P
P Frame
P-CAV
PAL
Pan & Scan
PBC
PCM
PCMCIA
Perceptual Coding
PhotoVCD
Physical Sector Number
PIP
Pit
Pixel
Pixel Aspect Ratio
POP
Portable DVD Player
PowerDVD
Premastering
Pro-Logic
Program Stream
Progressive Scan
PTT Menu
PULLDOWN
PC-DVD
Proprietary Format

P Frame
A P-frame is a video frame encoded relative to the past reference frame. A reference frame is a P- or I-frame . The past reference frame is the closest preceding reference frame.

Each macroblock in a P-frame can be encoded either as an I-macroblock or as a P-macroblock. An I-macroblock is encoded just like a macroblock in an I-frame. A P-macroblock is encoded as a 16x16 area of the past reference frame, plus an error term. To specify the 16x16 area of the reference frame, a motion vector is included. A motion vector (0, 0) means that the 16x16 area is in the same position as the macroblock we are encoding. Other motion vectors are relative to that position. Motion vectors may include half-pixel values, in which case pixels are averaged. The error term is encoded using the DCT, quantization, and run-length encoding. A macroblock may also be skipped which is equivalent to a (0, 0) vector and an all-zero error term. The search for good motion vector (the one that gives small error term and good compression) is the heart of any MPEG-1 video encoder and it is the primary reason why encoders are slow. MPEG FAQ



P-CAV
Partial-Constant Angular Velocity, the disc(CD/DVD) is being read/written at an increasing speed until a certain point (speed). After this point the speed will not increase anymore and remain at this speed.



PAL
Short for Phase Alternating Line, the dominant television standard in Europe. The United States uses a different standard, NTSC . PAL delivers 625 lines at 50 fields (half-frames interlaced) per second. The resolution of a PAL VCD is 352x288 pixels, a PAL SVCD is 480x576, and a PAL full D1 DVD is 704 or 720 x 576.



Pan & Scan
The technique of reframing a picture to conform to a different aspect ratio by cropping parts of the picture. DVD-Video players can automatically create a 4:3 pan & scan version from widescreen video by using a horizontal offset encoded with the video, which allows the focus of attention to always be visible.



PBC
Playback control, PBC, is available for Video CD ( VCD ) 2.0 and Super Video CD ( SVCD ) 1.0 disc formats. PBC allows control of the playback of play items and the possibility of interaction with the user through the remote control or some other input device available. VCDimager details



PCM
Pulse Code Modulation. An uncompressed, digitally coded representation of an analog signal. The waveform is sampled at regular intervals and a series of pulses in coded form (usually quantized) are generated to represent the amplitude.



PCMCIA
Short for Personal Computer Memory Card International Association, and pronounced as separate letters, PCMCIA is an organization consisting of some 500 companies that has developed a standard for small, credit card-sized devices, called PC Cards. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times and is now suitable for many types of devices. There are in fact three types of PCMCIA cards. Webopedia .



Perceptual Coding
Lossy compression techniques based on the study of human perception. Perceptual coding systems identify and remove information that is least likely to be missed by the average human observer.



PhotoVCD
Not a standard by itself, this term is used when a group of image files are placed on a VCD and displayed in a format like a slideshow. There are two ways of doing this with VCD 2.0 technology:

1) Import the pictures into a video editing program, adding optional music and transition effects as desired. The time between pictures is decided by the filmmaker, not the viewer. The result is output as a VCD or even SVCD motion video file and authored like any motion video to VCD or SVCD. The resolution is limited to VCD 352x240 NTSC , 352x288 PAL or SVCD 480x480 NTSC, 480x576 PAL which may appear grainy or low resolution compaired to the original pictures.

2) Author a photo VCD 2.0 disc encoding each picture as a still MPEG at 704x480 NTSC, 704x576 PAL. This allows better resolution but (probably) lacks transition effects. The resulting collection of still MPEG images can be authored with difficulty in VCDimager/VCDeasy or you can use a program that automates the whole process from images to disc like Ulead DVD Pictureshow 2 (which also does VCD well). VCDhelp PhotoVCD Guides



Physical Sector Number
Serial number assigned to physical sectors on a DVD disc. Serial incremented numbers are assigned to sectors from the head sector in the Data Area as 30000h from the start of the Lead In Area to the end of the Lead Out Area.



PIP
Picture in picture. A feature of some televisions that shows another channel or video source in a small window superimposed in a corner of the screen.



Pit
A microscopic depression in the recording layer of a disc. Pits are usually 1/4 of the laser wavelength so as to cause cancellation of the beam by diffraction.



Pixel
The smallest picture element of an image (one sample of each color component). A single dot of the array of dots that makes up a picture. Sometimes abbreviated to pel. The resolution of a digital display is typically specified in terms of pixels (width by height) and color depth (the number of bits required to represent each pixel).



Pixel Aspect Ratio
The ratio of width to height of a single pixel. Often means sample pitch aspect ratio (when referring to sampled digital video). Pixel aspect ratio for a given raster can be calculated as y/x multiplied by w/h (where x and y are the raster horizontal pixel count and vertical pixel count, and w and h are the display aspect ratio width and height). Pixel aspect ratios are also confusingly calculated as x/y multiplied by w/h, giving a height-to-width ratio.



POP
Picture outside picture. A feature of some widescreen displays that uses the unused area around a 4:3 picture to show additional pictures.



Portable DVD Player
Versatile portables play anywhere and also connect to your home TV.



PowerDVD
A software DVD player for the PC. Cyberlink product info



Premastering
The process of preparing data in the final format to create a DVD disc image for mastering. Includes creating DVD control and navigation data, multiplexing data streams together, generating error-correction codes, and performing channel modulation. Often includes the process of encoding video, audio, and subpictures.



Pro-Logic
An encoding technology developed by Dolby Laboratories , Pro-Logic and Pro-Logic II are methods of encoding 4 channels for Pro-Logic (left, right, center, surround) and 5 channels for Pro-Logic II (left, right, center, left surround, right surround), into a stereo (left, right) channel format to be decoded into 4 or 5 channels with a proper decoder. It is actually just a small amount of inaudible data slipped into a stereo audio stream that can be reconized by a decoder so that the decoder can separate the stereo signal into 4 or 5 channels. A Pro-Logic signal can be encoded into any form of stereo audio stream including digital files such as mpeg-1/2 layer 2, MP3 , uncompressed PCM, audio CD's, and it is also used to get multichannel in VHS tapes and other analog sources. You can listen to Pro-Logic encoded audio streams with any normal equitment but you will only have 2 channels. DVD players are required to have a capable Dolby Digital decoder to downmix a 5.1 Dolby Digital signal on DVDs to a Pro-Logic stereo signal to be output with analog RCA cables. Pro-Logic II can be decoded with Pro-Logic decoders but you will only get 4 channels instead of 5. Pro-Logic is also called Dolby Surround. Dolby



Program Stream
The Input of the Program Stream Multiplexer and the Output of the Program Stream Demultiplexer are the Video and Audio Packetized Elementary Streams (PES)
MPEG-2 Program Stream:
may contain a single program with a common time-base for the different PES; is suitable to error-free transmision environment;
has a variable length packet structure (where packets may be relatively large).



Progressive Scan
A video scanning system that displays all lines of a frame in one pass. Contrast with interlaced scan.



PTT Menu
In DVD-Video, a menu used to access specific Part of Title (PTT) in a Video Title Set (VTS). Usually referred to as a Chapter Menu.



PULLDOWN
Film is generally shot and projected at 24 frames per second (fps), so when film frames are converted to NTSC video, the rate must be modified to play at 29.97 fps. During the telecine process, twelve (12) fields are added to each 24 frames of film (12 fields = 6 frames) so the same images that made up 24 frames of film then comprise 30 frames of video.Video plays at a speed of 29.97 fps so the film actually runs at 23.976 fps when transferred to video.

AVID does a 2-3 pulldown (which is used in a lot of film editing)

But most other editors use 3-2 pulldown.

2-3 Pulldown vs. 3-2
It is commonly referred to as 3-2 pulldown; while modern telecine machines can go either way. Therefore, AA BB BC CD DD. If the telecine is set for 3-2, you'll get BB BC CD DD AA.

Another slightly confusing consideration: When the pulldown process occurs, it turns out that the video version of the film runs slightly SLOWER than the original film did. This occurs because the film is running at 24 frames per second, but in order to create the right pattern of A-B-C-D on the video tape, which runs at 29.97 frames per second, the film was actually played at 23.976 fps during the telecine (film->tape process).

PC-DVD
PC-DVD usually refers to DVDs on computers (eg. DVD-ROM, DVD decoder ...). Please refer to DVD Digest's PC-DVD Guide for more information.

Proprietary Format
The problem with any proprietary format is the format's specifications are closed, and therefore, there aren't as many tools (especially free ones) that will support them. This is why while DivX/AVI tools are plenty, ASF or WMV tools are not as common (except for tools released by Microsoft) - conversion from a closed proprietary format to another format is also limitd, as per the intentions of the people who owns the format.