Video Quality/Resolution Problem in Gstreamer

[Ian Davidson]

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.


On 06/08/19 20:47, pisymbol . wrote:
>
>
> On Tue, Aug 6, 2019 at 4:51 AM Ian Davidson 
> <id012c3076 at blueyonder.co.uk <mailto: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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