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The Audio/L16 MIME content type (RFC2586)

IP.com Disclosure Number: IPCOM000003173D
Original Publication Date: 1999-May-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 4 page(s) / 8K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Salsman: AUTHOR [+2]


This document defines the audio/L16 MIME type, a reasonable quality audio format for use in Internet applications.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 34% of the total text.

Network Working Group J. Salsman

Request for Comments: 2586 H. Alvestrand

Category: Informational UNINETT

May 1999

The Audio/L16 MIME content type

Status of this Memo

This memo provides information for the Internet community. It does

not specify an Internet standard of any kind. Distribution of this

memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1999). All Rights Reserved.

1. Introduction

This document defines the audio/L16 MIME type, a reasonable quality

audio format for use in Internet applications.

Possible application areas include E-mail, Web served content, file

upload in Web forms, and more.

2. The need for the Audio/L16 MIME type

The set of IETF standard MIME types for audio is small; it consists

of only the audio/basic and audio/32kadpcm types, which have a

sampling rate of 8000 samples/second.

Rates below 11025 may obscure consonant information, even for

single-voice speech. Common compressions, such as LPC, are known to

be microphone-dependant and lossy. Thus far all IETF MIME Audio

types either default to 8000 samples per second or use LPC.

In order for advanced speech recognition and related educational

applications to make use of internet transports (such as RFC 1867

file uploading) which use MIME typing, higher standards are required.

This type repairs that lack by registering a very simple MIME type

that allows higher rate, linear-encoded audio with multiple channels.

This is an IESG approved MIME type, and its definition is therefore

published as an RFC.

Please note that there are many other Audio types described in RFC

1890 [1] which IANA may wish to formally register; this one, of all

of them, seems to be most immediately needed. This document may also

serve as a template for further registrations of these audio types.

3. The definition of Audio/L16

Audio/L16 is based on the well know audio format "L16" described in

RFC 1890 section 4.4.8 for use with RTP transport. L16 denotes

uncompressed audio data, using 16-bit signed representation in twos-

complement notation and network byte order. (From section 4.4.8 of

RFC 1890)

It may be parametrized by varying the sample rate and the number of

channels; the parameters are given on the MIME type header.

In order to promote interoperability, only a few rate values are

standardized here. Other values may NOT be used except by bilateral


If multi...