Question about BD9 discs: Will they play on "8x" drives (1.7-4x reading speed)

[kurkosdr]

Hi there.

Some of us have "8x" dvd drives. This means that, when reading from a DVD9, the reading speed starts from 1.7x and gradually reaches 4x when at the middle of the disc. Of course, this is more than enough for DVD-Video content (which requires 1x speed).

However, 1080p video commands for 33Mbits (~3x speed), or even a whooping 56Mbits (~5x speed).

Does this mean that, if I create a BD9 with 1080p content (for example, a music video clip), I will suffer massive buffer underruns at the start and the end of the disc? (as the 1.7-2x speed on these areas of the disc will be inadequate, at least for the action scenes).

Which is the "safe" bitrate for 1080p BD9s that are intended to be read on "8x" drives? (peak and average).

What bitrates 720p BD9s command? (peak and average). Is 1.7x speed enough for 720p BD9s?

Thanks,
kurkosdr.

[SquallMX]

Hi there.

Some of us have "8x" dvd drives. This means that, when reading from a DVD9, the reading speed starts from 1.7x and gradually reaches 4x when at the middle of the disc. Of course, this is more than enough for DVD-Video content (which requires 1x speed).

However, 1080p video commands for 33Mbits (~3x speed), or even a whooping 56Mbits (~5x speed).

Does this mean that, if I create a BD9 with 1080p content (for example, a music video clip), I will suffer massive buffer underruns at the start and the end of the disc? (as the 1.7-2x speed on these areas of the disc will be inadequate, at least for the action scenes).

Which is the "safe" bitrate for 1080p BD9s that are intended to be read on "8x" drives? (peak and average).

What bitrates 720p BD9s command? (peak and average). Is 1.7x speed enough for 720p BD9s?

Thanks,
kurkosdr.

Recomended max bitrate for BD9 is 17500, if you want to be on the safe side use 15000 (Additionally with that bitrate you can use 2 seconds GOPs instead of 1 second GOP).

[mariush]

Look at blu-ray drive reviews to see how fast they reach a minimum speed.

For example see this one, for a 4x drive which starts at 1.77x: http://www.cdrlabs.com/Reviews/lite-on-dh-4o1s-4x-bd-rom/Performance-BD-Read.html

http://www.cdrlabs.com/images/images-view.php?imageid=16041

You can see it goes up pretty and at the start where there's slow speed, it's mostly likely just menus and extras

For this particular drive, the reviewers had no problems playing regular blu-ray drives so I guess 1.7x is enough

[Ghitulescu]

It is always forgotten that the speed of an optical drive is not given only by its rotational speed but also by its CPU (which actually dictates the spinning algorithm). How fast the optics work can be important for seek times ...

Remember, one of the CPU/firmware tasks is to descramble the content, verify it and repeat the reading if wrong. The faster the unit the more bitrate can be accomodated. The optics should however be able to read DVDR (I remember it were problems in the past, I don't think there are now as the technique is ripe).

So, to this end, since BD9 are usually used in BD players, their drives are capable of supporting the bitrates a BD has, thus the bottleneck is only the optical pick-up. My Pioneer which has an IDE/ATAPI drive could read DVDRs (Verbatim) having up to 25Mbps (there were also 3 seconds of bitrates above 19) - according to my Pio. Newer devices have probably better/faster optics ...

[kurkosdr]

For this particular drive, the reviewers had no problems playing regular blu-ray drives so I guess 1.7x is enough

The "1x" of Bluray is not equal to the "1x" of DVD.

This is because the "1x" for bluray was defined as 36Mbit/s transfer rate, while the "1x" for DVD was defined as 10.5Mbit/s.

As you can see, the "1x" for Bluray is about three times higher transfer rate when compared to the "1x" of DVD.

So, in order to play bluray content written on DVD DL discs properly, you actually need a 3.4x DVD reading speed, in order to match the 36Mbits of transfer rate required for proper playback.

Unfortunately, most DVD-ROM drivers start and end the read with 1.7-2x speed, so the required transfer rate for bluray content is not matched.

Thanks everyone who posted the maximum safe bitrate. 17,5Mbits. This is about 1.66x of DVD reading speed, so I guess it should do.

Now, if I use a 16x drive, will I be able to use higher bitrates? Which is the the speed 16x drives start and end the read for DVD DL discs?

Also, what are the speeds BD-ROM drives start and end the read when reading from DVD DL discs? (Do bluray drives function as 8x drives or as 16x drives when reading from DVDs?)

Thanks!

PS: Is there a program that can show me the peak bitrate of a given file?

[setarip_old]

Hi!Is there a program that can show me the peak bitrate of a given file?I believe you can find that when running "multiAVCHD" (Click on "Transcode")...

[SquallMX]

BDInfo can give you the max bitrate and the timecode of the max bitrate for BD5/BD9/AVCHD/Blu-ray.