MPEG-4 Overview
Submitted by Pocketcine on February 9, 2007 - 4:31pm.
Video is commonly compressed to an MPEG-4 format for playback on the mobile phone (3GP and MP4 are the most common formats).
MPEG-4 is an international standard to define, encode, and play back time-based media, like video. It is from the same committee, the Moving Pictures Expert Group (MPEG), that established MPEG-1 and MPEG-2 as standards for digital video.
The MPEG-4 file format, called MP4, is based on Apple QuickTime. When you see the extension .mp4 it is referencing the file format.
Video files with the .3gp extension (3GP) support one of the MPEG-4 standards. See the related article on the 3GP video format.
As MPEG standards evolve they get better and better at compressing video to smaller and smaller sizes. The first standard, MPEG-1, made video on interactive CD-ROMs possible, and the second standard, MPEG-2, made digital television possible. MPEG-4 was designed to be more flexible and scalable than previous standards. It can be used for all kinds of applications, from two-way video conferences to controlling animated 3D models. What's important to pocket video producers is that it makes mobile video possible because it scales to small power devices and tiny file sizes.
MPEG History
Here are the different MPEG standards and their capabilities:
The Many Flavors of MPEG-4
MPEG-4’s support of many different devices with many different capabilities is accomplished through levels and profiles. A profile is a subset of the MPEG-4 standard, defining what your codec can or cannot do. Levels describe how much your codec can do, such as the maximum screen resolution and bit rate (data rate).
Two profiles have evolved from the MPEG-4 standard (adapted in part from the MPEG-4 Industry Forum document "Simple and Advanced Simple Profiles":
Both profiles and levels are stored in the MPEG-4 file so that the program reading it knows what to do with it. such as Simple or Simple Advanced Profiles. So a device that is compliant with a certain profile at a specified level.
A current list video profiles can be found here.
MPEG-4 Parts
MPEG-4 a standard with many parts, such as a standard for the MPEG-4 file format. Here are some of the more relevant “parts.”
MPEG-4 Advanced Video Coding (AVC), also known as MPEG-4 Part 10 or ITU-T H.264, is considered the most advanced current standard, making full screen video possible at 1 Mbits, 50% less than H.263 or MPEG-2. It is more efficient in its coding algorithms than MPEG-4 Part 2. However it is more demanding in terms of computing power.
There are three profiles for AVC, baseline, main and extended. Baseline is the simplest of the three, providing less image clarity but requiring less computing power.
Other Flavours: H.263, H.264/AVC
H.263 is a legacy standard developed by the ITU-T telecom industry standards body as a low bit rate encoding solution for teleconferencing. It has largely been replaced by the H.264 standard, developed in partnership with MPEG. H.264 is also known as AVC (Advanced Video Encoding) and MPEG-4 Part 10. The partnership between ITU-T and MPEG was called the Joint Video Team (JVT).
The partners goal was to produce a solution that would produce good video quality at half the bit rate of previous standards (H.263 and MPEG-2 for example), while not increasing the complexity of the implementation to the point where it would become too expensive. The Baseline Profile (BP) for H.264/AVC was developed for mobile applications.
Codecs Compared
The main codecs include:
A subjective comparison of the codecs was conducted by the MSU Graphics and Media Lab. Videos compressed by the different codecs were shown to test subjects how rated them. The results show x264 coming out ahead. Check it out here.
Support for MPEG-4
Although MPEG-4 is scalable, allowing you to set data rate for the targetted transport device, from cell phone to HDTV, it has not been widely adopted until recently. It has languished somewhat since 2000 when it became official. This lack of support in authoring tools has made it difficult to work with. Only recently the ability to export to MPEG-4 format shown up as an option in video editing software.
The exception to the lack of support has been Apple, which included MPEG4 in QuickTime in 2002. The QuickTime Pro upgrade supports editing and exporting video in mobile phone formats. Microsoft supported an early draft of the MPEG-4 standard, but then went own to develop its own proprietary media file format. One of the factors that have slowed MPEG-4 growth is licensing fees. The market will ultimately decide which format succeeds.
MPEG-4 audio is covered in a separate article.
MPEG-4 is an international standard to define, encode, and play back time-based media, like video. It is from the same committee, the Moving Pictures Expert Group (MPEG), that established MPEG-1 and MPEG-2 as standards for digital video.
The MPEG-4 file format, called MP4, is based on Apple QuickTime. When you see the extension .mp4 it is referencing the file format.
Video files with the .3gp extension (3GP) support one of the MPEG-4 standards. See the related article on the 3GP video format.
As MPEG standards evolve they get better and better at compressing video to smaller and smaller sizes. The first standard, MPEG-1, made video on interactive CD-ROMs possible, and the second standard, MPEG-2, made digital television possible. MPEG-4 was designed to be more flexible and scalable than previous standards. It can be used for all kinds of applications, from two-way video conferences to controlling animated 3D models. What's important to pocket video producers is that it makes mobile video possible because it scales to small power devices and tiny file sizes.
MPEG History
Here are the different MPEG standards and their capabilities:
- MPEG-1: up to 1.5 Mbit/sec. Popular for distribution of non-interlaced .mpg files on the Internet, audio (MP3s), and VideoCD in Asia.
- MPEG-2: between 1.5 and 15 Mbit/sec. Its ability to efficiently compress both non-interlaced and interlaced video makes it suitable for digital television (and storage on DVDs). Because it scales to HDTV resolutions, it made the MPEG-3 standard redundant.
- MPEG-4: highly variable bit rate. It has many capabilities, including coding images, animations, interactivity, and protecting content. It overlaps to some extent with MPEG-2, although cable companies are supporting it over MPEG-2. For mobile applications it features a well-developed server spec and supports streaming media types, not only audio and video but synthetic content as well, such as face and body animation, streaming 3D textures, and more.
The Many Flavors of MPEG-4
MPEG-4’s support of many different devices with many different capabilities is accomplished through levels and profiles. A profile is a subset of the MPEG-4 standard, defining what your codec can or cannot do. Levels describe how much your codec can do, such as the maximum screen resolution and bit rate (data rate).
Two profiles have evolved from the MPEG-4 standard (adapted in part from the MPEG-4 Industry Forum document "Simple and Advanced Simple Profiles":
• MPEG-4 Visual – Simple Profile (SP) is designed primarily for low processing power coding, low latency and use in less-than-ideal transmission circumstances. Ideal for real-time desktop software encoding, mobile and wireless devices, video telephony and video–conferencing. This the profile used for digital video downloaded to the mobile phone.
• MPEG-4 Visual - Advanced Simple Profile (ASP) offers the best MPEG-4 coding performance and can be deployed into more demanding environments where video decoding at intermediate and higher bit rates is required. ASP is also ideal for broadcasters wishing to provide wide range of programming qualities suited to a variety of platforms, e.g. Broadcast, Internet and Mobile Phones. This is the profile used for video on demand.
• MPEG-4 Studio Profile is used for studio applications.
Both profiles and levels are stored in the MPEG-4 file so that the program reading it knows what to do with it. such as Simple or Simple Advanced Profiles. So a device that is compliant with a certain profile at a specified level.
A current list video profiles can be found here.
MPEG-4 Parts
MPEG-4 a standard with many parts, such as a standard for the MPEG-4 file format. Here are some of the more relevant “parts.”
Part 1 (ISO/IEC 14496-1): Systems: Describes synchronization and multiplexing of video and audio.A complete list of profiles can be found here.
Part 2 (ISO/IEC 14496-2): Visual: A compression codec for visual data (video, still textures, synthetic images, etc.). One of the many "profiles" in Part 2 is the Advanced Simple Profile (ASP).
Part 3 (ISO/IEC 14496-3): Audio: A set of compression codecs for perceptual coding of audio signals, including some variations of Advanced Audio Coding (AAC) as well as other audio/speech coding tools.
Part 10 (ISO/IEC 14496-10): Advanced Video Coding: A codec for video signals which is also called AVC and is technically identical to the ITU-T H.264 standard.
Part 14 (ISO/IEC 14496-14): MPEG-4 File Format: The designated container file format for MPEG-4 content, which is based on Part 12.
Part 15 (ISO/IEC 14496-15): AVC File Format: For storage of Part 10 video based on Part 12.
MPEG-4 Advanced Video Coding (AVC), also known as MPEG-4 Part 10 or ITU-T H.264, is considered the most advanced current standard, making full screen video possible at 1 Mbits, 50% less than H.263 or MPEG-2. It is more efficient in its coding algorithms than MPEG-4 Part 2. However it is more demanding in terms of computing power.
There are three profiles for AVC, baseline, main and extended. Baseline is the simplest of the three, providing less image clarity but requiring less computing power.
Other Flavours: H.263, H.264/AVC
H.263 is a legacy standard developed by the ITU-T telecom industry standards body as a low bit rate encoding solution for teleconferencing. It has largely been replaced by the H.264 standard, developed in partnership with MPEG. H.264 is also known as AVC (Advanced Video Encoding) and MPEG-4 Part 10. The partnership between ITU-T and MPEG was called the Joint Video Team (JVT).
The partners goal was to produce a solution that would produce good video quality at half the bit rate of previous standards (H.263 and MPEG-2 for example), while not increasing the complexity of the implementation to the point where it would become too expensive. The Baseline Profile (BP) for H.264/AVC was developed for mobile applications.
Codecs Compared
The main codecs include:
- DivX 6.0
- Xvid 1.1.0
- x264
- WMV 9.0
A subjective comparison of the codecs was conducted by the MSU Graphics and Media Lab. Videos compressed by the different codecs were shown to test subjects how rated them. The results show x264 coming out ahead. Check it out here.
Support for MPEG-4
Although MPEG-4 is scalable, allowing you to set data rate for the targetted transport device, from cell phone to HDTV, it has not been widely adopted until recently. It has languished somewhat since 2000 when it became official. This lack of support in authoring tools has made it difficult to work with. Only recently the ability to export to MPEG-4 format shown up as an option in video editing software.
The exception to the lack of support has been Apple, which included MPEG4 in QuickTime in 2002. The QuickTime Pro upgrade supports editing and exporting video in mobile phone formats. Microsoft supported an early draft of the MPEG-4 standard, but then went own to develop its own proprietary media file format. One of the factors that have slowed MPEG-4 growth is licensing fees. The market will ultimately decide which format succeeds.
MPEG-4 audio is covered in a separate article.
- Pocketcine's blog
- Login to post comments
