Rufael Mekuria
Unified Streaming
Internet Engineering Task Force Sam Geqiang Zhang
Internet-Draft Microsoft
Expires: January 15, 2019
Intended status: Best Current Practice July 15 2018
Live Media and Metadata Ingest Protocol
draft-mekuria-mmediaingest-01.txt
Abstract
This Internet draft presents a best industry practice for
ingesting encoded live media to media processing entities.
Two profiles of the media ingest are defined covering the most
common use cases. The first profile facilates active media
processing and is based on the fragmented MPEG-4 format.
The second profile enables efficient ingest of media streaming
presentations based on established streaming protocols
by also adding a manifest besides the fragmented MPEG-4 stream.
Details on carriage of metadata markers, timed text,
subtitles and encryption specific metadata are also included.
Status of This Memo
This Internet-Draft is submitted in full conformance
with the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet
Engineering Task Force (IETF). Note that other groups
may also distribute working documents as Internet-Drafts.
The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum
of six months and may be updated, replaced, or obsoleted
by other documents at any time. It is inappropriate to
use Internet-Drafts as reference material or to cite
them other than as "work in progress."
Mekuria & Zhang Expires January 15 2019 [Page1]
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described
in Section 4.e of the Trust Legal Provisions and are provided
without warranty as described in the Simplified BSD License
Table of Contents
1. Introduction
2. Conventions and Terminology
3. Media Ingest Workflows and Use Cases
4. General Media Ingest Protocol Behavior
5. Profile 1: Fragmented MPEG-4 Ingest General Considerations
6. Profile 1: Fragmented MPEG-4 Ingest Protocol Behavior
6.1 General Protocol Requirements
6.2 Requirements for Formatting Media Tracks
6.3 Requirements for Timed Text Captions and Subtitle Streams
6.4 Requirements for Timed Metadata
6.5 Requirements for Media Processing Entity Failover
6.6 Requirements for Live Media Source Failover
7. Profile 2: DASH and HLS Ingest General Considerations
8. Profile 2: DASH and HLS Ingest Protocol Behavior
8.1 General Protocol requirements
8.2 Requirements for Formatting Media Tracks
8.3 Requirements for Timed Text, Caption and Subtitle Streams
8.4 Requirements for Timed Metadata
8.5 Requirements for Media Processing Entity Failover
8.6 Requirements for Live Media Source Failover
9. Security Considerations
10. IANA Considerations
11. Contributors
12. References
12.1. Normative References
12.2. Informative References
12.3. URL References
Author's Address
Mekuria & Zhang Expires January 15 2019 [Page2]
1. Introduction
This document describes a best practice for ingesting
encoded media content from a live source such as a
live video encoder towards distributed media
processing entities. Examples of such entities
include media packagers, publishing points,
streaming origins and content delivery networks.
The combination of live sources ingesting
media and distributed media processing entities
is important in practical video streaming deployments.
In such deployments, interoperability between
live sources and downstream processing
entities can be challenging.
This challenge comes from the fact that
there are multiple levels of interoperability
that need to be adressed and achieved.
For example, the network protocol for transmission
of data and the setup of the connectivity are important.
This includes schemes for establishing the ingest
connection, handling disconnections and failures,
procedures for repeatedly sending and receving
the data, and timely resolution of hostnames.
A second level of interoperability lies
in the media container and coded media formats.
The Moving Picture Experts Group defined several media
container formats such as [ISOBMFF] and MPEG-2 Transport
Stream which are widely adopted and well supported.
However, these are general purpose formats,
targetting several different application areas.
To do so they provide many different profiles and options.
Detailed operability is often achieved through
other application standards such as those for
the broadcast or storage. In addition, the codec
and profile used, e.g. [HEVC] is an important
interoperability point that itself also
has different profiles and options.
A third level, is the way metadata is
inserted in streams which can be a source
of interoperability issues, especially for live
content that needs such meta-data to signal
opportunities for signalling ad insertion,
or other metadata like timed graphics. Examples
of such metadata include [SCTE-35] markers which
are often found in broadcast streams and other
metadata like ID3 tags [ID3v2].
Mekuria & Zhang Expires January 15 2019 [Page3]
Fourth, for live media handling the timeline
of the presentation consistently is important.
This includes correct sampling of media, avoiding
timeline discontinuities and synchronizing
timestamps attached by different live sources.
Fifth, in streaming workflows it is important
to have support for failovers of both the live sources
and the media processing entities. This is important
to avoid interruptions of 24/7 live services such
as Internet television where components can fail.
In practical deployments, multiple live sources
and media processing entities are used. This requires
the multile live sources and media processing to
work together in a redundant workflow where
some of the components might fail.
This document provides an industry best
practice approach for establishing these
interoperability points for live media ingest.
The approaches are based on known standardized
technologies and have been tested and deployed
in several streaming large scale streaming
deployments. Two key workflows have been
identified for which two different media
ingest profiles will be detailed.
In first workflow, encoded media is ingested
downstream for further processing of the media.
Examples of such media processing could be any
media transformation such as packaging,
encrypting or transcoding the stream.
Other operations could include watermarking,
content insertion and generating streaming manifests
based on [DASH] or HLS[RFC8216]. What is typical
of these operations is that they actively inspect,
or modify the media content and may
generate new derived media content.
In this workflow it is is important
to convey mediadata and metadata that
assists such active media processing operations.
This is workflow type will be adressed
in the first profile.
Mekuria & Zhang Expires January 15 2019 [Page4]
In the second workflow, the encoded media is ingested
into an entity that does none or very minimal inspection
or modification of the media content. The main aim
of such processing entities often lies in storage,
caching and delivery of the media content. An example
of such an entity is a Content Delivery Network (CDN)
for delivering and caching Internet content.
Content delivery networks are often designed for
Internet content like web pages and might
not be aware of media specific aspects. In fact, streaming
protocols like MPEG DASH and HTTP Live Streaming have been
developed with re-use of such a media agnostic
Content Delivery Networks in mind. For ingesting
encoded media into a content delivery network it
is important to have the media presentation in a form
that is very close or matching to the format
that the clients need to playback the presentation,
as changing or complementing the media presentation
will be difficult. This second workflow is addressed
in profile 2.
Diagram 1: Example with media ingest in profile 1
============ ============== ==============
|| live || ingest|| Active || HLS || Content || HLS
|| media ||====>>>||processing||===>>>|| Delivery ||==>>>Client
|| source || || entity || DASH || Network || DASH
============ ============== ==============
Diagram 2: Example with media ingest in profile 2
============ ==============
|| live || ingest|| Content ||
|| media ||====>>>||Delivery ||==>>>> Client
|| source || || Network ||
============ ==============
Diagram 1 shows the workflow with a live media ingest from a
live media source towards an active media processing entity.
In the example in diagram 1 the media processing entity
prepares the final media presentation for the client
that is delivered by the Content Delivery Network to a client.
Diagram 2 shows the example in workflow 2 were content
is ingested directly into a Content Delivery Network.
The content delivery network enables the delivery to the client.
An example of a media ingest protocol
is the ingest part of Microsoft Smooth
Streaming protocol [MS-SSTR]. This protocol
connects live encoders to
the Microsoft Smooth Streaming server and to
the Microsoft Azure cloud.
Mekuria & Zhang Expires January 15 2019 [Page5]
This protocol has shown
to be robust, flexible and easy to implement in live
encoders. In addition it provided features for
high availability and server side redundancy.
The first profile relating to workflow 1
advances over the smooth ingest procotol
including lessons learned over the last
ten years after the initial deployment of
smooth streaming in 2009 and several advances
on signalling of information
such as timed metadata markers for content insertion.
In addition, it incorporates the latest media formats
and protocols, making it ready for current and
next generation media codecs such as [HEVC]
and protocols like MPEG DASH [DASH].
A second profile is included for ingest of media
streaming presentations to entities were
the media is not altered actively, and further
media processing perhaps restricted to the manifests.
A key idea of this part of the specification is to re-use
the similarities of MPEG DASH [DASH] and HLS[RFC8216] protocols
to enable a simultaneous ingest of media
presentations of these two formats using
common media segments such as based on [ISOBMFF]
and [CMAF] formats. In addition, in this
approach naming is important to enable direct
processing and storage of the presentation.
Based on our experience we present
these two as separate profiles to
handle the two workflows.
We made this decision as it will
reduce a lot of overhead in the
information that needs to be signalled
compared to having both profiles
combined into one, as was the case
in a prior version of this draft.
We further motivate this best practice presented
in this document supporting using
HTTP [RFC2626] and [ISOBMFF] a bit more.
We believe that Smooth streaming [MS-SSTR]
and HLS [RFC8216] have shown that HTTP usage
can survive the Internet ecosystem for
media delivery. In addition, HTTP based
ingest fits well with current HTTP
based streaming protocols including [DASH].
In addition, there is good support for HTTP
middleboxes and HTTP routing available
making it easier to debug and trace errors.
The HTTP POST provides a push based
method for delivery for pusing the
live content when available.
Mekuria & Zhang Expires January 15 2019 [Page6]
The binary media format for conveying
the media is based on fragmented MPEG-4 as
specified in [ISOBMFF] [CMAF]. A key benefit of this
format is that it allows easy identification
of stream boundaries, enabling switching, redundancy,
re-transmission resulting in a good fit with the current
Internet infrastructures. Many problems in
practical streaming deployment often deal
with issues related to the binary
media format. We believe that the fragmented
MPEG-4 will make things easier
and that the industry is already heading
in this direction following recent specifications
like [CMAF] and HLS[RFC8216].
Regarding the transports protocol, in future versions,
alternative transport protocols could be considered
advancing over HTTP. We believe the proposed media format
will provide the same benefits with other transports
protocols. Our view is that for current and near future
deployments using [RFC2626] is still a good approach.
The document is structured as follows, in section 2
we present the conventions and terminology used throughout
this document. In section 3 we present use cases and
workflows related to media ingest and the two profiles
presented. Sections 4-8 will detail the protocol and
the two different profiles.
2. Conventions and Terminology
The following terminology is used in the rest of this document.
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 BCP 14, RFC 2119
[RFC2119].
ISOBMFF: the ISO Base Media File Format specified in [ISOBMFF].
<Mekuria> Expires January 15 2019 [Page7]
Live Ingest Stream:
the stream of media produced by the live source
transmitted to the media processing entity.
Live Stream Event:
the total live stream for the ingest.
(Live) encoder: entity performing live
encoding and producing a high quality live stream,
can serve as media ingest source
Media (Ingest) source:
a media source ingesting media content
, typically a live encoder but not restricted
to this,the media ingest source could by any
type of media ingest source such as a stored
file that is send in partial chunks.
Live Ingest Source:
Media Ingest source producing live content
Publishing point:
entity used to publish the media content,
consumes/receives the incoming media ingest stream
Media processing entity:
entity used to process the media content,
receives/consumes a media ingest stream.
Media processing function:
Media processing entity
Connection:
a connection setup between two hosts, typically the
media ingest source and media processing entity.
ftyp:
the filetype and compatibility "ftyp" box as described
in the ISOBMFF [ISOBMFF] that describes the "brand"
moov:
the container box for all metadata "moov" described in the
ISOBMFF base media file format [ISOBMFF]
moof:
the movie fragment "moof" box as described in the
ISOBMFF base media file format [ISOBMFF] that describes
the metadata of a fragment of media.
mdat:
the media data container "mdat" box contained in
an ISOBMFF [ISOBMFF], this box contains the
compressed media samples
kind:
the track kind box defined in the ISOBMFF [ISOBMFF]
to label a track with its usage
mfra:
the movie fragment random access "mfra" box defined in
the ISOBMFF [ISOBMFF] to signal random access samples
(these are samples that require no prior
or other samples for decoding) [ISOBMFF].
tfdt:
the TrackFragmentBaseMediaDecodeTimeBox box "tfdt"
in the base media file format [ISOBMFF] used
to signal the decode time of the media
fragment signalled in the moof box.
<Mekuria> Expires January 15 2019 [Page8]
mdhd:
The media header box "mdhd" as defined in [ISOBMFF],
this box contains information about the media such
as timescale, duration, language using ISO 639-2/T codes
[ISO639-2]
pssh:
The protection specific system header "pssh" box defined
in [CENC] that can be used to signal the content protection
information according to the MPEG Common Encryption [CENC]
sinf:
Protection scheme information box "sinf" defined in
[ISOBMFF] that provides information on the encryption
scheme used in the file
elng:
extended language box "elng" defined in [ISOBMFF] that
can override the language information
nmhd:
The null media header Box "nmhd" as defined in [ISOBMFF]
to signal a track for which no specific
media header is defined, often used for metadata tracks
HTTP:
Hyper Text Transfer Protocol,
version 1.1 as specified by [RFC2626]
HTTP POST:
Command used in the Hyper Text Transfer Protocol for
sending data from a source to a destination [RFC2626]
fragmentedMP4stream:
stream of [ISOBMFF] fragments
(moof and mdat), a more precise definition will follow
later in this section.
POST_URL:
Target URL of a POST command in the HTTP protocol
for posting data from a source to a destination.
TCP:
Transmission Control Protocol (TCP) as defined in [RFC793]
URI_SAFE_IDENTIFIER:
identifier/string formatted according to [RFC3986]
A fragmentedMP4stream can be defined
using the IETF RFC 5234 ANB [RFC5234] as follows.
fragmentedMP4stream = headerboxes fragments
headerboxes = ftyp moov
fragments = X fragment
fragment = Moof Mdat
This fragmentedMP4 stream is used in both profiles.
Mekuria & Zhang Expires January 15 2019 [Page9]
3. Media Ingest Workflows and Use Cases
In this section we highlight some of the target use cases
and example workflows for the media ingest.
Diagram 3 shows an example workflow of media ingest
with profile 1 in a streaming workflow. The live media
is ingested into the media processing entity that performs
operations like on-the-fly encryption, content stitching
packaging and possibly other operations before
delivery of the final media presentation to the client.
This type of distributed media processing offloads
many functionalities from the live media source.
As long as the stream originating from the media
source contains sufficient metadata, the media
processing entity can generate the media presentation
for streaming to clients or other derived media
presentations as needed by a client.
Diagram 4 shows an alternative example with ingest
to a content delivery network, or perhaps another
passive media entity such as a storage. In this case
the live media source posts the segments and the
manifests for the media presentation.
In this case, still fragmented MPEG-4 segments can be used,
but the ingest works slightly different.
Diagram 3:
Streaming workflow with fragmented MPEG-4 ingest in profile 1
============ ============== ==============
|| live ||ingest || Media || HLS || Content || HLS
|| media ||====>>>||processing||===>>>|| Delivery ||==>>> Client
|| source || fmp4 || entity || DASH || Network || DASH
============ ============== ==============
Diagram 4:
Streaming workflow with DASH ingest in profile 2
============ingest ==============
|| live || DASH || Content ||
|| media ||====>>>||Delivery ||==>>>> Client
|| source || || Network ||
============ ==============
Mekuria & Zhang Expires January 15 2019 [Page10]
Practice has shown that the ingest schemes
can be quite different for the two configurations
, and that combining them into a single protocol
will result in overhead such as sending
duplicate information in the manifest or
ISOBMFF moov box, and increased
signalling overhead for starting, closing
and resetting the connection. Therefore,
the two procedures for media ingest in
such two common workflows are presented
as separate profiles in the next two sections.
In Diagram 5 we highlight some of the key
differences for practical consideration between
the profiles. In profile 1 the encoder can be
simple as the media processing entity can
do many of the operations related to the
delivery such as encryption or generating the streaming
manifests. In addition the distribution of functionalities
can make it easier to scale a deployment with many
live media sources and media processing entities.
In some cases, an encoder has sufficient
capabilities to prepare the final presentation for the
client, in that case content can be ingested directly
to a more passive media processing entity that provides
a more pass through like functionality.
In this case also manifests and other client specific
information needs to be ingested. Besides these factors
, chosing a workflow for a video streaming platform depends
on many factors. The media ingest best practice
covers these two types of workflows by two different
profiles. The best choice for a specific platform depends
on many of the use case specific requirements, circumstances
and the available technologies.
Mekuria & Zhang Expires January 15 2019 [Page11]
In Diagram 6 we highlight another aspect taken into
consideration for large scale systems with many users.
Often one would like to run multiple encoders,
multiple processing entities and make them available
to the clients via a load balancer. This way requests
can be balanced over multiple processing nodes.
This approach is common when serving web pages,
and this architecture also applies to video
streaming platforms that also use HTTP. In Diagram
6 it is highlighted how one or more multiple live encoders can
be sending data to one or more processing entities. In
such a workflow it is important to handle the case
when one source or media processing entity fails over.
We call this support for failover. It is an important
consideration in practical video streaming systems that
need to run 24/7. Failovers must be handled robustly
and seamlesslessly without causing service interruption.
In both profiles we detail how this failover and redundancy
support can be achieved.
Diagram 5: Differences profile 1 and profile 2 for use cases
============================================================
|Profile | Encoder/Live source | Media processing |
|----------|----------------------|------------------------|
|Profile 1 |limited overview |DRM,transcode, watermark|
| | simple encoder |man. create, packaging|
| | multiple sources |content stitch, timed |
|Profile 2 |Global overview | cache, store, deliver |
| |encoder targets client| |
| |only duplicate sources| manifest manipulation |
============================================================
Diagram 6:
workflow with redundant sources and media processing entities
============ fmp4 ==============
|| live || stream|| Media ||
|| media ||====>>>||Processing|| \\
|| source || // || Entity || \\
============ // ============== \\ ============
|| live || // \\ || load ||
|| media ||// redundant stream >>||balancer|| ==>>> Client
|| source ||\\ stream // =============
============ \\ ============= //
|| live || \\ || Media || //
||ingest ||====>>>||Processing ||//
|| source || // || Entity ||
============ // ===============
|| live || //
||ingest ||// redundant stream
|| source ||
============
Mekuria & Zhang Expires January 15 2019 [Page11]
4. General Ingest Protocol Behavior
The media ingest follows the following
general requirements for both target profiles.
1. The live encoder or ingest source communicates to
the publishing point/processing entity using the HTTP
POST method as defined in the HTTP protocol [RFC2626]
2. The media ingest source SHOULD use HTTP over TLS [RFC2818]
to connect to the media processing entity
3. The live encoder/media source SHOULD repeatedly resolve
the Hostname to adapt to changes in the IP to Hostname mapping
such as for example by using the dynamic naming system
DNS [RFC1035] or any other system that is in place.
4. The Live encoder media source MUST update the IP to hostname
resolution respecting the TTL (time to live) from DNS
query responses, this will enable better resillience
to changes of the IP address in large scale deployments
where the IP adress of the publishing point media
processing nodes may change frequenty.
5. In case HTTPS[RFC2818] protocol is used,
basic authentication HTTP AUTH [RFC7617]
or better methods like TLS client certificates SHOULD be used
6. As compatibility profile for the TLS encryption
we recommend the ingest SHOULD use the mozzilla
intermediate compatibility profile which is supported
in many available implementations [MozillaTLS].
7. The encoder or ingest source SHOULD terminate
the HTTP POST request if data is not being sent
at a rate commensurate with the MP4 segment duration.
An HTTP POST request that does not send data can
prevent publishing points or media processing entities
from quickly disconnecting from the live encoder or
media ingest source in the event of a service update.
For this reason, the HTTP POST for sparse
data such as sparse tracks SHOULD be short-lived,
terminating as soon as
the sparse fragment is sent.
8. The POST request uses a POST_URL to the basepath of the
publishing point at the media processing entity and
MAY use a relative path for different streams and segments.
5. Profile 1: Fragmented MPEG-4 Ingest General Considerations
The first profile assumes ingest to an active media processing entity,
from one or more live ingest sources, ingesting one or more
types of media streams. This advances over the ingest
part of the smooth ingest protocol [MS-SSTR] by using
standardized media container formats based on [ISOBMFF][CMAF].
In addition this allows extension to codecs like [HEVC] and
timed metadata ingest of subtitle and timed text streams.
The workflow ingesting multiple media ingest streams with
fragmented MPEG-4 ingest is illustrated in Diagram 7.
Mekuria & Zhang Expires January 15 2019 [Page13]
Diagram 7: fragmented MPEG-4 ingest with multiple ingest sources
============ fmp4 ==============
|| live || video || ||
|| ingest ||====>>>|| ||
|| source || || ||
============ || ||
|| live || fmp4 || ||
|| ingest ||====>>>|| Active || ==============
|| source || audio || Media || HLS || Content || HLS
============ || procesing||===>>>|| Delivery ||==>>> Client
|| live || fmp4 || entity || DASH || Network || DASH
||ingest ||====>>>|| || =============
|| source || text || ||
============ || ||
|| live || fmp4 || ||
||ingest || meta || ||
|| source || data || ||
|| ||====>>>|| ||
============ ==============
In diagrams 8-10 we detail some of the concepts and structures.
Diagram 8 shows the data format structure of fragmented
MPEG-4 [ISOBMFF] and [CMAF]. In this format media meta data
(playback time, sample duration) and sample data (encoded samples)
are interleaved. the moof box as specified in [ISOBMFF] is used
to signal the information to playback and decode the samples
followed in the mdat box.
The ftyp and moov box contain the track specific information
and can be seen as a header of the stream, sometimes referred
as a [CMAF] header. The styp box can be used to signal the
type of segment. The combination of styp moof mdat can be referred
as a segment, the combination of ftyp and moof can be referred
to as an init segment or a CMAF header.
Diagram 8: fragmented mp4 stream:
=========================================================
||ftyp||moov||styp||moof||mdat||styp||moof||mdat|| .....=
=========================================================
In diagram 9 we illustrate the synchronisation model, that
is in many ways similar, but simplified, from the synchronisation
model propose in [CMAF]. Different bit-rate tracks
and or media streams are conveyed in separate fragmented mp4 streams.
by having the boundaries to the segments time alligned for tracks
comprising the same stream at different bit-rates, bit-rate
switching can be achieved. By using a common timeline
different streams can be synchronized at the receiver,
while they are in a separeted fragmented mp4 stream
send over a separate connection, possibly from a different
live ingest source.
Mekuria & Zhang Expires January 15 2019 [Page14]
In diagram 10 another advantage of this synchronisation model
is illustrated, the concept of late binding. In the case
of late binding a new stream becomes available. By using
the segment boundaries and a common timeline it can
be received by the media processing entity and embedded
in the presentation. Late binding is useful for many
practical use cases when broadcasting television
content with different types of metadata tracks.
Diagram 9: fmp4 stream synchronisation:
=========================================================
||ftyp||moov||styp||moof||mdat||styp||moof||mdat|| .....=
=========================================================
||ftyp||moov||styp||moof||mdat||styp||moof||mdat|| .....=
=========================================================
||ftyp||moov||styp||moof||mdat||styp||moof||mdat|| .....=
=========================================================
Diagram 10: fmp4 late binding:
===================================================
||ftyp||moov||styp||moof||mdat||moof||mdat|| .....=
===================================================
==========================
||ftyp||moov||styp||moof||
=========================
Diagram 11 shows the flow of the media ingest. It starts with a
DNS resolution (if needed) and an authentication step (Authy,
TLS certificate) to establish a secure TCP connection.
In some private datacenter deployments where nodes
are not reachable from outside, a non authenticated connection
MAY also be used. The ingest source then issues an empty POST
to test that the media processing entity is listening. It then
start sending the moov + ftyp box (the init segment), followed
by the rest of the segments in the fragmented MPEG-4 stream. In
the end of the session, for tear down the source can send an
empty mfra box to close the connection.
Mekuria & Zhang Expires January 15 2019 [Page15]
Diagram 11: fmp4 ingest flow
||===============================================================||
||===================== ============================ ||
||| live ingest source | | Media processing entity | ||
||===================== ============================ ||
|| || <<------ DNS Resolve -------->> || ||
|| || <<------ Authenticate -------->> || ||
|| || <<------POST fmp4stream -------->> || ||
||=============== empty POST to test connection ================||
|| || <<------ 404 Bad Request -----------|| ||
|| || <<------ 202 OK --------------------|| ||
|| || <<------ 403 Forbidden -------------|| ||
|| || <<------ 404 Bad Request || ||
|| || <<------ 400 Forbidden -------------|| ||
|| || Unsupported Media Type || ||
|| || <<------ 415 Forbidden -------------|| ||
||================== Moov + ftyp Sending =======================||
||============= fragmented MP4 Sending ==========================||
|| || <<------ 404 Bad Request -----------|| ||
||============= mfra box Sending (close) ========================||
|| || <<------ 200 OK --------------------|| ||
||===================== ============================ ||
||| live ingest source | | Media processing entity | ||
||===================== ============================ ||
|| || || ||
||===============================================================||
6. Profile 1: Fragmented MPEG-4 Ingest Protocol Behavior
This section describes the protocol behavior specific to
profile 1: fragmented MPEG-4 ingest. Operation of this
profile MUST also adhere to general requirements in secion 4.
6.1. General Protocol Requirements
1. The live encoder or ingest source SHOULD start
by sending an HTTP POST request with an empty "body"
(zero content length) by using the POSTURL
This can help the live encoder or media
ingest source to quickly detect whether the
live ingest publishing point is valid,
and if there are any authentication
or other conditions required.
2. The live encoder or ingest source MUST initiate
a media ingest connection by POSTING the
header boxes "ftyp" and "moov" after step 1
3. The encoder or ingest source SHOULD use chunked transfer
encoding option of the HTTP POST command [RFC2626]
as it might be difficult to predict the entire content length
of the segment. This can also be used for example to support
use cases that require low latency.
Mekuria & Zhang Expires January 15 2019 [Page16]
4. If the HTTP POST request terminates or times out with a TCP
error prior to the end of the stream, the encoder MUST issue
a new connection, and follow the
preceding requirements. Additionally, the encoder MAY resend
the previous segment that was already sent again.
5. The live encoder or ingest source MUST handle
any error or failed authentication responses
received from the media processing, by issueing
a new connection and following the preceding
requirements inlcluding retransmitting the ftyp and moov boxes.
6. In case the live stream event is over the live media
source or ingest source should signal
the stop by transmitting an empty "mfra" box
towards the publishing point/processing entity.
7. The live ingest source SHOULD use a separate TCP
connection for ingest of each different track
8. The live ingest source MAY use a separate relative path
in the POST_URL for ingest of each different track
6.2. Requirements for formatting Media Tracks
1. The trackFragmentDecodeTime box "tfdt" box
MUST be present for each segment posted.
2. The ISOBMFF media fragment duration SHOULD be constant,
the duration MAY fluctuate to compensate
for non-integer frame rates. By choosing an appropriate
timescale (a multiple of the frame rate is recommended)
this issue SHOULD be avoided.
3. The MPEG-4 fragment durations SHOULD be between
approximately 1 and 6 seconds.
4. The fragment decode timestamps "tfdt" of fragments in the
fragmentedMP4stream and the indexes base_media_decode_ time
SHOULD arrive in increasing order for each of the different
tracks/streams that are ingested.
5. The segments formatted as fragmented MP4 stream SHOULD use
a timescale for video streams based on the framerate
and 44.1 KHz or 48 KHz for audio streams
or any another timescale that enables integer
increments of the decode times of
fragments signalled in the "tfdt" box based on this scale.
6. The language of the stream SHOULD be signalled in the
"mdhd" box or "elng" boxes in the
init segment and/or moof headers ("mdhd").
7. Encryption specific information SHOULD be signalled
in the "pssh","schm" and "sinf" boxes following [ISOBMFF][CENC]
8. Segments posted towards the media procesing entity SHOULD
contain the bitrate "btrt" box specifying the target
bitrate of the segments
9. Segments posted towards the media procesing entity SHOULD
contain the "tfdt" box specifying the fragments decode time
and the "tfhd" box specifying the track id.
Mekuria & Zhang Expires January 15 2019 [Page17]
6.3 Requirements for Timed Text Captions and Subtitle streams
The media ingest follows the following requirements for ingesting
a track with timed text, captions and/or subtitle streams.
1. The track will be a sparse track signalled by a null media
header "nmhd" containing the timed text, images, captions
corresponding to the recommendation of storing tracks
in fragmented MPEG-4 [CMAF]
2. Based on this recommendation the trackhandler "hdlr" shall
be set to "text" for WebVTT and "subt" for TTML following
[MPEG-4-30]
3. In case TTML is used the track must use the XMLSampleEntry
to signal sample description of the sub-title stream [MPEG-4-30]
4. In case WebVTT is used the track must use the WVTTSampleEntry
to signal sample description of the text stream [MPEG-4-30]
5. These boxes SHOULD signal the mime type and specifics as
described in [CMAF] sections 11.3 ,11.4 and 11.5
6. The boxes described in 2-5 must be present in the init
segment (ftyp + moov) for the given track
7. subtitles in CTA-608 and CTA-708 format SHOULD be conveyed
following the recommendation section 11.5 in [CMAF] via
Supplemental Enhancement Information SEI messages
in the video track [CMAF]
8. The "ftyp" box in the init segment for the track
containing timed text, images, captions and sub-titles
MAY use signalling using CMAF profiles based on [CMAF]
8a. WebVTT Specified in 11.2 ISO/IEC 14496-30
[MPEG-4-30] 'cwvt'
8b.TTML IMSC1 Text Specified in 11.3.3 [MPEG-4-30]
IMSC1 Text Profile 'im1t'
8c.TTML IMSC1 Image Specified in 11.3.4 [MPEG-4-30]
IMSC1 Image Profile 'im1i'
8d. CEA CTA-608 and CTA-708 Specified in 11.4 [MPEG-4-30]
Caption data is embedded in SEI messages in video track;
'ccea'
6.4 Requirements for Timed Metadata
This section discusses the specific formatting requirements
for ingest of timed metadata related to events and markers for
ad insertion or other timed metadata An example of
these are opportunities for dynamic live ad insertion
signalled by SCTE-35 markers. This type of event signalling
is different from regular audio/video information
because of its sparse nature. In this case,
the signalling data usually does not
happen continuously, and the intervals can
be hard to predict. Examples of timed metadata are ID3 tags
[ID3v2], SCTE-35 markers [SCTE-35] and DASH emsg
messages defined in section 5.10.3.3 of [DASH]. For example,
DASH Event messages contain a schemeIdUri that defines
the payload of the message.
Mekuria & Zhang Expires January 15 2019 [Page18]
Table 1 provides some
example schemes in DASH event messages and Table 2
illustrates an example of a SCTE-35 marker stored
in a DASH emsg. The presented approach allows ingest of
timed metadata from different sources,
possibly on different locations by embedding them in
sparse metadata tracks.
Table 1 Example of DASH emsg schemes URI
Scheme URI | Reference
-------------------------|------------------
urn:mpeg:dash:event:2012 | [DASH], 5.10.4
urn:dvb:iptv:cpm:2014 | [DVB-DASH], 9.1.2.1
urn:scte:scte35:2013:bin | [SCTE-35] 14-3 (2015), 7.3.2
www.nielsen.com:id3:v1 | Nielsen ID3 in MPEG-DASH
Table 2 example of a SCTE-35 marker embedded in a DASH emsg
Tag | Value
------------------------|-----------------------------
scheme_uri_id | "urn:scte:scte35:2013:bin"
Value | the value of the SCTE 35 PID
Timescale | positive number
presentation_time_delta | non-negative number expressing splice time
| relative to tfdt
event_duration | duration of event
| "0xFFFFFFFF" indicates unknown duration
Id | unique identifier for message
message_data | splice info section including CRC
The following steps are recommended for timed metadata
ingest related to events, tags, ad markers and
program information:
1. Create the metadata stream as a
fragmentedMP4stream that conveys the metadata
, the media handler (hdlr) is "meta",
the track handler box is a null media header box "nmhd".
2. The metadata stream applies to the media streams
in the presentation ingested to active publishing
point at the media processing entity
3. The URIMetaSampleEntry entry contains, in a URIbox,
the URI following the URI syntax in [RFC3986]
defining the form of the metadata
(see the ISO Base media file format
specification [ISOBMFF]). For example, the URIBox
could contain for ID3 tags [ID3v2]
the URL http://www.id3.org or
or urn:scte:scte35:2013a:bin
for scte 35 markers [SCTE-35]
4. The timescale of the metadata should match the value
specified in the media header box "mdhd" of the
metadata track.
Mekuria & Zhang Expires January 15 2019 [Page19]
5. The Arrival time is signalled in the "tfdt" box
of the track fragment as the basemediadecode
time, this time is often different
from the media presentation time, which is occurs
when a message is applied. The duration of
a metadata fragment can be set to zero,
letting it be determined by the
time (tfdt) of a next metadata segment received.
6. All Timed Metadata samples SHOULD
be sync samples [ISOBMFF],
defining the entire set of
metadata for the time interval
they cover. Hence, the sync
sample table box SHOULD
not be present in the metadata stream.
7. The metadata segment becomes available to the
publishing point/ media processing entity
when the corresponding track fragment
from the media that has an equal
or larger timestamp compared to
the arrival time signalled
in the tfdt basemediadecodetime.
For example, if the sparse fragment
has a timestamp of t=1000, it is expected that after the
publishing point/processing entity sees "video"
(assuming the parent track name is "video")
fragment timestamp 1000 or beyond, it can retrieve the
sparse fragment from the binary payload.
8. The payload of sparse track fragments is conveyed
in the mdat box as sample information. This enables
muxing of the metadata tracks. For example
XML metadata can for example be coded as base64 as
common for [SCTE-35] metadata messages
6.5 Requirements for Media Processing Entity Failover
Given the nature of live streaming, good failover support is
critical for ensuring the availability of the service.
Typically, media services are designed to handle various types
of failures, including network errors, server errors, and storage
issues. When used in conjunction with proper failover
logic from the live encoder side, highly reliable live streaming
setups can be build. In this section, we discuss requirements
for failover scenarios.
The following steps are required for a live encoder or media
ingest source to deal with a failing media processing entity.
Mekuria & Zhang Expires January 15 2019 [Page20]
1. Use a 10-second timeout for establishing the
TCP connection.
If an attempt to establish the connection takes longer
than 10 seconds, abort the operation and try again.
2. Use a short timeout for sending the HTTP requests.
If the target segment duration is N seconds, use a send
timeout between N and 2 N seconds; for example, if
the segment duration is 6 seconds,
use a timeout of 6 to 12 seconds.
If a timeout occurs, reset the connection,
open a new connection,
and resume stream ingest on the new connection.
This is needed to avoid latency introduced
by failing connectivity in the workflow.
3. Resend track segments for which a
connection was terminated early
4. We recommend that the encoder or ingest source
does NOT limit the number of retries to establish a
connection or resume streaming after a TCP error occurs.
5. After a TCP error:
a. The current connection MUST be closed,
and a new connection MUST be created
for a new HTTP POST request.
b. The new HTTP POST URL MUST be the same
as the initial POST URL for the
segment to be ingested.
c. The new HTTP POST MUST include stream
headers ("ftyp", and "moov" boxes)
identical to the stream headers in the
initial POST request for fragmented media ingest.
6. In case the media processing entity cannot process the
POST request due to authentication or permission
problems then it SHOULD return a permission denied HTTP 403
7. In case the media processing entity can process the request
it SHOULD return an HTTP 200 OK or 202 Accepted
8. In case the media processing entity can process
the manifest or segment in the POST request body but finds
the media type cannot be supported it SHOULD return an HTTP 415
unsupported media type
9. In case an unknown error happened during
the processing of the HTTP
POST request a HTTP 404 Bad request SHOULD be returned
10. In case the media processing entity cannot
proces a segment posted
due to missing or incorrect init segment, an HTTP 412
unfulfilled condition SHOULD be returned
11. In case a media source receives an HTTP 412 response,
it SHOULD resend "ftyp" and "moov" boxes
Mekuria & Zhang Expires January 15 2019 [Page21]
6.6 Requirements for Live Media Source Failover
Live encoder or media ingest source failover is the second type
of failover scenario that needs to be addressed for end-to-end
live streaming delivery. In this scenario, the error condition
occurs on the encoder side. The following expectations apply
to the live ingestion endpoint when encoder failover happens:
1. A new encoder or media ingest source instance
SHOULD be instantiated to continue streaming
2. The new encoder or media ingest source MUST use
the same URL for HTTP POST requests as the failed instance.
3. The new encoder or media ingest source POST request
MUST include the same header boxes moov
and ftyp as the failed instance
4. The new encoder or media ingest source
MUST be properly synced with all other running encoders
for the same live presentation to generate synced audio/video
samples with aligned fragment boundaries.
This implies that UTC timestamps
for fragments in the "tdft" match between decoders,
and encoders start running at
an appropriate segment boundaries.
5. The new stream MUST be semantically equivalent
with the previous stream, and interchangeable
at the header and media fragment levels.
6. The new encoder or media ingest source SHOULD
try to minimize data loss. The basemediadecodetime tdft
of media fragments SHOULD increase from the point where
the encoder last stopped. The basemediadecodetime in the
tdft box SHOULD increase in a continuous manner, but it
is permissible to introduce a discontinuity, if necessary.
Media processing entities or publishing points can ignore
fragments that it has already received and processed, so
it is better to error on the side of resending fragments
than to introduce discontinuities in the media timeline.
Mekuria & Zhang Expires January 15 2019 [Page22]
7. Profile 2: DASH Ingest General Considerations
Profile 2 is designed to ingest media into entities that only
provide pass through functionality. In this case the media
ingest source also provides the manifest based on MPEG DASH[DASH]
or HTTP Live Streaming [RFC8216].
The key idea here is to reuse the fragmented MPEG-4 ingest to
enable simulataneous ingest of DASH and HLS based on the
fragmented MPEG-4 files using commonalities as
described in [CMAF] which is a format based on fragmented
MPEG-4 that can be used in both DASH and HLS presentations.
The flow of operation in profile 2 is shown in Diagram 12. In this
case the live ingest source (media source) sends a manifest first.
Based on this manifest the media processing entity can setup
reception paths for the ingest url
http://hostname/presentationpath
In the next step segments are send in individual post requests
using URLS corresponding to relative
paths and segment names in the manifest.
e.g. http://hostname/presentationpath/relative_path/segment1.cmf
This profile re-uses as much functionality as possible from
profile 1 as the manifest can be seen
as a complementary addition to the
fragmented MPEG-4 stream. A difference lies in the way
the connection is setup and the way data is transmitted,
which can use relative URL paths for the segments based on the
paths in the manifest. For the rest, it largely
uses the same fragmented MPEG-4 layer based on [ISOBMFF]
and [CMAF].
Mekuria & Zhang Expires January 15 2019 [Page23]
Diagram 12
||===============================================================||
||===================== ============================ ||
||| live media source | | Media processing entity | ||
||===================== ============================ ||
|| || || ||
||===============Initial Manifest Sending========================||
|| || || ||
|| ||-- POST /prefix/media.mpd -------->>|| ||
|| || Succes || ||
|| || <<------ 200 OK --------------------|| ||
|| || Permission denied || ||
|| || <<------ 403 Forbidden -------------|| ||
|| || Bad Request || ||
|| || <<------ 400 Forbidden -------------|| ||
|| || Unsupported Media Type || ||
|| || <<-- 412 Unfulfilled Condition -----|| ||
|| || Unsupported Media Type || ||
|| || <<------ 415 Unsupported Media -----|| ||
|| || || ||
||==================== Segment Sending ==========================||
|| ||-- POST /prefix/chunk.cmaf ------->>|| ||
|| || Succes/Accepted || ||
|| || <<------ 200 OK --------------------|| ||
|| || Succes/Accepted || ||
|| || <<------ 202 OK --------------------|| ||
|| || Premission Denied || ||
|| || <<------ 403 Forbidden -------------|| ||
|| || Bad Request || ||
|| || <<------ 400 Forbidden -------------|| ||
|| || Unsupported Media Type || ||
|| || <<------ 415 Forbidden -------------|| ||
|| || Unsupported Media Type || ||
|| || <<-- 412 Unfulfilled Condition -----|| ||
|| || || ||
|| || || ||
||===================== ============================ ||
||| live media source | | Media processing entity | ||
||===================== ============================ ||
|| || || ||
||===============================================================||
Mekuria & Zhang Expires January 15 2019 [Page24]
8. profile 2: DASH and HLS Ingest Protocol Behavior
Operation of this profile MUST also adhere
to general requirements in section 4.
8.1 General Protocol Requirements
1. Before sending the segments
based on fragmentedMP4Stream the live encoder/source
MUST send a manifest [DASH]
with the following the limitations/constraints.
1a. Only relative URL paths to be used for each segment
1b. Only unique paths are used for each new presentation
1c. In case the manifest contains these relative paths,
these paths SHOULD be used in combination with the
POST_URL to POST each of the different segments from
the live encoder or ingest source
to the processing entity.
2. The live encoder or ingest source MAY send
updated versions of the manifest,
this manifest cannot override current
settings and relative paths or break currently running and
incoming POST requests. The updated manifest can only be
slightly different from the one that was send previously,
e.g. introduce new segments available or event messages.
The updated manifest SHOULD be send using a PUT request
instead of a POST request.
3. Following media segment requests
POST_URLs SHOULD be corresponding to the segments listed
in the manifest as POST_URL + relative URLs.
4. The encoder or ingest source SHOULD use
individual HTTP POST commands [RFC2626]
for uploading media segments when available.
5. In case fixed length POST Commands are used, the live source
entity MUST resend the segment to be posted decribed
in the manifest entirely in case of responses HTTP 400, 404
412 or 415 together with the init segment consisting
of "moov" and "ftyp" boxes.
6. A persistent connection SHOULD be used for the different
individual POST requests as defined in [RFC2626] enabling
re-use of the TCP connection for multiple POST requests.
8.2 Requirements for Formatting Media Tracks
1. Media data tracks and segments MUST be formatted and delivered
conforming to the same requirements as stated in 6.2
2. Media specific information SHOULD be signalled in the manifest
3. Formatting described in manifest and media track MUST
correspond consistently
Mekuria & Zhang Expires January 152019 [Page25]
8.3 Requirements for Timed Text Captions and Subtitle stream
1. Timed Text, caption and subtitle stream tracks MUST
be formatted conforming to the same requirements as in 6.3
2. Timed Text captions and subtitle specific information
SHOULD also be signalled in the manifest
3. Formatting described in manifest and
media track MUST correspond consistently
8.4 Requirements for Timed Metadata
1. Timed Metadata tracks MAY be formatted conforming
to the same requirements as in 8.4
2. In addition, the emsg box containing the metadata
SHOULD also be signalled in inband in the media
track as recommended in [CMAF]
3. DASH event messages SHOULD also
be signalled in the Manifest
8.4 Requirements for Media Processing Entity Failover
1. Requirements for failover are similar as stated in 6.4
2. In addition the live encoder source SHOULD resend the manifest
before sending any of the other segments
8.5 Requirements for Live Media Source Failover
1. Requirements for failover are similar as stated in 6.5
2. In addition the live encoder source SHOULD
resend the manifest before sending any
of the other segments
9. Security Considerations
Security consideration are extremely important
for media ingest. Retrieving media from a illicit
source can cause inappropriate content
to be broadcasted
and possibly lead to failure of infrastructure.
Basic security requirements have been covered in
section 4.
No security considerations except the ones mentioned
in this part of the text are expelictly considered.
Further security considerations will be updated
once they have been investigated further based
on review of this draft.
10. IANA Considerations
This memo includes no request to IANA.
Mekuria & Zhang Expires January 15 2019 [Page26]
11. Contributors
Will Law Akamai
James Gruessing BBC R&D
Kevin Moore Amazon AWS Elemental
Kevin Johns CenturyLink
John Deutscher Microsoft
Patrick Gendron Harmonic Inc.
Nikos Kyriopoulos MediaExcel
Rufael Mekuria Unified Streaming
Sam Geqiang Microsoft
Arjen Wagenaar Unified Streaming
Dirk Griffioen Unified Streaming
Matt Poole ITV
Alex Giladi Comcast
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[DASH] MPEG ISO/IEC JTC1/SC29 WG11, "ISO/IEC 23009-1:2014:
Dynamic adaptive streaming over HTTP (DASH) -- Part 1:
Media presentation description and segment formats," 2014.
[SCTE-35] Society of Cable Television Engineers,
"SCTE-35 (ANSI/SCTE 35 2013)
Digital Program Insertion Cueing Message for Cable,"
SCTE-35 (ANSI/SCTE 35 2013).
[ISOBMFF] MPEG ISO/IEC JTC1/SC29 WG11, " Information technology
-- Coding of audio-visual objects Part 12: ISO base
media file format ISO/IEC 14496-12:2012"
[HEVC] MPEG ISO/IEC JTC1/SC29 WG11,
"Information technology -- High efficiency coding
and media delivery in heterogeneous environments
-- Part 2: High efficiency video coding",
ISO/IEC 23008-2:2015, 2015.
[RFC793] J Postel IETF DARPA, "TRANSMISSION CONTROL PROTOCOL,"
IETF RFC 793, 1981.
[RFC3986] R. Fielding, L. Masinter, T. Berners Lee,
"Uniform Resource Identifiers (URI): Generic Syntax,"
IETF RFC 3986, 2004.
Mekuria & Zhang Expires January 152019 [Page27]
[RFC1035] P. Mockapetris,
"DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION"
IETF RFC 1035, 1987.
[CMAF] MPEG ISO/IEC JTC1/SC29 WG11, "Information technology
(MPEG-A) -- Part 19: Common media application
format (CMAF) for segmented media,"
MPEG, ISO/IEC International standard
[RFC5234] D. Crocker "Augmented BNF for Syntax Specifications:
ABNF" IETF RFC 5234 2008
[CENC] MPEG ISO/IEC JTC1 SC29 WG11 "Information technology --
MPEG systems technologies -- Part 7: Common encryption
in ISO base media file format files"
ISO/IEC 23001-7:2016
[MPEG-4-30] MPEG ISO/IEC JTC1 SC29 WG11
"ISO/IEC 14496-30:2014 Information technology
Coding of audio-visual objects -- Part 30":
Timed text and other visual overlays in
ISO base media file format
[ISO639-2] ISO 639-2 "Codes for the Representation of Names
of Languages -- Part 2 ISO 639-2:1998"
[DVB-DASH] ETSI Digital Video Broadcasting
"MPEG-DASH Profile for Transport of ISOBMFF
Based DVB Services over IP Based Networks"
ETSI TS 103 285
[RFC7617] J Reschke "The 'Basic' HTTP Authentication Scheme"
IETF RFC 7617 September 2015
12.2. Informative References
[RFC2626] R. Fielding et al
"Hypertext Transfer Protocol HTTP/1.1",
RFC 2626 June 1999
[RFC2818] E. Rescorla RFC 2818 HTTP over TLS
IETF RFC 2818 May 2000
[RFC8216] R. Pantos, W. May "HTTP Live Streaming", August 2018
(last acessed)
Mekuria & Zhang Expires January 15 2019 [Page28]
12.3. URL References
[fmp4git] Unified Streaming github fmp4 ingest,
"https://github.com/unifiedstreaming/fmp4-ingest".
[MozillaTLS] Mozilla Wikie Security/Server Side TLS
https://wiki.mozilla.org/Security/Server_Side_TLS
#Intermediate_compatibility_.28default.29
(last acessed 30th of March 2018)
[ID3v2] M. Nilsson "ID3 Tag version 2.4.0 Main structure"
http://id3.org/id3v2.4.0-structure
November 2000 (last acessed 2nd of May 2018)
[MS-SSTR] Smooth streaming protocol
https://msdn.microsoft.com/en-us/library/ff469518.aspx
last updated March 16 2018 (last acessed June 11 2018)
Author's Address
Rufael Mekuria (editor)
Unified Streaming
Overtoom 60 1054HK
Phone: +31 (0)202338801
E-Mail: rufael@unified-streaming.com
Sam Geqiang Zhang
Microsoft
E-mail: Geqiang.Zhang@microsoft.com
Mekuria & Zhang Expires August 1 2019 [Page29]