Blu-Ray - BD50 bitrates overkill?

[jfcarbel]

In doing some backups to BD25, I am noticing more and more releases from Studios on BD50 even for movies where its probably not necessary. Take for instance Airplane - this is only an 88min movie, with no bonus video features. This should surely fit on a BD25 even with the DTS-MA audio.

My practice for many titles is to just use the core from DTS-MA, but now I am just deciding to keep the DTS-MA if the movie is 125min or less as I think studios are just using BD50 even if its not needed.

So why are studios doing this? I would assume they are maxing out the bitrate on the video since they have the space. Perhaps this makes for cheaper production costs as they do not need to QA the film as much knowing its maxed out bitrate.
Or is it to prevent easy movie backups since BD50 media is still expensive?

Found this forum post on dvdtown, so I ask are latest BD50 bitrates overkill?

Let's take the most advanced video codec available today, H.264. Assuming that to make a HD movie that is next to indistinguishable from the original at 1080p, what is the bit rate required. A research by Blu-Ray disc committee gives the answer: 16 Mbps. (“Subjective quality evaluation of H.264/AVC FRExt for HD movie content”) At this bit rate, video quality is "nominally transparent" - blind tested volunteers have a hard time distinguishing the original from the encoded material.

Now if we add HD quality surround tracks, Dolby HD at 3 Mbps (the mandatory bit rate) and a DTS HD track (not specified, but let's assume it to be slightly higher, say at 5 Mbps?), we have a combined audio rate of 8 Mbps.

So in total, we can assume that at 24 Mbps (16 + 8 ) , we will have the ability to store the highest possible HD video with HD quality DTS and Dolby tracks in all. How much space is there on a dual-disc HD DVD for that?

Simple math will give something like 10.4 GB per hour, which means that one can store some 2.5 hr (27 GB) of the highest quality HD audiovisual materials. With 50 GB, one wonders what else Blu-Ray can squeeze in the other 28 GB when all one needs is 22 GB for an entire 2- hr movie.


So in the end, should I use BD-Rebuilder to keep the DTS-MA and just let it shrink the bitrate down on the video since its probably overkill anyway on 2 hours or less movies?
What are the guidelines or best practice others use here for backups to BD25?

P.S. The new blank feature and ability to create bonus only BD5/9 discs is working perfect so far. Anf I don't think I have seen many posts here either with anyone reporting any issues. Then again, I am about to do Drumline which has many extra streams for branched play.

Here is an example comparison (these are both with DTS-MA):

Disc Title: RED_DRAGON R1 (BD-Rebuilder)
Disc Size: 23,441,105,049 bytes
Protection: AACS
BD-Java: Yes
Playlist: 00000.MPLS
Size: 21,650,042,880 bytes
Length: 2:04:33
Total Bitrate: 23.17 Mbps
Video: MPEG-4 AVC Video / 17685 kbps / 1080p / 23.976 fps / 16:9 / High Profile 4.1 <---- So even with a recode and keep HD Audio for 125min movie, its still above 16 kbps
Audio: English / DTS-HD Master Audio / 5.1 / 48 kHz / 4203 kbps / 24-bit (DTS Core: 5.1 / 48 kHz / 1509 kbps / 24-bit)
Subtitle: English / 37.774 kbps


Disc Title: RED_DRAGON R1 (ORIGINAL)
Disc Size: 46,040,122,027 bytes
Protection: AACS
BD-Java: Yes
Playlist: 00000.MPLS
Size: 38,158,301,184 bytes
Length: 2:04:33
Total Bitrate: 40.85 Mbps
Video: MPEG-4 AVC Video / 32409 kbps / 1080p / 23.976 fps / 16:9 / High Profile 4.1
Audio: English / DTS-HD Master Audio / 5.1 / 48 kHz / 4203 kbps / 24-bit (DTS Core: 5.1 / 48 kHz / 1509 kbps / 24-bit)

[setarip_old]

@jfcarbel

Hi! Let's take the most advanced video codec available today, H.264. Assuming that to make a HD movie that is next to indistinguishable from the original at 1080p, what is the bit rate required. A research by Blu-Ray disc committee gives the answer: 16 Mbps.The lack of reference to the additional "magic" performed by the utilization of x264 as well, leads me to believe that it may actually require even fewer Mbps, while retaining subjective "transparency"...

It's my opinion that the studios unnecessarily "swell up"/pad the bitrate to try to convince the consumer that he/she is getting something "really special" by purchasing Blu-rays, rather than continuing to purchase DVDs and play them on a good upconverting standalone player ;>}

[Chetwood]

To combat upscaling they actually lower bitrates on DVDs. Back in the day I'd always need Shrink to make a movie fit on a single-layer blank. These days even 2 hour movies are often < 4 GB.

[Ghitulescu]

To combat upscaling they actually lower bitrates on DVDs. Back in the day I'd always need Shrink to make a movie fit on a single-layer blank. These days even 2 hour movies are often < 4 GB.

Indeed, a good upscaler (TV or player) can often yield very good visual results if the source is good, which will render the BD economically obsolete. Unfortunately I have no combi-package yet (BD+DVD), but good quality DVDs (like those issued by Criterion, MK2, Kinowelt etc.) are from normal viewing distance, almost indistinct from a BD. Only a direct comparison will show the differences to the untrained eye.

H.264 is quite powerful in terms of achieved quality at a specific bitrate. BD DL are probably used more as a copyright control (a BD-RE 50GB costs in Germany, through official channels, more than a regular original BD, a BD-R 50 almost the same) than as a technical requirement.

However, it happened to MP3 and then to DVD/DivX, so it will probably happen to BD too: the longer the people are "exposed" to higher quality material (and get used to), the better they will notice the artefacts (more objectionable), and the more they will increase the bitrate to compensate for it.

The "correct" bitrate is the one you consider to be, taking into account your quality expectations, your viewing capacities, your experience, and your budget. Quality is personal.

[Rumbah]

I'm even satisfied with movie only BD-9 copies. They are about 6-8 Mbit/s and although you can spot the difference if you know where to look the general viewing quality is very good (thanks to x264).

[jdobbs]

I'm even satisfied with movie only BD-9 copies. They are about 6-8 Mbit/s and although you can spot the difference if you know where to look the general viewing quality is very good (thanks to x264).

I find them to be virtually identical to the original, and I in fact do most of my movie-only backups to BD-9.

[Sharc]

I do most of my backups to BD5: Movie only 720p + 2 audio ac3 448. The viewing quality (viewing, not overanalyzing) from normal distance on LCD TV and on LCD projector is very good IMHO.
Even downscaling to 720p does in most cases not really or noticeably loose details, and applying a slight sharpening like sharpen(0.15) to the downscaled 720p (before encoding) can bring it very close the original viewing experience.

(http://forum.doom9.org/showthread.php?p=1497357#post1497357) ;)

[abbadon]

I find them to be virtually identical to the original, and I in fact do most of my movie-only backups to BD-9.

the Master has spoken. answers all my questions.