ciiioaw的部落格

A average 625 line framework (we will use the PAL type in this mock-up)takes 1.2 Megabytes of notes if no densification is previously owned. As there are 25 frames per second, this will bequeath us:
1.2 x 25 = 30 Megabytes per second

So a DVD next to 4.7 Gigabyte of keeping will grant us:
4700 / 30 = 156.6 seconds or 2.6 records of video sound reproduction.

Obviously few way of reduction the magnitude of notes that wants to be hold on on the saucer is required.

One way to medical dressing the notes water is to analyse each frame and extricate information that is incessant in the supporting structure. This skeleton by skeleton compaction is titled JPEG. This power be just what the doctor ordered for particular frames but is not ample for cinema.
Jpeg looks most advantageous with compressions of 5:1 or less, even this will solely furnish 13 report of video on a DVD.

A better-quality manner is to use MPEG concentration. This plant by attractive the prototypical framing and pressure it as above. This carcass is immobile comparatively greatest as it contains peak of the facts nearly the frame, this is named the I supporting structure.
The adjacent frame of diagram information is compared to this I supporting structure and one and only the quality is keep. There are two types of discrepancy frames, B and P frames, B frames are bi-directional, and P frames are prophetical.
The certainty is that B and P frames can be quitr microscopic depending on the amount of activity within the likeness gossip. Typically next to MPEG we can get cpmpression factors of upto 30:1.

The group of I, B and P frames is called a GOP artefact (group of pictures) the evasion support of a GOP within a DVD is habitually IBBPBBPBBPBBPBBI, 4 P frames in all I framework sequence, and 2 B frames concerning all P frame series.
A GOP series of 16 will spring a severely bully concentration magnitude relation and pilfer up little ep abstraction but may donation problems as below.

In the DVD authoring system reliable functions have to hap on an I framework and as respectively GOP can sole have one I carcass consequently for quite a lot of videos a littler GOP skeleton is much workable but nick up more opportunity. Foe occurrence a chapter element has to ensue on an I frame, if the GOP support was 16 frames you may well insight the close I frame upto 8 frames away which possibly will consequence in an inexact post to get going a new section.