[Libav-user] re-encoding and transcode (codec copy) on same file.

[YIRAN LI]

2017-04-10 7:16 GMT+10:00 bowljoman <bowljoman at gmail.com>:

>
> sorry if this client top posts, but to answer, you can do 1 of 2 things.
> assume it is different and insert it before returning to the unprocessed
> clip. or you can check if they are different by doing a comparison.
>
>
> ​Thanks for your suggestion. Let's say if original H.264 video stream has
AVCC bitstream, no matter you encode 1st part with Annex-b or AVCC, as long
as it's different from orginal format, I won't be able to do codec copy
using readpacket/writepacket, right?

Thanks
​

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>
> -------- Original message --------
> From: YIRAN LI <mrfun.china at gmail.com>
> Date: 4/7/17 3:15 PM (GMT-08:00)
> To: "This list is about using libavcodec, libavformat, libavutil,
> libavdevice and libavfilter." <libav-user at ffmpeg.org>, FFmpeg user
> questions <ffmpeg-user at ffmpeg.org>
> Subject: [Libav-user] re-encoding and transcode (codec copy) on same file.
>
> Hi guys,
>
> I'm investigating if it's possible to do editing and transcode on same
> file.
>
> I mean use -vcodec copy, we can readout packets and write them directly
> into output file without re-encoding. But if it's possible, for example if
> I have a 2 mins video, re-encode 1st min because there're some effects
> applied to that region but copy 2nd part?
>
> My concern is, for example we know H.264 has extradata, if I re-encode
> first part but keep 2nd part, how if new extradata is different from old
> extradta?
>
> Anyone have suggestion on this? and any other possible problems doing this?
>
> Thanks
>
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