When I started working on video related stuff, I didn't expect that one of the biggest issue will be to deal with a bunch of acronyms, organization names such AES, DVB, EBU, ETSI, IEC, IEEE, IETF, ISMA, ISO, ITU, SMPTE, ... The standardization and broadcasting worlds are not accessible at first, and can be very confusing for the mainstream. This blog post will try to popularize a little how everything is related.
Since this is basically an overview, a lot of things I'll say here will look obvious and I will not enter in the details.
All Paths Lead To MPEG
One of the first word you hear when you enter in the Audio/Video world is
"MPEG". At some point you realized this acronym is used to define an obscure
group of persons, some kind of video format, but also a
codec, and actually a bunch of other things which make
almost everything related to video linked by one mean or another to this
But in order to get a grip on all of this, a few things need to be clarified
first, especially concerning the
ISO and various other related organizations,
unions, societies, groups or whatever they like to call themselves.
ISO, International Organization for Standardization
When we talk for example about the
MPEG-1, we are actually talking about the
ISO/IEC 11172. What does that mean?
The ISO is the International Organization for Standardization. As the name suggest, this organization is responsible for writing standards, which are by the way not only related to digital video broadcasting. Note these standards are most of the time NOT free to download, you need to pay to read them. The restricted list of free ISO standards is available.
What about the
IEC? What's actually happening here with
MPEG-1 is simply
ISO is cooperating with the IEC (or International
Electrotechnical Commission) to write this standard. They form the
ISO/IEC JTC 1, or Joint Technical Committee 1.
If you look for the this
ISO/IEC 11172 standard on the
ISO website, you may
be redirected to the ISO/IEC 11172-1:1993 one. What is this
extra name complexity for?
First, the extra
-1 is the part of the standard. Indeed, this standard is
split into 5 different parts (Systems, Video, Audio, Compliance testing
and Software simulation).
Then come the date, 1993. This is the first public release, or first edition.
Some modifications are sometimes needed (corrections, or amendments). For
example, the part 1 was revised a first time in 1996, which led to
11172-1:1993/Cor 1:1996. This paper and the following other updates are free
to download unlike the original release (of course, they have not much meaning
without the main paper).
Some parts are written later than others. For example, the software simulation
(part 5, providing a reference implementation) was released in 1998. This part 5
is a bit special, with a
TR in its name, which means technical report.
Note the part order is arbitrary and not chronological; for instance, the
MPEG-4 part 14 was written before
MPEG-4 part 12 (we will go back on them
A group of experts
When we said the
MPEG-1 standard was written with a cooperation group between
IEC, this meant a working group was formed. Its full name is
ISO/IEC JTC1/SC29 WG11, or Joint Technical Committee 1, Subcommittee 29,
Working Group 11. This group is called
MPEG or Moving Picture Experts
Group. They by the way own a website.
These two working groups are part of the Subcommittee 29
SC29), which is dedicated to multimedia coding research (officially Coding
of audio, picture, multimedia and hypermedia information).
and a bunch of standards
MPEG group actually wrote a bunch of standards, the most commonly known
- MPEG-1, as
ISO/IEC 11172, in 5 parts
- MPEG-2, as
ISO/IEC 13818, in 11 parts
- MPEG-4, as
ISO/IEC 14496, in 28 parts
MPEG-1 is not really interesting from a broadcasting point of view. It
defines a relatively simple container in the first part
(Systems), and how to encode audio and video (respectively in part 3 and 2).
A few years later, the
MPEG-2 standards were written and introduced two
MPEG-PS or Program Stream, targeting relatively reliable medium such as DVD (the
.vobyou find in your DVDs are actually in
MPEG-PS) since the error protection is limited. It is actually analogous and similar to the layer specified in the
MPEG-TS or Transport Stream, mainly aiming for transmission purposes where environments are error-prone, such as satellite broadcasting. However, it is also being in use for Blu-Ray devices (the .m2ts you find in your Blu-Ray Discs are in a slightly modified
MPEG-TSformat) as it is easier to do some interchanges with the broadcasting world.
Before we enter in the
MPEG-4 standards details, it is now important to
ITU who get involved with the
MPEG group to write these
ITU, International Telecommunication Union
The ITU (formerly
CCIR) jointly developed with the
parts of the standards.
For example, in the
MPEG-2 standard, the part 1 and part 2 (Systems and
Video) are also respectively known as
H.262. To put it simply:
MPEG-2 part 1= ISO/IEC 13818-1 = ITU-T Rec. H.222.0
MPEG-2 part 2= ISO/IEC 13818-2 = ITU-T Rec. H.262
MPEG-4, they are responsible for the popular part 10, or
You might have noticed the 'T' in
ITU-T for these recommendations. The 'T' is
for Telecommunications. They are also behind some Radiocommunication papers
ITU-R). For example, the popular ITU-R BT.601, or
601 (freely available on the ITU website) is being re-used in the
MPEG standards and various others.
MPEG-4 standards has a few interesting parts to note. The part 2
(Visual) defines what we know as the "mpeg4" video codec in
FFmpeg. This video compression technology is based on the
MPEG-2 (part 2 for both), and include a bunch
of profiles targeting different applications. Using the classic DCT
method, it is used as a base for several other well known codecs such as
DivX or Xvid.
The MPEG-4 part 10 (known as
H.264) being written
ITU, is another standard of video compression, way more
effective than "MPEG-4" for various reasons. You can look for H.264 and MPEG-4
Video Compression: Video Coding for Next Generation Multimedia book by lain
Richardson for more details. Since you are reading this article, you certainly
have already heard about
H.264 and know it is pretty widespread.
x264 is a
H.264 encoder software, the program you use to encode the
media; it is sometimes called a codec even though it is just an encoder (and
not a coder-encoder).
H.264 refers to the codec standard. Other encoders
x264 exist, it is just a well known one for being
pretty efficient and complete. And additionnaly, it is a free/libre
If you have already heard about
H.264, you might also be a bit familiar with
AAC or Advanced Audio Coding, as a lossy audio
encoding standard. It is defined in the part 3 of the
MPEG-4 standards. You
might notice there is also an
AAC part (7th) in the
MPEG-2 standard, but
what you are looking for is most certainly the one in
AAC is simply a popular lossy audio encoding "format" more efficient than the
MP3 (which is
What happened to the container? The
MPEG-4 defines the MP4
container format in the part 14. It is interesting to note this standard is
directly based upon the QuickTime Format (you know, the
released in 2001. Unlike the
QT specifications are freely
available for download.
MP4 format get then generalized later in the part 12 of the standards as
ISO base media file format. It is freely
available. This allowed for instance the 3GPP file
format (mobile phone multimedia) and F4V to be derived
We've seen mostly what the mainstream knows about (it is common to hear stuff
.mp4 videos). But now in this last
section I'd like to make a small summary of some common knowledge in the
SMPTE, Society of Motion Picture and Television Engineers
They are notably known for the TimeCode standardizing (see
SMPTE 12M) which
is used for editing purposes (identify the frames and do various scene cuts for
instance), and the MXF format, being one of the most popular
broadcast media container (
SMPTE 377M is the base
A few hundreds of
SMPTE standards are available, and cover a lot of
television/cinema production technical needs.
AES, Audio Engineering Society
As the name suggests, AES is publishing a number of standards
related to audio (
AES3 is accepted as a standard in the professional and
broadcasting world since years, and has been widely used as one of the primary
means of transmitting digital audio at the end of the chain.
AES3 is by the
way also known as
AES/EBU, EBU being the European Broadcasting
Union, which is yet another group of broadcasting engineers who mainly try to
maintain collaboration and interoperability.
DVB, Digital Video Broadcasting
The DVB Project has been developing a high amount of
specifications for the Digital Video Broadcasting. They for instance
define some restrictions on the settings to be used with
MPEG-2 as well as
various recommendations for
DVB applications; there are various transmissions
or diffusions constraints from the broadcasters to the end user.
The standards can be freely downloaded from the ETSI website in the Standards page. ETSI, or European Telecommunications Standards Institute is -again- another standardization organization in the telecommunications industry, which also has a specific notation for there standards.
The amount of different organizations in this big business might be overwhelming, but having a few hints about how everything is tied together will most certainly help you understanding why the digital and analog audio/video is in its current state.
If you are willing to get more into this, I personally recommend the lurker's guide which presents a nice technical introduction to video systems for a programmer mind. Some good books such as Video Demystified by Keith Jack may also help.