Commit 554aef9d authored by Timothy B. Terriberry's avatar Timothy B. Terriberry

Additional edits from Mark Harris.

parent a3bb5412
......@@ -222,8 +222,8 @@ That is, the first page in the logical stream, and the last header
The granule position of an audio data page encodes the total number of PCM
samples in the stream up to and including the last fully-decodable sample from
the last packet completed on that page.
The granule position of the first audio data page MAY be larger than zero as
described in <xref target="start_granpos_restrictions"/>.
The granule position of the first audio data page will usually be larger than
zero, as described in <xref target="start_granpos_restrictions"/>.
</t>
<t>
......@@ -749,8 +749,7 @@ Future versions of this specification, even backwards-compatible versions,
might include additional fields in the ID header.
If an ID header has a compatible major version, but a larger minor version,
an implementation MUST NOT reject it for containing additional data not
specified here, unless it contains so much additional data that it does not
complete on the first page.
specified here, provided it still completes on the first page.
</t>
<section anchor="channel_mapping" title="Channel Mapping">
......@@ -794,22 +793,23 @@ For channel mapping family&nbsp;0, this value defaults to 1, and is not coded.
</t>
<t>Coupled Stream Count 'M' (8 bits, unsigned):
This is the number of streams whose decoders are to be configured to produce
two channels.
two channels (stereo).
This MUST be no larger than the total number of streams, N.
<vspace blankLines="1"/>
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 audio being
encoded.
The original channel count of the audio passed to the encoder is not preserved
by the lossy compression.
The original channel count of the audio passed to the encoder is not
necessarily preserved by the lossy compression.
<vspace blankLines="1"/>
Regardless of the internal channel count, any Opus stream can be decoded as
mono (a single channel) or stereo (two channels) by appropriate initialization
of the decoder.
The 'coupled stream count' field indicates that the first M Opus decoders are
to be initialized for stereo output, and the remaining (N&nbsp;-&nbsp;M)
decoders are to be initialized for mono only.
The 'coupled stream count' field indicates that the decoders for the first M
Opus streams are to be initialized for stereo (two-channel) output, and the
remaining (N&nbsp;-&nbsp;M) decoders are to be initialized for mono (a single
channel) only.
The total number of decoded channels, (M&nbsp;+&nbsp;N), MUST be no larger than
255, as there is no way to index more channels than that in the channel
mapping.
......
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