PDA

View Full Version : blue-ray rip question


dimtim
23rd October 2008, 04:39
Hey I'm a complete newbie to blu-ray and hd rips, and my question is, how much can you compress one of those movies before it starts to look worse. I know that if you compress a regular dvd to mp4 it looks almost identical to the original movie at about half the file size. What would be a similar comparison for blu-ray generally speaking? What are typical encoded sizes?

Thanks
Tim

dat720
23rd October 2008, 08:08
About half is a good guideline, i have done all my BD's and HD's and the difference is so minute you can barely notice.

I use h264 with CRF set to between 18 and 22 depending on the length/genre of movie (there are other considerations but these 2 are my main)

Adub
23rd October 2008, 08:58
It depends on a lot of things. Varying from video codec to audio codec, to final resolution, to encode settings and so on. Sure you say half size. Are you compressing your audio as well? What settings are you using for you video codec? What video codec are you using?

The answer to a lot of these things is: Video codec=h.264, resolution=720p or 1080p, audio codec=ac3, video bitrate=varies, audio bitrate=448-640kbps. The factor that will have the most affect on size is your video resolution and video codec/bitrate selection.

If you want some answers to your questions, use search, do some reading, and then run some of your own tests.

dat720
23rd October 2008, 09:40
I'm with Merlin on this one, to find the quality vs size you are happy with you need to do some of your own trial and error.

Start with some base settings then tweak to suit..... you may want to test with a short section of a bluray as encoding is very slow!

I have a Q9550 and only manage to get about 12fps using h264 while encoding a 1080p movie!

RunningSkittle
23rd October 2008, 13:17
using directshowsource() ?

dimtim
24th October 2008, 01:37
Sorry, guess I should have been more specific, but I have a few blu-ray dvds to backup, and I was just kind of curious how much hard drive space I would need to allocate so I really didn't have any specifics.

dat720
24th October 2008, 11:37
You will need between 15 and 30gb for the files directly off the disc, then depending what you do with them, you could need upto 100gb free to process......

As an example Transformers comes off the disc at roughly 23gb with no extra streams, my compressed copy is 9gb and to the untrained eye looks identical!

Why do you want to compress them if all you are doing is a backup, isnt the idea of a backup to have a copy that is the same as the original?

QuadcoreHD
24th October 2008, 23:54
@dat720,

Just out of curiousity, what display do you watch your compresed BD vids on? I watch stuff in 1080 and 720 on my projector and definitely see a difference.

Q

dat720
25th October 2008, 02:22
42" Plasma (RGB 1080i) via a PS3 in the bedroom
60" Rear Projection (DVI 1080P) via Myth TV in the lounge room

and there is a difference, but only slight, to spot it i have to frame cap from original source then compare it to a cap from the compressed copy, you can notice it on direct comparison, but not when playing back one of the compressed movies.....

I can handle the trade off to fit more movies on my media server!

If you'd like i can do a cap from an original source vs my compressed source?

Blue_MiSfit
31st October 2008, 00:23
When ripping a BluRay disc, I find it very useful to compare 1080p with 720p on a per-movie basis, since most titles honestly don't look any worse in 720p. Here's how I do it:


DSS2("source.mkv")
a=last
spline36resize(1280,720)
interleave(a,last.spline36resize(1920,1080))


You can step through and compare on a frame-by-frame basis and see how things look. In most cases (even zoomed in to 200%) you'll be pressed to find a meaningful difference. Slight grain softening is the usual side effect.

I usually end up cropping the raw source to remove the mattes, and then resizing to 1280x720, and setting the apropriate AR flag in MKVToolnix (2.35 most of the time).

~MiSfit

73ChargerFan
1st November 2008, 03:09
To make the testing easier, find a good point in the movie with lots of contract, good colors, lots of motion. These scenes will show compression as ok, good, or ugly. Encode those 2 or 3 minutes, and compare.

Adub
1st November 2008, 06:39
Excellent advice there 73ChargerFan. Another idea is to make use of the SelectRangeEvery() function of Avisynth. That way you can get a decent sampling of the total movie.