"pipeline is prerolling" debug strategy?

[Stefan Sauer]

On 08/09/2012 08:00 PM, Matt Pekar wrote:
> I run this in response to user input:
>
> void display_pipeline_in_chrome(GstElement *pipeline) {
> const char* temp_filename = "gst_bin_graph_tmp";
>
> char dot_command[1024];
> char chrome_command[1024];
>
> const char* DIR = getenv("GST_DEBUG_DUMP_DOT_DIR");
> //GstDebugGraphDetails output_flags =
> GstDebugGraphDetails(GST_DEBUG_GRAPH_SHOW_MEDIA_TYPE |
> GST_DEBUG_GRAPH_SHOW_STATES | GST_DEBUG_GRAPH_SHOW_NON_DEFAULT_PARAMS);
> GstDebugGraphDetails output_flags =
> GstDebugGraphDetails(GST_DEBUG_GRAPH_SHOW_ALL);
> GST_DEBUG_BIN_TO_DOT_FILE(GST_BIN(pipeline), output_flags, temp_filename);
>
> snprintf(dot_command, sizeof(dot_command), "dot -Tpng %s/%s.dot -o
> %s/%s.png", DIR, temp_filename, DIR, temp_filename);
> snprintf(chrome_command, sizeof(chrome_command), "google-chrome
> %s/%s.png", DIR, temp_filename);
FYI: you can also use xdg-open to open it with a suitable viewer. Also
using svg is sometimes better when zooming.
>
> system(dot_command);
> system(chrome_command);
> }
>
> It displays the whole pipeline as an image in Chrome, using the
> Gstreamer debug output from graphviz.

Thing worth looking for in the graph are:
* disconnected elements (obvious)
* pads with uppercase 'F' (= flushing) (missing flush stop or activation)
* not negotiated elements (some elements have a long list of caps,
instead simple caps)

If there are good ideas how, the graphs can be improved to highlight
more issues, let us know.

Stefan
>
> However, that usually isn't enough to tell what's wrong.  For example,
> I recently had a pipeline along these lines:
>
> appsrc ! ffmpegcolorspace ! theoraenc ! rtptheorapay ! udpsink
>
> This pipeline looked fine in the graph output, so to debug it I used
> the GST_DEBUG environment variable on each element in the pipeline,
> starting at the top:
>
> GST_DEBUG=appsrc:5
> --kill and restart
> GST_DEBUG=ffmpegcolorspace:5
> --kill and restart
> GST_DEBUG=theoraenc:5
> --ahhh theoraenc is dropping buffers...
>
> Doing this one step at a time let me discover which element was
> blocking.  It turns out the problem was I wasn't timestamping the
> appsrc buffers, and therefore theoraenc was just dropping them.
>
> On Thu, Aug 9, 2012 at 12:38 PM, Eric Montellese
> <eric.montellese at videon-central.com
> <mailto:eric.montellese at videon-central.com>> wrote:
>
>     Folks, in development I've run into various malformed or buggy
>     pipelines that give this output:
>
>     gst-launch  launch ! a ! pipeline
>     Setting pipeline to PAUSED ...
>     Pipeline is PREROLLING ...
>
>     Generally I have debugged these issues through a mixture of brute
>     force and intuition (looking for common sorts of problems, etc).
>
>     But perhaps there is a better way to determine which element has
>     held up the pipeline?  Some swanky debug command I'm totally
>     unaware of that shows the buffers in-flight perhaps?
>
>     Any advice?
>
>     Thanks,
>     Eric
>
>     _______________________________________________
>     gstreamer-devel mailing list
>     gstreamer-devel at lists.freedesktop.org
>     <mailto:gstreamer-devel at lists.freedesktop.org>
>     http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
>
>
>
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/gstreamer-devel/attachments/20120809/9db48c4a/attachment.html>