GST_BUFFER_FLAG_DROPPABLE to detect keyframes?

[Olivier Crête]

Hi,

DROPPABLE isn't related to keyframes.. !DELTA is all you need. A
keyframe could even be droppable.

Olivier

On Mon, 2020-02-17 at 17:26 +0100, Juan Navarro wrote:
> Should GST_BUFFER_FLAG_DROPPABLE be considered when trying to identify
> video keyframes?
> 
> Docs on buffer flags are a bit too precise about what each flag does,
> but tend to be vague about what it actually _means_ in the more general
> sense, so I haven't been able to discern if this is enough to classify a
> buffer as keyframe:
> 
> !GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_DELTA_UNIT)
> 
> or if this would be a better / more robust choice:
> 
> !( GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_DELTA_UNIT)
>      || GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_DROPPABLE) )
> 
> or if these two flags are related in such way that they will always come
> together when the frame is indeed a keyframe, and thus this expression
> would be better:
> 
> !( GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_DELTA_UNIT)
>      && GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_DROPPABLE) )
> 
> Here they say "maybe" it's a good idea checking for "DROPPABLE":
> https://stackoverflow.com/a/52873803
> 
> And here it is mentioned that "NON_DROPPABLE" might mean keyframe, so I
> guess by extension we should assume that "DROPPABLE" might mean
> non-keyframe:
> https://gstreamer.freedesktop.org/releases/1.14/ (under "New RTP
> features and improvements")
> 
> But I'm missing a more concrete piece of text talking about the
> implications of DELTA_UNIT, DROPPABLE / NON_DROPPABLE, and the meaning
> of their possible combinations, if any.
> 
> Could someone that knows about this share a bit of know-how?
> 
> Thanks :)
> Juan
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-- 
Olivier Crête
olivier.crete at collabora.com