Can you find key frame in h264 video without decoding?

John McDermott egglue at
Tue May 31 12:16:24 UTC 2022

Hi Michael,

I’ve noticed that rtph264depay also sets the flag:

Would that mean setting the flag again in h264parse is redundant if rtph264depay is in the pipeline?


On 31 May 2022, 5:48 AM +1000, Michael Gruner <michael.gruner at>, wrote:
> The h264parse will set the DELTA_UNIT flag based on the NAL units.
> > On 30 May 2022, at 12:52, John McDermott via gstreamer-devel <gstreamer-devel at> wrote:
> >
> > Hi
> >
> > Does anyone know if key frames can be found without decoding? In the context of the pipeline rtspsrc->rtph264depay->h264parse->appsink, which element sets the GST_BUFFER_FLAG_DELTA_UNIT flag? I read that a keyframe has a unique start code in the NAL unit. In that case, does that mean rtph264depay sets the flag?
> >
> > Thanks
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