Why is AVISYNTH so great?

[TRILIGHT]

I'm trying to figure out why everyone says it is so much faster than VFAPI. I seem to get roughly the same speed out of both (just over 1.0X realtime) on my P4 1.6Ghz. Can anyone give me some facts on this? Thanks!

[Fox Mulder]

http://www.doom9.org/mpg/d2a-mpeg2dec.htm

[TRILIGHT]

Ok, so that would seem it's a tool better suited for those doing Divx and SVCD projects. Like I said though, I'm noticing roughly the same speed on Avisynth and VFAPI. Does someone have some numbers on what they get with the two frameserving techniques? Any reason I would not notice a difference when so many people say there is a huge difference?

[Kedirekin]

AviSynth is faster than VFAPI only when frameserving from a dvd2avi project file, and only when using the the mpeg2source plugin provided by mpeg2dec.dll. AviSynth is faster under these circumstances because it eliminates two color-space conversions; from YUV to RGB for frame serving (ala VFAPI), and from RGB back to YUV for encoding.

If you're frame serving a dvd2avi project file and not seeing a performance improvement over VFAPI, then post your AviSynth script so we can see if we can figure out why.

[Kedirekin]

Oh, and in my experience (all other things being equal), AviSynth is roughly twice as fast.

[TRILIGHT]

Wow! Twice as fast? That's incredible! I am using a DVD2AVI project file as you mentioned. I'm not doing anything fancy with the script. Just using the basic method as listed in the guide...

LoadPlugin("C:\PROGRA~1\GORDIA~1\mpeg2dec.dll")
mpeg2source("D:\rmd\rmd.d2v")
ResampleAudio(44100)

Of course, I'm pointing to my own mpeg2dec.dll location and d2v project file. It works. I just don't see the speed everyone else does. Perhaps I'm using old versions or something?

[Milkman Dan]

What kind of settings are you using in CCE? The reason you might not be seeing the speed increase is because the slowdown is further down the pipe than the frameserver.

But yeah, making sure you're using current versions would be a great place to start. Also checking that you are enabling the YUV output of DVD2AVI is a something to check as well.

[TRILIGHT]

Perhaps there is only a speed increase on lower bitrates? I don't know. The bitrates I use are usually between 2000-9500. The settings I use in CCE are as listed in the CCE advanced guide (The Robshot method).

As for the slowdown being "further down the pipe", where would that be? The system is a Pentium 4 1.6Ghz, 512MB, Adaptec Ultra160 SCSI controller, Quantum Atlas 10k RPM Ultra160 SCSI drive, OS is Windows XP Professional.

Oh yes, my DVD2AVI is version 1.76, my CCE is 2.50 SP, my AviSynth is 1.05 b5, and my VFAPI is 1.04.

[Milkman Dan]

I meant further down the software pipe from the frameserver, not your specific hardware.

Perhaps it's just your processor? I have a 1GHz Morgan-based Duron, and with no filters or anything in my script, Robshot compliant, and I get .9 realtime. So your setup seems to be running slower than it should overall for some reason.

Dunno. I guess you've got me. You got DMA and all that jazz turned on? 4way bank interleaving turned on in your BIOS? (I'm assuming you're using DDR SDRAM)

Just seems to be slow for that setup.

[jdobbs]

TRILIGHT,

I personally see about 10-25% improvement (depending on the source material) using AVISYNTH v.s. the VFAPI codec most of the time. I also use the Robshot method and VBR encoding between 0-9000Kbs. Most of the time I get 1.25 realtime in AVISYNTH. My system uses an Athlon TB at 1.3GHZ. As Kedirekin says above, and from what I've read in the programmer posts the speed improvement is said to be because the DVD2AVI/MPEG2DEC/AVISYNTH/CCE sequence doesn't have to do any conversions between RGB and YUV.