moq C. Jennings
Internet-Draft Cisco
Intended status: Standards Track 2 March 2025
Expires: 3 September 2025
Serialization of MoQ Objects to Files
draft-jennings-moq-file-03
Abstract
This specification provides a way to save the metadata about each MoQ
Object in one or more files as well as pointers to other files that
contain the contents of the object. Separating of the metadata and
payload data allows the payload data to remain in files that are used
for other purposes such as serving HLS/DASH video. This format makes
it easier to test and develop caching relays and create test data
they can serve to clients.
Status of This Memo
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This Internet-Draft will expire on 3 September 2025.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. JSON Meta Object . . . . . . . . . . . . . . . . . . . . . . 2
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Base64 Encoding . . . . . . . . . . . . . . . . . . . . . 4
4. File Naming . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. MoQT Track DataFile . . . . . . . . . . . . . . . . . . . . . 4
6. Playback . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Time Object Example . . . . . . . . . . . . . . . . . . . 4
8. IANA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
9. Security Considerations . . . . . . . . . . . . . . . . . . . 5
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
11. Normative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
This specification defines a way of serializing the MoQ Objects
defined in [MoQT] into files. The payload data and the metadata are
separated into separate files to allows reuse of existing files with
the payload data.
2. JSON Meta Object
The .moq files consist of an array of one or more JSON objects. Each
JSON object contains information about the MoQT object as well as
pointers to the where the original data can be found.
The following fields are defined for JSON object:
* trackNamespace: Array of strings that have a Base64 encoded
version of the data in each tuple of MoQT Track Namespace as
defined in [MoQT].
* trackName: string with Base64 encoded version of the MoQT
Trackname as defined in [MoQT].
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* objectID: integer corresponding to the MoQT Object ID as defined
in [MoQT].
* groupID: integer corresponding to the MoQT Group ID as defined in
[MoQT].
* subGroupID: integer corresponding to the MoQT Subgroup as defined
in [MoQT].
* forwardingPref: String with value of "Subgroup" or "Datagram" to
represent the Object Forwarding Preference as defined in [MoQT].
Open Issue: string or use the binary values used in spec?
* objectStatus: Numeric value representing Object Status as defined
in [MoQT].
* publisherPriority: integer corresponding to the MoQT Publisher
Priority as defined in [MoQT].
* maxCacheDuration: integer corresponding to the MoQT publisher MAX
CACHE DURATION Parameter as defined in [MoQT].
* publisherDeliveryTimeout: integer corresponding to the MoQT
DELIVERY TIMEOUT Parameter sent by the publisher as defined in
[MoQT].
* receiveTime: time original object was created (if known) or time
object was received by the relay. This is saved as an integer in
milliseconds since the unix epoch which is 00:00:00 UTC on January
first, 1970.
* dataFile: string with relative path name to the file that stores
the MoQT Object, including header and its payload data.
* dataOffset: number of bytes into file where the objects starts ( 0
is first byte of file )
* dataLength: number of bytes of data in the object
Any Object Extension Headers, as defined in [MoQT], should also be
saved using a field name formed by the string "ext" then the base 10
integer representation of the extension type with a value that is the
Base64 encoded version of the extension header data. Open Issue:
this will not preserve the order of the extension headers. Is that a
problem?
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3. Terminology
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 [RFC2119].
This specification uses the terminology defined in [MoQT].
3.1. Base64 Encoding
The Base64 encoding used in this specification is the "Base64
Encoding with URL and Filename Safe Alphabet" as defined in
[RFC4648], Section 5. Additionally, the encoding is performed
without any padding or extra blank space characters
4. File Naming
It is RECOMMENDED to use a URL encoding version of the FullTrackName
with a suffix of ".moq" as the file name for the meta file. In this
context FullTrackName is concatenation of Track Namespace with the
TrackName, separated by "_". Optionally, the filename can be
extended with information about group as needed.
5. MoQT Track DataFile
When saving a whole MoQT Track to a file, a common way to do this
would be to make one ".dat" file with all the object data and another
".moq" file with all the array of JSON object for each MoQT Object.
An implementation can choose to have one file per MoQT group. In
such a case, it does so by creating one metadata (".moq") file and
one datafile (".dat") containing data for each object in the MoQT
group.
6. Playback
Some use cases will want to just load a file into the relay as
quickly as possible. Others may decide to rename the track name to a
new track name and publish the objects at a rate based on differences
of the receiveTime of the JSON objects.
7. Example
TODO More complete example
7.1. Time Object Example
Data file named time1.dat contains:
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{"time":17294570764566}
Metadata file contains:
[
{
"namesSpace": "bW9xOi8vbW9xLXRpbWUuYXJwYS90aW1lLXYxLw=",
"trackName": "bWFjOjcyOjVjOmYwOjdjOmJmOmIw",
"objectID": 0,
"groupID": 123,
"subGroup": 0,
"publisherPriority": 0,
"maxCacheDuration": 3600000,
"publisherDeliveryTimeout": 60000,
"receiveTime": 1729457464000,
"dataFile": "time1.dat",
"dataOffset": 0,
"dataLength": 25
}
]
8. IANA
TODO file extension registrations.
9. Security Considerations
TODO
10. Acknowledgements
Thank you to Suhas Nandakumar, Tomas Rigaux, Carsten Bormann and
Gwendal Simon for their reviews and suggestions.
11. Normative References
[MoQT] Curley, L., Pugin, K., Nandakumar, S., Vasiliev, V., and
I. Swett, "Media over QUIC Transport", Work in Progress,
Internet-Draft, draft-ietf-moq-transport-09, 1 March 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-moq-
transport-09>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
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[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/rfc/rfc4648>.
Author's Address
Cullen Jennings
Cisco
Canada
Email: fluffy@iii.ca
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