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  1. Member Budman1's Avatar
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    Jul 2012
    Search Comp PM
    I have a video that is 13 seconds long. I padded it front and back for 5 seconds with Tpad filter making the entire video 23 seconds long. I copied null audio to the front for 5 seconds so that now I have a video with 5 seconds silence(during the cloned/subtitled portion), 13 seconds original that syncs with the video. But anything I join to it moves the second videos audio up to fill the gap at the end of the first video, causing sync problems.

    I have looked everywhere for some way to pad the end of the first videos 18 seconds to achieve a total of 23 seconds that matches with the video (5 seconds silence, 18 seconds original audio, 5 seconds silent audio). Nothing works since none of the hits I have found want to add at the end.
    So far I have tried from examples:

    ffmpeg -i VIDEO -i AUDIO -filter_complex "[1:0]apad" -shortest OUTPUT

    Mediainfo says 18 seconds audio no matter what I try.
    Does anyone know a way to add silent audio to the end of the first, or join a second video without losing sync as mentioned anove, preferably with ffmpeg.?
    Thank you
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  2. Member Cornucopia's Avatar
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    Oct 2001
    Deep in the Heart of Texas
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    Just concat with an ACTUAL clip of silence. 2 second search found "random noise generator" online, which you could generate noise for 5 sec & save as wav file. The trick: use 0% volume.

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  3. I'm hopeless with ffmpeg, but in Avisynth, if I understand correctly.

    Audio = FFAudioSource("E:\Video.mkv")
    Silence = BlankClip(Audio)

    NewAudio = \
    Silence.AudioTrim(0, 5.000)\
    +Audio.AudioTrim(0, 0)\
    +Silence.AudioTrim(0, 5.000)

    return NewAudio

    Foobar2000 while converting, with the Affix Silence DSP in the conversion chain (screenshot below).

    I received your PM but haven't managed to look at your links yet. I'm finally getting over some bug I picked up and I've had a few other distractions, but I thought I'd let you know I'm not ignoring it. Hopefully by tomorrow my brain will be working again.

    Image Attached Thumbnails Click image for larger version

Name:	Affix Silence.jpg
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  4. Member Budman1's Avatar
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    Jul 2012
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    Thank you Cornucopia. The problem with that is that my intentions are to freeze frame the 1st and last frames for 5 seconds and embed subtitles in them to be read for 5 seconds.
    If I use a blank 'Clip' it will actually be a video that's added, which I did not wish. I also tried creating a silent AAC for 5 seconds but that is a lor of effort and causes encoding multiple times (one to clone, once to add silence, maybe once to add subtitles. I found a way to do all at once.

    I finally, after much trial and error,found what works. My video is 13.247 seconds so I pull the stats and create the following string;

    ffmpeg -i "C:\Users\Bud\Documents\Applian\Replay Media Catcher\Segments\Video.mp4" -vf scale=w=854:h=480:force_original_aspect_ratio=1,pad=854:480:(ow-iw)/2:(oh-ih)/2,tpad=start_mode=clone:start_duration=5,tpad=stop_mode=clone:stop_duration=10,"subtitles='C\:\\Users\\Bud\\Desktop\\TrimNMerge\\TrimNMerge\\bin\\Debug\\work\\':force_style=FontName='Arial,PrimaryColour=&H00FFFFFF,Fontsize=30,Alignment=10'" -af "adelay=5000|5000,apad=whole_dur=23.247" -vcodec libx264 -crf 20 -b:v 400K -bufsize:v 400K -r 29.97 -acodec aac -ab 129k -ar 44.1k -max_muxing_queue_size 9999 "C:\Users\Bud\Documents\Applian\Replay Media Catcher\Segments\Subbed_Resized_5_10_Video.mp4"
    The stop duration of clone is 5 seconds but has to be adjusted to 10 seconds (also noted in the name) because FFMPEG uses TOTAL padding (5 front + 5 end = 10). All single quotes and double quotes are necessary or it fails. As it is it throws some kind of error about reading only the -VF and -AF and disregarding others but it works anyway. NOt sure what it means since they are separated with ',' and they are the only ones???

    Only '-vf scale=w=854:h=480:force_original_aspect_ratio=1,pad=854:480:(ow-iw)/2:(oh-ih)/2,tpad=start_mode=clone:start_duration=5,tpad=stop_mode=clone:stop_durat
    ze=30,Alignment=10'' read, ignoring remaining -vf options: Use ',' to separate filters Only '-af adelay=5000|5000,apad=whole_dur=23.247' read, ignoring remaining -af o
    ptions: Use ',' to separate filters
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