FLAC to SLN Converter

Create Asterisk PBX audio from lossless FLAC files

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Best VoIP Quality

Lossless FLAC gives Asterisk SLN files the clearest possible voice prompts.

PBX Native

SLN is what Asterisk expects — produce from lossless FLAC for best results.

Bulk Deployment

Convert all FLAC prompts to SLN at once — deploy a complete Asterisk library.

How to convert FLAC to SLN

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose sln or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your sln file right afterwards

About formats

FLAC (Free Lossless Audio Codec) delivers mathematically perfect audio reproduction at roughly half the size of an uncompressed WAV file. Maintained by the Xiph.Org Foundation and released in 2001, it quickly became the de facto open standard for lossless music archival. The encoder applies linear prediction to model each audio block, then codes the residual through Rice partitioning — exploiting the statistical distribution of prediction errors for strong compression without discarding data. Bit depths up to 32 and sample rates up to 655 kHz are supported, exceeding the requirements of high-resolution recordings. Hardware support is extensive: smartphones, car stereos, Blu-ray players, and virtually every desktop media application decode FLAC natively. Streaming services such as Tidal and Amazon Music use FLAC for lossless tiers, underscoring industry trust in the codec. Three standout benefits make FLAC compelling. First, complete bit-for-bit restoration of the original signal upon decoding. Second, embedded metadata via Vorbis comments and album art keeps libraries organized without sidecar files. Third, open-source licensing means no patents or royalties, removing legal friction for developers and hardware vendors.
Initial release: July 20, 2001
SLN (Signed Linear) is a headerless raw audio format storing 16-bit signed linear PCM samples at 8000 Hz mono, most closely associated with Asterisk) — the open-source PBX framework developed by Digium (now Sangoma Technologies). Within Asterisk, SLN serves as the native internal audio representation: every codec transcoding operation passes through signed linear as an intermediate step. This makes SLN the backbone of Asterisk's codec translation architecture. The format contains nothing but raw samples — no headers, no metadata, no framing — so parameters must be known in advance. While this lack of self-description might seem limiting, it is actually an advantage in telephony where sample format is fixed by convention and every overhead byte matters across thousands of simultaneous channels. The 8000 Hz rate aligns with the G.711 standard for traditional telephony, capturing the full 300-3400 Hz voice band. Asterisk also supports extended variants (sln16, sln32, sln48) for wideband audio. SLN files require no decoding — just direct memory mapping — making them ideal for real-time mixing, conferencing, and prompt playback in high-density VoIP environments.
Initial release: 1999

Frequently Asked Questions

Why convert FLAC to SLN?

SLN is native to Asterisk PBX. Lossless FLAC input produces the clearest voice prompts and hold music.

What uses SLN?

Asterisk PBX, FreePBX, and VoIP platforms use SLN for prompts, hold music, and system audio.

What are SLN specs?

SLN is 8 kHz, 16-bit signed integer, little-endian raw PCM for telephony.

Does FLAC improve VoIP audio?

Yes — lossless source means the SLN output has the best possible speech clarity.

Can I batch convert?

Upload all FLAC prompts and convert them to SLN at once.

FLAC to SLN Quality Rating

5.0 (2 votes)
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