[Libav-user] Editing a video file

[Joshua Kordani]

On 10/14/14 6:46 PM, Ben Mesander wrote:
>
>
> On Tue, Oct 14, 2014 at 1:50 PM, Sethuraman V 
> <techmail.sethu at gmail.com <mailto:techmail.sethu at gmail.com>> wrote:
>
>
>     I can't understand why an 'I' frame read from a video file can't
>     be written/encoded back to the video file. For other frames 'P'
>     and 'B' there are dependencies, so writing/encoding the complete
>     frame can't be done, but why this applies to 'I' frame too, which
>     is a separate frame on its own.
>
>
> Hi,
>
>   The P and B frames depend on nearby I frames. Also, when you 
> re-encode an I frame, there is no reason to expect it to be the same 
> size as it was  before.
>
>   So in the general case, you have to re-encode every frame after the 
> I frame in addition to the I frame. This can of course vary based on 
> GOP structure.
>
>   It's not a practical thing to do.
>
> Regards,
> Ben
>
>
>
> -- 
> *Ben Mesander*
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why does the differing size of the new I frame matter?

Joshua Kordani
LSA Autonomy

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