MXF (Material Exchange Format) is
a file format aimed at
exchange of audiovisual material with associated metadata between
different applications. Its technical characteristics are defined in
the SMPTE 377M standard and was developed by the Pro-MPEG Forum, the
EBU organization and the AAF association, together with the main
companies and manufacturers in the broadcast industry. The ultimate goal is
an open file format that facilitates video sharing,
audio, data and associated metadata within a workflow based
An MXF file works as a container that can carry video,
audio, graphics, etc. and its associated metadata, in addition to the
necessary information that makes up the structure of the file. A factor
important is that MXF is independent of the compression format
used as it can transport different types of format such as
MPEG, DV or a sequence of TIFFs. The great advantage of MXF is that
allows you to save and exchange associated metadata, which describes
the content and the way the file should be read.
Metadata can contain information about:
The file structure
The content itself (MPEG, DV, ProRes, DnxHD, JPG, PCM, etc.)
Keywords or titles
Date and version number of a clip -Etc.
MXF is based on the AAF (Advanced Authoring Format) data model and are
complementary to each other. The difference between this format and MXF is
that the AAF format is optimized for post-production processes,
because it allows to store a greater wealth of metadata and because
makes it possible to use references to external materials. MXF files
can be embedded within AAF files, this means that a
AAF project can include audiovisual content and metadata
partners, but you can also call other MXF content hosted from
Achieving interoperability is the primary goal of MXF and is
establish three areas:
-Multi platform. It will work through different network protocols
and operating systems, including Windows, Mac OS, Unix, and Linux.
-Independent compression. Do not convert between compression formats,
makes it easier to handle more than one native format. Can handle the
-Transfer in streaming. MXF interacts seamlessly with
bi-directional streaming media. SDTI is an example of
file-based streaming that works seamlessly with this
Format. Transmission over IP networks is also optimal.
An MXF file has a structure that houses a file header
where the content of the file and its synchronization are detailed, the
metadata associated with multimedia, the body that contains the essence
of the original media data and the queue that closes the file.
The data contained in MXF files is stored using
a subdivision into a trio of KLV (Key-Length-Value) values. This is
a unique identification key (key) of 16 bytes for each trio, the
value of the length (length) of the data stored in that triplet and
the data itself (value). This way of organizing data allows
locate any specific element within the MXF file, with so
just read the keys. This structure also allows the
file can grow and add new features with new
compression techniques and metadata schemes that are defined.
We can curl the curl a little more and it is that they are allowed
partitions within a KLV trio. This is that the data of a trio
can be fragmented into a succession of KLV trios and gives you more
robustness to the file structure. This has an advantage, for
For example, in the transmission of MXF files over networks, where if
we lose the connection and the MXF transfer is cut off,
recover it, it will not be necessary to send the entire file again since
that we can hook into the trio where the transfer broke.
So far I suppose that you all have it quite clear and
you will ask why an MXF that generates an XDCAM camera is not
compatible with that generated by a P2 if the MXF format was created to
ensure compatibility. Well, the great flexibility of the MXF
allows different interpretations and applications of the standard by the
different manufacturers, and this is how the MXFs that generate the products
of each are not compatible with each other. This has led to implement
a number of different physical versions to improve the
interoperability based on your applications. In this way
establish the so-called Operational Patterns and each one will have its own
specifications under its own standard that will define the type of
image / sound containing the essence and structure of the metadata.
Of these patterns, OP-1a and OP-Atom are the ones that we find most
The generic operational pattern is OP-1a and was created as a replacement for the
videotape, where a single MXF file contains video, multiple
audio channels and time codes. It is very simple and flexible but
it has many limitations as to what you have to work on.
An example in this case would be the XDCAM format or JVC cameras that
they record on cards, where each of their clips have a single file
with video and audio.
OP-Atom is a very simple file format that you can only have in your
essentially a single item, be it a video or audio track. For the
In general, the metadata linked to the media contained in the MXF OP-Atom
it is in AAF or XML files. A typical example is the P2 format, where
video and audio tracks are wrapped in separate MXF-Atom files
and the metadata that associates them goes in a separate XML file.
The media files that AVID generates are also OP-Atom and its metadata
associate is in AAF. This is the most used in environments of
edition, where individual access to the
audiovisual components. In the case of AVID, these files have the
particularity of incorporating non-standard MXF metadata that
use the applications of this manufacturer to index them and that
can create incompatibility problems if exchanged with others
systems other than AVID.
In the case of digital cinema, the MXFs that carry the image and audio
they are also OP-Atom. In this case they are restricted to compression and
specific color space for this function (JPEG 2000 and XYZ) in the
for video and 16 PCM tracks for audio, so your
compatibility outside of this environment is very limited. Your timing
and metadata is the information that XML files carry.
We can establish a group of operation patterns (OP) with
various levels of complexity where the OP-1a pattern is the most
low. A single continuous track with video, audio, and metadata
packed into a file is what defines the OP-1a pattern. Level
more complex within these patterns is OP-3c, with the combination
multiple clips (packed files) with multiple playlists
playback (playlist) combined. Here you have a table with them.
The AMWA Association (Advanced Media Workflow Association) is
created to lead the development and promotion of the use of
standards and technologies that enable more workflows
effective for the use of network media. Her current projects are the
advance in the use of AAF, BXF, MXF and XML formats in the luxuries of
work based on data files. This association works in
close collaboration with SMPTE and other standards bodies.
Among his projects is one that refers to MXF files and
defines a set of rules that limit the MXF specification of face
to the adaptation of this format to different applications and flows of
AMWA specifications can be summarized as follows
AS-02 - MXF with mastering versions. This was
support the storage and management of the components of a program
in MXF, to allow versions, multi-languages and deliveries to the
different media. It is a file package that has
all the necessary elements of video, audio and metadata to generate
multiple versions of a product. Who should use it? Environments
post-production, broadcasters and distributors of
AS-03 - Delivery of programs. This MXF specification is
for the distribution of the program and its direct broadcast from a
video server. It is a single file that incorporates audio, video and
metadata for a single program. Who should use it? Networks
AS-10 - MXF for Production. The specification of the
AS-10 is aimed at establishing a common MXF file format for
entire production workflow, including recording to
camera, ingesting to a server, editing, playback,
digital distribution and archiving.
An example is the use of MPEG Long-GOP. The project includes the
development of an application to validate files as an aid
for quality control processes. Who should use it?
Production and post-production, broadcasters and
AS-11 - MXF for redistribution. This is a format of
for the delivery of finished products from stations
dissemination of the creators of the programs. AS-11 includes the
functionality of the AS-03 and is extended to include AVC-Intra 100, and
includes support for standard definition D-10 video standard with
AES3 audio. AS-11 defines a minimal basic metadata set, and a
metadata schema with program segmentation. Who owes it
use? Broadcasters, and distributors of
AS-12 - Commercial Delivery. AS-12 is a subset of
MXF format for delivery of finished advertisements to stations
television or broadcast networks. The specification provides a
clapperboard and other metadata to associate with the essence of the sound and
of the video. AS-12 establishes that the explicit identification of
content is made assisted by a computer and that it will control
the playlist. Who should use it? Production and
post production, commercial distribution, broadcasters
and cable networks.
The main characteristics of these MXF are in the following
table, AS-02 does not appear because it has not yet definitively closed its
And speaking of these formats, AVID since version 7 of the
MediaComposer supports these formats. A new
AMA (Avid Media Access) component called Avid Media Authoring we
allows users to deliver and archive multiple formats of
output, among them are the AS-02 and AS-11.
These formats are the support for the delivery of our
work in content broadcasting and distribution centers on a regular basis. SMPTE has also approved as a standard the IMF (Interoperable Master Format) format with a structure very similar to that of the DCP (Digital Cinema Package) but designed for the broadcast world, and that NETFLIX uses for the deliveries it receives.