[FFmpeg-user] JPGs->video1 ; MOV -> Mp4 video2 ; Concatenate - video2 audio OK but video is slow . .

Carl Eugen Hoyos ceffmpeg at gmail.com
Tue Mar 26 22:22:29 EET 2019

2019-03-26 21:15 GMT+01:00, Philip Rhoades <phil at pricom.com.au>:

> I converted 21 JPGs to a video with:

Usually, converting jpgs with the image2 input works better than concat.

>    ffmpeg -f concat -i concat_demuxer1.txt -vf scale=1024:576 -r 29.97

This framerate is never correct, a possible frame rate is 30000/1001
You can add the audio already in this step.

> output1.mp4
> I then added a silent audio track with:
>    ffmpeg -ar 44100 -acodec pcm_s16le -f s16le -ac 2 -channel_layout 2.1

The channel number and layout do not match.

> -i /dev/zero \
>      -i output${i}.mp4 \
>      -vcodec copy \
>      -acodec aac \
>      -shortest output${i}_silent.mp4

> I had another MOV file (fr=29.97) that I converted with:
>    newfn=`basename $fn .MOV`
>    ffmpeg  -i $fn -vf scale=1024:576 ./${newfn}.mp4
> When I concatenate them with (and other converted JPGs and MOVS on the
> end) using:
>    ffmpeg -f concat -i inputs.txt -vcodec copy -acodec copy \
> 2019-03-22_#1_XR_ClimateEmergencyDeclarationDayNSW_LoRes.mp4
> the concat succeeds OK but when I play the video, the audio is OK but
> then when it gets to the converted MOV section, people are moving in
> slow motion . .
> Another odd thing, the first 21 converted JPGs at 4 sec each correctly
> shows 84 sec when viewed with mpv but when the converted MOV starts it
> jumps to ~3m 50s . .
> So there is at least one problem but maybe two?  Can anyone tell me what
> I am missing?

You may have to re-encode, feel free to provide the complete, uncut
console output.

Carl Eugen

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