File Types

I’ve put full sized rips of Blu-ray on my Hub. Once you go blu-ray, you can’t go back! I have a home theater setup, 90" screen, etc. and want the best possible picture. Some of the files are upwards of 15 gigs and this is with no extras. I can’t seem to find a good answer on converting them to smaller files, mkv, iso, etc. Can anyone tell me through their experience on how much quality is lost converting to more reasonable sizes, like 4 gigs?


Converting a full Bluray to a file of 4G in size will very likely have noticible compression artifiacts.

“most” BD features start at around 30 gig or so for the main feature.   Compressing down to 12 to 15 gig is reasonable with only minor differences in quality.   But down to 4?   No way.

My re-coded rip of Avatar is 14 gigabytes.

So MKV and ISO can have IDENTICAL characteristics; those are just CONTAINERS.   It’s the CODEC and compression settings used in the VIDEO track that make a substantial difference.

What I’ve been doing lately to rip my BDs:

Use BDINFO to find the primary feature film’s “PLAYLIST” file.

Import that Playlist into TSMuxerGUI and rip out the main movie, and all ENGLISH audio tracks and subtitle tracks.

Remux that into its own .TS file.

Done.  No further recompression.

If I want MORE compression, then I use TSMuxerGUI to pull out the primary stream and all audio tracks, into ONE file, and use Handbrake’s High Profile preset (maybe with some tweaks) to convert to MKV.

Then I have to use BDSup2Sub in conjunction with TSMuxer to convert the BD Subtitles into VOBSUB subtitles, and then use MKVMerge to add them into the MKV file.

Depending on settings, it’s a 12-16 hour job.

Cosber wrote:

Can anyone tell me through their experience on how much quality is lost converting to more reasonable sizes, like 4 gigs?


Let’s consider a 2-hour movie at 23.976 frames per second and ignore audio and subtitles – just the video stream…

2 hours * 60 minutes/hour * 60 seconds/minute * 23.976 frames/second = 172627.2 frames of video.

Let’s now consider each frame to be 1920x1080 pixels.

172627.2 * 1920 * 1080 = 357,959,761,920 individual pixels to store.

With a standard “8-bit” colourspace, each pixel has 24 bits of colour information.

357,959,761,920 * 24 = 8,591,034,286,080 bits of information making up the video stream, as displayed.

With 8 bits per byte, and 1024 bytes/ KB and 1024 KB/MB and 1024 MB/GB we have:

8,591,034,286,080 / 8 / 1024 / 1024 / 1024 = 1000.128 GB of information.  (0.976688 TB).

And that’s just over-simplifying, and not taking into account any of the header information and everything else that goes into the stream… that’s just how much space is necessary to store all the pictures’ individual pixels’ colour information.

When the studio encodes your retail BluRay, there’s massive compression.  That 1000GB is compressed down to 20 or 30 GB.  We’ve already “thrown out” as much as 98% of the video information.  The compression schemes used are designed exactly for that, so that you hopefully don’t really notice the missing information.

But, the compression used isn’t the best available, in terms of size… the file can be made somewhat smaller, with no further apparent loss of quality, as Tony points out.

But, with the audio track taking up close to 1GB on its own, your 4GB target filesize leaves you around 3GB to actually represent the video.  With current compression algorithms, it’s physically impossible to throw that much more out and not significantly notice it.

If you’re bent on having <4GB files, you’re looking at either drastic image quality issues, or resizing the video down to 720p and reducing the quality somewhat.  A “comparable” 720p h264 encode to a 15GB 1080p encode will still be over 6GB.

“Best possible picture” and what you’re calling a “reasonable” file size are mutually exclusive.  The best possible picture would be stored uncompressed right from the start, and would be 1000 GB… absolutely no information would be missing, whether visually discernible, or not.

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