Video Quality/Resolution Problem in Gstreamer

[Nicolas Dufresne]

Le mardi 06 août 2019 à 21:08 +0100, Ian Davidson a écrit :
>     Yes - although once you have seen a Key Frame, you can watch as
>       many (or as few) Deltas as you want.  But you can't start midway
>       through.
> 
>     If you want to be able to go backwards, you want to have lots of
>       key frames.  If you have a Key Frame followed by 100 Deltas, you
>       cannot view the last Delta frame without finding the Key frame and
>       then constructing all the intermediate deltas.

Also, strictly speaking, the key frame is not self sufficient.  You also need in many format sufficient headers, which are stream information. That why you often have option on pay-loaders and other peace of code to configure the "config-interval".
>     
> 
>     
> 
>     On 06/08/19 20:47, pisymbol . wrote:
> 
>     
> 
>     
> >       
> >         
> > 
> >         
> >         
> > 
> >         
> >           On Tue, Aug 6, 2019 at 4:51
> >             AM Ian Davidson <id012c3076 at blueyonder.co.uk>
> >             wrote:
> > 
> >           
> >           
> > > You asked "What is a Key
> > >             Frame?"
> > > 
> > >             
> > > 
> > >             If you think of a typical TV picture, much of the image
> > >             stays the same 
> > > 
> > >             from one frame to another.  You could create your video file
> > >             by storing 
> > > 
> > >             each frame in its entirety - but in order to reduce the
> > >             overall file 
> > > 
> > >             size we use 'Key Frames' and 'Delta Frames'. The Key Frame
> > >             has all the 
> > > 
> > >             pixels required to make up the picture - just like a still
> > >             photo. That 
> > > 
> > >             key frame will then be followed by a series of Delta Frames
> > >             which simply 
> > > 
> > >             note the differences from the previous frame.  If your video
> > >             is of a 
> > > 
> > >             news reader reading the news, the delta frames would detail
> > >             the mouth 
> > > 
> > >             moving and not much more.  If you were to try to pick up
> > >             your video in 
> > > 
> > >             the middle, you would have the detail of the mouth moving -
> > >             but you 
> > > 
> > >             would know nothing about the news reader's face.  Therefore,
> > >             you need to 
> > > 
> > >             include Key Frames from time to time to enable starting
> > >             'part-way through'.
> > > 
> > >           
> > 
> >           
> > 
> >           
> >           Ian, isn't the Key Frame also the start of what is known
> >             as a Group of Pictures (which is a complete set of Key and
> >             Delta frames)?
> >           
> > 
> >           
> >           -aps
> > 
> >           
> >         
> >       
> >       
> > 
> >       
> >       
> > 
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> >     
> 
>     
> 
>   
> 
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