[Libav-user] Editing a video file
jkordani at lsa2.com
Wed Oct 15 18:29:54 CEST 2014
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.
> 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.
> *Ben Mesander*
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why does the differing size of the new I frame matter?
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