S
SACD
Sample Rate
Sampling
SATA
Scalability
Screener
SCSI
SDTV
SECAM
Sequence
Sequence Header
SIF
Slice
Square Pixels
SSDL
SSSL
SVCD
Super VideoCD

SACD
Super Audio CD is the next generation of audio disc, offering full-range, uncompressed digital multi-channel surround sound. SACD can also be backward compatible using so called hybrid discs with an extra layer that allows them to be played on conventional CD players but then only with ordinary CD quality. SACD can be played on SACD Players, DVD Players with SACD support and if using hybrid discs also CD Players. SACD is currently competing with DVD-Audio as the new audio defacto standard. Philips SACD information .



Sample Rate
The number of times a digital sample is taken, measured in samples per second, or Hertz. The more often samples are taken, the better a digital signal can represent the original analog signal. Sampling theory states that the sampling frequency must be more than twice the signal frequency in order to reproduce the signal without aliasing. DVD PCM audio allows sampling rates of 48 and 96 kHz.



Sampling
Converting analog information into a digital representation by measuring the value of the analog signal at regular intervals, called samples, and encoding these numerical values in digital form. Sampling is often based on specified quantization levels. Sampling may also be used to adjust for differences between different digital systems.



SATA
Serial ATA is an evolution of the Parallel ATA storage interface. Serial ATA is a serial link, a single cable with a minimum of four wires creates a point-to-point connection between devices. Transfer rates for Serial ATA begin at 150MBps.
http://www.serialata.org/
http://www.webopedia.com/TERM/S/Serial_ATA.html

See ATA



Scalability
Scalability offers a set of tools by which video can be coded at different Resolutions (different scales) in one total bitstream.
On the decoder side, video can be decoded at the suitable resolution (scale) extracting a portion of the total bitstream.
It adds compatibility and error concealment.

Types of Scalability
Quality (SNR)
The SNR scalability allows the enhancement of the video quality by means of an enhancement layer bitstream. The DCT coefficients encoded by an another layer are refined between the inverse quantisation and the inverse DCT processes. See also the block layer.
So two different goals are obtained: compatibility, as the base layer bitstream can be decoded by a simpler decoder, and graceful degradation, as the base layer can be better protected in transmission with errors.
Spatial
The spatial scalability allows the increasing of the picture size. The enhancement layer bitstream refers to the lower layer bitstream in order to get a possible spatial prediction for the macroblock. The spatial prediction is made from the lower layer decoded picture referenced by the lower layer temporal reference, that picture needs to be upsampled to the enhancement layer picture size. In the enhancement layer, prediction can be: only temporal, only spatial or a weighted combination of both. Spatial prediction may be used also in Intra pictures.
The base layer bitstream can be decoded by simpler decoders, while the more complex ones may have larger displays. Error concealment is possible protecting better the lower bitstream during transmission and displaying the upconverted images.
Temporal
The temporal scalability allows an ehancement of the picture rate. It hasn't been included yet as a tool of a defined Profile.
Frequency (Data Partitioning)
Frequency scalabilty provides an ehancement in terms of "bands" of DCT coefficients. The upper layer would contain those DCT coefficients that have been set to zero in the lower layer stream. It hasn't been included yet as a tool of a defined Profile



Screener
A video usually recorded form a promotional video tape or DVD which is sent to censors and film critics etc. The quality is usually as good as a commercial video or DVD. Sometimes a copyright message appears on the screen.



SCSI
S mall C omputer S ystem I nterface is a standard electronic interface between your computer and its peripherals(hard drives, CD and DVD Readers and Writers and other peripherals). SCSIFAQ .



SDTV
Standard Definition Television or SDTV refers to DIGITAL transmissions with 480-line resolution, either interlaced or progressive scanned formats. SDTV offers significant improvement over today's conventional NTSC picture resolution, similar to comparing DVD quality to VHS, primarily because the digital transmission eliminates snow and ghosts, common with the current NTSC analog format. However, SDTV does not come close to HDTV in both visual and audio quality.
http://www.the-satellite-source.com/satellite-tv/hdtv.php



SECAM
Séquential Couleur Avec Mémoire/Sequential Color with Memory. A composite color standard similar to PAL (image format 4:3, 625 lines, 50 Hz and 6 Mhz video bandwidth), but currently used only as a transmission standard in France and a few other countries. Video is produced using the 625/50 PAL standard and is then transcoded to SECAM by the player or transmitter.



Sequence
A sequence consists of all the pictures that follow a sequence header till a sequence_end_code.
Encoding and displaying parameters are transmitted with the sequence header.
The sequence header can be repeated in order to allow random access, but all the data elements of the repeated sequence header, except those concerning quantisation matrices, must have the same values as in the first sequence header.
The repeated sequence header must precede in the bitstream either an I-picture or a P-picture. In the case that random access is performed to a P-picture, it's possible that the decoded pictures may not be correct.

As the GOP layer is optional the management of the pictures is performed at the sequence layer.
An important item is the fact that the frames are not coded in the order in which they are displayed.
In particular the B_frames, that use references "from the future", are always coded after the P_frame (or the I_frame) used for backward predictions.


The frame reordering causes a delay in the coding and decoding processes. On the coder side the delay is given by the number of B_frames, that must wait for the following P_frame (or I_frame), while the decoder should wait for having full the two frame-memories before starting the display.
For special application is possible to code the sequence without any B_frame with the mode low_delay, set at the sequence layer. In this case the decoder needs only one frame-memory.



Sequence Header
In an MPEG file, a sequence header is placed before one or more groups of pictures ( GOPs ) and contains encoding and displaying parameters. The sequence header can be repeated in order to allow random access, but all the data elements of the repeated sequence header, except those concerning quantisation matrices, must have the same values as in the first sequence header. The repeated sequence header must precede in the bitstream either an I Frame or a P Frame .

To allow for better access and editing, many people place a sequence header after every GOP. In final output, some place fewer sequence headers in (every 5 GOPs, etc.) to save bitrate or make the file smaller.

If you need to add sequence headers to a file you can use the tool MPEG SequenceMaker in the Tools Section .



SIF
Source Interchange Format is a video resolution standard defined as 352x240 for NTSC and 352x288 for PAL and SECAM .



Slice
A slice is a portion of image of 16 lines x ( n x16) pels.
Each slice is coded indipendently from the other slices of the picture.
Therefore the slice layer allows error confinement because, when errors in the bitstream are detected, the decoder can try to continue the decoding process looking for the next slice header.
Video decoding process at the slice layer
Decode slice_vertical_position.
Decode quantiser_scale_code.
Decode all the macroblocks that compose the slice.



Square Pixels
Uses a 1.0 pixel aspect ratio. Use this setting if your video has a 640x480 or 648x486 frame size.



SSDL
Single Sided Dual Layer DVD. See DVD-9 .



SSSL
Single Sided Single Layer DVD. See DVD-5 .



SVCD
SVCD stands for 'Super VideoCD'. A SVCD is very similiar to a VCD , it has the capacity to hold about 35-60 minutes on 74/80 min CDs of very good quality full-motion MPEG-2 video along with up to 2 stereo audio tracks and also 4 selectable subtitles. A SVCD can be played on many standalone DVD Players and of course on all computers with a DVD-ROM or CD-ROM drive with the help of a software based decoder / player. SVCDHelp.com .

Super VideoCD
Also known as SVCDs or SuperVCDs. Please refer to this page for more information.