green artifacts at start, h264 rtsp

[Jan Schmidt]

On 09/10/14 02:01, Swen Kooij wrote:
> Hello everyone
>
> We’re using the gstreamer rtsp plugin (gst-rtsp-server) and gst-launch
> to play a H.264 video stream from a security camera. We’ve configured
> the RTSP server to share the streams.
>
> However, when I open a stream using gst-launch, I observe a green
> overlay (looks like artifacts) that is displayed for about 1-2 seconds
> and then the stream becomes visible and everything is normal and there
> are no artifacts during the remainder of the stream.

This is generally because in order to start faster, gst-libav will 
output 'corrupted' video frames at the beginning. That happens when the 
first data it receives is not a keyframe. It starts decoding the data it 
has, and the video will become less corrupted over time - such as at the 
next keyframe, or there might never be a keyframe with intra-refresh H.264.

The only way to avoid it at the moment is a pad probe at the video sink. 
Check the CORRUPTED flag on the video buffer, and drop corrupted buffers 
at the start, however that has a cost in terms of how soon the pipeline 
switches to 'playing' state - that can't happen until the sink receives 
at least one decoded buffer.

- Jan.

> On the server we are using the following pipeline description:
>
> ( rtspsrc latency=150
> location=rtsp://10.0.10.64/ONVIF/MediaInput?profile=bb_h264_256 ! queue
> ! rtph264depay ! rtph264pay name=pay0 pt=96 )
>
> And we are starting gst-launch like this:
>
> gst-launch-1.0.exe rtspsrc location=rtsp://localhost:8554/1_bb_h264_512
> latency=0 buffer-mode=auto ! decodebin ! autovideosink
>
> Does anyone know what is the cause of this and how we might resolve it?
> I’ve attached a screenshot to clarify what we observed.
>
> Thank you in advance.
>
>
> Met vriendelijke groet, Sincerely,
>
> Swen Kooij
> Research & Development
>
> 	sk at bigbrother.nl <mailto:sk at bigbrother.nl>
> 	+31 (0)318 666699
>
>
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>
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