From 274b7550ba3dab157c2b5ed40710dbce694ea167 Mon Sep 17 00:00:00 2001 From: Jean-Marc Valin Date: Mon, 5 Jul 2010 16:56:42 -0400 Subject: IETF draft --- doc/draft-valin-codec-prototype.xml | 57 ++++++++++++++++++++++++++++++++----- 1 file changed, 50 insertions(+), 7 deletions(-) (limited to 'doc') diff --git a/doc/draft-valin-codec-prototype.xml b/doc/draft-valin-codec-prototype.xml index 681b4f42..f02bec34 100644 --- a/doc/draft-valin-codec-prototype.xml +++ b/doc/draft-valin-codec-prototype.xml @@ -48,7 +48,8 @@ This document provides a quick overview of a prototype codec combining a linear -prediction layer (SILK) with an MDCT-based layer (CELT). These codecs are +prediction layer (SILK) with an MDCT-based layer (CELT). +These codecs are used because of the authors' familiarity with the source code, but it does not prevent inclusion of code from other codecs as well. This is a work in progress. @@ -71,10 +72,11 @@ using linear prediction, so for music only the MDCT-based layer is used. -In this proposed prototype, the LP layer is based on the SILK codec and the -MDCT layer is based on CELT codec. These codecs are +In this proposed prototype, the LP layer is based on the SILK codec + and the MDCT layer is based on CELT codec + . These codecs are used because of the authors' familiarity with the source code, but it does -not prevent inclusion of code from other codecs as well. +not prevent inclusion of code from other codecs in the future. This is a work in progress. @@ -88,7 +90,10 @@ layer. In the current prototype, the cutoff frequency is 8 kHz. In the MDCT layer, all bands below 8 kHz are discarded, such that there is no coding redundancy between the two layers. Also both layers use the same instance of the range coder to encode the signal, which ensures that no "padding bits" are -wasted. +wasted. The hybrid approach makes it easy to support both constant bit-rate +(CBR) and varaible bit-rate (VBR) coding. Although the SILK layer used is VBR, +it is easy to make the bit allocation of the CELT layer produce a final stream +that is CBR by using all the bits left unused by the SILK layer.
@@ -99,7 +104,9 @@ which references two other repositories (for SILK and CELT). Although the build system is very primitive (and inconsistent), some instructions are provided in the toplevel README file. This is very early development so both the quality and feature set should -greatly improve over time. +greatly improve over time. In the current version, only 48 kHz audio with 20 ms +frames are supported, but support for all configurations listed in + is planned.
@@ -275,7 +282,43 @@ This document has no actions for IANA. - + + + + +SILK Speech Codec + + + + + + + + + + + + + + + + +Constrained-Energy Lapped Transform (CELT) Codec + + + + + + + + + + + + + + + -- cgit v1.2.3