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genderbee
Asked: 2019-09-24 13:17:17 +0800 CST

Use bash and ffmpeg in 18.04 to concatenate multiple 3GP files to one 3GP file, matching by date YYYYMMDD in filename

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I have these example files in an Ubuntu 18.04 system: 

VID_20190407_160033.3gp  
VID_20190407_161444.3gp  
VID_20190407_161609.3gp  

VID_20190415_183315.3gp  
VID_20190415_183411.3gp  
VID_20190415_192712.3gp  

VID_20190420_124435.3gp  
VID_20190420_125755.3gp  
VID_20190420_130214.3gp  
VID_20190420_141700.3gp

And I want to concatenate 3GP files by a script (perhaps with ffmpeg ?) into one file, selecting files by the YYYYMMDD date in the file name, with a result of:

VID_20190407.3gp
VID_20190415.3gp
VID_20190420.3gp

What is the best way to script that?

System

Linux local 5.0.0-29-lowlatency #31-Ubuntu SMP PREEMPT Thu Sep 12 14:13:01 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

Thank you.

bash files ffmpeg join 18.04

1 Answers

  1. Best Answer

    3GP files can be concatenated with the use of ffmpeg by a command similar to:

    ffmpeg -f concat -i <(find . -name 'YYYYMMDD_XXXXXX.3gp' -printf "file '$PWD/%p'\n") -c copy YYYYMMDD.3gp

    once you create a for-next loop to filter on the YYYYMMDD using the first instance of the first value for that as a variable, collect the _XXXXXX file name components, and step through them sequentially; then, move on to the next YYYYMMDD value and step through all its files.

    --

    An alternate and more elegant method using a virtual concat demuxer which has brought to my attention by llogan would be to

    A) count the number of files with the first YYYYMMDD prefix, then
    B) create a control file mylist.txt with a line for each of the files matching that date prefix, which would look like:

    $ cat mylist.txt
    file '/path/to/file1'
    file '/path/to/file2'
    file '/path/to/file3'
    file '/path/to/file4'

    or

    $ cat mylist.txt
    file '/path/to/YYYYMMDD_XXXXX1.3gp'
    file '/path/to/YYYYMMDD_XXXXX2.3gp'
    file '/path/to/YYYYMMDD_XXXXX3.3gp'
    file '/path/to/YYYYMMDD_XXXXX4.3gp'

    then C) execute 

    ffmpeg -f concat -i mylist.txt -c copy YYYYMMDD.mp4

    Now, you've concatenated the first file set. Step on to the next YYYYMMDD group and repeat.

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