Convert M4B to SPX

Turn M4B recordings into Speex. Re-encoded as Speex speech coding in an Ogg file at 8, 16 or 32 kHz in mono or stereo, unless audio.sample_rate or audio.channels say otherwise, which loses a little more than the AAC already did.

Converted in an isolated sandbox on our serversDeleted after 24 hours

Drop M4B files on the dialor turn it to pick what to do

M4B and SPX

From

M4B Audiobook

AAC audiobooks in an MP4 container with chapters. What Apple Books and most audiobook apps play.

Extensions: .m4b
MIME type: audio/mp4
Kind: Audio

To

Speex

Speex speech audio in an Ogg container, the predecessor of Opus.

Extensions: .spx
MIME type: audio/x-speex
Kind: Audio

Options for M4B to SPX

audio.channels: Number of audio channels. 1 is mono, 2 is stereo.
audio.denoise: Reduce steady background noise.
audio.normalize: Normalize loudness to -16 LUFS as streaming services do.
audio.sample_rate: Audio sample rate in Hz.
speed: Playback speed multiplier. 2 plays twice as fast.
trim_end: Second at which the audio or video stops.
trim_start: Seconds to cut from the start of audio or video.