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author | Jean-Marc Valin <jean-marc.valin@octasic.com> | 2010-06-30 18:08:35 -0400 |
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committer | Jean-Marc Valin <jean-marc.valin@octasic.com> | 2010-06-30 18:08:35 -0400 |
commit | a9718e497c0b272f8604be21b06aa580b462ab05 (patch) | |
tree | 60d08b9fb87e5afb6c52b6d04e5abd2ec1214962 /doc | |
parent | 04584eac3178e3f68dc5f0b07cfc4a1ec3cd2406 (diff) | |
download | opus-a9718e497c0b272f8604be21b06aa580b462ab05.tar.gz |
IETF draft update
Diffstat (limited to 'doc')
-rw-r--r-- | doc/draft-valin-codec-prototype.xml | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/doc/draft-valin-codec-prototype.xml b/doc/draft-valin-codec-prototype.xml index 8890c60b..92fd029c 100644 --- a/doc/draft-valin-codec-prototype.xml +++ b/doc/draft-valin-codec-prototype.xml @@ -45,7 +45,11 @@ <abstract> <t> -This document provides a quick overview of a prototype codec combining the SILK and CELT. Inclusion of other codecs is also possible, we just haven't had time to look into that. +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 +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. </t> </abstract> </front> @@ -54,9 +58,24 @@ This document provides a quick overview of a prototype codec combining the SILK <section anchor="introduction" title="Introduction"> <t> +We propose a hybrid codec based on a linear prediction layer (LP) and an +MDCT-based enhancement layer. The main idea behind the proposal is that +the speech low frequencies are usually more efficiently coded using +linear prediction codecs (such as CELP variants), while the higher frequencies +are more efficiently coded in the transform domain (e.g. MDCT). For low +sampling rates, the MDCT layer is not useful and only the LP-based layer is +used. On the other hand, non-speech signals are sometimes adequately coded +using linear prediction, so for music only the MDCT-based layer is used. +</t> +<t> +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. </t> +<t>This is a work in progress.</t> </section> <section anchor="modes" title="Codec Modes"> @@ -67,7 +86,11 @@ There are three possible operating modes for the proposed prototype: <t>A hybrid (LP+MDCT) mode for full-bandwidth speech at medium bitrates</t> <t>An MDCT-only mode for very low delay speech transmission as well as music transmission.</t> </list> -Each of these modes supports a number of difference frame sizes and sampling rates. +Each of these modes supports a number of difference frame sizes and sampling +rates. In order to distinguish between the various modes and configurations, +we need to define a simple header that can used in the transport layer +(e.g RTP) to signal this information. The following describes the proposed +header. </t> <t> @@ -221,11 +244,12 @@ This document has no actions for IANA. </t> </section> - +<!-- <section anchor="Acknowledgments" title="Acknowledgments"> <t> </t> </section> +--> </middle> |