Can't get pipeline (rtspsrc ! rtph264depay ! h264parse ! nvv4l2decoder ) to work on Jetson Nano

[Konstantin Stein]

Hi,

a quick overview before I go into details.

I'm trying to receive and decode a rtsp-h264 stream from my IP-camera on a
Jetson Nano singleboard-computer connected to the same network.
Jetson Nano (OS is Ubuntu) provides some platform-specific
hardware-accelerated GStreamer elements (e.g.: nvv4l2decoder, omxh264dec,
nv3dsink, etc.).

At this point, I'm evaluating the desirable GStreamer-pipline which
fullfills my intention stated above by using the gst-launch-1.0 tool.
I was able to succesfully receive, decode and display the ip-camera stream
by using the  platform-specific hardware-accelerated omxh264dec element as
video-decoder.

Unfortunately the omxh264dec element is deprecated in Linux for Tegra (L4T)
and its recomended to use nvv4l2decoder for new projects instead.
Problem is, if I use nvv4l2decoder instead of omxh264dec within my working
pipeline, the pipeline does't work any more.

My working-command (deprecated omxh264dec is used as video-decoder) is:
gst-launch-1.0 rtspsrc location=rtsp://
192.168.188.112:554/user=admin_password=tlJwpbo6_channel=1_stream=0.sdp?real_stream
caps = "application/x-rtp, media=(string)video, encoding-name=(string)H264,
payload=(int)96" ! rtph264depay ! h264parse ! omxh264dec ! nvvidconv !
nv3dsink

I created a pipeline-graph which looks as follows (just the area of
interest / end of pipeline is shown):
[image: 01_omxh264dec_working_but_deprecated.png]


My desired-but-not-working-command (recomended nvv4l2decoder is used as
video-decoder) is:
gst-launch-1.0 rtspsrc location=rtsp://
192.168.188.112:554/user=admin_password=tlJwpbo6_channel=1_stream=0.sdp?real_stream
caps = "application/x-rtp, media=(string)video, encoding-name=(string)H264,
payload=(int)96" ! rtph264depay ! h264parse ! nvv4l2decoder ! nvvidconv !
nv3dsink

It's pipeline-graph looks as follows (just the area of interest / end of
pipeline is shown):
[image: 02_nvv4l2decoder_recomended_but_not_working.png]

The graph suggests, that the decoder's format-changed-event on the output
side is never called.

Unwilling to give up, I tried to conquer GStreamer by splitting my NOT
working command into two commands.

First, receive the ip-camera stream and write it to a file with:
gst-launch-1.0 rtspsrc location=rtsp://
192.168.188.112:554/user=admin_password=tlJwpbo6_channel=1_stream=0.sdp?real_stream
 ! queue ! "application/x-rtp,media=video" ! rtph264depay ! h264parse !
video/x-h264, stream-format="byte-stream" ! filesink location="test.264"

Second, read from file, decode (with priviously not working video-decoder)
and display with:
gst-launch-1.0 filesrc location=test.264 ! h264parse ! nvv4l2decoder !
nv3dsink

To my amazement this splitted approach was successfull.
My question is: why is my desired-but-not-working-command not working while
the altenative splitted commands are working just fine?

Although I studied the GStreamer Documentation closely, I'm very new to
GStreamer.
I hope I did a novice mistake, which an experienced developer/user spots
right away.
If you do, please give me a hint what to do to solve the issue.

Thank You!
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