

tail -n 1000 -f /home/pi/test.txt | /opt/gst/bin/gst-launch-1.0 -v fdsrc ! subparse ! txt. videotestsrc is-live=true ! video/x-raw, width =800, height=480, framerate=10/1 ! videoconvert ! decodebin ! textoverlay name=txt !  omxh264enc target-bitrate=800000 control-rate=3 ! tcpserversink host=0.0.0.0 port=9000

I can inject items to test.txt from the shell like this:

printf "7\n00:01:59,826 --> 00:02:59,000\nNOW I SAY WORK\n\n" >> /home/pi/test.txt

Now my challenge is, how do I post the proper time ranges?  Unfortunately it seems I can’t keep appending 00:00:00,000 --> 99:99:99,000 because it will only show one subtitle at a time and it seems to always be the first one for that time-range.  So the second sub-title wouldn’t overwrite the first one (which is basically what I need).

So I think these are my options:

-          Is there another format or something that the subtitles can be written in?

-          Or a way to cause newer sub-titles take precedence over older ones?

-          Or am I going to need to keep track of the play-time from my secondary process and regularly append accurate times to the file/stdout?

Thank you

-Adam

From: gstreamer-devel [mailto:gstreamer-devel-bounces at lists.freedesktop.org] On Behalf Of Nicolas Dufresne
Sent: Monday, February 27, 2017 7:34 AM
To: Discussion of the development of and with GStreamer <gstreamer-devel at lists.freedesktop.org>
Subject: Re: Dynamic text-overlay on live-stream using gst-launch-1.0

Le lundi 27 février 2017 à 07:05 -0800, Adam Plocher a écrit :

Nicolas, thank you for your response.  fdsrc seems like it would be a good solution, but I'm having issues getting it to work.

It seems like I need to specify the caps after the fdsrc, otherwise it fails in other ways.  e.g.

Specifying text/x-raw:

tail -f /home/pi/test.txt | /opt/gst/bin/gst-launch-1.0 fdsrc fd=0 ! "text/x-raw" ! txt. videotestsrc ! videoconvert ! decodebin ! textoverlay name=txt ! omxh264enc target-bitrate=800000 control-rate=3 ! tcpserversink host=0.0.0.0 port=9000

I think you forgot to keep subparse element.

Results in:

Pipeline is PREROLLING ...

ERROR: from element /GstPipeline:pipeline0/GstCapsFilter:capsfilter0: Filter caps do not completely specify the output format

Additional debug info:

gstcapsfilter.c(455): gst_capsfilter_prepare_buf (): /GstPipeline:pipeline0/GstCapsFilter:capsfilter0:

Output caps are unfixed: text/x-raw, format=(string){ pango-markup, utf8 }

ERROR: pipeline doesn't want to preroll.

Specifying text/plain:

tail -f /home/pi/test.txt | /opt/gst/bin/gst-launch-1.0 fdsrc fd=0 ! "text/plain" ! txt. videotestsrc ! videoconvert ! decodebin ! textoverlay name=txt ! omxh264enc target-bitrate=800000 control-rate=3 ! tcpserversink host=0.0.0.0 port=9000

Results in:

0:00:00.501757360  4549  0x1e085c0 ERROR           GST_PIPELINE grammar.y:714:gst_parse_perform_link: could not link fdsrc0 to txt, txt can't handle caps text/plain

WARNING: erroneous pipeline: could not link fdsrc0 to txt, txt can't handle caps text/plain

No caps at all:

tail -f /home/pi/test.txt | /opt/gst/bin/gst-launch-1.0 fdsrc fd=0 ! txt. videotestsrc ! videoconvert ! decodebin ! textoverlay name=txt !  omxh264enc target-bitrate=800000 control-rate=3 ! tcpserversink host=0.0.0.0 port=9000

Results in:

Pipeline is PREROLLING ...

WARNING: from element /GstPipeline:pipeline0/GstTextOverlay:txt: Could not multiplex stream.

Additional debug info:

gstbasetextoverlay.c(2449): gst_base_text_overlay_video_event (): /GstPipeline:pipeline0/GstTextOverlay:txt:

received non-TIME newsegment event on video input

WARNING: from element /GstPipeline:pipeline0/GstDecodeBin:decodebin0: Delayed linking failed.

Additional debug info:

./grammar.y(510): gst_parse_no_more_pads (): /GstPipeline:pipeline0/GstDecodeBin:decodebin0:

failed delayed linking some pad of GstDecodeBin named decodebin0 to some pad of GstTextOverlay named txt

ERROR: from element /GstPipeline:pipeline0/GstVideoTestSrc:videotestsrc0: Internal data stream error.

Additional debug info:

gstbasesrc.c(2951): gst_base_src_loop (): /GstPipeline:pipeline0/GstVideoTestSrc:videotestsrc0:

streaming stopped, reason not-linked (-1)

ERROR: pipeline doesn't want to preroll.

There is some information here (regarding the older version of gst-launch): 

http://gstreamer-devel.966125.n4.nabble.com/Dynamic-text-again-td3676141.html

And that links to this bug that was resolved (again, old gst-launch): 

https://bugzilla.gnome.org/show_bug.cgi?id=654959

I've seen a couple examples which used the "text/plain" caps.

I'm certainly open to cracking open the Python lib and giving it a shot.  I would need to read up on it a bit and I'm not familiar with the appsrc, either, but that's something else I'm open to. I have done very basic stuff with the Python libs but nothing too fancy or dynamic (basic pipelines, no more complex than I would get from gst-launch-1.0).

What would you recommend?  Is there an example or resource you could point me towards?

Thank you for your help

On Sun, Feb 26, 2017 at 2:46 PM, Nicolas Dufresne <nicolas at ndufresne.ca <mailto:nicolas at ndufresne.ca> > wrote:

Le dimanche 26 février 2017 à 06:18 -0800, Adam Plocher a écrit :
> Hello, I apologize if I'm posting this in the wrong place. I've
> previously asked this on stackoverflow and never got a response: http
> ://stackoverflow.com/questions/42128804/polling-a-text-file-and- <http://stackoverflow.com/questions/42128804/polling-a-text-file-and-> 
> overlaying-the-result-in-gstreamer
>
> I have a Raspberry Pi with a camera and I'm live streaming that back
> to another unit (it's for a baby monitor).  On the same Pi, I have a
> temperature sensor that is dumping the current temp to a file every 5
> seconds.
>
> My question: Is it possible to somehow poll that txt file and update
> a text-overlay on the live stream based on the current contents of
> that file?

filsesrc does not have this feature unfortunatly. I believe using
fdsrc, you could:

  tail -f text.txt | gst-launch-1.0 fdsrc ! ...

Let me know if that is a good work-around. If you are writing an app,
this can be done with a pipe, or if you prefer, with appsrc.

>
> I've tried using a filesrc and subparse, and it will grab it
> initially if I format the input text file properly, but it doesn't
> seem to update itself:
>
> gst-launch-1.0 -v \
>     filesrc location=/home/pi/temp.txt ! subparse ! txt. rpicamsrc
> awb-mode=0 awb-gain-red=1 awb-gain-blue=2 rotation=0 bitrate=820000
> preview=false brightness=67 contrast=30 sharpness=40 \
>     ! video/x-h264,width=800,height=480,framerate=10/1 \
>     ! h264parse ! decodebin ! videoconvert ! clockoverlay shaded-
> background=true draw-shadow=true font-desc="Nimbus Mono" \
>     ! textoverlay name=txt shaded-background=yes \
>     ! omxh264enc control-rate=3 target-bitrate=850000 \
>     ! tcpserversink host=0.0.0.0 port=5555 sync=true
>
> The input file looks like this:
> 1
> 00:00:00,000 --> 99:59:59,000
> 69 degrees
> Thank you!
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