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Thread: Unbelievably slow rendering on a monster PC. What am I doing wrong?

  1. #1

    Default Unbelievably slow rendering on a monster PC. What am I doing wrong?

    Hi there guys, I've just signed up to this forum because I'm at my wit's end and really hoping you'll be able to help me. I'm using Sony Vegas movie studio HD platinum 11 to stitch together a bunch of home movies and create longer vids from them - nothing unusual. There's bugger all in terms of fancy stuff going on, just the occasional fade in and out between clips. Really basic stuff. Now, in terms of setting the software up, I've found the advanced thingy where you tell it to use GPU rendering (my cards are OpenCL compatible and have the very latest drivers - oh yeah, and I have the latest version of SVMSHDP). I've also given the process high priority in task manager.

    Now the source video files are 1080p/50i AVCHD files from a Canon Legria HF S20. My output file is Sony AVCHD 1080p/50i also, the idea being that I want to keep all the quality and basically just stitch the clips together. My current project is a 55m video from Christmas last year and it's take 1hr 20m to render. That can't be right, surely.

    Using Asus AI suite, I can see that all 8 cores are using from 70-80% most of the time and the fans on my GPUs have sped up so I can only assume they're busy even though I can't prove it. One thing I find odd is that task manager says SVMSHDP is only using around 600MB of RAM, twice that if you add in the FileIOSurrogate. I am only showing 3GB being used in total on the machine. I have my source files on an OCZ Agility 3 SSD and my destination on another, identical drive. I/O seems to be around 270MB/s writing at the moment although that doesn't make sense because over 80 minutes that's 13TB of data .

    OS: Windows 8 x64 (I'm a Microsoft Partner with a MAPS subscription before you ask)
    CPU: Intel 2600K @ 4.6GHz
    MoBo: Asus Maximus V Extreme
    RAM: 16GB 1600MHz DDR3
    GPU1: ATI HD6970
    GPU2: ATI HD6970
    HD1: Crucial M4 512Gb SSD (Main drive)
    HD2: OCZ Agility 240GB SSD (Destination)
    HD3: OCZ Agility 240GB SSD (Source)
    HD4: Crucial M4 mSATA 128GB SSD (cache / Pagefile)

    I must be missing something! I can't believe all that hardware is soooo sloooooow at rendering

    I've provided a screenshot of it in action just in case it helps ...


    Thanks in advance guys. Help me Obi Wan. You're my only hope!

  2. #2


    That is quite a beast of a PC, 1:20 rendering time for a 55min video isn't a bad time.

    There are things you can do to improve this. Firstly make sure you match the render setting to your original footage resolution, bit rate, pixel aspect ratio, etc. this means the CPU is having to do less work. The format you are rendering from and to can make a difference. With my work-flow mpeg2 is quicker to render than mpeg4 or Windows Media Video. BUT this may be that mpeg2 more closely matches my original footage format. You can tell Vegas to only render those clips that are altered in some way and not the rest. In the Vegas preferences there is an option on the General tab called "Enable non re-compress of long-GOP rendering". This is only helpful with certain file types.

    This is what Sony help says about it:
    Select this check box if you want to pass through
    unedited frames without recompression (smart render) for the following

    • DV AVI

    • DV MXF

    • IMX MXF (IMX 24p MXF is not supported for
      no-recompress rendering)

    • HD MXF

    • MPEG-2 (for files such as those from HDV and DVD camcorders)

    • XDCAM EX supports smart rendering across the following formats:

      • SP 18.3 Mbps CBR 1280x720p to/from XDCAM EX and HDV HD-1

      • SP 25 Mbps CBR 1440x1080i to/from XDCAM EX, XDCAM HD, and HDV HD-2

      • HQ 35 Mbps VBR 1440x1080 to/from XDCAM EX and XDCAM HD

      • HQ 35 Mbps VBR 1280x720p to/from XDCAM EX

      • HQ 35 Mbps VBR 1920x1080 to/from XDCAM EX

        For more information, see "XDCAM EX

    In order to perform rendering without recompression, the width, height, frame
    rate, field order, profile, level, and bit rate of the source media, project
    settings, and rendering template must match. Frames that have effects,
    compositing, or transitions applied will be rendered.

  3. #3


    Thanks for the reply I'll check and double check my source Vs output options. I thought I'd selected the closest match but I can't be sure.

    Quote Originally Posted by Midnight Blue View Post
    1:20 rendering time for a 55min video isn't a bad time.
    Well if that's the case then I suppose it's just a case of inflated expectation! I'm only using the tick box for "match project settings" so that should help but I guess I'll just do a bunch of benchmarks on a smaller file to see what full HD outputs take the least time.

    Thanks again

  4. #4


    Interestingly enough ... I noticed I'd been doing the whole "project" as NTSC and not PAL so that won't have helped much.

    Anyh00 - I did a whole bunch of renders of a 19s clip with some full HD formats ...

    This is the renders I did:
    Then in ascending order of time:
    What's most crazy though is the files are all 30-60 MB each except the AVIs which are 2GB! The original was only 60MB ... shalln't be using AVIs then

  5. #5


    I noticed I'd been doing the whole "project" as NTSC and not PAL
    Ha Ha, that's would be quite an important point to get right.

    Interesting tests. Those .avi files are uncompressed, that just goes to show how good these modern CODEXs are at compressing a 2 Gb file down to around 30-60Mb. It kind of gives you an idea as to the amount of processing that is going on with HD video.

  6. #6


    Well I settled on Sony AVCHD 1920x1080-50i as the format with the best quality - both the MP4 and MPEG2 were less than perfect compared to the original so not an option. Now it's all set up correctly, it's very close to 1:1 real-time encoding which I guess will just have to do

  7. #7


    that's VERY fast encoding. I know it can take several hours on some of my 2 or 3 minutes long videos. I had to let the PC run all night or half a day a couple of times and I believe my longest vid must have been around 7 or 8 minute (that wasn't that long to encode as there was very little post stuff).
    HD video processing takes a long time, if you can get your encoding at top quality at 1:1/real time, that's pretty amazing in itself, to me at least. I'd be happy with half as fast.

    Make sure your PC is also properly cooled, had issues with my power supply at first and I had to "upgrade" the cooling. it only occurred during video rendering so I assume it was that.

  8. #8


    Thanks for the response It's quite obvious my expectations were just an order of magnitude out!
    Quote Originally Posted by hadoq View Post
    Make sure your PC is also properly cooled, had issues with my power supply at first and I had to "upgrade" the cooling. it only occurred during video rendering so I assume it was that.
    It's actually watercooled so I'm hoping that won't be a problem. Hasn't been an issue for the last year or so with pretty heavy use

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