Create Short Preview from Video

Discussion

1. hatoro

   As always thanks for sharing your thoughts. I am interested in the details of said and element swap. Surely it involves async loading of video onhover? I would use webpack, what about you?
2. John Brown

   “We’re all grown ups” Absolutely wrong! I’m in my early 17’s. Still visiting this site. Moreover if we grown up so it means we seen porn or gave reference from those nasty sites? ridiculus logic.
• Tom

  He was referring to personal mindset not physical age. Get over it.
3. Jonathan

   Awesome! Thanks for the post + script. :) I’m interested in writing a script to pull a poster image out of a webm or mp4 file in order to automate the process a little. Just started scripting with ffmpeg. I’ll checkout your “Create an Image Preview from a Video” post now.
4. Sander

   To calculate the correct duration I had to change the ‘interval’ line to:

   interval=$((($length-$starttimeseconds)/$desiredsnippets))
5. Sander

   If you want more than 9 snippets, the sorting of the snippets is out of order (1, 10, 11, 12, 2, 3, 4…). I’ve changed this part of the code to work with leading zeros (as many as needed) to have the snippets in the correct order when they are concatenated:

   for i in $(seq -w 1 $desiredsnippets)
     do
       # Format the second marks into hh:mm:ss format
       start=$(($(($(echo $i | sed 's/^0*//')*$interval))+$starttimeseconds))
       formattedstart=$(printf "%02d:%02d:%02d\n" $(($start/3600)) $(($start%3600/60)) $(($start%60)))
       echo 'Generating preview part ' $i $formattedstart
       # Generate the snippet at calculated time
       ffmpeg -i $sourcefile -vf scale=$dimensions -preset fast -qmin 1 -qmax 1 -ss $formattedstart -t $snippetlengthinseconds $tempdir/$i.$extension &>/dev/null
   done
   
• john nguyen

  this fixed order but
  60mins video, 30 snippets -> 2mins each snippets
  so it will start at 0:02:00 -> 0:04:00 ->
  is there have anyway to make it start at 0:00:00 (1st snippet) -> 0:02:00 (2nd snippet) -> ….

  on pornhub i see it use 12 snippets, each snippets is 1s i think, and it start from beginning of each snippets
6. user135711

   I would change:

   extension=${destfile#*.}

   to

   extension=${destfile##*.}

   in case the file name has periods.
7. user

   i keep getting

   list.txt: No such file or directory

   even if i create the list.txt file it gets removed when i run the script and the same error appears ?
8. Fatih Akgun

   i get this error when i run

   $ ./preview.sh input.mp4 output.mp4
   
   list.txt: No such file or directory
   Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
     Metadata:
       major_brand     : isom
       minor_version   : 512
       compatible_brands: isomiso2avc1mp41
       encoder         : Lavf56.40.101
     Duration: 00:42:01.20, start: 0.000000, bitrate: 255 kb/s
       Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 480x270, 219 kb/s, 15 fps, 15 tbr, 15360 tbn, 30 tbc (default)
       Metadata:
         handler_name    : VideoHandler
       Stream #0:1(und): Audio: mp3 (mp4a / 0x6134706D), 22050 Hz, mono, s16p, 32 kb/s (default)
       Metadata:
         handler_name    : SoundHandler
   snippets/1.mp4: No such file or directory
   
9. Fatih Akgun

   removing

   &>/dev/null

   fixed it but why ?
10. Fatih Akgun

    btw could this script be converted in php
11. Fatih Akgun

    ok i finnaly made it in php

    here is the file https://gist.github.com/AkgunFatih/88c2241865c25e40a50edc4e24679a94

    i only need some checks and refactor but it works :)
• Edward French

  What happened to the link? Could do with this in PHP if anyone has it.
12. Armin

    To speed things up you should put the -ss switch before the -i switch. Doing it your way is slower. You’re doing output filtering, so it takes a frame, translates it and then checks if it is in the legal range. The other way around it checks the legal range before translating the frame.
    You can also use the -thread switch with $(nproc) as argument. This spawns as many threads as there are cores in the CPU.
13. Philip

    Mr. Walsh, this is exactly what I was looking for! Thank you!
    And @Armin, thank you. Using Linux time bringing the -ss to the front brought my real time down from 34 seconds to 4 SECONDS. Wow. Thanks.

    I was familiar with trimming clips with ffmpeg and definitely skimmed past a post or two about the -ss placement in the past but this was a real-life example and definitely made me take it more seriously
14. Rundik

    Here is a working optimized version with faster encoding and optimized mp4 parameters which makes the file size 10 times less in my case.

    sourcefile=$1
    destfile=$2
    
    # Overly simple validation
    if [ ! -e "$sourcefile" ]; then
      echo 'Please provide an existing input file.'
      exit
    fi
    
    if [ "$destfile" == "" ]; then
      echo 'Please provide an output preview file name.'
      exit
    fi
    
    # Get video length in seconds
    length=$(ffprobe $sourcefile  -show_format 2>&1 | sed -n 's/duration=//p' | awk '{print int($0)}')
    
    # Start 20 seconds into the video to avoid opening credits (arbitrary)
    starttimeseconds=20
    
    # Mini-snippets will be 2 seconds in length
    snippetlengthinseconds=2
    
    # We'll aim for 5 snippets spread throughout the video
    desiredsnippets=5
    
    # Ensure the video is long enough to even bother previewing
    minlength=$(($snippetlengthinseconds*$desiredsnippets))
    
    # Video dimensions (these could probably be command line arguments)
    dimensions=640:-1
    
    # Temporary directory and text file where we'll store snippets
    # These will be cleaned up and removed when the preview image is generated
    tempdir=snippets
    listfile=list.txt
    
    # Display and check video length
    echo 'Video length: ' $length
    if [ "$length" -lt "$minlength" ]
    then
      echo 'Video is too short.  Exiting.'
      exit
    fi
    
    # Loop and generate video snippets
    mkdir $tempdir
    interval=$(($length/$desiredsnippets-$starttimeseconds))
    for i in $(seq 1 $desiredsnippets)
    do
        # Format the second marks into hh:mm:ss format
        start=$(($(($i*$interval))+$starttimeseconds))
        formattedstart=$(printf "%02d:%02d:%02d\n" $(($start/3600)) $(($start%3600/60)) $(($start%60)))
        echo 'Generating preview part ' $i $formattedstart
        # Generate the snippet at calculated time
        ffmpeg -i $sourcefile -vf scale=$dimensions -preset fast -qmin 1 -qmax 1 -ss $formattedstart -t $snippetlengthinseconds -threads $(nproc) $tempdir/$i.mp4
    done
    
    # Concat videos
    echo 'Generating final preview file'
    
    # Generate a text file with one snippet video location per line
    # (https://trac.ffmpeg.org/wiki/Concatenate)
    for f in $tempdir/*; do echo "file '$f'" >> $listfile; done
    
    # Concatenate the files based on the generated list
    ffmpeg -f concat -safe 0 -i $listfile -threads $(nproc) -an -tune zerolatency -x264opts bitrate=2000:vbv-maxrate=2000:vbv-bufsize=166 -vcodec libx264 -f mpegts -muxrate 2000K -y $destfile.mp4
    
    echo 'Done!  Check ' $destfile '.mp4!'
    
    # Cleanup
    rm -rf $tempdir $listfile
    
    
15. Rundik

    Unfortunately I can’t edit my comment. Move -ss to the beginning like that for much faster speeds

    ffmpeg -ss $formattedstart -t $snippetlengthinseconds -i $sourcefile -vf scale=$dimensions -preset fast -qmin 1 -qmax 1 -threads $(nproc) $tempdir/$i.mp4
    
16. Mod

    I’m trying to do the exact same thing but using JavaScript. By chance do you know how this is done?
17. Mod

    I’m trying to do the same exact thing but using JavaScript and Python; I’m using Django for my web site. By any chance do you know how to do it this way or can maybe point me in the right direction. Thank you very much.
18. ARandomGuy

    Does know how to predict which frames are going to be used to let the uploader choose the video thumbnail in pornhub and similar sites? The workaround I found is to upload a video with the same number of frames with only a frame counter, check which frames are selected and then re-render the video with a title thumbnail in one of those frames. Of course, it’s a pain and it would be great if I could do the rendering only once..
19. Vladimir Bartalos

    Hi guys, you guys are coding gods to me. Thank you very much, I had problems even to make this work but now I finally did.

    Is it please possible to use this in batch mode and without need to manually naming input output files ?

    Thank you
    Vlad
20. faragona

    Here is a working PowerShell script for Windows users.

    $sourcefile = $args[0]
    $destfile = $args[1]
    
    # Overly simple validation
    if (-not (Test-Path $sourcefile)) {
        Write-Host 'Please provide an existing input file.'
        exit
    }
    
    if ($destfile -eq "") {
        Write-Host 'Please provide an output preview file name.'
        exit
    }
    
    # Get video length in seconds
    $length = (ffprobe $sourcefile  -show_format 2>&1 | Select-String -Pattern 'duration=').Line -replace 'duration='
    $length = $length.split(".")[0]
    
    # Start 20 seconds into the video to avoid opening credits (arbitrary)
    $starttimeseconds = 20
    
    # Mini-snippets will be 2 seconds in length
    $snippetlengthinseconds = 2
    
    # We'll aim for 5 snippets spread throughout the video
    $desiredsnippets = 10
    
    # Ensure the video is long enough to even bother previewing
    $minlength = $snippetlengthinseconds * $desiredsnippets
    
    # Video dimensions (these could probably be command line arguments)
    $dimensions = "640:-1"
    
    # Temporary directory and text file where we'll store snippets
    # These will be cleaned up and removed when the preview image is generated
    $tempdir = "snippets"
    $listfile = "list.txt"
    
    # Display and check video length
    Write-Host "Video length: $length"
    Write-Host "$minlength"
    if ($minlength -gt $length) {
        Write-Host 'Video is too short. Exiting.'
        exit
    }
    
    # Loop and generate video snippets
    mkdir $tempdir
    $interval = ($length - $starttimeseconds) / $desiredsnippets - $desiredsnippets
    for ($i = 1; $i -le $desiredsnippets; $i++) {
        # Format the second marks into hh:mm:ss format
        $start = ($i * $interval) + $starttimeseconds
        $formattedstart = "{0:hh\:mm\:ss}" -f ([timespan]::FromSeconds($start))
        Write-Host "Generating preview part $i $formattedstart"
        # Generate the snippet at calculated time
        ffmpeg -ss $formattedstart -t $snippetlengthinseconds -i $sourcefile -vf scale=$dimensions -preset fast -qmin 1 -qmax 1 -threads 8 $tempdir/$i.mp4
    }
    # Concat videos
    Write-Host 'Generating final preview file'
    gci -path "./snippets"| ren -n {[regex]::replace($_.BaseName, '\d+', {"$args".PadLeft(2, '0')})}
    # Generate a text file with one snippet video location per line
    # (https://trac.ffmpeg.org/wiki/Concatenate)
    Get-ChildItem $tempdir | ForEach-Object { "file '$($_.FullName)'" } | Out-File -encoding ASCII list.txt
    # Concatenate the files based on the generated list
    ffmpeg -f concat -safe 0 -i $listfile -threads 8 -an -tune zerolatency "$destfile" | Out-Null
    
    Write-Host "Done! Check $destfile!"
    
    # Cleanup
    Remove-Item -Path $tempdir, $listfile -Recurse -Force