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  1. Member
    Join Date: Dec 2013
    Location: Los Altos
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    Hi, I have a ffmpeg problem that I'm hoping someone can help me sort out:

    I'm trying to create a fade-in effect and fade-out effect on a video, but it ends up with some corruption.

    Here are the major steps I'm doing:

    1) get 3 second segment from the beginning of the video and 3 second segment from end of the video (and keeping a copy of the middle part)
    2) add fade in and fade out effects to the small begin/end clips
    3) rejoin the three clips back together for an overall fade-in/fade-out

    The corruption appears to only effect the middle segment of the video - I get Green Screen flashes, etc.

    (there are a few other minor steps I do which I will mention below)

    Here is a copy of the ffprobe on the input video (in case it helps)

    user@ubuntu:/var/www$ /home/user/bin/ffprobe all.mp4
    ffprobe version git-2013-12-06-59398c1 Copyright (c) 2007-2013 the FFmpeg developers
    built on Nov 30 2013 09:45:12 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
    configuration: --prefix=/home/user/ffmpeg_build --extra-cflags=-I/home/user/ffmpeg_build/include --extra-ldflags=-L/home/user/ffmpeg_build/lib --bindir=/home/user/bin --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree
    libavutil 52. 56.100 / 52. 56.100
    libavcodec 55. 45.100 / 55. 45.100
    libavformat 55. 22.100 / 55. 22.100
    libavdevice 55. 5.102 / 55. 5.102
    libavfilter 3. 92.100 / 3. 92.100
    libswscale 2. 5.101 / 2. 5.101
    libswresample 0. 17.104 / 0. 17.104
    libpostproc 52. 3.100 / 52. 3.100
    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'all.mp4':
    major_brand : isom
    minor_version : 512
    compatible_brands: isomiso2avc1mp41
    encoder : Lavf55.22.100
    Duration: 00:00:14.14, start: 0.000000, bitrate: 5980 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 5762 kb/s, 29.97 fps, 30 tbr, 30k tbn, 59.94 tbc (default)
    handler_name : VideoHandler
    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 235 kb/s (default)
    handler_name : SoundHandler

    I have a routine that will tell me the number of seconds in a video, the all.mp4 video is 14 seconds in length

    Here is my command I am using to extract the three parts of the video:
    ffmpeg -y -i /var/www/all.mp4 -vcodec copy -acodec copy -ss 00:00:00 -to 00:00:03 -sn /var/www/a.tmp.mp4 \
    -vcodec copy -acodec copy -ss 00:00:03 -to 00:00:11 -sn /var/www/b.tmp.mp4 \
    -vcodec copy -acodec copy -ss 00:00:11 -to 00:00:14 -sn /var/www/c.tmp.mp4

    I have a routine that counts the number of frames in a segment, I use it on the a.tmp.mp4 and c.tmp.mp4 files (python code below)
    cmd = "ffmpeg -i " + fileName + " -vcodec copy -f rawvideo -y /dev/null 2>&1"

    I look at the output and find the number of frames: (python code below)
    numFrames ='frame\W+(\d+)', output).group(1)

    using the numFrames for a.tmp.mp4 (89) and c.tmp.mp4 (58) I add the fade in and fade out effect:

    ffmpeg -i /var/www/a.tmp.mp4 -vf 'fade=in:0:89' -y /var/www/a_withfade.tmp.mp4
    ffmpeg -i /var/www/c.tmp.mp4 -vf 'fade=out:0:58' -y /var/www/c_withfade.tmp.mp4

    I then create a concat.txt file with the contents:
    file 'a_withfade.tmp.mp4'
    file 'b.tmp.mp4'
    file 'c_withfade.tmp.mp4'

    ffmpeg -f concat -i /var/www/concat.txt -c copy -y /var/www/all.mp4

    (yes, I want to overwrite my original file)

    I have examined each of the three parts of the video individually and they all play fine
    (ie, a_withfade.tmp.mp4, b.tmp.mp4 and c_withfade.tmp.mp4)

    As I mentioned, the middle portion becomes corrupted as a result of the joining of the files.

    Any pointers would be appreciated, I have been working with video for a week+ now so I'm still somewhat of a newcomer to ffmpeg, etc.

    I'm guessing that this has to do with the way the mp4 video is compressed vs rawvideo but I'm not really sure.

    I have found that some people have fixed corrupted videos using a command like the following (which doesn't help me):

    ffmpeg -i all.mp4 -vcodec copy -acodec copy all_fixed.mp4

    I can upload the video if it will help, but I suspect that it won't help with this problem.
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  2. try the free NLE AviUtl. At least that will be much easier to do the fading in a GUI.
    Make sure you check the "video guide" by x-racer first, and you may dig into the details from the "Non-official guide" by me.
    The links to both guides are already listed on AviUtl 's page.
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