Map Multiple Audio and Subtitle Streams in FFmpeg

This article provides a straightforward guide on how to use FFmpeg in Linux to map multiple audio and subtitle streams from one or more input files into a single output file. You will learn the core syntax of the -map option, how to select specific language tracks, and how to preserve all available streams without automatic filtering.

Understanding the FFmpeg Map Syntax

By default, when FFmpeg processes an input file, it only selects one stream of each type (one video, one audio, one subtitle) based on the highest quality or default flags. To override this behavior and manually select multiple streams, you must use the -map option.

The basic syntax for mapping uses the input file index and the stream index, separated by a colon:

-map input_file_index:stream_type_specifier:stream_index

• input_file_index: The order of the input file starting at 0 for the first file, 1 for the second, etc.
• stream_type_specifier: Letters like v for video, a for audio, and s for subtitles.
• stream_index: The sequence number of that specific stream type, starting at 0.

Command to Map All Streams

If your goal is to copy every single video, audio, and subtitle stream from a single input file into the output file without discarding anything, use the following command:

ffmpeg -i input.mkv -map 0:v -map 0:a -map 0:s -c copy output.mkv

In this command, -map 0:v grabs all video streams from the first input, -map 0:a grabs all audio streams, and -map 0:s grabs all subtitle streams. The -c copy flag ensures the streams are copied directly without re-encoding, which saves time and preserves quality.

Command to Map Specific Audio and Subtitle Tracks

If you have a file with multiple language tracks and you only want to include specific ones, you can target them directly by their index numbers.

For example, to create an output file containing the main video, the first two audio tracks (e.g., English and Spanish), and the second subtitle track, use:

ffmpeg -i input.mkv -map 0:v:0 -map 0:a:0 -map 0:a:1 -map 0:s:1 -c copy output.mkv

Combining Streams from Multiple Input Files

FFmpeg also allows you to merge audio and subtitle streams from entirely separate files into a single container.

The following command takes the video from the first file (0:v:0), an English audio track from a second file (1:a:0), and a French subtitle track from a third file (2:s:0):

ffmpeg -i video.mp4 -i audio.mp3 -i subtitles.srt -map 0:v:0 -map 1:a:0 -map 2:s:0 -c:v copy -c:a aac -c:s srt output.mkv

Note: When mixing different file formats, you may need to specify encoders (like -c:a aac or -c:s srt) instead of using -c copy if the destination container does not support the original source codecs natively.