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- <glossary>
-
- <warning> <para>
- Please note that this book is in no way a reference documentation
- on how DVDs work. Its only purpose is to describe the API
- available for programmers in VLC media player. It is assumed that
- you have basic knowledge of what MPEG is. The following paragraph
- is just here as a reminder :
- </para> </warning>
-
- <glossentry>
- <glossterm> <acronym> AC3 </acronym> :
- Digital Audio Compression Standard </glossterm>
- <glossdef> <para> Specification for coding audio data, used in DVD.
- The documentation is
- <ulink url="http://www.linuxvideo.org/devel/library/ac3-standard_a_52.pdf">
- freely available </ulink>.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> B </acronym> (bi-directional) picture </glossterm>
- <glossdef> <para> Picture decoded from its own data, <emphasis>
- and </emphasis> from the data of the previous and next (that
- means <emphasis>in the future</emphasis>) reference
- pictures (I or P pictures). It is the most compressed picture
- format, but it is less fault-tolerant.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> DVD </acronym> :
- Digital Versatile Disc </glossterm>
- <glossdef> <para> Disc hardware format, using the UDF file system,
- an extension of the ISO 9660 file system format and a video format
- which is an extension of the MPEG-2 specification.
- It basically uses MPEG-2 PS files, with subtitles and sound
- tracks encoded as private data and fed into non-MPEG decoders,
- along with .ifo files describing the contents of the DVD. DVD
- specifications are very hard to get, and it takes some
- time to reverse-engineer it. Sometimes DVD are zoned and
- scrambled, so we use a brute-force algorithm to find the key.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> ES </acronym> : Elementary Stream </glossterm>
- <glossdef> <para> Continuous stream of data fed into a decoder,
- without any multiplexing layer. ES streams can be MPEG video
- MPEG audio, AC3 audio, LPCM audio, SPU subpictures...
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> Field picture </glossterm>
- <glossdef> <para> Picture split in two fields, even and odd, like
- television does. DVDs coming from TV shows typically use field
- pictures.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> Frame picture </glossterm>
- <glossdef> <para> Picture without even/odd discontinuities, unlike
- field pictures. DVDs coming from movies typically use frame
- pictures.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym>I</acronym> (intra) picture </glossterm>
- <glossdef> <para> Picture independantly coded. It can be
- decoded without any other reference frame. It is regularly
- sent (like twice a second) for resynchronization purposes.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> IDCT </acronym> : Inverse Discrete
- Cosinus Transform </glossterm>
- <glossdef> <para> IDCT is a classical mathematical algorithm
- to convert from a space domain to a frequency domain. In a
- nutshell, it codes differences instead of coding all absolute
- pixels. MPEG uses an 2-D IDCT in the video decoder, and a 1-D
- IDCT in the audio decoder.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> LPCM </acronym> :
- Linear Pulse Code Modulation </glossterm>
- <glossdef> <para> LPCM is a non-compressed audio encoding,
- available in DVDs.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> MPEG </acronym> :
- Motion Picture Expert Group </glossterm>
- <glossdef> <para> Specification describing a standard syntax of files
- and streams for carrying motion pictures and sound. MPEG-1 is
- ISO/IEC 11172 (three books), MPEG-2 is ISO/IEC 13818. MPEG-4
- version 1 is out, but this player doesn't support it. It is
- relatively easy to get an MPEG specification from ISO or
- equivalent, drafts are even freely available on the Internet.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> P </acronym> (predictive) picture </glossterm>
- <glossdef> <para> Picture decoded from its own data <emphasis>
- and </emphasis> data from a reference picture, which is the
- last I or P picture received.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> PES </acronym> :
- Packetized Elementary Stream </glossterm>
- <glossdef> <para> A chunk of elementary stream. It often corresponds
- to a logical boundary of the stream (for instance a picture
- change), but it is not mandatory. PES carry the synchronization
- information.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> PTS </acronym> :
- Presentation Time Stamp </glossterm>
- <glossdef> <para> Time at which the content of a PES packet is supposed
- to be played. It is used for A/V synchronization.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> PS </acronym> : Program Stream </glossterm>
- <glossdef> <para> File format obtained by concatenating PES packets
- and inserting Pack headers and System headers (for timing
- information). It is the only format described in MPEG-1, and
- the most used format in MPEG-2.
- </para></glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> RGB </acronym> : Red Green Blue </glossterm>
- <glossdef> <para> Picture format where every pixel is calculated in a
- vector space whose coordinates are red, green, and blue. This
- is natively used by monitors and TV sets.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> SPU </acronym> : Sub Picture Unit </glossterm>
- <glossdef> <para> Picture format allowing to do overlays, such
- as subtitles or DVD menus.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> SCR </acronym> :
- System Clock Reference </glossterm>
- <glossdef> <para> Time at which the first byte of a particular pack
- is supposed to be fed to the decoder. VLC uses it to read the
- stream at the right pace.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> SDL </acronym> :
- Simple DirectMedia Layer </glossterm>
- <glossdef> <para> <ulink url="http://www.libsdl.org/"> SDL </ulink>
- is a cross-platform multimedia library
- designed to provide fast access to the video framebuffer and
- the audio device. Since version 1.1, it features YUV overlay
- support, which reduces decoding times by a third.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> TS </acronym> : Transport Stream </glossterm>
- <glossdef> <para> Stream format constituted of fixed size packets
- (188 bytes), defined by ISO/IEC 13818-1. PES packets are
- split among several TS packets.
- A TS stream can contain several programs. It is used in
- streaming applications, in particular for satellite or cable
- broadcasting.
- </para> </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm> <acronym> YUV </acronym> :
- Luminance/Chrominance </glossterm>
- <glossdef> <para> Picture format with 1 coordinate of luminance (black
- and white) and 2 coordinates of chrominance (red and blue).
- This is natively used by PAL video system, for backward
- compatibility with older black and white TV sets. Your eyes
- distinguish luminance variations much better than chrominance
- variations, so you can compress them more. It is therefore
- well suited for image compression, and is used by the MPEG
- specification. The RGB picture can be obtained from the YUV one
- via a costly matrix multiply operation, which can be done in
- hardware by most modern video cards ("YUV acceleration").
- </para> </glossdef>
- </glossentry>
- </glossary>
projects / vlc / blobdiff