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Support for 10ms frame size

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Jean-Marc Valin 2010-07-08 13:10:28 -04:00
parent 63c325acf6
commit ed8e1b4937
3 changed files with 23 additions and 15 deletions
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27
doc/draft-valin-codec-prototype.xml
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@ -115,11 +115,11 @@ which references two other
repositories (for SILK and CELT). Some snapshots are provided for
convenience at <eref target='http://people.xiph.org/~jm/ietfcodec/'/> along
with sample files.
Although the build system is very primitive
(and inconsistent), some instructions are provided in the toplevel README file.
Although the build system is very primitive, some instructions are provided
in the toplevel README file.
This is very early development so both the quality and feature set should
greatly improve over time. In the current version, only 48 kHz audio with 20 ms
frames are supported, but support for all configurations listed in
greatly improve over time. In the current version, only 48 kHz audio is
supported, but support for all configurations listed in
<xref target="modes"></xref> is planned.
</t>
</section>
@ -176,11 +176,13 @@ There is thus a total of 30 configurations, so 5 bits are necessary (with 2 code
indicate the mode, frame size and sampling rate (MFS). This leaves 3 bits for the number of frames per packets (codes 0 to 7):
<list style="symbols">
<t>0-2: 1-3 frames in the packet, each with equal compressed size</t>
<t>3: arbitrary number of frames in the packet, each with equal compressed size (size needs to be signalled)</t>
<t>3: arbitrary number of frames in the packet, each with equal compressed size (one size needs to be encoded)</t>
<t>4-5: 2-3 frames in the packet, with different compressed sizes, which need to be encoded (except the last one)</t>
<t>6: arbitrary number of frames in the packet, with different compressed sizes, each of which needs to be encoded</t>
<t>7: The first frame has this MFS, but others have different MFS. Compressed sizes need to be encoded.</t>
<t>7: The first frame has this MFS, but others have different MFS. Each compressed size needs to be encoded.</t>
</list>
When code 7 is used and the last frames of a packet have the same MFS, it is
allowed to switch to another code for them.
</t>
<t>
@ -248,7 +250,7 @@ Two frames of different compressed size:
</t>
<t>
Three frames of different *durations*:
Three frames of different <spanx style="emph">durations</spanx>:
</t>
@ -273,9 +275,14 @@ Three frames of different *durations*:
<section anchor="security" title="Security Considerations">
<t>
The codec needs to take appropriate
security considerations into account, for example as outlined in
<xref target="DOS"/> and <xref target="SECGUIDE"/>.
The codec needs to take appropriate security considerations
into account, as outlined in <xref target="DOS"/> and <xref target="SECGUIDE"/>.
It is extremely important for the decoder to be robust against malicious
payloads. Malicious payloads must not cause the decoder to overrun its
allocated memory or to take much more resources to decode. Although problems
in encoders are typically rarer, the same applies to the encoder. Malicious
audio stream must not cause the encoder to misbehave because this would
allow an attacker to attack transcoding gateways.
</t>
</section>