What is alignment capability in h264parse or rtph264depay element?

shubhamr rastogishubham20 at gmail.com
Tue Dec 26 13:09:02 UTC 2017


I have created a pipeline to capture the h264 raw and decoded frames from a
camera. 

Pipeline is shown below:

*rtspsrc location="cam url" ! tee name=t ! queue ! rtph264depay !
video/x-h264, stream-format=byte-stream ! queue ! h264parse ! appsink
name=sinkRaw max -buffers=100 drop=true t. ! queue ! rtph264depay ! queue !
h264parse ! omxh264dec ! nvvidconv ! video/x-raw, format=I420 ! appsink
name=sinkDec max-buffers=100 drop=true*

Everything works fine.
I am able to pull raw data form "sinkRaw" appsink and write it into a video
file to create a video.
Video is playable. 

*But if I skip some raw data frames and then start writing them to a file,
the video file created is corrupted(contain some green-black patterns).

But if I set alignment=au in rtph264depay element , everything works fine.*

/*So can someone please explain me how by setting the alignment. the above
corrupted video problem is solved and what is the difference between nal and
au alignment?*/

I have already read the post :
http://gstreamer-devel.966125.n4.nabble.com/What-is-the-alignment-capability-in-video-x-h264-td4665044.html
but can't understand the difference between au and nal alignment.



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