• VEGAS Pro

  SVP12.770 MainConcept AVC render CPU-only vs GPU accelerated yields different size files

  Posted by Stephen Crye on January 19, 2014 at 6:44 pm

  Hi;

  This is interesting but probably not worth worrying about.

  Been doing testing of various things. Rendered a 10-minute video using the same settings – Internet HD 1080 for MainConcept AVC/AAC (*.mp4; *.avc) . Only difference was for one render, used “render using CPU-only” and the other, used “render using CUDA if available”. My card is the nVidia Quadro 2000. Source footage was 1920×1080 60i from Sony HDR-CX550V; cam on tripod pointed at a symphony conductor (the “conductor cam” that shows his face from point of view of the musicians).

  Render time was horribly long for CPU-only, .mp4 file size was 1,084,956 KB.
  Render time for CUDA was about 30% as long, file size was 923,640 KB.

  I can’t see any difference in quality.

  Clearly though, something is different.

  Anyone else noticed this? Thoughts?

  Win7 Pro X64 on Dell T7500, MultiTB SATA, 8GB RAM, nVidia Quadro 2000, Vegas 12, 11, 10, 9 DVDA 6.0 & 5.2(build 135) Sony HDR-CX550V, Panasonic GH3 with LUMIX G X VARIO 12-35mm / F2.8 ASPH, LUMIX G X VARIO 35-100mm / F2.8

  Stephen Crye replied 12 years, 3 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Steve Rhoden

  January 19, 2014 at 8:14 pm

  Interesting…Maybe CUDA does some further compression.

  Steve Rhoden
  (Cow Leader)
  Film Editor & Compositor.
  Filmex Creative Media.
  https://www.facebook.com/FilmexCreativeMedia
  1-876-461-9019
• 

  Norman Black

  January 20, 2014 at 12:00 am

  The Mainconcept CUDA encoder is a completely different encoder than the CPU only encoder. It is not the same encoder with GPU acceleration. Contrast this with Sony AVC, which is mostly the same encoder with some functions done on GPU.

  Different encoders are doing things slightly different and unless the two encoders target the same bitrate, EXACTLY, then the file sizes will be different. Even at EXACTLY equal bitrates there can be quality differences. Maybe not visible but PSNR and SSIM will not be the same.

  Also Mainconcept is very poor at targeting an average bitrate. No very accurate. One or even two pass. This statement I am comparing to x264 which can really nail a specific bitrate.
• 

  Stephen Crye

  January 21, 2014 at 3:48 am

  [Norman Black] “The Mainconcept CUDA encoder is a completely different encoder than the CPU only encoder. It is not the same encoder with GPU acceleration. Contrast this with Sony AVC, which is mostly the same encoder with some functions done on GPU.”

  Ahh … very interesting.

  I guess it makes sense, because an encoder is in essence just a bunch of code, and the CUDA API is way complicated.

  https://docs.nvidia.com/cuda/kepler-tuning-guide/

  Thanks,

  Steve

  Win7 Pro X64 on Dell T7500, MultiTB SATA, 8GB RAM, nVidia Quadro 2000, Vegas 12, 11, 10, 9 DVDA 6.0 & 5.2(build 135) Sony HDR-CX550V, Panasonic GH3 with LUMIX G X VARIO 12-35mm / F2.8 ASPH, LUMIX G X VARIO 35-100mm / F2.8

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