[FFmpeg-user] Suggestions for FFmpeg: support a simpler command line for concatenating audio files with a specified overlap

a microspec2k1 at hotmail.com
Sun Jan 29 19:30:46 EET 2017

Hello, after hunting around ffmepg.org, I could not find where to post suggestions for FFmpeg developers, so if this mailing list is the appropriate place here you go otherwise please let me know:

  1.  I have a need to concatenate programmatically several short (< 1 second) mp3 files but with a specific overlap for example 100ms, the current solution is a command line of this form
1.  ffmpeg -i 1.mp3 -i 2.mp3 -i 3.mp3 -i 4.mp3
2.         -filter_complex
3.           "[1]adelay=delay1[b];
4.            [2]adelay=delay2[c];
5.            [3]adelay=delay3[d];
6.            [0][b][c][d]amix=4"
7.  out.mp3

     *   However this forces me to derive each file durations and do the math.  I was hoping if you would consider supporting something that would not require retrieving the durations and just specify the relative delays during concatenation.  Here are a couple of examples

     *   Delay all input file by the same amount
ffmpeg -i 1.mp3 -i 2.mp3 -i 3.mp3 -i 4.mp3 -filter_complex "delay=100; amix=4"

     *   Delay each input by the specified amount or zero if not specified.
ffmpeg -i 1.mp3 -i 2.mp3 -i 3.mp3 -i 4.mp3 -filter_complex "[1]delay=100; [2]delay=20; amix=4"

     *   Of course this may not be generalized enough to offer the most flexibility so I will let you decide on the final form of the options, but you get the point.

     *   NOTE: I am using C-Sharp to build the command line for other FFmpeg tasks, however the simpler command line above would allow easier prototyping from a batch file without requiring hardcoding exact value for delay1, delay2,...., delayN
Thank you.

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