8 Replies Latest reply on Aug 26, 2011 12:14 PM by ExactImage

    Do me a favour (timings) ?

    ExactImage Level 3

      We need to find a way through the DVD encoding bottleneck, so we're thinking of building another system (Windows 7) pretty much for this purpose. 


      Before we spend the extra cash on an nVidia graphics cards I'm looking for some indication of how much time the GPU may help. We typically don't use the GPU assisted effects, so those don't come in to play at all.   It's all about the time saved on resizing 1080p to DVD frame sizes.


      What I'm looking for is help with this:


      1) Create a 1920x1080 25p sequence and fill with 1 minute of video (you can choose your own length from a few seconds upwards).

      2) Disable GPU acceleration

      3) Export to MPEG DVD, PAL Progressive Widescreen Highest Quality

      4) Change the Bitrate settings to VBR 2 Pass 2.8, 6, 8  (just so we're on the same settings)

      5) Set audio to PCM (just so we're on the same settings)

      6) Check the Use Maximum Render Quality

      7) Uncheck the Use Previews (so it's not using previews)


      Now export this and time it.


      8) Repeat the above but with GPU enabled.


      How much (if any) difference is there?    I'm not worried about the absolute 'real time' scores, more about how much the GPU assist helps


      Also, if you have time, add the export to the Queue instead of direct export (with GPU enabled) and see how long that takes via Media Encoder.


      I don't mind if it's only 10 seconds or 30 seconds of video source, I'm really only interested in the difference the GPU makes.


      For reference, my 8 core mac (2.8Ghz) would take 3m 35s to export directly (no GPU).   Via Media Encoder it takes 38 seconds to feed the project to Media Encoder (which was not running) and 5m29s for Media Encoder to run (with all 8 cores at 100% - why the difference in time?  Argghh!!).


      So, if any one is willing to run this comparison of GPU vs non GPU for me I would REALLY appreciate it!   I'm really not worried how long your systems take, just whether it's faster or not with the GPU enabled.



        • 1. Re: Do me a favour (timings) ?

          1 Minute of footage exported with the settings you asked for.


          Windows 7 64bit

          i7 960

          12GB Ram

          4x WD 1GB 7200rpm

          GTX 570


          38 Seconds With GPU enabled

          3 minutes 20 seconds With GPU disabled


          Direct export and not using AME. I would imagine a better processor would see this time improve further.


          Quite a difference!!



          • 2. Re: Do me a favour (timings) ?
            Colin Brougham Level 6



            If you still have the project and sequence set up, could you try the export without MRQ set, both software and hardware? I suspect you won't see much difference between the two, but it's good to have a control.


            With hardware MPE, you're ALWAYS exporting with MRQ, so setting the MRQ option in the Export Settings should have no effect, either on output quality or export duration. Hardware MPE/CUDA scaling is actually higher quality than the scaling done in Software Only mode with MRQ set, so you get the benefits of better scaling and faster exports. For segments that aren't processed by CUDA--that is, they have a red bar--the MRQ option will force higher quality software scaling, but on a pure CUDA-accelerated sequence, the MRQ option should make no difference.


            Most folks have witnessed a 3-6x greater export time with Software Only mode and MRQ versus Hardware Accelerated rendering; the times you posted are right in line with that (about 5x longer).

            • 3. Re: Do me a favour (timings) ?
              ExactImage Level 3

              WOW!    Really?  More than 3mins vs 38 seconds?    That's HUGE!  


              I need to try to digest Colin's reply a little more because I'm not yet certain I understand what is being said here.....

              • 4. Re: Do me a favour (timings) ?
                Colin Brougham Level 6

                I think I pointed you to this blog post by Todd before, but most of it is explained here: some details about scaling in Premiere Pro CS5 and CS5.5 « Premiere Pro work area


                Excerpt from that post:

                Moving a lot of processing to the GPU can also make things better, not just faster.


                A good example is scaling. There are lots of different scaling algorithms, and they each have their pros and cons. Some are better for scaling things up, some are better for scaling things down; some are better for sharp graphics, and some are better for gradual changes in color across an image. The real tradeoff, though, is that the high-quality algorithms are also—in general—the slow algorithms.


                However, these higher-quality algorithms are only really slow if you are forced to execute them serially, but they are relatively fast when you can run them in parallel. One of the huge advantages of GPU processing is that GPUs are massively parallel, with hundreds of parallel processing units. There are a lot of pixel operations that are very amenable to parallel processing, since you don’t need to know the result of the operation on one pixel to do the same operation on its neighbor in the same image. Scaling is just such an operation. When you move scaling operations to the GPU, you get to take advantage of scaling algorithms that were just plain unfeasible on the CPU.


                So, scaling using CUDA can be better. And faster. In some tests done here, scaling was more than 40 times faster on the GPU than on the CPU at maximum quality.


                When Premiere Pro is just using the CPU for the processing of scaling operations, it uses the following scaling methods:


                The variable-radius bicubic scaling done on the CPU is very similar to the standard bicubic mode in Photoshop, though the Premiere Pro version is multi-threaded and optimized with some SSE instructions. Even with these optimizations, it is still extremely slow. For high-quality scaling at faster-than-real-time processing, you need to use a CUDA card.


                When Premiere Pro is using CUDA on the GPU to accelerate the processing of scaling operations, it uses the following scaling methods:


                For export, scaling with CUDA is always at maximum quality, regardless of quality settings. (This only applies to scaling done on the GPU.) Maximum Render Quality can still make a difference with CUDA-accelerated exports for any parts of the render that are processed on the CPU.


                I added the emphasis at a couple of points to highlight what I was referring to. Basically, the export quality (when it comes to scaling) tiers out like this, from highest to lowest:


                1. GPU on (Lanczos 2 low-pass sampled with bicubic) [typically fastest]
                2. GPU off, MRQ on (variable radius bicubic) [typically slowest]
                3. GPU off, MRQ off (Gaussian low-pass sampled with bilinear) [somewhere in between]


                GPU off with MRQ on can--practically speaking--get close to GPU on, but may still be a bit lower quality, and it will take many times longer to export. GPU on with MRQ on may or may not be any different from GPU on with MRQ off; it depends on whether the segments of the sequence are being processed by CUDA or not (yellow vs. red bar).


                Clear as mud?

                1 person found this helpful
                • 5. Re: Do me a favour (timings) ?
                  joewilde Level 1



                  38 Seconds With GPU enabled

                  3 minutes 20 seconds With GPU disabled


                  37 Seconds with GPU enabled and MRQ disabled

                  48 Seconds with GPU disabled and MRQ disabled



                  Interesting results




                  1 person found this helpful
                  • 6. Re: Do me a favour (timings) ?
                    ExactImage Level 3

                    Again - thanks very much.  I can see this costing me money


                    So, clearly the GPU is helping big time for resizing.......  which is exactly what I needed to know.




                    Now, I just need to figure out how Colorista II is screwing with things too.....

                    • 7. Re: Do me a favour (timings) ?
                      Jim_Simon Level 8

                      MB Looks and Colorista do have a tendency to slow things down to a crawl by comparison.

                      • 8. Re: Do me a favour (timings) ?
                        ExactImage Level 3

                        I just wanted to say THANKS to all who helped me on this one.   We took the plunge and built a new Windows 7 PC with i7 (2600), 16GB and a CUDA card (570).    All I can say is WOW!   DVD encoding (without Colorista) from a completely unrendered 92 min sequence was 32 mins with GPU and 7.5 hours without GPU, but 11.7 hours on the 8 core Mac!   


                        It has generated a few more questions..... but I'll ask those in other threads....