Author: lu_zero
Date: Thu Sep 27 01:17:09 2007
New Revision: 506
Log:
First commit
Added:
docs/draft-niedermayer-nut-00.xml
Added: docs/draft-niedermayer-nut-00.xml
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--- (empty file)
+++ docs/draft-niedermayer-nut-00.xml Thu Sep 27 01:17:09
2007
 -0,0
+1,276
+<?xml version="1.0"
encoding="UTF-8"?>
+<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
+<!ENTITY rfc2119 SYSTEM "http://xml.resource.org/public/rfc/bib
xml/reference.RFC.2119.xml">
+]>
+<?rfc toc="yes"?>
+<?rfc symrefs="yes"?>
+<?rfc compact="yes"?>
+<?rfc subcompact="no"?>
+<?rfc strict="no"?>
+<?rfc rfcedstyle="yes"?>
+<rfc category="std" docName=""
+ ipr="full3978">
+ <front>
+
+ <title abbrev="NUT Container
Format">NUT Multimedia Container File Format
+ </title>
+
+ <!-- see RFC2223 for guidelines regarding author
names -->
+
+ <author fullname="Michael Niedermayer"
initials="M"
+ surname="Niedermayer">
+ <organization>FFmpeg</organization>
+
+ <address>
+ <email>michaelnigmx.at</email>
+ </address>
+ </author>
+ <author fullname="Luca Barbato"
initials="L" role="editor"
+ surname="Barbato">
+ <organization>Politecnico di
Torino</organization>
+
+ <address>
+ <postal>
+ <street>Corso Duca degli Abruzzi
25</street>
+
+ <city>10135 Torino</city>
+
+ <country>Italy</country>
+ </postal>
+
+ <email>lu_zerogentoo.org</email>
+ </address>
+ </author>
+
+ <date year="2007" />
+
+ <area>General</area>
+
+<!-- <workgroup>AVT Working
Group</workgroup> -->
+
+ <keyword>Internet-Draft</keyword>
+
+ <keyword>RTP</keyword>
+
+ <keyword>SCTP</keyword>
+
+ <abstract>
+ <t>This memo defines a method for efficiently
storing generic multimedia
+ streams so that operation like seeking and recover
for error can be
+ performed with minimal computational cost. Minimal
overhead and maximal
+ extensibility had been considered in the development
of the format.</t>
+ </abstract>
+
+ <note title="Editors Note">
+ <t>All references to RFC XXXX are to be
replaced by references to the
+ RFC number of this memo, when
published.</t>
+ </note>
+
+ </front>
+
+ <middle>
+ <section title="Introduction">
+ <!-- It is good practice to echo the abstract in
the Introduction,
+providing citations here. -->
+
+ <t>NUT is a multimedia container format for
storage of audio, video,
+ subtitles and related user defined streams, it
provides exact timestamps
+ for synchronization and seeking, is simple, has low
overhead and can
+ recover in case of errors in the stream.</t>
+ <t>This document defines:
+ <list style="hanging">
+ <t> The file format layout
+ </t>
+ <t> The common stream interleaving rules
+ </t>
+<!-- <t> A simple provision how to map nut
streams to rtp.
+ </t> -->
+ </list>
+ </t>
+
+ <section title="Terminology">
+ <t>The key words "MUST", "MUST
NOT", "REQUIRED", "SHALL",
"SHALL NOT",
+ "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and
"OPTIONAL" in this
+ document are to be interpreted as described in
<xref target="RFC2119" />.</t>
+ <t> This document refers to the following
definitions
+ <list style="hanging">
+ <t hangText="pts"> Presentation
time of the first frame/sample that
+ is completed by decoding the coded frame.
+ </t>
+ <t hangText="dts"> The time
when a frame is input into a
+ synchronous 1-in-1-out decoder.
+ </t>
+ <t hangText="frame"> Minimal
unit of information that can be
+ decoded completely, it is usually holds a full
frame video frame,
+ a group of audio samples or a subtitle line.
+ </t>
+ <t hangText="Keyframe"> A
keyframe is a frame from which you can
+ start decoding.
+ The nth frame is a keyframe if and only if
frames n, n+1, ... in
+ presentation order (that are all frames with a
pts >= frame[n].pts)
+ can be decoded successfully without reference
to frames prior n in
+ storage order (that are all frames with a dts
< frame[n].dts).
+ If no such frames exist (for example due to
using overlapped
+ transforms like the MDCT in an audio codec),
then the definition
+ shall be extended by dropping n out of the set
of frames which
+ must be decodable, if this is still
insufficient then n+1 shall
+ be dropped, and so on until there is a
keyframe.
+ Every frame which is marked as a keyframe MUST
be a keyframe
+ according to the definition above, a muxer MUST
mark every frame
+ it knows is a keyframe as such, a muxer SHOULD
NOT analyze future
+ frames to determine the keyframe status of the
current frame but
+ instead just set the frame as non-keyframe.
+ </t>
+ </list>
+ </t>
+ </section>
+ <section title="Syntax Convetions">
+ <t> Since NUT heavily uses variable length
fields, the simplest way to
+ describe it is using a pseudocode approach instead
of graphical
+ bitfield descriptions.
+ </t>
+ <t> The syntax uses datatypes, tagnames and
C-like constructs. </t>
+
+ <section title="Datatypes">
+
+ <t>
+ <list style="hanging">
+ <t hangText="f(n)"> n fixed
bits in bigendian order</t>
+ <t hangText="u(n)"> Unsigned
value encoded in n bits MSB-first</t>
+
+ <t hangText="v"> Unsigned
variable length value.
+ <figure anchor="Variable Length
Unsigned Figure" title="Variable
+ Length Unsigned Value">
+ <artwork><![CDATA[
+ value=0
+ do{
+ more_data u(1)
+ data u(7)
+ value= 128*value + data
+ }while(more_data)]]>
+ </artwork>
+ </figure>
+ Values can be encoded using the following logic:
the data is in
+ network order, every byte has the most
significant bit used as
+ flag and the following 7 used to store the
value.
+ The first N bit are to be taken, where N is
number of bits
+ representing the value modulo 7, and stored in
the first byte.
+ If there are more bits, the flag bit is set to 1
and the subsequent
+ 7bit are stored in the following byte, if there
are remaining bits
+ set the flag to 1 and the same procedure is
repeated. <br />
+ The ending byte has the flag bit set to 0.
+ In order to decode it is enough to iterate over
the bytes until the
+ flag bit set to 0, for every byte the data is
added to the
+ accumulated value multiplied by 128.
+ </t>
+ <t hangText="s"> Signed
variable length value.
+ <figure anchor="Variable Length
Signed Figure" title="Variable
+ Length Signed Value">
+ <artwork><![CDATA[
+ temp v
+ temp++
+ if(temp&1) value= -(temp>>1)
+ else value= (temp>>1)]]>
+ </artwork>
+ </figure>
+ The signed values are encoded as the absolute
value multiplied by
+ 2, positive numbers have 1 subtracted to the
value. [FIXME: why not
+ just shift&sign]
+ </t>
+ <t hangText="vb"> Variable
length binary data (or utf-8 string).
+ <figure anchor="Variable Length
String Figure" title="Variable
+ Length Signed Value">
+ <artwork><![CDATA[
+ length v
+ for(i=0; i<length; i++){
+ data[i] u(8)
+ }]]>
+ </artwork>
+ </figure>
+ Strings and binary data can be encoded
basically writing the byte
+ count as a Variable Length Unsigned Value and
the the string.
+ The strings MUST be encoded in utf-8
+ </t>
+ <t hangText="t"> Universal
timestamp.
+ <figure anchor="Universal
Timestamp" title="Variable
+ Length Timestamp">
+ <artwork><![CDATA[
+ tmp v
+ id= tmp % time_base_count
+ value= (tmp / time_base_count) * time_base[id]]]>
+ </artwork>
+ </figure>
+ [FIXME]
+ </t>
+ </list>
+ </t>
+
+ </section>
+
+ </section>
+ </section>
+
+ <section title="NUT file layout">
+
+ <t></t>
+
+ <section title="High level File
structure">
+ <t>[TODO]</t>
+ </section>
+ <section title="Main Header">
+ <t>[TODO]</t>
+ </section>
+ <section title="Reserved Headers">
+ <t>[TODO]</t>
+ </section>
+ <section title="Stream Header">
+ <t>[TODO]</t>
+ </section>
+ <section title="Info Packet">
+ <t>[TODO]</t>
+ </section>
+ <section title="Index">
+ <t>[TODO]</t>
+ </section>
+ <section title="Syncpoint">
+ <t>[TODO]</t>
+ </section>
+ </section>
+
+ <section title="Interleaving Rules">
+ </section>
+
+ <section title="IANA Considerations">
+ <t>[TODO] In order to comply with IESG policy
as set forth in
+ http://www.ietf
.org/ID-Checklist.html, every Internet-Draft that is
+ submitted to the IESG for publication MUST contain an
IANA
+ Considerations section. </t>
+
+ </section>
+
+ <section title="Security
Considerations">
+ <t>[TODO]</t>
+ </section>
+
+ <section title="Acknowledgements">
+ <t>Thanks to Marshall Rose for developing the
XML2RFC format.</t>
+
+ </section>
+ </middle>
+
+ <back>
+
+ <references title="Normative
References">
+
+ &rfc2119;
+
+ <!-- <t>[TODO]: Add your own normative
references.</t>-->
+ </references>
+
+ <references title="Informative
References">
+
+ <!-- <t>[TODO] Add your own informative
references</t>-->
+ </references>
+ </back>
+</rfc>
+<!-- vim: set sw=2 sts=2 et tw=79: -->
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