Free online ULAW to OGG converter

What the ULAW format is

ULAW usually means raw G.711 μ-law audio, an 8-bit companding format designed for voice calls. It is commonly produced by Asterisk and other PBX systems, FreeSWITCH, VoIP gateways, telephone recording equipment, and RTP or SIP capture tools.

A ULAW file often has a .ulaw extension but no header. The usual telephony parameters are 8,000 Hz, mono, and 8-bit μ-law samples. Because raw files lack metadata, the converter must be told the sample rate, channel count, and encoding explicitly. Some systems store the same audio with a different extension or inside a WAV file with a μ-law codec.

What the OGG format is

OGG is a multimedia container rather than one specific audio codec. An OGG file can contain Vorbis, Opus, and other streams; Ogg Opus is generally the best choice for speech, while Ogg Vorbis is useful when the destination application specifically expects Vorbis.

Opus usually provides better speech quality at low bitrates and is supported by current browsers, media players, and communication software. Vorbis has broader support in older OGG-focused applications. Neither codec restores quality discarded by the original μ-law recording.

How to actually convert ULAW to OGG

Using FFmpeg

Install FFmpeg, place the input file in a working folder, and run this command for the standard 8 kHz mono telephony format:

ffmpeg -f mulaw -ar 8000 -ac 1 -i input.ulaw -c:a libopus -b:a 24k output.ogg

The -f mulaw option identifies the raw μ-law encoding, while -ar 8000 and -ac 1 describe its sample rate and channel count. The command creates an OGG container with Opus audio at 24 kbps.

For software that does not support Opus in OGG, use Vorbis instead:

ffmpeg -f mulaw -ar 8000 -ac 1 -i input.ulaw -c:a libvorbis -q:a 3 output.ogg

If the recording was made with different parameters, replace 8000 and 1 with the actual sample rate and channel count. If the source is a WAV file containing μ-law audio, omit -f mulaw and use the WAV filename directly:

ffmpeg -i input.wav -c:a libopus -b:a 24k output.ogg

Use ffprobe input.ulaw only when the file contains a recognizable header. For a headerless file, inspect the recording system’s configuration or test the standard 8 kHz mono settings; the extension alone cannot identify those properties.

Using the online converter

You can convert the file on 101convert.com for free without installing software. Select the Audio conversion option, upload the ULAW file, choose OGG as the output format, and select the available codec or quality setting. For headerless recordings, provide 8 kHz and mono information if the converter asks for source parameters.

Quality and compatibility limitations

G.711 μ-law is already a lossy speech format, normally limited to telephone bandwidth of roughly 300–3,400 Hz. Converting it to Opus or Vorbis cannot recover missing high frequencies; it only changes the encoding and container.

Keep the output at 8 kHz when the file is strictly telephony speech. Upsampling to 44.1 or 48 kHz makes a larger file without adding source detail, although a particular editor may require one of those rates. Use a modest bitrate such as 16–32 kbps for speech; higher values mainly increase size.

Some older applications identify OGG with Vorbis support only. Choose the Vorbis command in that case; choose Opus for current software and lower-bitrate speech delivery.