Convert audio channel layout

The result identifies every source and destination channel, classifies the operation as an identity, downmix, or upmix, and expresses each output as a readable formula. It is useful for planning pipelines, documenting transcoding behavior, validating configuration, and explaining why a converted file sounds different without uploading or decoding any audio.

Read the mapping before changing the audio

A channel-layout conversion is more than changing a label in a container. Each output speaker needs a defined signal, and careless routing can remove dialogue, duplicate ambience, or create a surprising level increase. Supply source_layout and target_layout using one of the supported names: mono, stereo, or 5.1. The response lists the canonical channels in order and gives one formula for every target channel. Mono uses M; stereo uses L and R; 5.1 uses FL, FR, FC, LFE, SL, and SR. A formula such as 0.5*L + 0.5*R means that both stereo inputs contribute equally to the mono output. The returned rule is a specification, not processed media: this capability does not receive an audio file or alter samples. That makes it suitable for configuration previews, technical documentation, test expectations, and user interfaces that need to explain a conversion before a separate encoder performs it. Layout names are matched without regard to surrounding whitespace or letter case, while unsupported names are rejected instead of guessed.

Understand downmix coefficients and headroom

Downmixing combines more input channels into fewer outputs. Stereo to mono uses half of the left signal plus half of the right signal, preserving a sensible average rather than simply summing both at full level. For a 5.1 to stereo conversion, the front left and front right channels remain on their respective sides. The center contributes to both sides at 0.707, approximately minus three decibels, and each surround contributes to its corresponding side at the same coefficient. The LFE channel is deliberately omitted because it is an effects channel, not a complete bass-only copy of the program, and including it by default can produce excessive low-frequency energy. The 5.1 to mono rule is the stereo rule folded equally into one channel: front left and right each contribute 0.5, the center contributes 0.707, and the surround channels each contribute 0.3535. Several correlated signals can still add beyond full scale. For that reason the response warns that practical rendering may need gain reduction or a limiter. The formulas define routing proportions; they do not promise clipping prevention, loudness normalization, or compliance with every broadcaster's delivery profile.

Treat upmixing as routing, not source separation

Upmixing cannot recover spatial information that was never captured. Mono to stereo therefore duplicates M into L and R. Mono to 5.1 places M in the front center channel and fills the other destinations with silence, which keeps a centered source centered without inventing surround or effects material. Stereo to 5.1 preserves L and R in the front pair, derives the center as an equal half-level combination, copies the left and right signals to their corresponding surrounds, and leaves LFE silent. These choices provide an explicit, reproducible routing plan, but they are not a psychoacoustic surround decoder. A production workflow may choose decorrelation, delay, filtering, bass management, or a matrix standard according to its listening environment; those processes fall outside this result. Conversions where source and target are identical are reported as identity operations, with every channel passing through unchanged. Keeping identity behavior explicit is helpful when one configuration path handles many files and needs an auditable answer even when no remix occurs. Any pair containing a layout other than mono, stereo, or 5.1 returns an invalid-input error, ensuring that unfamiliar arrangements such as 7.1 are never silently treated as something else.