From e7aa6cb9a09cbd3538b0d41fc86eb28c2fc3c0bd Mon Sep 17 00:00:00 2001 From: Ralph Giles Date: Fri, 11 Jan 2013 17:11:07 -0800 Subject: Minor clarifications to the channel mapping section. Mostly just being more verbose. --- doc/draft-ietf-codec-oggopus.xml | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/doc/draft-ietf-codec-oggopus.xml b/doc/draft-ietf-codec-oggopus.xml index 5162dd8d..7d55af90 100644 --- a/doc/draft-ietf-codec-oggopus.xml +++ b/doc/draft-ietf-codec-oggopus.xml @@ -666,7 +666,7 @@ This MUST be no larger than the total number of streams, N. Each packet in an Opus stream has an internal channel count of 1 or 2, which can change from packet to packet. -This is selected by the encoder depending on the bitrate and the contents being +This is selected by the encoder depending on the bitrate and the audio being encoded. The original channel count of the encoder input is not preserved by the lossy compression. @@ -723,8 +723,9 @@ Allowed numbers of channels: 1 or 2. Special mapping: This channel mapping value also indicates that the contents consists of a single Opus stream that is stereo if - and only if C==2, with stream index 0 mapped to channel 0, and (if stereo) - stream index 1 mapped to channel 1. + and only if C==2, with stream index 0 mapped to output channel 0 (mono, or + left channel) and stream index 1 mapped to output channel 1 (right channel) + if stereo. When the 'channel mapping family' octet has this value, the channel mapping table MUST be omitted from the ID header packet. @@ -754,9 +755,11 @@ The ordering is different from the one used by the FLAC formats, although the configurations match, so correct ordering requires permutation of the output channels when encoding from or decoding to those formats. +'LFE' here refers to a Low Frequency Effects, often mapped to a subwoofer + with no particular spacial position. Implementations SHOULD identify 'side' or 'rear' speaker locations with - 'surround' as appropriate when interfacing with audio formats or systems - which prefer that terminology. + 'surround' and 'back' as appropriate when interfacing with audio formats + or systems which prefer that terminology. Family 255 (no defined channel meaning): -- cgit v1.2.1