DVD Shrink Compression Method???

[Jaded101]

So I'm somewhat new to backing up DVDs and someone suggested DVD Shrink. It occured to me that this software basically re-encodes/compresses the data as if I were to use VirtualDub and XVID except able to read VOB files. What method/algorithm does DVD Shrink use? Would it be any better than if I wanted manually do it with XVID? What about DVD Rebuilder? Is there any way to make a backup at the same quality of the commercial DVD? What compression does the commercial industry use?

TIA

[guns1inger]

DVD Shrink, DVD Rebuilder and Virtualdub all work in different ways. It is difficult to directly compare them because of this.

All commercial DVDs are encoded as per the DVD specification, using mpeg2 video compression. How they compress varies, depending on their budget. Some use very expensive hardware compression, others use the type of software owned by users here - ProCoder or CCE, for example.

DVD Shrink does not encode, and cannot encode. It is a Domain Transcoder, and basically analises the data usage from the original encoding, and tries to find further unnecessary data that can be removed to reduce size. It relies entirely on the existing encoding. This makes it much faster that a program that re-encodes, however it tends it hit quality threshholds much faster that an encoder.

DVD Rebuilder uses different methods depending on how you run it. It can transcode using Rejig, or it can re-encode using a variety of encoders - CCE, ProCoder, HCEnc, Quenc etc. Re-encoding takes a lot longer than transcoding as all the same analysis as was done for the original encode is done again, this time with different bitrate targets.

Virtualdub is closer to DVD Rebuilder than it is to DVD Shrink, in that it has multiple modes, but at heart drives encoding engines. It has effectively three modes of operation. Direct Stream Copy, which does no encoding, but also does not reduce overall size, Fast Recompress, which does re-encode, but does no colour space conversion and is generally faster than the final mode, Full Processing Mode. Full Processing Mode involves colourspace conversion to RGB (virtualdub's native colourspace) and outputs re-encoded video (depending on codec chosen). It is the only mode that filters can be used in.

As for your other questions . . .

Can you make a backup of the same quality as a commercial DVD - yes, very easily. Use DVD Decrypter to rip to an ISO, then write that ISO back to a disc without doing any further compression. You will have an indentical copy. In most cases this will require a dual layer disc for output.

Once you start encoding, you start to affect quality. To what degree depends on what method and tools you use, and how much you compress the video when you re-encode. In somes cases the results can be indistinguishable from the original. In others they will be chalk and cheese.

You cannot create a DVD or DVD output using virtualdub. Wrong tool completely. You can use it to frameserve to an mpeg2 encoder, and from there author a disc, but that is a longer process.

[Jaded101]

Thank you very much for the descriptive post and answering my questions. So which one you prefer for quality? DVD Shrink or DVD Rebuilder? Or are there even better software out there besides these two? I have all the time in the world so that's not an issue for me, quality is.

Thanks again!

[A_51]

Rebuilder is better for movies that need high compression. If the movie don't need that much, Dvdshrink is better due to feature and ease of use. Me personally prefer shrink and only use Rebuilder when needed.

[guns1inger]

Agreed - horses for courses. For shaving a few percent here and there, Shrink is fast, good quality, and simple. It is also quicker to set for re-authoring than DVD Rebuilder, so I will often use it to strip down a disc without compressing it, then feeding the results to DVD Rebuilder. I actually use DVD Rebuilder Pro now, which has many refinements and features not i the basic version. It too can re-author, but Shrink is more visual and flexible.

For heavy compression, Rebuilder with CCE or ProCoder is king. I recently compressed my boxset of The Prisoner using DVDRBPro to compress all episodes down to half-D1 (something Shrink cannot do), and fitting four episodes (200mins) to a disc. Great quality output.