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

[Andy Shaules]

On 4/10/2017 4:37 PM, YIRAN LI wrote:
>
>
> 2017-04-10 7:16 GMT+10:00 bowljoman <bowljoman at gmail.com 
> <mailto: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
> ​
>
>     Sent from my T-Mobile 4G LTE Device
>
>     -------- Original message --------
>     From: YIRAN LI <mrfun.china at gmail.com <mailto: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
>     <mailto:libav-user at ffmpeg.org>>, FFmpeg user questions
>     <ffmpeg-user at ffmpeg.org <mailto: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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It doesnt matter what the inputs are. just convert them to one or the 
other type. the final stream can be assembled with all avc or avcc 
packets. choose one or the other.

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