Speeding up playback speed

[suntong]

Speeding up playback speed needed.

[suntong]

Fixed:

$ ffcvt -force -f "$FFCVT_FTC" --Speed 1.28

== Transcoding: Nice_scenic_videos_from_dashcam_With_Evening_sunset_view.mp4
] ffmpeg -i Nice_scenic_videos_from_dashcam_With_Evening_sunset_view.mp4 -speed 2 -c:v libvpx-vp9 -b:v 0 -crf 42 -c:a libopus -b:a 64k -c:s copy -y -filter_complex [0:v]setpts=PTS/1.28[v];[0:a]atempo=1.28[a] -map [v] -map [a] Nice_scenic_videos_from_dashcam_With_Evening_sunset_view_.mkv

Done.
Org Size: 9765 KB
New Size: 6713 KB
Saved:    31% with 3052 KB
Time: 1m55.215753905s at 2022-01-02 17:48:07


Transcoding completed in 1m55.216193021s
Org Size: 9 MB
New Size: 6 MB
Saved:    31%

It works. However, there is a caveat --

Using --Speed and -Cut together doesn't work as expected:

$ ffcvt -force -f "$FFCVT_FTC" --Speed 1.28 -C 00:00:40-00:00:50 -C 00:00:53-00:00:56

== Transcoding: Nice_scenic_videos_from_dashcam_With_Evening_sunset_view.mp4
] ffmpeg -i Nice_scenic_videos_from_dashcam_With_Evening_sunset_view.mp4 -speed 2 -c:v libvpx-vp9 -b:v 0 -crf 42 -c:a libopus -b:a 64k -c:s copy -y -filter_complex [0:v]setpts=PTS/1.28[v];[0:a]atempo=1.28[a] -map [v] -map [a] -filter_complex [0:v]trim=start=40:end=50,setpts=PTS-STARTPTS[v0];[0:a]atrim=start=40:end=50,asetpts=PTS-STARTPTS[a0];[0:v]trim=start=53:end=56,setpts=PTS-STARTPTS[v1];[0:a]atrim=start=53:end=56,asetpts=PTS-STARTPTS[a1];[v0][a0][v1][a1]concat=n=2:v=1:a=1[vo][ao] -map [vo] -map [ao] Nice_scenic_videos_from_dashcam_With_Evening_sunset_view_.mkv

Done.
Org Size: 9765 KB
New Size: 7112 KB
Saved:    27% with 2653 KB
Time: 2m2.876558318s at 2022-01-02 17:52:08


Transcoding completed in 2m2.876771032s
Org Size: 9 MB
New Size: 6 MB
Saved:    27%

What I got was a full video, not the cut version.

I don't know why and whether that can be fixed. I'll worry about it later...

[suntong]

Tried

ffmpeg -i Nice_scenic_videos_from_dashcam_With_Evening_sunset_view.mp4 -speed 2 -c:v libvpx-vp9 -b:v 0 -crf 42 -c:a libopus -b:a 64k -c:s copy -y -filter_complex '[0:v]setpts=PTS/1.28;[0:a]atempo=1.28;[0:v]trim=start=40:end=50,setpts=PTS-STARTPTS[v0];[0:a]atrim=start=40:end=50,asetpts=PTS-STARTPTS[a0];[0:v]trim=start=53:end=56,setpts=PTS-STARTPTS[v1];[0:a]atrim=start=53:end=56,asetpts=PTS-STARTPTS[a1];[v0][a0][v1][a1]concat=n=2:v=1:a=1[vo][ao]' -map '[vo]' -map '[ao]' Nice_scenic_videos_from_dashcam_With_Evening_sunset_view_.mkv

and

ffmpeg -i Nice_scenic_videos_from_dashcam_With_Evening_sunset_view.mp4 -speed 2 -c:v libvpx-vp9 -b:v 0 -crf 42 -c:a libopus -b:a 64k -c:s copy -y -filter_complex '[0:v]setpts=PTS/1.28[v];[0:a]atempo=1.28[a];[v]trim=start=40:end=50,setpts=PTS-STARTPTS[v0];[a]atrim=start=40:end=50,asetpts=PTS-STARTPTS[a0];[v]trim=start=53:end=56,setpts=PTS-STARTPTS[v1];[a]atrim=start=53:end=56,asetpts=PTS-STARTPTS[a1];[v0][a0][v1][a1]concat=n=2:v=1:a=1[vo][ao]' -map '[vo]' -map '[ao]' Nice_scenic_videos_from_dashcam_With_Evening_sunset_view_.mkv

The first one still got full video, and the second one's timestamp doesn't seems right.

So, --Speed and -Cut cannot be used together.

Do them in separated steps instead, if needed.