A few questions regarding quality, file size, etc...

[smackyourfupa]

OK so I recently ripped my complete DVD collection and stored them all on hard drives to watch on my HTPC. I did exact backups of each disc. On average, each disc is between 6-8 GB. I figured why not just download a 720p or 1080p version of the movie? The file size will be smaller and the quality will be better. My question is, how is this possible? Say, for example, the Alien DVD has a size (the movie alone) of 7GB. How can an MKV or m2ts file of only 4GB have better quality than a 7GB file? I understand the res of DVDs is 480p. Does resolution alone make the image better or are there more variables? Can a 4 GB file have true 720p/1080p resolution?
I also notice that m2ts files seem to have the best quality (better than mkv,mp4, etc) ..is this true?

[Baldrick]

Because the avc/h264 compression that is used in the mkv/m2ts is much better than the dvd mpeg2 compression.

And m2ts, mkv, mp4 are just containers and can all contain same video.

[smackyourfupa]

Because the avc/h264 compression that is used in the mkv/m2ts is much better than the dvd mpeg2 compression.

And m2ts, mkv, mp4 are just containers and can all contain same video.

... Does resolution alone make the image better or are there more variables? Can a 4 GB file have true 720p/1080p resolution?

[Baldrick]

THe quality depends on the resolution, bitrate and video codec.


The output file size depends on the bitrate*runtime.....lower bitrate=lower quality.

[smackyourfupa]

OK so one more question. Say, for example you have 2 mkv or m2ts files, both of the same exact movie from the same source. One is 1080p and 4GB and the other 720p and 7GB. The 720p has a MUCH higher bitrate than the 1080p file. Is the 720p movie going to look better even though the resolution is lower?

[Baldrick]

The 1080p will be a bit sharper BUT probably with much more compression artifacts like blocks in scenes with lots of motions and details.

[Vladrial]

1080p videos found on a Blu-Ray are sourced from original masters... same for DVD but it is compressed at a lower bitrate... and uses a less capable compression codec ( MPEG-2 )... When youl rip a DVD and Blu-Ray and compress both using same settings.. the Blu-Ray compress will look better because your source is of higher quality...

If compressed from same source ... and keeping encoding parameters same for both 1080p and 720p all except bitrate, the 720p quality will be better.. though 1080p will appear a little sharper with possible artifacts ( Colour, blocks.. etc.. ) as Baldrick pointed out above, however 720p can be overall better looking

[RabidDog]

The output file size depends on the bitrate*runtime.....lower bit-rate=lower quality.

Strangely this is true of all Films EXCEPT anything by the Rock or Steven Seagal, where lowering the bit-rate increases the quality.

In general a 4gb rip (compressed using x264) will retain more detail than a 6gb rip (compressed using mpeg2)

mpeg2 was designed when computers were barely 16bit, whereas x264/VC1/mpeg10 is designed for 2008+ when computers are multicore 32/64 bit running at gighertz speeds.

History of codecs
2000BC Noah shoots 1st video in mpeg1
1955 AD 1st Video in mpeg2
1994 mpeg4 (divx/xvid rmvb?)
2006 mpeg10 (insert technical guff here, wiki link http://en.wikipedia.org/wiki/List_of_codecs)