diff --git a/doc/ietf/draft-valin-celt-codec.xml b/doc/ietf/draft-valin-celt-codec.xml
index c4c4eac0..65a1872d 100644
--- a/doc/ietf/draft-valin-celt-codec.xml
+++ b/doc/ietf/draft-valin-celt-codec.xml
@@ -12,7 +12,6 @@
Octasic Semiconductor
-jean-marc.valin@octasic.com
4101, Molson Street, suite 300
Montreal
@@ -20,12 +19,14 @@
H1Y 3L1
Canada
+jean-marc.valin@octasic.com
-
+
@@ -37,7 +38,7 @@
CELT
-CELT is an open-source voice codec suitable for use in very low delay
+CELT is an open-source voice codec suitable for use in very low delay
Voice over IP (VoIP) type applications. This document describes the encoding
and decoding process.
@@ -72,18 +73,32 @@ CELT stands for "Constrained Energy Lapped Transform". It applies some of the CE
+CELT is designed for transmission over RTP
+
Insert encoder overview
-Pre-emphasis
+The input audio first goes through a pre-emphasis filter, which attenuates the
+"spectral tilt". The filter is has the transfer function A(z)=1-alpha_p*z^-1, with
+alpha_p=0.8. The inverse of the pre-emphasis is applied at the decoder.
+
+CELT is a transform codec, based on the Modified Discrete Cosine Transform
+, which is based on a DCT-IV, with overlap and time-domain
+aliasing calcellation. The MDCT implementation has no special characteristic. The
+input is a windowed signal (after pre-emphasis) of 2*N samples and the output is N
+frequency-domain samples. A "low-overlap" window is used to reduce the algorithmc delay.
+It is composed of a smaller window with symmetric zero padding on both sides. The window
+is the same as the one used in the Vorbis codec and defined as: W(n)=[sin(pi/2*sin(pi/2*(n+.5)/L))]^2
+
+
@@ -101,8 +116,8 @@ that the result is always exactly the same. Any mismatch would cause an error in
-CELT uses a Pyramid Vector Quantization (PVQ) [] codebook for quantising the details
-of the spectrum in each band that haven't been predicted by the pitch predictor.
+CELT uses a Pyramid Vector Quantization (PVQ) codebook for quantising the details
+of the spectrum in each band that haven't been predicted by the pitch predictor.
@@ -125,8 +140,8 @@ Some more text
-CELT uses a Pyramid Vector Quantization (PVQ) [] codebook for quantising the details
-of the spectrum in each band that haven't been predicted by the pitch predictor.
+CELT uses a Pyramid Vector Quantization (PVQ) [] codebook for quantising the details
+of the spectrum in each band that haven't been predicted by the pitch predictor.
@@ -139,8 +154,6 @@ of the spectrum in each band that haven't been predicted by the pitch predictor.
-De-emphasis
-
@@ -197,7 +210,7 @@ CELT and AVT communities for their input:
Key words for use in RFCs to Indicate Requirement Levels
-
+
@@ -205,69 +218,14 @@ CELT and AVT communities for their input:
RTP: A Transport Protocol for real-time applications
-
-
-
-
+
+
+
+
-
-
-Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies
-
-
-
-
-
-
-
-
-SDP: Session Description Protocol
-
-
-
-
-
-
-
-
-
-Packet-based Multimedia Communications Systems
-
-
-
-
-
-
-
-
-Control of communications between Visual Telephone Systems and Terminal Equipment
-
-
-
-
-
-
-
-
-RTP Profile for Audio and Video Conferences with Minimal Control.
-
-
-
-
-
-
-
-
-
-The application/ogg Media Type
-
-
-
-
-
@@ -276,11 +234,29 @@ CELT and AVT communities for their input:
The CELT ultra-low delay audio codec
+
-
+
+
+Modified Discrete Cosine Transform
+
+
+
+
+
+
+
+A Pyramid Vector Quantizer
+
+
+
+
+
+
+