7 Replies Latest reply on Nov 21, 2013 9:49 PM by KMD1984

    Trying to do the math... (HDD related)

    KMD1984

      Hi,

       

      I am putting together a new PC for editing and was wondering, how fast a HDD really has to be?! I read all the FAQ and understand, that there are plenty of suggestions out there, on how to setup your HDD's! However, I would like to be able to do the math myself and understand, why a given setup is recommended! If I take some 4K Cin footage of my GoPro Hero 3 BE, and enter the information here:

       

      http://web.forret.com/tools/video_fps.asp?width=4096&height=2160&fps=15&space=rgb444&depth =10 

       

      (4096 x 2160, 15FPS, RGB 4:4:4 and 10 bits/color... I just picked something for demonstration purposes only) it tells me, that the Uncompressed bitrate is 497,66 MB/s.

       

      If I now look at a chart like this:

       

      http://www.tomshardware.com/charts/hdd-charts-2013/-01-Read-Throughput-Average-h2benchw-3. 16,2901.html 

       

      and pick a HDD, with lets say 150MB/s, what does this now mean?! The bitrate is clearly higher than the "speed" of the HDD. Does this mean, my playback is going to be jerky?! I believe so, but I am not sure what part a graphics Card plays here?! I also understand, that a slow HDD, can act as the bottle neck of a given system. So no matter how fast your CPU is, a slow HDD setup will slow the whole system down. But how fast does a HDD really have to be, so it doesn't slow the system down?! Is there some way to do the math and know in advance, what is going to work and what not?! Or is it as simple as picking a SD card for a GoPro?! If my video format delivers, lets say 500MB/s, I would need a SD card that is at LEAST this fast, so it can capture the video without dropping frames, right?! At least this is how I understand it, ha ha.

       

      It must work a little bit different on a PC though, since the footage doesn't have to be captured in real time, correct?! A slow HDD is now going to just increase render times, right?!

       

      G, I am so tired of trying to explain, what I mean, LOL. Hopefully all of this will make sense to someone out there?!

       

      thanks,

       

      KMD

       

      p.s. Maybe it is really as simpe as just taking the bitrate for one track, adding all tracks up and whatever number comes up, your HDD has to be at least that fast, LOL?!

        • 1. Re: Trying to do the math... (HDD related)
          cc_merchant Level 4

          Read Harm's articles on disk setup, raids, balanced systems and much more here: Tweakers Page

          • 2. Re: Trying to do the math... (HDD related)
            SAFEHARBOR11 Most Valuable Participant

            Hi KMD,

             

            The hard drive requirements for the original GoPro files are almost nil - hard drive speed is measured in MB/s, while cameras are Mb/s. I believe that MB/s is about 8x larger than Mb/s is. I don't know what bitrate the GoPro 4k recordings are, but for GoPro HD it is 15Mb/s standard or 35Mb/s using ProTune (35Mb/s is only about 4MB/s). So again, camera files whether from GoPro or a typical AVCHD camcorder are very light in terms of bitrate. A typical hard drive could plays dozens of clips at once with ease.

             

            The problem then is not hard drive speed, but rather being able to decode the highly compressed video for playback - that is the true issue and that relies on the computer processor. GoPro footage is notoriously hard to play smoothly on all but the fastest computers, and that is why the GoPro Studio software does the conversion to .avi or .mov files. The resulting files are much larger (higher bitrate), but are much easier for the computer to play since there is far less compression to deal with. So it's a trade off.

             

            I just got a GoPro, but the White version that doesn't do 4k so I have no experience with 4k myself. When converting the 4k to .avi, I'd suspect the .avi files are going to be much larger than HD conversions, but how big I don't know. Now you are getting back to the area of the computer possibly having a hard time playing the video, and probably not hard-drive related, but just because the images are so large - lots of data to process even with less compression.

             

            The example you gave of 4:4:4 10-bit uncompressed video is off the charts for file size, and would require a very expensive RAID hard drive with 8 or more drives to reach that kind of sustained speed, but the GoPro files are compressed and not 4:4:4 so will be MUCH smaller (again, don't have specifics, but nothing like uncompressed in size). I don't claim to know the specifics of the GoPro 4k workflow, but just trying to add a little to the conversation and hope it helps put things in perspective a little better.

             

            Thanks

             

            Jeff Pulera

            Safe Harbor Computers

            1 person found this helpful
            • 3. Re: Trying to do the math... (HDD related)
              KMD1984 Level 1

              Jeff,

               

              Thanks for the info. Not exactly the answer I was looking for, but still very helpful!!! It really helps me to better understand, why my current PC is not able to play any of my higher resolution GoPro files! What I really want to know is, why you say that a RAID configuration of 8 or more HDDs would be required?! Is it because someone else told you?! You tried it?! How do you know?1 There must be a really simple way of "doing the math" and finding out for oneself?!

               

              thanks again.

               

              KMD

              • 4. Re: Trying to do the math... (HDD related)
                cc_merchant Level 4

                You already had the link to this info, but to repeat it, scroll down almost to the bottom of this page where you see Indicative Raid Performance tables: Tweakers Page - To Raid or not to Raid

                • 5. Re: Trying to do the math... (HDD related)
                  SAFEHARBOR11 Most Valuable Participant

                  The 8-drive RAID reference was in regards to the "4:4:4 10-bit uncompressed HD" example that you offered. I sell those drives, part of my job, that is how I know. But this does not apply to GoPro footage, the above example is very rare, stuff Hollywood-types might use and not for you or I to worry about.

                   

                  Black Magic Design has a drive speed test utility that you can run and it will tell you what video formats will work with your drive setup. There are also charts and tools out there, such as AJA Data Rate Calculator for PC or Mac, and now available from Apple App Store for iPhones - http://www.aja.com/en/software

                   

                  Please note when playing with the calculator that if the format is "8-bit" or "10-bit" that references UNCOMPRESSED video, and you are not working with that. Since the calculator doesn't list the GoPro (Cineform) codec, not sure what the data rate is going to be, but much lower for sure.

                   

                  Looking at the requirements for GoPro Studio Premium, they are recommending a 7200rpm unit, and fast connection if external, but nothing fancy so I wouldn't worry about needing any special drives.

                   

                  Thanks

                   

                  Jeff Pulera

                  Safe Harbor Computers

                  • 6. Re: Trying to do the math... (HDD related)
                    KMD1984 Level 1

                    cc_merchant wrote:

                     

                    You already had the link to this info, but to repeat it, scroll down almost to the bottom of this page where you see Indicative Raid Performance tables: Tweakers Page - To Raid or not to Raid

                    Well, I had looked at the page before and it didn't really tell me, what I wanted to know. However, after taking a look at it again, I was able to figure something out! So thanks again for pointing it out to me!

                     

                    KMD

                    • 7. Re: Trying to do the math... (HDD related)
                      KMD1984 Level 1

                      SAFEHARBOR11 wrote:

                       

                      The 8-drive RAID reference was in regards to the "4:4:4 10-bit uncompressed HD" example that you offered. I sell those drives, part of my job, that is how I know. But this does not apply to GoPro footage, the above example is very rare, stuff Hollywood-types might use and not for you or I to worry about.

                       

                      Black Magic Design has a drive speed test utility that you can run and it will tell you what video formats will work with your drive setup. There are also charts and tools out there, such as AJA Data Rate Calculator for PC or Mac, and now available from Apple App Store for iPhones - http://www.aja.com/en/software

                       

                      Please note when playing with the calculator that if the format is "8-bit" or "10-bit" that references UNCOMPRESSED video, and you are not working with that. Since the calculator doesn't list the GoPro (Cineform) codec, not sure what the data rate is going to be, but much lower for sure.

                       

                      Looking at the requirements for GoPro Studio Premium, they are recommending a 7200rpm unit, and fast connection if external, but nothing fancy so I wouldn't worry about needing any special drives.

                       

                      Thanks

                       

                      Jeff Pulera

                      Safe Harbor Computers

                       

                      Jeff,

                       

                      I am planning on using 4k in the near Future, so I need to worry about it, ha ha. The other thing is, a tool that measures my drive speed is useless for me, as of right now, since I do not have a system yet! Working on putting one together as we "speak". Anyhow, you pointing out the AJA Data Rate Calculator to me, is what made me realize, that I had the answer in front of me, the whole time!

                       

                      http://web.forret.com/tools/video_fps.asp?width=4096&height=2160&fps=15&space=rgb444&depth =10

                       

                      Either AJA or this site, will help me figuring out the data rate of most video formats... I have no idea why I didn't realize that the first time?! I read my OP and I want to delete it, ha ha...

                       

                      Thanks again for all the help!

                       

                      KMD