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Topic: Audio capacity of a Blu-ray disc? (Read 12075 times) previous topic - next topic
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Audio capacity of a Blu-ray disc?

How many minutes of uncompressed CD-quality audio fits on a Blu-ray disc?

If a 700MB CD is said to hold 80 minutes...
700 / 80 = 8.75
so each minute of audio requires 8.75MB

Test hypothesis...
Capacity of CD is 700MB
700 / 8.75 = 80 minutes
OK


Capacity of DVD is 4.7GB or 4812.8MB
4812.8 / 8.75 = 550 minutes?

Capacity of single layer Blu-ray disc is 25GB or 25600MB
25600 / 8.75 = 2925 minutes?

Capacity of double layer Blu-ray disc is 50GB or 51200MB
51200 / 8.75 = 5851 minutes?

Over 97 hours of uncompressed music on one disc???

Audio capacity of a Blu-ray disc?

Reply #1 –
Quote from: toronado455 on
If a 700MB CD is said to hold 80 minutes...
700 / 80 = 8.75
so each minute of audio requires 8.75MB

Test hypothesis...
Capacity of CD is 700MB
700 / 8.75 = 80 minutes
OK


Thats not a test of anything except algebra.  It'll always be true assuming you divide correctly even if everything you plug in is wrong

Incidentally, you plugged in the wrong values.  CD audio is 10.1MB/s, and an 80 minute CD holds a little over 800MB of audio data.

Quote from: toronado455 on
Over 97 hours of uncompressed music on one disc???


I don't think you can use 44.1kHz LPCM on a bluray disk, so that number will be a bit off.  But yes, you can hold a lot of audio on a bluray disk.  They hold ~35 time more data.

Audio capacity of a Blu-ray disc?

Reply #2 –
Quote from: saratoga on
Quote from: toronado455 on
If a 700MB CD is said to hold 80 minutes...
700 / 80 = 8.75
so each minute of audio requires 8.75MB

Test hypothesis...
Capacity of CD is 700MB
700 / 8.75 = 80 minutes
OK


Thats not a test of anything except algebra. 


True, but when one is as bad at math as I am, that sort of testing is essential.

Quote from: saratoga on
It'll always be true assuming you divide correctly even if everything you plug in is wrong

Incidentally, you plugged in the wrong values.  CD audio is 10.1MB/s, and an 80 minute CD holds a little over 800MB of audio data.


There are 800MB CDs now? I thought 650MB CDs held 74 minutes, and 700MB CDs held 80 mins.

Audio capacity of a Blu-ray disc?

Reply #3 –
http://en.wikipedia.org/wiki/Red_Book_(CD_standard)

Quote
The audio bit rate is 1411.2 kbit/s: 2 channels x 44,100 samples per second per channel × 16 bits per sample = 1,411,200 bit/s = 1,411.2 kbit/s.

On the disc, the data is stored in sectors of 2352 bytes each, read at 75 sectors per second.

By comparison, the bit rate of a "1x" data CD is defined as 2048 bytes per sector × 75 sectors per second = 150 KiB/s (1228.8 kbit/s), or approximately 9.2 million bytes per minute.


(emphasis mine)

Audio capacity of a Blu-ray disc?

Reply #4 –
Quote from: toronado455 on
There are 800MB CDs now? I thought 650MB CDs held 74 minutes, and 700MB CDs held 80 mins.


A 700MB CD is 80 minutes long, which works out to about 800MB of audio data.  ~100MB less is available for storing regular files in order to provide better error correction.

Audio capacity of a Blu-ray disc?

Reply #5 –
Quote from: saratoga on
A 700MB CD is 80 minutes long, which works out to about 800MB of audio data.  ~100MB less is available for storing regular files in order to provide better error correction.


So you mean a "700MB/80min" CD is actually a 800MB CD, but they tell you it's only 700MB because that's the data capacity for storing regular files?

What about a "4.7GB" DVD? Are they lying about the true capacity of those as well? And if so, what is the true capacity (for audio)?

Same question for Blu-ray.

Audio capacity of a Blu-ray disc?

Reply #6 –
CD discs store audio and data differently, thus the difference in capacity. A DVD stores audio like any other data, so no difference in capacity.

Audio capacity of a Blu-ray disc?

Reply #7 –
Quote from: pdq on
CD discs store audio and data differently, thus the difference in capacity. A DVD stores audio like any other data, so no difference in capacity.


OK, thanks.

So a CD is actually using 800MB to store 80 minutes of audio.

So the rate becomes 10MB per minute.

Now applied to DVD...

Capacity of DVD is 4.7GB or 4812.8MB
4812.8 / 10 =  481 minutes

And Blu-ray...

Capacity of single layer Blu-ray disc is 25GB or 25600MB
25600 / 10 = 2560 minutes

Capacity of double layer Blu-ray disc is 50GB or 51200MB
51200 / 10 = 5120 minutes

Am I getting closer to reality here?

Audio capacity of a Blu-ray disc?

Reply #8 –
Quote from: toronado455 on
So you mean a "700MB/80min" CD is actually a 800MB CD, but they tell you it's only 700MB because that's the data capacity for storing regular files?

What about a "4.7GB" DVD? Are they lying about the true capacity of those as well? And if so, what is the true capacity (for audio)?

Same question for Blu-ray.


44100*4*60 = 10584000 bytes/minute, not 8.75 MB. CDs in data mode add considerable error detection/correction which eats up the difference. Nobody is 'lying' about the capacity, it's just arranged differently. Your 80 minute disc holds 846.72 MB of data plus TOC. If the Blu-Ray is indeed 25GB it would be 2362 minutes per layer, somewhat less than your calculations.

G²

Audio capacity of a Blu-ray disc?

Reply #9 –
Blu-ray can contain 48kHz/16bit audio, but not 44.1/16. So the right bitrate is 48000*2*2=192000 bytes/sec

According to Wiki ( http://en.wikipedia.org/wiki/Blu-ray_Disc ), the capacity of dual layer BDs is 50050629632 bytes.

50050629632/192000 = 260680 sec = 4344 min = 72.4 hours.

Audio capacity of a Blu-ray disc?

Reply #11 –
Quote from: lvqcl on
Blu-ray can contain 48kHz/16bit audio, but not 44.1/16. So the right bitrate is 48000*2*2=192000 bytes/sec

According to Wiki ( http://en.wikipedia.org/wiki/Blu-ray_Disc ), the capacity of dual layer BDs is 50050629632 bytes.

50050629632/192000 = 260680 sec = 4344 min = 72.4 hours.

Depends on if you're actually using the blu-ray video spec, or if you're just putting WAVs or flacs or whatever in the blu-ray as data, same as with DVDs. If you are putting it on a blu-ray video spec, then you'll lose some space to video and also the m2ts container is less efficient than say, mkv. If you're not, then you're not limited to 48/96/192 kHz.

BTW toronado455, DVD's aren't 4.7 "gigabytes", just like blu-rays aren't 25 gigabytes. They just do what hard drive manufacturers do (1 "gigabyte"=1000 "megabytes". In reality, DVDs are more like 4.37 GB.

Audio capacity of a Blu-ray disc?

Reply #12 –
Of course my calculations are just approximate...

Audio capacity of a Blu-ray disc?

Reply #14 –
There's supposed to be a blu-ray "audio" spec, but I don't see that ever getting off the ground.

Audio capacity of a Blu-ray disc?

Reply #15 –
Quote from: andy o on
There's supposed to be a blu-ray "audio" spec, but I don't see that ever getting off the ground.


well, technically it is off the ground as it exists and there are Bluray audio discs about.

but its really not worth is as even DVD audio isn't that popular and for all practical purposes can have the same audio output as the bluray spec.

we might need it if we go to a crazy number of channels all at 192kHz and 48 bit but then you should really be using harddrives or something.

Audio capacity of a Blu-ray disc?

Reply #16 –
48 bit? Also, I'm not exactly sure if those discs like Divertimenti are blu-ray profile 3.0, instead of just regular blu-ray. As far as I could tell from the reviews, there's still video there. There doesn't seem to be a marked difference like with DVD video and DVD-A.

Audio capacity of a Blu-ray disc?

Reply #17 –
Quote from: andy o on
48 bit? Also, I'm not exactly sure if those discs like Divertimenti are blu-ray profile 3.0, instead of just regular blu-ray. As far as I could tell from the reviews, there's still video there. There doesn't seem to be a marked difference like with DVD video and DVD-A.


well, i was taking a bit too far with 48 bit sampling but i couldn't think of anything else to bring up the data enough to fill a bluray.

the bluray spec allows for more channels at full 192kHz/24bit resolution than DVD-A can handle because of its increased data transfer rates at 1X. thats the major difference really. oh and i believe it makes provisions for using compressed audio as well(though why you'd need to is beyond me)

the divertimenti release was 3.0 compatable, video is allowed to accompany it i believe.

Audio capacity of a Blu-ray disc?

Reply #18 –
I meant that there doesn't seem to be a marked difference between blu-ray "audio", and blu-ray video specs, regarding audio. No like it was with DVD-V and DVD-A, which required new players and audio formats were expanded considerably. I seem to remember that proper blu-ray 3.0 discs would require new players, but I might be wrong.

Audio capacity of a Blu-ray disc?

Reply #19 –
Thanks. My question is purely theoretical. And unless (consumer) software exists to burn a Blu-ray "audio disc", then I suppose this discussion is purely theoretical as well.

With the Library of Congress National Jukebox going online, I've been listening to a lot of the historical recordings which are approx 3 to 4 min of audio on a side. I just got to thinking about how far media has come since then (not to mention all the crazy hoops musicians had to jump through to record music at that time like taking faster tempos just to fit the music to the media).

Audio capacity of a Blu-ray disc?

Reply #20 –
The problem is that hard drive space is cheaper per GB than blu-ray by about... I don't see that changing, especially since people aren't using blu-ray as a storage medium, like we used DVD back in the day.

oops math is wrong... wait...

EDIT, the cheapest bd-r single layer I could find is about the same price per GB as a WD 2TB hard drive. Dual layer are more expensive.