shithub: opus

Download patch

ref: 360a41172a839caf4bff19f3d88d4b9b6981b9ce
parent: 0cf8628528f53e07ed3679b6f6bc0acd750607d1
author: Ralph Giles <[email protected]>
date: Mon Jul 16 09:53:29 EDT 2012 

Various small improvements.

Remove a redundant phrase from the previous commit.
Thanks to Tim for pointing this out.

Clarify what 'skipped' means.

Give a reference for the vorbis granulepos-trimming.

Commas and semicolons in the resampling decision list.

Capital SHOULD on treating unknown channel mapping families
as discrete.

Clarify why goes in the vendor string. Maybe needs an example?
'gstoggmux 1.0.12; libopus 1.2.3'

Remove a redundant word. 'could' already covers 'potential' and
the line is stronger without it.


--- a/doc/draft-terriberry-oggopus.xml
+++ b/doc/draft-terriberry-oggopus.xml
@@ -167,9 +167,8 @@
 The first N-1 Opus packets, if any, are packed one after another in sequence
  into the Ogg packet, using the self-delimiting framing from Appendix&nbsp;B
  of <xref target="RFCOpus"/>.
-The remaining Opus packet is packed at the end of the audio data packet
- using the regular, undelimited framing from Section&nbsp;3 of
- <xref target="RFCOpus"/>.
+The remaining Opus packet is packed at the end of the Ogg packet using the
+ regular, undelimited framing from Section&nbsp;3 of <xref target="RFCOpus"/>.
 All of the Opus packets in a single Ogg packet MUST be constrained to have the
  same duration.
 The duration and coding modes of each Opus packet are contained in the
@@ -261,7 +260,8 @@
 
 <t>
 A 'pre-skip' field in the ID header (see <xref target="id_header"/>) signals
- the number of samples which should be skipped at the beginning of the stream.
+ the number of samples which should be skipped (decoded but discarded) at the
+ beginning of the stream.
 This provides sufficient history to the decoder so that it has already
  converged before the stream's output begins.
 It may also be used to perform sample-accurate cropping of existing encoded
@@ -306,7 +306,7 @@
 <t>
 Vorbis streams use a granule position smaller than the number of audio samples
  contained in the first audio data page to indicate that some of those samples
- must be trimmed from the output.
+ must be trimmed from the output. See <xref target="vorbis-trim"/>.
 However, to do so, Vorbis requires that the first audio data page contains
  exactly two packets, in order to allow the decoder to perform PCM position
  adjustments before needing to return any PCM data.
@@ -473,12 +473,12 @@
 An Ogg Opus player SHOULD select the playback sample rate according to the
  following procedure:
 <list style="numbers">
-<t>If the hardware supports 48&nbsp;kHz playback, decode at 48&nbsp;kHz</t>
-<t>Else if the hardware's highest available sample rate is a supported rate,
- decode at this sample rate,</t>
-<t>Else if the hardware's highest available sample rate is less than
- 48&nbsp;kHz, decode at the highest supported rate above this and resample.</t>
-<t>Else decode at 48&nbsp;kHz and resample.</t>
+<t>If the hardware supports 48&nbsp;kHz playback, decode at 48&nbsp;kHz;</t>
+<t>Else, if the hardware's highest available sample rate is a supported
+ rate, decode at this sample rate;</t>
+<t>Else, if the hardware's highest available sample rate is less than
+ 48&nbsp;kHz, decode at the highest supported rate above this and resample;</t>
+<t>Else, decode at 48&nbsp;kHz and resample.</t>
 </list>
 However, the 'Input Sample Rate' field allows the encoder to pass the sample
  rate of the original input stream as metadata.
@@ -675,7 +675,7 @@
 </t>
 </list>
 The remaining channel mapping families (2...254) are reserved.
-A decoder encountering a reserved channel mapping family value should act as
+A decoder encountering a reserved channel mapping family value SHOULD act as
  though the value is 255.
 <vspace blankLines="1"/>
 An Ogg Opus player MUST play any Ogg Opus stream with a channel mapping family
@@ -759,6 +759,11 @@
  string.
 No terminating NUL octet is required.
 <vspace blankLines="1"/>
+This tag is intended to identify the codec encoder and encapsulation
+ implementations, for tracing differences in technical behavior. The
+ user-facing encoding application can use the 'Encoded-by' user commment
+ tag name to identify themselves.
+<vspace blankLines="1"/>
 </t>
 <t><spanx style="strong">User Comment List Length</spanx> (32 bits, unsigned,
  little endian):
@@ -853,7 +858,7 @@
 Decoders SHOULD avoid attempting to allocate excessive amounts of memory when
  presented with a very large packet.
 The presence of an extremely large packet in the stream could indicate a
- potential memory exhaustion attack or stream corruption.
+ memory exhaustion attack or stream corruption.
 Decoders SHOULD reject a packet that is too large to process, and display a
  warning message.
 </t>
@@ -985,6 +990,15 @@
 <author initials="T.B." surname="Terriberry" fullname="Timothy B. Terriberry"/>
 </front>
 <seriesInfo name="RFC" value="XXXX"/>
+</reference>
+
+<reference anchor="vorbis-trim"
+  target="http://xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-130000A.2">
+<front>
+<title>The Vorbis I Specification, Appendix A Embedding Vorbis into an Ogg stream</title>
+<author initials="C." surname="Montgomery"
+ fullname="Christopher &quot;Monty&quot; Montgomery"/>
+</front>
 </reference>
 
 <reference anchor="vorbis-mapping"