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More minor gen-art part 2 edits.

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Includes the addition of a band-layout table.
This commit is contained in:
Timothy B. Terriberry 2012-05-15 13:45:40 -07:00 • committed by Jean-Marc Valin
parent e249b0b205
commit 53e6782ea5
2 changed files with 46 additions and 6 deletions
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5
doc/build_draft.sh
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@ -50,6 +50,11 @@ cat opus_source.tar.gz| base64 | tr -d '\n' | fold -w 64 | \
#echo '</artwork>' >> opus_compare_escaped.c
#echo '</figure>' >> opus_compare_escaped.c
if [[ ! -d ../opus_testvectors ]] ; then
echo "Downloading test vectors..."
wget 'http://www.opus-codec.org/testvectors/opus_testvectors-draft11.tar.gz'
tar -C .. -xvzf opus_testvectors-draft11.tar.gz
fi
echo '<figure>' > testvectors_sha1
echo '<artwork>' >> testvectors_sha1
echo '<![CDATA[' >> testvectors_sha1

47
doc/draft-ietf-codec-opus.xml
View file

@ -4827,13 +4827,46 @@ bands that (roughly) follow the Bark scale, i.e. the scale of the ear's
critical bands. The normal CELT layer uses 21 of those bands, though Opus
Custom (see <xref target="opus-custom"/>) may use a different number of bands.
A band can contain as little as one MDCT bin per channel, and as many as 176
bins per channel.
bins per channel, as detailed in <xref target="celt_band_sizes"/>.
In each band, the gain (energy) is coded separately from
the shape of the spectrum. Coding the gain explicitly makes it easy to
preserve the spectral envelope of the signal. The remaining unit-norm shape
vector is encoded using a Pyramid Vector Quantizer (PVQ)&nbsp;<xref target='PVQ-decoder'/>.
</t>
<texttable anchor="celt_band_sizes"
title="MDCT Bins Per Channel Per Band for Each Frame Size">
<ttcol>Frame Size:</ttcol>
<ttcol align="right">2.5&nbsp;ms</ttcol>
<ttcol align="right">5&nbsp;ms</ttcol>
<ttcol align="right">10&nbsp;ms</ttcol>
<ttcol align="right">20&nbsp;ms</ttcol>
<ttcol align="right">Start Frequency</ttcol>
<ttcol align="right">Stop Frequency</ttcol>
<c>Band</c> <c>Bins:</c> <c/> <c/> <c/> <c/> <c/>
<c>0</c> <c>1</c> <c>2</c> <c>4</c> <c>8</c> <c>0&nbsp;Hz</c> <c>200&nbsp;Hz</c>
<c>1</c> <c>1</c> <c>2</c> <c>4</c> <c>8</c> <c>200&nbsp;Hz</c> <c>400&nbsp;Hz</c>
<c>2</c> <c>1</c> <c>2</c> <c>4</c> <c>8</c> <c>400&nbsp;Hz</c> <c>600&nbsp;Hz</c>
<c>3</c> <c>1</c> <c>2</c> <c>4</c> <c>8</c> <c>600&nbsp;Hz</c> <c>800&nbsp;Hz</c>
<c>4</c> <c>1</c> <c>2</c> <c>4</c> <c>8</c> <c>800&nbsp;Hz</c> <c>1000&nbsp;Hz</c>
<c>5</c> <c>1</c> <c>2</c> <c>4</c> <c>8</c> <c>1000&nbsp;Hz</c> <c>1200&nbsp;Hz</c>
<c>6</c> <c>1</c> <c>2</c> <c>4</c> <c>8</c> <c>1200&nbsp;Hz</c> <c>1400&nbsp;Hz</c>
<c>7</c> <c>1</c> <c>2</c> <c>4</c> <c>8</c> <c>1400&nbsp;Hz</c> <c>1600&nbsp;Hz</c>
<c>8</c> <c>2</c> <c>4</c> <c>8</c> <c>16</c> <c>1600&nbsp;Hz</c> <c>2000&nbsp;Hz</c>
<c>9</c> <c>2</c> <c>4</c> <c>8</c> <c>16</c> <c>2000&nbsp;Hz</c> <c>2400&nbsp;Hz</c>
<c>10</c> <c>2</c> <c>4</c> <c>8</c> <c>16</c> <c>2400&nbsp;Hz</c> <c>2800&nbsp;Hz</c>
<c>11</c> <c>2</c> <c>4</c> <c>8</c> <c>16</c> <c>2800&nbsp;Hz</c> <c>3200&nbsp;Hz</c>
<c>12</c> <c>4</c> <c>8</c> <c>16</c> <c>32</c> <c>3200&nbsp;Hz</c> <c>4000&nbsp;Hz</c>
<c>13</c> <c>4</c> <c>8</c> <c>16</c> <c>32</c> <c>4000&nbsp;Hz</c> <c>4800&nbsp;Hz</c>
<c>14</c> <c>4</c> <c>8</c> <c>16</c> <c>32</c> <c>4800&nbsp;Hz</c> <c>5600&nbsp;Hz</c>
<c>15</c> <c>6</c> <c>12</c> <c>24</c> <c>48</c> <c>5600&nbsp;Hz</c> <c>6800&nbsp;Hz</c>
<c>16</c> <c>6</c> <c>12</c> <c>24</c> <c>48</c> <c>6800&nbsp;Hz</c> <c>8000&nbsp;Hz</c>
<c>17</c> <c>8</c> <c>16</c> <c>32</c> <c>64</c> <c>8000&nbsp;Hz</c> <c>9600&nbsp;Hz</c>
<c>18</c> <c>12</c> <c>24</c> <c>48</c> <c>96</c> <c>9600&nbsp;Hz</c> <c>12000&nbsp;Hz</c>
<c>19</c> <c>18</c> <c>36</c> <c>72</c> <c>144</c> <c>12000&nbsp;Hz</c> <c>15600&nbsp;Hz</c>
<c>20</c> <c>22</c> <c>44</c> <c>88</c> <c>176</c> <c>15600&nbsp;Hz</c> <c>20000&nbsp;Hz</c>
</texttable>
<t>
Transients are notoriously difficult for transform codecs to code.
CELT uses two different strategies for them:
@ -5035,11 +5068,13 @@ free to implement the procedure in any way which produces identical results.</t>
<t>The per-band gain-shape structure of the CELT layer ensures that using
the same number of bits for the spectral shape of a band in every frame will
result in a roughly constant signal-to-noise ratio in that band.
This results in a coding noise that has the same spectral envelope as the signal,
as is expected when using a standard psychoacoustic model. This provides a fairly
consistent perceptual performance&nbsp;<xref target='Valin2010'/>.
This structure means that the ideal allocation is more consistent from frame
to frame than it is for other codecs without an equivalent structure.</t>
This results in coding noise that has the same spectral envelope as the signal.
The masking curve produced by a standard psychoacoustic model also closely
follows the spectral envelope of the signal.
This structure means that the ideal allocation is more consistent from frame to
frame than it is for other codecs without an equivalent structure, and that a
fixed allocation provides fairly consistent perceptual
performance&nbsp;<xref target='Valin2010'/>.</t>
<t>Many codecs transmit significant amounts of side information to control the
bit allocation within a frame.