I have the recording of a zoom meeting where I need to cut out a
portion from and the first little bit has to be blacked out.
I use the following command:
ffmpeg -y \
-ss 00:26:05 \
-to 00:44:04 \
-i input.mp4 \
-vf "
drawbox=enable='between(t, 0, 1.6)' :
color = black :
w = in_w :
h = in_h :
thickness = fill
" \
-acodec copy \
-vcodec libx264 \
-crf 23 \
-preset veryfast \
output.mkv
This creates a seemingly correct file, with one little problem: the
time starts at 00:00:27 and ends at 00:18:26. (As displayed by the
player mpv.)
When I play it with vlc I find out that the 27 seconds of audio are
before the video. Mpv starts with the video, but vlc starts with the
audio.
What could be the problem?
I am using ffmpeg version 4.3.3-0+deb11u.
The metadata of the input file:
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from
'GMT20211216-184321_Recording_640x360.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: isommp42
creation_time : 2021-12-16T18:43:21.000000Z
Duration: 01:21:57.47, start: 0.000000, bitrate: 646 kb/s
Chapter #0:0: start 0.000000, end 4917.440000
Metadata:
title : Recording Started
Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 32000 Hz, mono,
fltp, 126 kb/s (default)
Metadata:
creation_time : 2021-12-16T18:43:21.000000Z
handler_name : AAC audio
Stream #0:1(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x360,
518 kb/s, 25 fps, 25 tbr, 30k tbn, 60k tbc (default)
Metadata:
creation_time : 2021-12-16T18:43:21.000000Z
handler_name : H.264/AVC video
encoder : AVC Coding
Stream #0:2(und): Data: bin_data (text / 0x74786574)
Metadata:
creation_time : 2021-12-16T18:43:21.000000Z
handler_name : Text
The metadata of the output file:
Input #0, matroska,webm, from 'howToReachYourNewYearsResolutionsIn2022.mkv':
Metadata:
COMPATIBLE_BRANDS: isommp42
MAJOR_BRAND : mp42
MINOR_VERSION : 0
ENCODER : Lavf58.45.100
Duration: 00:18:26.34, start: 0.000000, bitrate: 346 kb/s
Chapter #0:0: start 0.000000, end 3352.440000
Metadata:
title : Recording Started
Stream #0:0: Video: h264, none, 640x360, 25 fps, 25 tbr, 1k tbn, 2k tbc
(default)
Metadata:
HANDLER_NAME : H.264/AVC video
ENCODER : Lavc58.91.100 libx264
DURATION : 00:18:26.336000000
Stream #0:1: Audio: aac (LC), 32000 Hz, mono, fltp (default)
Metadata:
HANDLER_NAME : AAC audio
DURATION : 00:18:26.336000000
By the way when I create a mp4 file (which is not really an option,
because I need to create chapters), the video seems to be correct,
with one strange thing: both mpv and vlc think it is 00:55:52 long.
Which it is not: it stops where it should 00:17:59.
--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof
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