3.3 Multimedia Enriched Html - Codec
3.3.3 CODEC of Multimedia Content
3.3.3.1 Meaning
A codec is a device or computer program capable of encoding and/or decoding a digital data stream or signal with a distinctive codec algorithm. The word codec is a portmanteau of 'compressor-decompressor' or, more commonly, 'coder-decoder'. A codec encodes a data stream or signal for transmission, storage or encryption, or decodes it for playback or editing. Codecs are used in videoconferencing, streaming media and video editing applications. Different codecs are featured by the compression quality and capability:
Lossy codecs:
Many of the more popular codecs in the software world are lossy, meaning that they reduce quality by some amount in order to achieve compression. Often, this type of compression is virtually indistinguishable from the original uncompressed sound or images, depending on the codec and the settings used. Smaller data sets ease the strain on relatively expensive storage sub-systems such as non-volatile memory and hard disk, as well as write-once-read-many formats such as CD-ROM, DVD and Blu-ray Disc. Lower data rates also reduce cost and improve performance when the data is transmitted.
Lossless codecs:
There are also many lossless codecs which are typically used for archiving data in a compressed form while retaining all of the information present in the original stream. If preserving the original quality of the stream is more important than eliminating the correspondingly larger data sizes, lossless codecs are preferred. This is especially true if the data is to undergo further processing (for example editing) in which case the repeated application of processing (encoding and decoding) on lossy codecs will degrade the quality of the resulting data such that it is no longer identifiable (visually, audibly or both). Using more than one codec or encoding scheme successively can also degrade quality significantly. The decreasing cost of storage capacity and network bandwidth has a tendency to reduce the need for lossy codecs for some media.
Many of the more popular codecs in the software world are lossy, meaning that they reduce quality by some amount in order to achieve compression. Often, this type of compression is virtually indistinguishable from the original uncompressed sound or images, depending on the codec and the settings used. Smaller data sets ease the strain on relatively expensive storage sub-systems such as non-volatile memory and hard disk, as well as write-once-read-many formats such as CD-ROM, DVD and Blu-ray Disc. Lower data rates also reduce cost and improve performance when the data is transmitted.
Lossless codecs:
There are also many lossless codecs which are typically used for archiving data in a compressed form while retaining all of the information present in the original stream. If preserving the original quality of the stream is more important than eliminating the correspondingly larger data sizes, lossless codecs are preferred. This is especially true if the data is to undergo further processing (for example editing) in which case the repeated application of processing (encoding and decoding) on lossy codecs will degrade the quality of the resulting data such that it is no longer identifiable (visually, audibly or both). Using more than one codec or encoding scheme successively can also degrade quality significantly. The decreasing cost of storage capacity and network bandwidth has a tendency to reduce the need for lossy codecs for some media.
3.3.3.2 Practical Problems Related to the Use of Codec
The existence of various codec has complicated the application of multimedia in publishing industry. Many of the codec are proprietary owned intellectual proerty. Using the codec implies royalty charge. Therefore, not all multimedia player, especially the freeware, include all the codecs for decoding the multimedia file.
3.3.3.3 Commonly used audio codecs
In software, an "audio codec" is a computer program implementing an algorithm that compresses and decompresses digital audio data according to a given audio file format or streaming media audio format. The object of the algorithm is to represent the high-fidelity audio signal with minimum number of bits while retaining the quality. This can effectively reduce the storage space and the bandwidth required for transmission of the stored audio file
In hardware, "audio codec" refers to a single device that encodes analog audio as digital signals and decodes digital back into analog. In other words, it contains both an Analog-to-digital converter (ADC) and Digital-to-analog converter (DAC) running off the same clock. This is used in sound cards that support both audio in and out, for instance.
Ref:
http://en.wikipedia.org/wiki/Comparison_of_audio_formatshttp://en.wikipedia.org/wiki/List_of_codecs#Audio_codecs
3.3.3.4 Commonly used video codec (Source: wikipedia)
| List of codecs A variety of video compression formats can be implemented on PCs and in consumer electronics equipment. It is therefore possible for multiple codecs to be available in the same product, avoiding the need to choose a single dominant video compression format for compatibility reasons. Video in most of the publicly documented or standardized video compression formats can be created with multiple encoders made by different people. Many video codecs use common, standard video compression formats, which makes them compatible. For example, video created with a standard MPEG-4 Part 2 codec such as Xvid can be decoded (played back) using any other standard MPEG-4 Part 2 codec such as FFmpeg MPEG-4 or DivX Pro Codec, because they all use the same video format. Some widely-used software codecs are listed below. Lossless codecs
FFv1: FFv1's compression factor is comparable to Motion JPEG 2000, but
based on quicker algorithms (allows real-time capture). Written by
Michael Niedermayer and published as part of FFmpeg under to GNU GPL.
Huffyuv: Huffyuv (or HuffYUV) is a very fast, lossless Win32 video codec written by Ben Rudiak-Gould and published under the terms of the GNU GPL as free software, meant to replace uncompressed YCbCr as a video capture format. Lagarith: A more up-to-date fork of Huffyuv is available as Lagarith. YULS x264 has a lossless mode. MPEG-4 Part 2 codecs
DivX Pro Codec: A proprietary MPEG-4 ASP codec made by DivX, Inc.
Xvid: Free/open-source implementation of MPEG-4 ASP, originally based on the OpenDivX project. FFmpeg MPEG-4: Included in the open-source libavcodec codec library, which is used by default for decoding and/or encoding in many open-source video players, frameworks, editors and encoding tools such as MPlayer, VLC, ffdshow or GStreamer. Compatible with other standard MPEG-4 codecs like Xvid or DivX Pro Codec. 3ivx: A commercial MPEG-4 codec created by 3ivx Technologies. H.264/MPEG-4 AVC codecs
x264: A GPL-licensed implementation of the H.264 video standard. x264 is only an encoder.
Nero Digital: Commercial MPEG-4 ASP and AVC codecs developed by Nero AG. QuickTime H.264: H.264 implementation released by Apple. DivX Pro Codec: An H.264 decoder and encoder was added in version 7. Microsoft codecs
WMV (Windows Media Video): Microsoft's family of proprietary video
codec designs including WMV 7, WMV 8, and WMV 9. The latest generation
of WMV is standardized by SMPTE as the VC-1 standard.
On2 codecsMS MPEG-4v3: A proprietary and not MPEG-4 compliant video codec created by Microsoft. Released as a part of Windows Media Tools 4. A hacked version of Microsoft's MPEG-4v3 codec became known as DivX ;-).
VP6, VP6-E, VP6-S, VP7, VP8: Proprietary high definition video
compression formats and codecs developed by On2 Technologies used in
platforms such as Adobe Flash Player 8 and above, Adobe Flash Lite,
Java FX and other mobile and desktop video platforms. Supports
resolution up to 720p and 1080p. VP8 has been made open source by
Google under the name libvpx or VP8 codec library.
Other codecslibtheora: A reference implementation of the Theora video compression format developed by the Xiph.org Foundation, based upon On2 Technologies' VP3 codec, and christened by On2 as the successor in VP3's lineage. Theora is targeted at competing with MPEG-4 video and similar lower-bitrate video compression schemes.
Schrödinger and dirac-research: implementations of the Dirac
compression format developed by BBC Research at the BBC. Dirac provides
video compression from web video up to ultra HD and beyond.
All of the codecs above have their qualities and drawbacks. Comparisons
are frequently published. The trade-off between compression power,
speed, and fidelity (including artifacts) is usually considered the
most important figure of technical merit.DNxHD codec: a lossy high-definition video production codec developed by Avid Technology. It is an implementation of VC-3. Sorenson 3: A video compression format and codec that is popularly used by Apple's QuickTime, sharing many features with H.264. Many movie trailers found on the web use this compression format. Sorenson Spark: A codec and compression format that was licensed to Macromedia for use in its Flash Video starting with Flash Player 6. It is considered as an incomplete implementation of the H.263 standard. RealVideo: Developed by RealNetworks. A popular compression format and codec technology a few years ago, now fading in importance for a variety of reasons. Cinepak: A very early codec used by Apple's QuickTime. Indeo, an older video compression format and codec initially developed by Intel. |
Tips for Using Multimedia Content:
Try not to use any proprietary commercial codec or the content may not be able to play back on the vistors' computer. It is not just the file format (i.e. the container) that really matters but that the codec algorithm is also critical to the compatibility. The following is our suggestion:
- The audio stream is compressed using an audio codec such as MP3, Vorbis or AAC.
- The video stream is compressed using a video codec such as H.264 or V8.
- Encoded audio and video streams are assembled in a container bitstream such as FLV, WebM, ASF or ISMA.
- The bitstream is delivered from a streaming server to a streaming client using a transport protocol, such as MMS or RTP.
- The streaming client may interact with the streaming server using a control protocol, such as MMS or RTSP.
Ref:
http://en.wikipedia.org/wiki/Video_compressionhttp://en.wikipedia.org/wiki/Video_codec
http://en.wikipedia.org/wiki/Comparison_of_video_codecs
3.3.4 Streaming and Multimedia
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider. The name refers to the delivery method of the medium rather than to the medium itself. The distinction is usually applied to media that are distributed over telecommunications networks, as most other delivery systems are either inherently streaming (e.g., radio, television) or inherently non-streaming (e.g., books, video cassettes, audio CDs). The verb 'to stream' is also derived from this term, meaning to deliver media in this manner. Internet television is a commonly streamed medium.
3.3.4.1 Technical Considerations
- more powerful computer
- greater network bandwidth, especially in the last mile
- increased access to networks, especially the Internet
- use of standard protocols and formats, such as TCP/IP, HTTP, and HTML
- more advanced data compression algorithm
3.3.4.2 Copyright Issues
- copyright arrangement acceptable to content providers.
- codec and plugin installation and licensing
