GStreamer Debugging: Difference between revisions

To see what debug can be enabled, add <tt>--gst-debug-help</tt> to your GStreamer application arguments, such as:

gst-launch --gst-debug-help

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Then you can see which debug you are interested in, such as reference counting and buffer movement, and enable all debug output (level output 5).

gst-launch videotestsrc num-buffers=3 ! fakesink --gst-debug=GST_REFCOUNTING:5,GST_BUFFER:5 --gst-debug-no-color=1  2>&1 | grep "\->0" > log.txt

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Another way you can generate the same output is set the <tt>GST_DEBUG</tt> shell variable:

GST_DEBUG=GST_REFCOUNTING:5 gst-launch videotestsrc num-buffers=3 ! fakesink

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Here is a simple way to count the number of frames in a (h264/quicktime) video file:

MOVIE=slomo_1425510055_2.mov

gst-launch -v filesrc location=$MOVIE ! qtdemux ! ffdec_h264 ! fakesink | fgrep chain | wc -l

1) Install "dot" tool on your host machine...to do so simply install graphviz:

sudo apt-get install graphviz

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2) On your target board, set the environment dot dump variable:

export GST_DEBUG_DUMP_DOT_DIR=/root

mkdir -p $GST_DEBUG_DUMP_DOT_DIR

4) Convert the dot files to PNG image files or SVG graphics files

dot -Tpng input.dot > output.png

Example usage:

export GSTTL_HIDE="caps;chk;topo"

export GSTTL_LOG_SIZE=1048576

Run the telnet daemon on the target - likely:

/etc/init.d/inetd start

telnet into the target hardware and watch the interrupt count

while sleep 1 ; do cat /proc/interrupts ; done

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If your GStreamer application is crashing with a segfault or similar condition, enable saving a core dump before running the application.

ulimit -c 100000

mkdir -m 777 /root/dumps

Once you have a <tt>/root/dumps/*.core</tt> file, copy it to your workstation and and inspect it with

ddd  -debugger arm-linux-gnueabi-gdb $GSTREAMER_APPLICATION

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Then in gdb,

target core <core file>

bt

For TI DMAI plugin and other gstreamer components in the RidgeRun SDK, the can be done via:

cd $DEVDIR/proprietary/gst-dmai-plugins

make clean

Attach to your running GStreamer application using gdbserver

ps

PID=4512 # set the right value based on your application's PID

Then start the cross-compile version of the GNU debugger, like

arm-linux-gnueabi-gdb -tui $GSTREAMER_APP

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and get the gdb debugger connected to gdb server on the target

set solib-absolute-prefix <path to devdir>/fs/fs

file <path to file>

List the threads and do a backtrace on each one

info threads

bt

On the target (assuming your program's name is <tt>gstd</tt>), first list the PIDs for all the threads in your application:

PROG=gstd

ls /proc/`pidof $PROG`/task

Then start gdbserver in multi-process mode:

gdbserver --multi :2345

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Then on the host start the cross-compile version of the GNU debugger, like

arm-linux-gnueabi-gdb -tui $GSTREAMER_APP

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and get the gdb debugger connected to gdb server on the target

set solib-absolute-prefix <path to devdir>/fs/fs

file <path to file>

Now you can attach to a specific PID, do a backtrack, snoop around, and detach from that PID.  Once detached, you can do the same thing again using a different PID from the output of the <tt>ls</tt> command above.

attach <pid>

bt

If you are using the TI DMAI GStreamer plug-in for the TI Davinci and OMAP SoCs, then you can enable DMAI debug to get more information if a hardware-accelerated encoder or decoder is throwing an error.

DMAI_DEBUG=2 gst-launch -e alsasrc num-buffers=50 ! 'audio/x-raw-int,rate=(int)44100,channels=(int)2' ! queue ! dmaienc_aac bitrate=128000 ! qtmux ! filesink location=gstaudio_aac_2ch_128k.mp4

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If you are using the TI DMAI GStreamer plug-in for the TI Davinci and OMAP SoCs, then you can enable CE debug to get more information if a hardware-accelerated encoder or decoder is throwing an error.  Note that the stack is GStreamer DMAI plug-in which uses DMAI which uses CE which uses codecs that take advantage of the hardware accelerators.

CE_DEBUG=3 gst-launch -e alsasrc num-buffers=50 ! 'audio/x-raw-int,rate=(int)44100,channels=(int)2' ! queue ! dmaienc_aac bitrate=128000 ! qtmux ! filesink location=gstaudio_aac_2ch_128k.mp4

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And you can combine DMAI and CE debug

CE_DEBUG=3 DMAI_DEBUG=2 gst-launch -e alsasrc num-buffers=50 ! 'audio/x-raw-int,rate=(int)44100,channels=(int)2' ! queue ! dmaienc_aac bitrate=128000 ! qtmux ! filesink location=gstaudio_aac_2ch_128k.mp4

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To write the debug to a file on tmpfs, which should reduce the performance impact of enabling debug, add  

2>&1 | cat - > /tmp/gst-debug.txt

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If you are creating files on a network-connected embedded device, you can use NFS mount (which is different than NFS root mount) so that once you generate a file, it is easy to get it on your desktop machine.  For any real-time debugging, don't use NFS root mount as the network activity will affect the timing of your pipelines.  See [[Setting Up A NFS Service]] for instructions on configuring your desktop machine.

HOST_IP=10.0.1.1

HOST_NFS_SHARE_DIR=/local/home/tfischer/work/sdk/fs/fs

Add the following to your application's command line parameters:

--gst-debug=GST_REFCOUNTING:5

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Another option is to set the GStreamer debugging shell variable, then run your program:

export GST_DEBUG=GST_REFCOUNTING:5

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You can see which objects disappear, meaning their reference count reaches zero:

gst-launch --gst-debug=GST_REFCOUNTING:5 videotestsrc num-buffers=3 ! fakesink 2>&1 | grep "\->0" | cut -d' ' -f 19

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If your application generates output, you can redirect it to Syslog as follows:

MY_APP=gst-render

With MP4Box you can use the -info in order to get more info from a generated mp4 file:

MP4Box -info test.mp4

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If you are creating an element you plan to use in an embedded device, you might find it helpful to build and test the element on your development machine first.

./autogen.sh

CFLAGS=-ggdb ./configure

Use GST_PLUGIN_PATH to enable GStreamer to find your element library:

export GST_PLUGIN_PATH=$HOME/projects/gst-emboverlay/src/.libs  

gst-inspect emboverlay

Test out your element.  Better to use GStreamer daemon than gst-launch.

TEXT_OVERLAY="text=Hello\ There text-offseth=50 text-offsetv=100 text-font-height=50 text-color=0x800040 text-enable=true"

TEXT2_OVERLAY="text2=World text2-offseth=50 text2-offsetv=150 text2-font-height=50 text2-color=0x800040 text2-enable"

* [[GStreamer_Debugging_Using_GDB |'''GStreamer Debugging Using GDB''']]

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