mkv shrinking (reduse size) without losing qulity

[badadrian]

hello,

i have a big mkv 3D movie and i want to shrink its size without losing much of its quality ,, and here is the detailed information of the file , is it possible and what software to use ?

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L5.1
Format settings, CABAC : Yes
Format settings, ReFrames : 2 frames
Muxing mode : Container profile=Unknown@5.1
Codec ID : V_MPEG4/ISO/AVC
Duration : 2h 41mn
Bit rate : 13.6 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.273
Stream size : 15.4 GiB (88%)
Writing library : x264 core
Color primaries : BT.709-5, BT.1361, IEC 61966-2-4, SMPTE RP177
Transfer characteristics : BT.709-5, BT.1361
Matrix coefficients : BT.709-5, BT.1361, IEC 61966-2-4 709, SMPTE RP177


Audio
ID : 2
Format : DTS
Format/Info : Digital Theater Systems
Codec ID : A_DTS
Duration : 2h 41mn
Bit rate mode : Constant
Bit rate : 1 510 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 24 bits
Stream size : 1.71 GiB (10%)

[codemaster]

You could try MeGui to:
1. reduce the bitrate of the audio, from 1510 kbps DTS to a downmixed 2 channel aac at 160 kbps;
2. scale the video frames from 1080p to 720p;
3. encode with x264, in crf mode, but the crf value should not be lower than 18, or greater than 24, and the preset should not be below --preset slow.

The encoding of the video could take between 10 to 20 hours, depending on the cpu speed and number of cores. On a Athlon64 X2 at 2500 MHz for example, it may take 15h to encode 2h of 1080i to 720p, but this is normal.

[MilesAhead]

BD Rebuilder now accepts .mkv file input in addition to BluRay folder structures. I've had very good luck with BD-5 output. Of course how it looks will vary with your HDTV. Mine is a 27" CRT type HDTV. For a large flat screen you may want to go for a bit more quality. But it may surprise you. Try one using BD-5 output size and see how it looks.

[Cornucopia]

The REAL answer is: NO, you cannot reduce the bitrate without reducing the quality - ever. Because that would entail a re-encoding to lossy codec. *
What can make it worthwhile or not will depend on the settings & codec options you choose, and what in your personal opinion is an acceptable/unnoticeable amount of quality loss. That is totally subjective and unique to you, so you will have to do some of your own tests to find that equilibrium.

Scott

*exception would be higher lossless to slightly lower bitrate lossless (using more efficient coding), but that is not the case here, or even common.

[MilesAhead]

BD Rebuilder now accepts .mkv file input in addition to BluRay folder structures. I've had very good luck with BD-5 output. Of course how it looks will vary with your HDTV. Mine is a 27" CRT type HDTV. For a large flat screen you may want to go for a bit more quality. But it may surprise you. Try one using BD-5 output size and see how it looks.

edit: missed the "3D" part. I don't know if BDRB even encodes 3D stuff yet. I would tend to doubt it.

[MilesAhead]

The REAL answer is: NO

...

Instead of asking this question people should ask "Is there a way to encode this type of video to a smaller size and still have it look good when displayed on such and such equipment?" Otherwise it's like asking "Is there such as thing as free money?" Unless you're a banker, the answer is no.

[Hoser Rob]

In the first post (not the thread title) the OP did say without losing much of the quality, not none of it. But I guess that depends upon what you mean by by much.

I've seen excellent encodes downsized to 720p. But those came from the original br. The file in question has already been encoded. You can't get the same quality from a br reencode as you can from the original.

And I don't have a damn clue how you'd do it with a 3d video.

[Cornucopia]

I would be able to give suggestion, re: 3d, if I were given the whole info but the OP didn't give the Mediainfo container section, nor any "provenance" (compression history), so that's a total nonstarter until further info is provided.

Scott

[MilesAhead]

In the first post (not the thread title) the OP did say without losing much of the quality, not none of it. But I guess that depends upon what you mean by by much.

I've seen excellent encodes downsized to 720p. But those came from the original br. The file in question has already been encoded. You can't get the same quality from a br reencode as you can from the original.

And I don't have a damn clue how you'd do it with a 3d video.

It's a toss up. Inside the post he says "much" but not in the subject line. Just says "without losing quality" there. They should put in a forum filter that scans posts for the phrase "without losing quality" end delete 'em. That way we wouldn't have to read the mantra about lossy codecs for the 1000th time. It gets old.