OggOpus draft updates.
Bump version and date for draft-ietf-codec-oggopus-03 submission.
Move more text into figure pre/postamble to fix rendering issues
in the xml2rfc html output. These need to be manually re-indented
in the txt output before submission. :(
Fix resampling frequency choice algorithm, which was missing a word.
Fix some spelling and make some minor enphasis changes.
diff --git a/doc/draft-ietf-codec-oggopus.xml b/doc/draft-ietf-codec-oggopus.xml
index a916403..cb1f739 100644
--- a/doc/draft-ietf-codec-oggopus.xml
+++ b/doc/draft-ietf-codec-oggopus.xml
@@ -11,7 +11,7 @@
]>
<?rfc toc="yes" symrefs="yes" ?>
-<rfc ipr="trust200902" category="std" docName="draft-ietf-codec-oggopus-02">
+<rfc ipr="trust200902" category="std" docName="draft-ietf-codec-oggopus-03">
<front>
<title abbrev="Ogg Opus">Ogg Encapsulation for the Opus Audio Codec</title>
@@ -60,7 +60,7 @@
</address>
</author>
-<date day="17" month="January" year="2014"/>
+<date day="7" month="February" year="2014"/>
<area>RAI</area>
<workgroup>codec</workgroup>
@@ -167,7 +167,7 @@
audio data packets.
Each audio data packet contains one Opus packet for each of N different
streams, where N is typically one for mono or stereo, but may be greater than
- one for, e.g., multichannel audio.
+ one for multichannel audio.
The value N is specified in the ID header (see
<xref target="channel_mapping"/>), and is fixed over the entire length of the
logical Ogg bitstream.
@@ -189,7 +189,7 @@
duration (frame size), and number of frames per packet, are indicated in the
TOC (table of contents) in the first byte of each Opus packet, as described
in Section 3.1 of <xref target="RFC6716"/>.
-The combination of mode, audio bandwidth, and frame size, is referred to as
+The combination of mode, audio bandwidth, and frame size is referred to as
the configuration of an Opus packet.
</t>
<t>
@@ -375,9 +375,11 @@
<section anchor="pcm_sample_position" title="PCM Sample Position">
<t>
+<figure align="center">
+<preamble>
The PCM sample position is determined from the granule position using the
formula
-<figure align="center">
+</preamble>
<artwork align="center"><![CDATA[
'PCM sample position' = 'granule position' - 'pre-skip' .
]]></artwork>
@@ -388,8 +390,10 @@
For example, if the granule position of the first audio data page is 59,971,
and the pre-skip is 11,971, then the PCM sample position of the last decoded
sample from that page is 48,000.
-This can be converted into a playback time using the formula
<figure align="center">
+<preamble>
+This can be converted into a playback time using the formula
+</preamble>
<artwork align="center"><![CDATA[
'PCM sample position'
'playback time' = --------------------- .
@@ -626,7 +630,8 @@
<t>Otherwise, if the hardware's highest available sample rate is a supported
rate, decode at this sample rate.</t>
<t>Otherwise, if the hardware's highest available sample rate is less than
- 48 kHz, decode at the highest supported rate above this and resample.</t>
+ 48 kHz, decode at the next highest supported rate above this and
+ resample.</t>
<t>Otherwise, decode at 48 kHz and resample.</t>
</list>
However, the 'Input Sample Rate' field allows the encoder to pass the sample
@@ -652,13 +657,17 @@
It is 20*log10 of the factor to scale the decoder output by to achieve the
desired playback volume, stored in a 16-bit, signed, two's complement
fixed-point value with 8 fractional bits (i.e., Q7.8).
-To apply the gain, a decoder could use
<figure align="center">
+<preamble>
+To apply the gain, a decoder could use
+</preamble>
<artwork align="center"><![CDATA[
sample *= pow(10, output_gain/(20.0*256)) ,
]]></artwork>
-</figure>
+<postamble>
where output_gain is the raw 16-bit value from the header.
+</postamble>
+</figure>
<vspace blankLines="1"/>
Virtually all players and media frameworks should apply it by default.
If a player chooses to apply any volume adjustment or gain modification, such
@@ -848,15 +857,17 @@
<t>7 channels: 6.1 surround (front left, front center, front right, side left, side right, rear center, LFE).</t>
<t>8 channels: 7.1 surround (front left, front center, front right, side left, side right, rear left, rear right, LFE)</t>
</list>
+</t>
+<t>
This set of surround options and speaker location orderings is the same
as those used by the Vorbis codec <xref target="vorbis-mapping"/>.
The ordering is different from the one used by the
WAVE <xref target="wave-multichannel"/> and
FLAC <xref target="flac"/> formats,
- so correct ordering requires permutation of the output channels when encoding
- from or decoding to those formats.
+ so correct ordering requires permutation of the output channels when decoding
+ to or encoding from those formats.
'LFE' here refers to a Low Frequency Effects, often mapped to a subwoofer
- with no particular spacial position.
+ with no particular spatial position.
Implementations SHOULD identify 'side' or 'rear' speaker locations with
'surround' and 'back' as appropriate when interfacing with audio formats
or systems which prefer that terminology.
@@ -903,7 +914,7 @@
Family 1</xref>, which are known to give acceptable results for stereo.
Matricies for 3 and 4 channels are normalized so each coefficent row sums
to 1 to avoid clipping.
-For 5 or more channels they are normalized to 2 as a compromize between
+For 5 or more channels they are normalized to 2 as a compromise between
clipping and dynamic range reduction.
</t>
<t>
@@ -1134,7 +1145,7 @@
for these fields, or that do not contain enough data for the corresponding
vendor string or user comments they describe.
Making this check before allocating the associated memory to contain the data
- may help prevent a possible Denial-of-Service (DoS) attack from small comment
+ helps prevent a possible Denial-of-Service (DoS) attack from small comment
headers that claim to contain strings longer than the entire packet or more
user comments than than could possibly fit in the packet.
</t>
@@ -1142,15 +1153,19 @@
<t>
The user comment strings follow the NAME=value format described by
<xref target="vorbis-comment"/> with the same recommended tag names.
-One new comment tag is introduced for Ogg Opus:
+</t>
<figure align="center">
+ <preamble>One new comment tag is introduced for Ogg Opus:</preamble>
<artwork align="left"><![CDATA[
R128_TRACK_GAIN=-573
]]></artwork>
-</figure>
+<postamble>
representing the volume shift needed to normalize the track's volume.
The gain is a Q7.8 fixed point number in dB, as in the ID header's 'output
gain' field.
+</postamble>
+</figure>
+<t>
This tag is similar to the REPLAYGAIN_TRACK_GAIN tag in
Vorbis <xref target="replay-gain"/>, except that the normal volume
reference is the <xref target="EBU-R128"/> standard.
