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What's wrong with DVD Shrink?

Over the course of the past couple of years DVD ripping techniques have changed dramatically. Newer "one click" programs have made backing up a DVD a fairly simple process... but there is a significant trade-off. The quality that can be attained by even the best of these programs is poor in comparison to original techniques that used Cinemacraft Encoder, HC Encoder, QuEnc, or other top-notch encoders. The reason is simple. When using one of these encoders the picture is rebuilt from scratch and optimized for the resulting bitrate. One-touch transcoders usually drop DCT coefficients or change quantization info in order to lower the bitrate. This can result in pixelation and poor overall picture quality.

But, they sure are convenient.

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What's the difference between DVD Shrink and DVD Rebuilder?


DVD Shrink is a transcoding program. Transcoding or more specifically Compressed-domain Transcoding means normally a re-encoding process that changes the video or audio features, such as resolution or bitrate, by changing parts of the a/v content, but not by reconstructing the content again (which is the case in encoding process). Compressed-domain transcoding also maintains the format of the file same as in the original file. Transcoding doesn't encode it takes out small bits of detail to make the DVD video smaller. Faster then encoding.

DVD Rebuilder can be used as both an encoding and transcoding program by using different modes and is a good program to re-encode a DVD. Encoding is the process of changing data from one form into another according to a set of rules specifiec by a codec. Often the encoding is done to make a file compatible with specific hardware (such as a DVD Player) or to compress or reduce the space the data occupies.

Encoding will give you a better picture quality when you need to 'shrink' your original DVD down to a very low bit rate.


Bit rates

Another common word in the encoding world. Generally, higher bit rates allow for higher quality, because more information is moved.

Think of bit rate as water coming out of a hose. If each drop of water in the stream of water leaving the hose is a single bit, then as you turn up the water pressure more bits are passed along. When the hose is turned down low only a trickle of water is moved meaning that few bits of water are moving resulting in a low bit rate. When the hose is turned to its maximum pressure, a great number of water droplets or water bits are moving each second resulting in a high bit rate.

Very often people are asking about the compression percentage and what results in a good quality backup.

Put simply, it is not the compression percentage which matters but the bit rate which is devoted to the video encoding.

These bit rates should give you a clue on the quality:

1 Mbit/s ? VHS quality
5 Mbit/s ? DVD quality
10 Mbit/s ? HDTV quality
For example, if a movie was originally encoded with a "high" bit rate (say 6 Mbps - "mega bits per second") and compressed by a lot, (say to 50%), on average, this would result in a bitrate of 3 MBps.

But if the movie was originally encoded with a "low" bitrate (say 3.5 Mbps) and was compressed only by 20% (to 80%), the resulting average bitrate would be 2.8 Mbps - worse than the 50% compression!!!

Now, what you can detect as "bad quality" will most likely depend on the final bitrate and the size of your screen. If your are projecting onto a huge screen, the higher numbers are probably necessary (say over 3.5 and preferably 4.5+). But on a regular TV, you can probably get away with the 3 Mbps range (and even lower).

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