What is H.264?
H.264 is a standard for video compression. It is also known as MPEG-4 Part 10, or MPEG-4 AVC (for Advanced Video Coding). It is one of the latest block-oriented motion-estimation-based codecs developed by the ITU-T Video Coding Experts Group (VCEG) together with the ISO/IEC Moving Picture Experts Group (MPEG) as the product of a partnership effort known as the Joint Video Team (JVT). The ITU-T H.264 standard and the ISO/IEC MPEG-4 Part 10 standard (formally, ISO/IEC 14496-10) are jointly maintained so that they have identical technical content.
H.264/AVC/MPEG-4 Part 10 contains a number of new features that allow it to compress video much more effectively than older standards and to provide more flexibility for application to a wide variety of network environments.With the new features, H.264 performs significantly better than any prior standard under a wide variety of circumstances in a wide variety of application environments. H.264 can often perform radically better than MPEG-2 videotypically obtaining the same quality at half of the bit rate or less, especially on high bit rate and high resolution situations. It is employed widely in applications ranging from television broadcast to video for mobile devices.
What is RM,RMVB?
RealMedia Variable Bitrate (RMVB) is a variable bitrate extension of the RealMedia multimedia container format developed by RealNetworks.
As opposed to the more common RealMedia container, which holds streaming media encoded at a constant bit rate, RMVB is typically used for multimedia content stored locally. Files using this format have the file extension ".rmvb".
Allegedly, RealMedia formats typically achieve much more efficient compression than MPEG-4 Part 2 codecs, such as DivX and Xvid, using compression similar to MPEG-4 Part 10 codecs, such as x264. For this reason, they have become noticeably present (though not entirely popular) on file sharing platforms such as BitTorrent, eDonkey and Gnutella.
What is Codec?
A codec is a device or program capable of encoding and/or decoding a digital data stream or signal. The word codec may be a combination of any of the following: 'compressor-decompressor', 'coder-decoder', or 'compression/decompression algorithm'.
In the recent software sense, codecs encode a data stream or signal for transmission, storage or encryption, or decode it for viewing or editing. Codecs are often used in videoconferencing and streaming media applications.
Codecs are often designed to emphasise certain aspects of the media to be encoded. For example, a digital video (using a DV codec) of a sports event, such as baseball or soccer, needs to encode motion well but not necessarily exact colours, while a video of an art exhibit needs to perform well encoding colour and surface texture. For example, audio codecs for cell phones need to be very low latency between a word being spoken and that word being heard; while audio codecs for recording or broadcast can use high-latency audio compression techniques to achieve higher fidelity at a lower bit-rate.
Many multimedia data streams need to contain both audio and video data, and often some form of metadata that permits synchronisation of audio and video. Each of these three streams may be handled by different programs, processes, or hardware; but for the multimedia data stream to be useful in stored or transmitted form, they must be encapsulated together in a container format.
The widely spread notion of AVI being a codec is incorrect as AVI is a container format, which many codecs might use (although not to ISO standard). There are other well-known alternative containers such as Ogg, ASF, QuickTime, RealMedia, Matroska, DivX, and MP4.
What do 720p, 1080i and 1080p mean?
High definition programs are encoded with a type of resolution: 720p, 1080i or 1080p. The number stands for the amount of lines embedded within the signal. The letter describes the type of scan the television uses to display the picture. The 'i'means interlaced and the 'p' means progressive.
The number of lines on a television is important because it allows for greater detail in the image. This is a similar concept to digital photos and how dpi determines print quality. The type of televisions all of us grew up watching had 480 visible lines on the screen. By doubling the amount of lines in combination with the type of scan, HD essentially doubles the quality of picture.
The type of scan is arguable considering the amount of lines for each HD format. Progressive scan is a better type of scan because it doubles the amount of times the TV displays the image per one second in comparison to interlaced. Still, the difference between 720p and 1080i is so minimal that is isn't an issue at all. While 1080p is better than 720p and 1080i, very few programs are made in this resolution so it really isn't a factor right now. |
