Microsoft Bob

Just a short, simple blog for Bob to share some tips and tricks.

Be sure to check out my non-technical blog at www.bobsbasement.net.

Month List

Fixing Underwater Videos with FFMPEG

I ran into an interesting predicament: I couldn't get the right color adjustment settings to work in my video editor to correct some underwater videos from a scuba diving trip. After much trial and error, I came up with an alternative method: I have been able to successfully edit underwater photos to restore their color, so I used FFMPEG to export all of the frames from the source video as individual images, then I used a script to automate my photo editor to batch process all of the images, then I used FFMPEG to reassemble the finished results into a new MP4 file.

The following video of a Goliath Triggerfish in Bora Bora shows a before and after of what that looks like. Overall, I think the results are promising, albeit via a weird and somewhat time-consuming hack.

Exporting Videos as Images with FFMPEG

Here is the basic syntax for automating FFMPEG to export the individual frames:

ffmpeg.exe -i "input.mp4" -r 60 -s hd1080 "C:\path\%6d.png"

Where the following items are defined:

-i "input.mp4" specifies the source MP4 file
-r 60 specifies the frame rate for the video at 60fps
-s hd1080 specifies 1920x1080 resolution (there are others)
"C:\path\%6d.png" specifies the directory for storing the images, and specifies PNG images with file names which are numerically sequenced with a width of 6 digits (e.g. 000000.png to 999999.png)

Combining Images as a Video with FFMPEG

Here is the basic syntax for automating FFMPEG to combine the individual frames back into an MP4 file:

ffmpeg.exe -framerate 60 -i "C:\path\%6d.png" -c:v libx264 -f mp4 -pix_fmt yuv420p "output.mp4"

Where the following items are defined:

-framerate 60 specifies the frame rate for the output video at 60fps (note that specifying a different framerate than you used for exporting could be used to alter the playback speed of the final video)
-i "C:\path\%6d.png" specifies the directory where the images are stored, and specifies PNG images with file names which are numerically sequenced with a width of 6 digits (e.g. 000000.png to 999999.png)
-c:v libx264 specifies the H.264 codec
-f mp4 specifies an MP4 file
-pix_fmt yuv420p specifies the pixel format, which could also specify "rgb24" instead of "yuv420p"
"output.mp4" specifies the final MP4 file
Posted: Sep 23 2016, 02:45 by Bob | Comments (0)
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How to Merge a Folder of MP4 Files with FFmpeg (Revisted)

I ran into an interesting situation the other day: I had a bunch of H.264 MP4 files which I had created with Handbrake that I needed to combine, and I didn't want to use my normal video editor (Sony Vegas) to perform the merge. I'm a big fan of FFmpeg, so I figured that there was some way to automate the merge without having to use an editor.

I did some searching around the Internet, and I couldn't find anyone who was doing exactly what I was doing, so I wrote my own batch file that combines some tricks that I have used to automate FFmpeg in the past with some ideas that I found through some video hacking forums. Here is the resulting batch file, which will combine all of the MP4 files in a directory into a single MP4 file named "ffmpeg_merge.mp4", which can be renamed to something else:

@echo off

if exist ffmpeg_merge.mp4 del ffmpeg_merge.mp4
if exist ffmpeg_merge.tmp del ffmpeg_merge.tmp
if exist *.ts del *.ts

for /f "usebackq delims=|" %%a in (`dir /on /b *.mp4`) do (
ffmpeg.exe -i "%%a" -c copy -bsf h264_mp4toannexb -f mpegts "%%a.ts"
)

for /f "usebackq delims=|" %%a in (`dir /b *.ts`) do (
echo file %%a>>ffmpeg_merge.tmp
)

ffmpeg.exe -f concat -i ffmpeg_merge.tmp -c copy -bsf aac_adtstoasc ffmpeg_merge.mp4

if exist ffmpeg_merge.tmp del ffmpeg_merge.tmp
if exist *.ts del *.ts

The merging process in this batch file is performed in two steps:

  • First, all of the individual MP4 files are remuxed into individual transport streams
  • Second, all of the individual transport streams are remuxed into a merged MP4 file

Here are the URLs for the official documentation on each of the FFmpeg switches and parameters that I used:

By the way, I realize that there may be better ways to do this with FFmpeg, so I am open to suggestions. ;-]

Posted: Jul 06 2014, 00:04 by Bob | Comments (0)
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