Transcoding: trying to figure out the bottleneck in my setup

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Transcoding: trying to figure out the bottleneck in my setup

Postby tezster » Wed Jun 03, 2009 1:24 am

I have a 32-bit WinXP SP3 box running with an AMD Athlon X2 7850 (overclocked @ 3ghz), 4gb PC-8500/1066mhz DDR2 ram along w/ two terabyte sata drives installed, using the latest build of PMS (1.10.51) over a wired gigabit network using Cat6 cables. I have the transcoding settings set to Best Quality (keyint=1:vqscale=1:vqmin=2)

It seems that this system can't keep up with certain 1080P videos played because the video begins to stutter i.e. the buffer is being emptied. The sample/test video I use is a VC1 video in a .WMV container. When I stream it natively on the PS3, it will play properly (since VC1 is supported by the PS3), but the audio stream isn't compatible so there's no sound. The only way to get sound is transcoding it.

The transcoded MPEG-2 stream will on occasion peak at up to 150+ Mbit/s, but this isn't really the problem, since my network should be able to handle the bandwith. I've verified this by pausing the video at the beginning until the buffer is full, at which point the video plays flawlessly, regardless of how high the throughput goes.

I know the CPU I have isn't the best, but I'm thinking it should still be able to handle transcoding pretty much all HD content?

Incidentally, using AVISynth yields better results - playing the same video at normal speed, the buffer will eventually fill up to the maximum, although does take a minute or two, but my preference is to use Mencoder.

If anyone has any suggestions on what settings I can tweak, I would greatly appreciate it.

thanks!
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Re: Transcoding: trying to figure out the bottleneck in my setup

Postby meskibob » Wed Jun 03, 2009 1:45 am

VC1 doesn't fall under the "Enhanced multicore support" for MEncoder, so it's probably your CPU that's limiting.
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Re: Transcoding: trying to figure out the bottleneck in my setup

Postby tezster » Wed Jun 03, 2009 2:51 am

Thanks for the info... I did notice that the CPU usage was only at 50%, whereas AVISynth was using ~70-80%.
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Re: Transcoding: trying to figure out the bottleneck in my setup

Postby psebos » Wed Jun 03, 2009 8:47 am

Had similar problems with some H.264 videos and when start using Avisynth with CoreAVC (in a CUDA supported video card)
all skipping dissapeared. However I do not know if CoreAVC support VC-1.
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Re: Transcoding: trying to figure out the bottleneck in my setup

Postby meskibob » Wed Jun 03, 2009 1:01 pm

CoreAVC/CUDA only supports GPU-decoding of H.264 videos.
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