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From: Jolly Roger <jollyroger@pobox.com>
Newsgroups: comp.sys.mac.apps,comp.sys.mac.system
Subject: Re: Video Editing
Date: 13 Nov 2020 21:06:53 GMT
Organization: People for the Ethical Treatment of Pirates
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On 2020-11-13, gtr <xxx@yyy.zzz> wrote:
> On 2020-11-13 10:22:07 +0000, Lewis said:
>
>> In message <rojmhs$eqc$1@dont-email.me> gtr <xxx@yyy.zzz> wrote:
>>> I'm looking for an app or utility, that will allow me to do the following:
>> 
>>> Feed it a video file, *type in a starting time code and and ending time
>>> code*, and have it spit out the clip into separate file.  I need to
>>> feed it 30 or more such files, culling 4 portions of video from each,
>>> all of them at different times, so it has to be a realitively clean
>>> interaction like this.
>> 
>> I do this via the command line with ffmpeg
>> 
>> #v+
>> ffmpeg -i infile.mp4 -ss START -to END outfile.mp4
>> #v-
>
> I heard that upstream and appreciate it.  There the command is somewhat 
> different from yours:
>
> ffmpeg -i input.mov -ss START -t LENGTH -acodec copy -vcodec copy output.mov

You can choose which to use based on your needs:

* The -t switch is for specifying the length of the clip.
* The -to switch is for specifying the end time.

The "-*codec copy" switch just enables this optional feature:

---
Stream copy

Stream copy is a mode selected by supplying the "copy" parameter to the
-codec option. It makes ffmpeg omit the decoding and encoding step for
the specified stream, so it does only demuxing and muxing. It is useful
for changing the container format or modifying container-level metadata.

The diagram above will, in this case, simplify to this:

                _______              ______________            ________
               |       |            |              |          |        |
               | input |  demuxer   | encoded data |  muxer   | output |
               | file  | ---------> | packets      | -------> | file   |
               |_______|            |______________|          |________|

Since there is no decoding or encoding, it is very fast and there is no
quality loss. However, it might not work in some cases because of many
factors. Applying filters is obviously also impossible, since filters
work on uncompressed data.
---
Reference: ffmpeg manual

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JR