For recording HD video...is it limited to 25gb or 120 minutes? Can I get 4hrs 720p video on one disc if the file size is under 25gb?

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Hi Styles ....As you can clearly read on the product information, the M-disc Blu Ray blanks have a maximum capacity of 25Gb of information. By the standards established by the industry, BR discs all have a maximum capacity of 25Gb.  You can always load less than that.  The blank discs have no playback time spec or time limitation.  It all comes down to how you've encoded and compressed the media you plan to put on there.  Whether you use the M-disc branded BR blanks as a file storage medium or whether you use them to encode via the BR specification, it will still max out at 25Gb of data.  If the 720p video was encoded using AVCHD or MP4 codecs, you can probably fit four hours on there.  I normally do the full bandwidth 1920X1080 HD on BR blanks, and at generous bit rates I can cram 3 to 4 hours on one BR blank.  If you encode using MPEG2, which is a less efficient codec compared to AVCHD or MP4, you will probably max out at just over 2 hours for full 1920 X 1080 HD, and somewhat more than that for 720p.  I assume you are aware that M-disc blanks require a certified M-disc burner, and virtually all the new BR Burners that are coming out have M-disc certification.  M-discs are burned by actually punching pits in the record media, as opposed to creating a slightly different color in an organic dye media for standard BR (or DVD) blanks.  So the burner manufacturers have to make the burner slow down, or use a more powerful laser compared to non-M-disc certified burners.   The M-disc burners are pretty reasonable.  I got one for about 60 bucks.  When you put the blank M-disc in the M-disc certified burner, it recognizes what it is, and makes the adjustments for burning accordingly.  I mentioned earlier some complex stuff about how you plan to encode your 720p video.  Sometimes people just take the file out of a camera chip, and dump it on the blank disc.  You should be able to go into the file structure area of your computer and check the size of the 720p file you want to dump on the disc, and make sure it's under 25Gb.  This is assuming you are using the blank disc just as you would a hard drive or flash drive....simply a file storage medium.  If you're getting complicated and building an actually Blu-Ray encoded disc with menus and such, then you'll have to get sucked into selecting codecs.  Stick with the MP4 or AVCHD.  They are more efficieint (half the bit rate for the same quality) compared to MPEG2.

M-Disc Bluray 25 GB (10 Disc Pack)

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