BluRay rip -> BD format or mp4?

[rwc]

Hello,

I've read the thread about mts vs. bd folders..and my question is similar (sort of).

We tend to watch only the "main movie" of a bluray (and usually without subtitles). A straight rip can be 35Gig, but converting it to an mp4 is 2....

The specs on the file seem like the video and the audio quality hasn't been comprimised...why is it so much smaller? Am I missing somethign? OR is all that "extra stuff" adding THAT MUCH to the rip?

[Naylia]

The resolution might be the same...what's the bitrate?

Have you watched a 2GB rip of a blu-ray?

You could compress a DVD to about 2GB without quality loss by converting from MPEG-2 to H.264, but not a BR.

[rwc]

I'll check when I get home, but...

Please don't flame, but how does bitrate and resolution relate?

Is bitrate how 'quickly' the image can change, and resolution is how "big" the picture is?

thanks,

rwc

[Naylia]

High level - the compression works by grouping pixels in a frame, and from one frame to the next and then representing these with an equation or by stating they are all the same or some such.

So if I have a video that is a black screen for an hour, I could say hey, this whole frame looks the same as a single pixel, and the next frame looks just like this one, so regardless of length or resolution I could very easily represent that the whole video is just black.

Now think about a video with lots of motion, moving objects, brihgt, dark, variety of colors, etc. The more/faster the motion the less the pixels are likely to be from one frame to the next making it more difficult to compress the information. If I limit the bitrate, I limit how much information can be stored about the video in each frame and what happens is the compression software starts to "artifact" which is what happens when it is no longer acurately representing the video properly. You can see this quite often with some cable tv HD channels that are "bit starved" - which is that the tv stantion is not being given enough bandwidth to carry the required information to reproduct the video properly. The video can stay the same resolution (1920x1080) but the image being shown is not the same (or sometimes even remotely close) to the original video image.

That's very much a layman's explanation, if you google video compression there is lots of good information out there about how it's done:

http://www.animemusicvideos.org/guid...ech/video3.htm

[rwc]

Thanks for that explanaition, it helped a lot...

For the rip, I get

ArcSoft-H264 1920x1080 between 1.5 -3.5 Mbps
AAC 309kbps

For the bluray disk directly I get:
Mpeg4 AVC: 1920x1080 between 18-30Mbps


I know that h.264 is "part 10 of the mp4 spec" (which doesn't mean much to me)..does one have "more compression" or a different type of compression?

I see how higher bitrates would definately help with an action movie or sports, but for a movie that doesn't "change much" (I'm thinking 2001 A Space Odessy for example), do you need the high bit rate? Does more change that I expect because of lighting, etc?

What is a good "sweet spot" for file size vs. picture quality?

Thanks!

rwc

[Naylia]

If you really want to compress to save space I would consider reducing resolution down 1280x720 and experiment with bitrate. Maybe try encoding using a multi-pass variable bitrate option with an averagae of 15mbps. That should still give you a pretty good picture most of the time. From there you can experiment. If you are going to do a lot of movies, I'd pick one you know and do a couple encodes to see what things look like at different bitrates.

[SWKerr]

m2ts and mp4 are just containers that hold the associated video, audio, subtitles etc. You can use the same h.264 file in both containers regardless of how much you compressed it. Each has slightly different support for the various video and audio formats. I typically see mp4 files with h.264 video and AAC audio. You can also use the mkv container in much the same way.

There are a number of tools to convert Blu-rays to other formats or even just to shrink the m2ts file. I tend to use a free tool called RipBot or on occasion MeGui. RipBot is easier to use but MeGui give you control over every aspect of the output.
RipBot Guide: http://www.videohelp.com/tools/RipBot264

There are several ways to reduce the size of the file.
1. Remove excess crap. Each file generally contains excess subtitles audio and sometimes video tracks that can be removed if you will not want them. This may reduce the file size by lets say 10% .

2. Reduce the resolution. Full HD is 1920x1080 but you can often reduce it to 1280x720 and not notice much difference. I found that after I upgraded to a 50in plasma that I could tell the difference between them but on the old 42" screen I really could not tell a difference. As you screen size grows the more important the resolution becomes.

3. Compress the audio and video files more. This is to taste but you can easily cut it in half and not tell the difference in most cases. The rate at which you compress the file is usually referred to as the bit rate and the smaller the file size the worse the quality. A lot of tools have profiles for different source types where someone has predefined all the setting to make life easier.

At this point I usually compress everything to a m2ts file at the original resolution using AC3 audio. I use the CQ mode in RipBot of 22. (18 is close to original resolution. for something like Avatar I used 20) Average movie size is usually 5-6GB (animation 3-4GB)

[Taddeusz]

I use MeGUI to transcode my BD's. I keep the original width of the video but crop the black bars off. I use 2-pass with a bitrate of 6300 kbps if the video is about 1920x800 or 7000 kbps if the video is at or near a full 1920x1080. This produces good enough video for storage on my server. Good enough that I can still see much of the film grain. Going much lower than that will cause some or all of the film grain to be blurred out due to the compression.

Sure, transcoding is certainly a trade-off but hard drives aren't nearly cheap enough for me to keep all my BD's in full quality. Personally I think that the high bitrate of most BD movies is overkill. You can have more than watchable 1080p video at much lower bitrates. IMHO, the only real advantage for the movie studios to make the movies at such an insanely high quality makes them very unwieldy to transmit unmodified over the internet. In other words they make them huge to prevent their movies from easily being pirated in an unmodified form.

[stanger89]

The killer for me is the transcoding, the work to do it right. It takes the better part of a day, and you've got to verify that it all went OK. With 2TB drives for ~$100, it's just not worth it IMO.

Originally Posted by rwc

Thanks for that explanaition, it helped a lot...

For the rip, I get

ArcSoft-H264 1920x1080 between 1.5 -3.5 Mbps
AAC 309kbps

For the bluray disk directly I get:
Mpeg4 AVC: 1920x1080 between 18-30Mbps


I know that h.264 is "part 10 of the mp4 spec" (which doesn't mean much to me)..does one have "more compression" or a different type of compression?

MPEG-4 AVC (Advanced Video Coding), AVC, H.264, MPEG-4 part-10, they're all names for the same thing, the same codec.

I see how higher bitrates would definately help with an action movie or sports, but for a movie that doesn't "change much" (I'm thinking 2001 A Space Odessy for example), do you need the high bit rate? Does more change that I expect because of lighting, etc?

It just depends. It depends on the movie, the viewer, the display (size and quality). There is no right answer. I generally have much "harsher" view of transcoding than a lot here, but I run a lot larger, more revealing display than most and sit much closer (relative to it's size), so even small defects are noticeable.

What is a good "sweet spot" for file size vs. picture quality?

IMO, whatever came on the disc, minus the extras that aren't needed (extra audio tracks, trailers, special features,etc). With that it's as good as it can get, you don't have to worry about evaluating it, tuning things, none of that futzing. You don't end up watching it later wondering if anything odd you see is something you "added" that could be fixed by using different parameters.

Yeah, it takes a bit of disk space, but like I said, at about $2.50 or less (usually less) per movie in disk space, that's the sweet spot IMO.

[Naylia]

Originally Posted by stanger89

IMO, whatever came on the disc, minus the extras that aren't needed (extra audio tracks, trailers, special features,etc). With that it's as good as it can get, you don't have to worry about evaluating it, tuning things, none of that futzing. You don't end up watching it later wondering if anything odd you see is something you "added" that could be fixed by using different parameters.

Yeah, it takes a bit of disk space, but like I said, at about $2.50 or less (usually less) per movie in disk space, that's the sweet spot IMO.

It's my sweet spot too...

[paulbeers]

While I have only ripped a handful of Blu-Ray (but have over 600+ DVD rips), it just isn't worth it to me to transcode the video. Frankly, storage is only going to get cheaper (3TB drives are starting to arrive) and displays (tv's) are only going to get better (super HD anyone?), I do not want to transcode to save a few GB's now and be annoyed later when I have to do it all over again. Spend a little now for my future enjoyment later.

On the other hand, I've found that most older movies that have been "remastered" to Blu-Ray quality really aren't much better than their DVD counterparts (especially anything filmed prior to 1980), so often times you can save space by not going Blu-Ray. Lipstick on a pig....

Just my .02 worth....

[Taddeusz]

While I would agree that the price of storage is usually at an all time low being able to afford lots of it all depends on your financial situation. My desire for new technology and storage far outstrips any income my family has coming in. I'm currently going back to college for an MIS degree after getting laid off late last year. The GI Bill pays well but it doesn't pay THAT well. Currently just scraping by with what I have, 2 1TB drives for movie storage. Would like to increase that but I really can't swing the cost. A few hours crunching on my C2Q is far cheaper than the storage.

[stanger89]

Personally, if buying more storages isn't an options, if I had to pick between having my movies "online" or having full quality, I'd rather get the disc off the shelf and know I have a perfect copy than transcode and always question if the one on the shelf looked better.

I'm a stickler for quality. I bought the Matrix trillogy 3 times, 2 on DVD (second was "re"mastered better) and one on HD DVD. And that's repeated itself quite a lot (Top Gun, one copy on non-anamorphic, one anamorphic copy, still need to get the BD though) etc. So ripping just isn't worth it for me if I don't know it's as good as it could be, and if I transcode, I don't know that anymore.

[Taddeusz]

I also can't afford to buy a BD Player but I already had a BD-ROM drive prior to getting married. :-D