Dumb Question - How Big Is 1 Minute Of Blu-Ray?

[hech54]

I'm trying to get my head around the difference between DVD and Blu-Ray...and the
overall disc capacities don't help my old brain much.

[jagabo]

Just like with DVD it depends on the average bitrate of that minute of video.

[hech54]

How about an educated guess. The max for Blu-Ray is 40 MBps right?

[Baldrick]

Maximum total bitrate 48 Mbits

So 1 minute = 360MB/s....but most movies are usually around half, 150-200MB/s or 15-25GB/2hours(just the movie, no extras).

[Kerry56]

You can go to Bluray stats http://www.blu-raystats.com/Stats/FeatureStats.php and pick whichever movie you are interested in, click on that movie and find out the average bitrate used in it. For example, Gran Torino is VC-1 encoded at 26.994mbps. They also give bitrates for the audio streams.

That should give you a rough way to estimate the size of the movie per minute, though not an exact one for any particular section of the film.

[hech54]

I don't really care about individual movies....I'm just trying to get a ballpark figure.
Shock and Awe so to speak.

[redwudz]

Using MediaInfo on one BD main movie, I see about 24Mbps video bitrate. On one of my DVD rips, I see about 9.8Kbps. Not a fair comparison, but it might give you somewhat of an idea of the differences. That doesn't include audio and subs.

For size, that would be about 39MB a minute filesize for DVD video and about 151MB per minute for the BD video. Those are both VBR, so not too accurate, just averages.

[edDV]

I don't really care about individual movies....I'm just trying to get a ballpark figure.
Shock and Awe so to speak.

2 hr DVD at 4.8 Mb/s (ave) is 4.4GB

2 hr Blu-Ray at 25Mb/s (ave) is about 23GB

Ball bark enough?

Blu-Ray can have bit rates up to ~35 Mb/s.

For context, the master transfer file used to make a movie Blu-Ray disc was probably in the range of 440 to 2970 Mb/s* so in that context, Blu-Ray is way compressed.


* 1920x1080p/24 uncompressed SDI (dual SMPTE-292m or SMPTE 424M)

[edDV]

Another useful stat, Blu-Ray 1920x1080 has six times the pixels vs. DVD 720x480.

25/4.8 = 5.2 (not quite 6x)

[jagabo]

And Blu-ray usually uses h.264 compression, not MPEG 2.

[edDV]

And Blu-ray usually uses h.264 compression, not MPEG 2.

Yes I was avoiding the codec as the next level of complexity. The use of h.264 or VC-1 from a near uncompressed film transfer is very different vs. consumer camcorders or off TV captures which are mostly low bit rate and interlace. The mid ground is higher bit rate prosumer or realty pro interlace source that record in the 25 to 100 Mb/s range.

In general h.264 and VC-1 are good for twice the compression vs. MPeg2 but suffer more loss if recoded.

[poisondeathray]

In general h.264 and VC-1 are good for twice the compression vs. MPeg2 but suffer more loss if recoded.

I think we've had this discussion before. I don't buy this "h.264 will suffer more loss if recoded" statement. It doesn't make any sense from a signal processing point of view. What are you basing this statement on?

If you have 2 theoretical streams with similar "identical quality" , the decoder picture is the same (or similar). It doesn't matter if it's MPEG2, VC-1, VP6, more compressed, less compressed. We are measuring the decoder picture quality. That is what is important.

The format and settings you encode TO are more important than the source format, given similar initial quality. The initial quality is the important thing here, regardless of format.

Having said that, if you compare initial quality of 2 equivalent bitrate sources of h.264 vs MPEG2 , the h.264 initial quality will exhibit higher quality, higher psnr, and exibit less loss than the MPEG2 recorded format. e.g. if you took the exact same camera, and used HDMI or say 2 separate HD-SDI feeds into 2 separate portable recorders for simultaneous recordings, so the only difference is recording format (i.e. remove the lens, sensor, processing etc.. out of the equation, the only difference is h.264 vs. MPEG2).

Or, you could take and equivalent source, and encode to h.264 and MPEG2 at equivalent bitrate once or over several generations - which do you think will exhibit higher quality, and have a higher signal to noise ratio at the end of "n" generations ? ie. which will suffer less loss? You can clearly tell the difference even after 1 generation.

The loss compounded by re-encoding MPEG2 over and over again to MPEG2 is mcuh greater than the loss of , h264 encoded again and again to h.264. Think about it: You start with higher quality and you lose less per generation when using h.264.

[Cornucopia]

So to summarize another way:

1 min. of FLV web average video (320x240 @ 30fps @ 600kbps h.264) = 4.4 MB

1 min. of VCD CBR video (352x240p @ 30fps @ 1150kbps MPEG1) = 8.4 MB

1 min. of DVD average video (720x480i @ 30fps @ 4.8Mbps MPEG2) = 36 MB

1 min. of Blu-Ray average video (1920x1080i @ 30fps @ 25 Mbps MPEG2, VC-1 or h.264) = 187.5 MB

Scott