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03. November 2015 · Comments Off on Concatenating Audio Files in Windows with FFmpeg · Categories: Audio, Multimedia · Tags:
This guide demonstrates how to automate concatenating two or more audio files of the same format using FFmpeg while preserving the metadata in the merged file. A tested example batch file is provided to help illustrate. This guide is related to a previous post for concatenating audio files also with a batch file, but with using a different set of command-line tools for joining them.

clapper board

What is FFmpeg?

FFmpeg is an open-source and cross-platform command-line set of SW programs for recording, converting and streaming audio and video. First developed under Linux, compiled versions are available for most operating systems and platforms. It has since become one of the best-known and most widely used products of its type. FFmpeg is compatible with a large number of SW applications and it’s used in many popular SW products such as VLC Media Player, YouTube, and Handbrake. Although FFmpeg includes over 100 codecs and a mind-boggling number of possible combined command-line options, it’s not that difficult to use.

To demonstrate how easy it can be, FFmpeg.org provides this example command for converting input.mp4 to output.avi on its homepage:

$ ffmpeg -i input.mp4 output.avi

While the above example is simple, FFmpeg commands can also be more complex.

Main FFmpeg Tools

The FFmpeg version used for this guide is a Windows complied version availiable from Zeranoe FFmpeg. Simply download the latest 32 or 64-bit static build from the builds page here and extract it to a folder (builds are compressed in 7z format). The version used was git-dee7440 (2015-11-01).

The FFmpeg package contains the following three main executable tools in the bin folder:

  • ffmpeg.exe – a command-line encoder and media converter
  • ffmprobe.exe – a command-line tool to analyze and display media information
  • ffplay.exe – a simple media player

Note that there are a number of commands that are common between the three tools. Only ffmpeg.exe and ffmprobe.exe are used in this guide.

FFmpeg Help Files

FFmpeg provides three levels of help files: basic, long, and full. To view the commands available in the help files, click the ff-prompt.bat file in the root directory to open a command window or open your own in the bin folder and type in one of the following commands:

ffmpeg -h -- print basic options
ffmpeg -h long -- print more options
ffmpeg -h full -- print all options (including all format and codec specific options, very long

Here are links to the basic help file: ffmpeg_help and the full help file: ffmpeg_help_full. When printed to text, the help file sizes are: 5kB for the basic, 25kB for the full, and 487kB for the long help files. The long help file contains about 7,000 lines, which provides a hint as to how many commands are available.

Batch File

Batch file link: tasks_FFmpeg.bat

The link for the batch file used for this guide is provided above. Be sure to remove the txt extension before using it. The batch file is setup to work by the drag and drop method only.

To concatenate the audio files and write the metadata to the merged file, the batch file steps through the following:

  1. Delete any previous metadata text files, listfiles, or json data files.
  2. Write metadata for each audio file to a separate metadata text file
  3. Write the filenames of the audio files to confiles.txt (see below format), a listfile FFmpeg uses to identify the audio files to concatenate
  4. Concatenate the audio files and write the metadata from the first audio file’s metadata.txt file to the joined audio file.

For FFmpeg to use a listfile (confiles.txt), the filenames must be written to the confiles.txt file on separate lines using the following format.

file 'filename1.ext'
file 'filename2.ext'

The provided batch script should work for most audio formats of the same type provided they were encoded using the same codec (although they can be different containers). It was tested with opus, mp3, and aac files on a PC running Windows XP.

The batch script also provides options to separately print out audio file metadata, basic data, or stream and container (format) data to screen or to a file in json format (human readable form), with options to change the format in the script.

Command-Line Description

The main FFmpeg commands for extracting the metadata and concatenating the audio files are explained below. Although the ffprobe command was also used, it’s fairly simple to understand and should be self-explanatory by examining the code and the help files. The filenames used below are not actually in the batch script but have been simplified for explaination purposes.

The below command extracts and writes the metadata to a text file:

ffmpeg -i infile.ext -f ffmetadata metadatafile1.txt
  • ffmpeg – calls ffmpeg
  • -i infile.ext – specifies infile.ext as an input file
  • -f ffmetadata metadatafile1.txt  – formats the metadata to file metadatafile1.txt

The metadata1.txt file is formatted as below:

album=Name of Album
artist=Artist Name
genre=Music Genre Name
title=Title Name
track=Track #
encoder=Encoder Used

The next command is used to process mp3 files only. It concatenates the mp3 files and writes the metadatafile1.txt contents in id3 format of the first mp3 file to the merged mp3 file:

ffmpeg -f concat -i confiles.txt -i metadatafile1.txt -map_metadata 1 -id3v2_version 3 -write_id3v1 1 -c copy filename1_merged.mp3
  • ffmpeg – calls ffmpeg
  • -f concat -i confiles.txt – use concat demuxer to concatenate the mp3 files listed in confiles.txt (treats confiiles.txt as a single file and specifies it as input file 0)
  • -i metadatafile1.txt – specify metadatafile1.txt as input file 1
  • -map_metadata 1 – map input file 1 as the source for metadata (metadatafile1.txt)
  • -id3v2_version 3 – select ID3v2 version 3 to write
  • -write_id3v1 1 – enable ID3v1 writing
  • -c copy filename1_merged.mp3 – stream copy to filename1_merged.mp3 (-c copy = stream copy)

The next command listed processes audio files other than mp3. It functions the same as the previous command but writes standard metadata (if present) from the first audio file to the merged file:

ffmpeg -f concat -i confiles.txt -i metadatafile1.txt -map_metadata 1 -c copy filename1_merged.ext
  • ffmpeg – calls ffmpeg
  • -f concat -i confiles.txt – use concat demuxer to concatenate the files listed in confiles.txt (treats confiiles.txt as a single file and specifies it as input file 0)
  • -i metadatafile1.txt – specify metadatafile1.txt as input file 1
  • -map_metadata 1 – map input file 1 as the source for metadata (metadatafile1.txt)
  • -c copy filename1_merged.mp3 – stream copy to filename1_merged.ext (-c copy = stream copy)

Additional Help – Online Command-line Generators

There are a number of online FFmpeg command-line generators that can help construct various audio and video FFmpeg commands. A few of them are listed below:

FFmpeg Little Helper – Rodrigo Polo

FFmpeg Helper

FFmpeg Command Generator


Useful FFmpeg Commands

Concatenating media files


FFmpeg & FFprobe Cheatsheet




16. October 2015 · Comments Off on Where to find Command-line Utilities for Batch Files · Categories: Development, TechBits · Tags:
Command-line utilities are useful for expanding the capabilities of batch files. There are many more available, but the below list can be used as a starting point.

Free Command-line Utilities for Batch Scripts

NameDescriptionSourceSize Uncompressed (kB)More info/License
BusyBoxA single binary with many common Unix tools. Often used in embedded Linux systems. Fewer options than originals due to size optimizationRon Yorston647kGNU General Public License
DSToolBoxTwelve utilitiesDreamCycle Studios40-158kFreeware
F2KO SoftwareOver 40 utilitiesCMD ToolsVariousFreeware
Gammadyne's Free DOS UtilitiesSixteen various utilities including timers, file management tools, and a DOS shellGammadyne's Free DOS Utilities76-421kFreeware
GnuWinOver 160 separately downloadable native Win32 open source utilities for Windows 2k-Win7GnuWinVariousGNU General Public License
Gow (Gnu On Windows)Over 100 useful open source UNIX applications compiled as native win32 binariesBrent Matzelle1-1795kOpen Source MIT License
GtoolsSeveral command-line and GUI Windows Administrative Toolsgtools current version19- 520kOpen Source
HexatomiumAbout a dozen utilitiesWindows Apps by FS112-320kFree for personal use
Horst Schaeffer's Software PagesSeveral various utilities  CMD 32/64 bit 4-35kFreeware
NircmdA small command-line utility that can perform many different tasksNirSoft43kFreeware. 32 and 64 bit versions also available
Ritchie LawrenceA somewhat outdated (2005), but still useful list of command-line utilitiesRitchie LawrenceVariousMostly Freeware
Rob nan der Woude's Scripting PagesDescriptions and download links for a many utilities. Probably the most up-to-date and comprehensive listing of its kindBatch UtilitiesVariousAlmost entirely Freeware
RubyPdf Software Download CenterSpecialized PDF ToolsRubypdf TechnologiesUp to a few MBMostly Freeware
Small command line utilitiesOver 150 system utilities. Archive package or separately. Page also has small GUI tools and NET utilities.LTRData6-100k. Most under 20kFreeware
SwissFileKnifeCombines many functions into a single, portable executableStahlWorks Technologies 1,576kBSD License. Binaries and source code available. Versions for Mac and Linux.
SystemTools UtilitiesA dozen utilities focusing on user account and networking tasksSystemTools SoftwareMost under 50kFreeware
Util32Twenty 32-bit useful command-line utilitiesPersoft23-180kFreeware
Uwe Sieber's HomepageFile, drive, USB and misc toolsUwe Sieber's HomepageVariousFreeware


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