[Libav-user] Editing a video file

[Ben Mesander]

On Tue, Oct 14, 2014 at 1:50 PM, Sethuraman V <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



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