VIDEO FILE INFORMATION  

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Some Points before going to know what is video how it is

• Professional movies are filmed at 24 or 48 FPS (Frames Per Second) and Television runs at 25 or 30 FPS.

• A lot of computer video only runs at 10 or 15 frames per second. (Look a bit jerky)

• High frame rats take a lot space for all the individual frames.

• Delta Frame - only stores the differences between the two frames.

• Key Frame - is the main frame which is used to design Delta Frame.

• Most video files have key frames every 5-30 frames.

• Video Resolutions 352x240, Normal 320x240, Minimum upto 240x180 (shrink the picture)

• Realistic ratios for Mpeg are 26:1

DV - Digital Video

Video - it is a sequence of individual images (frames) the frame ratio typically ranges from 24 to 30 fps (frames per second)

Audio tracks are synchronized to Video.

1) NTSC - American Standard  (National Television Standard Committee)
2) PAL - European Standard (Phase Alternating Line)
3) SECAM - French Standard (Sequential Couleur Avec Memoire)

a) 30 frames per second in interlaced fashion - odd lines in one path and even lines in the next. This divides each frame into 60 fields.
b) 25 interlaced frames per second with 625 scale lines. Greater bandwidth for chrominance modulation, yielding better colour resolution. The chrominance signals as UV taken with luminance YUV color space.
c) Same as PAL. FM is used to encode the Chrominance signal.

There are two main types of streaming
1) Progressive Streaming (on demand) whole via http compressed.
2) Real-time streaming (live or in real-time) via RTSP whole.

• NTSC and PAL-M 30 fps.

• PAL, SECAM and MESECAM 25 fps (highspeed)

Polar Coordinates

Analog or Digital Video canbe classified as interlaced or non-interlaced (progressive scan), video prgs using NTSC, PAL and SECAM are interlaced each frame consists of two fields displayed in two passes. PC's use progressive scans in which all lines in a frame are displayed in one pass from top to bottom.

In interlaced video, a frame is divided into 2 fields. Each contains every other horizontal line in the frame. TV disp the first field of alternating line over the entire screen and then displays the second field. One NTSC video frame displayed approx every 1/30th of a second.

Contains two interlaced fields, that are displayed approximately every 1/60th of a Sec.

Whereas PAL, SECAM video frames display every 1/25th of a second and 1/50th second

The field that contains the topmost scan line in the frame is called the upper field and the other field is called the lower field.

Drop Frame time code is a SMPTE (Society of Motion Picture and Television Eng) standard that maintains time accuracy by eliminating the error.

AVI - Audio-video interleaved. WAV - Audio Wave Format.
AVC - Perception Audio Video PVD - Perception Video.
AIF - Audio Interchange Format. ASF - Advanced Streaming Format.


Wave PCM (uncompressed) audio format is usually supported for decoding (PLAYBACK) by all the codecs and has format tag 1. other formats have different (unique) tag values. Windows uses the format tag (stored in the file header) to find an appropriate audio codec.