Dropped frames using WMV9 VCM in VDubMod

[Beastie Boy]

After carrying out a few tests (see results here (http://homepage.ntlworld.com/paulwbeastall/details.html) if you are interested. Beware 2.8MB of images on page) and decided to give WMV9 VCM a go for a full movie.

I did the encode via Avisynth using VDubMod without any resizing and at a bit-rate of 3430 kb/s using the Complex setting and 2 Pass VBR (Peak) with the peak set at 7Mb/s.

After the 22hour encode finished, the resulting file looks as if there are dropped frames. Certain areas played back very jerky. I opened the file in VDubMod and as I stepped through the frames, some are duplicated for 3 or 4 frames and then it suddenly jumps foreward.
I wondered if this was anything to do with the Peak setting. Has it wanted to go above the peak and so effectively dropped frames to stay below it. If so then that is pretty lame. I would expect a lower rate to be used for each frame rather than drop frames.

I carried out a test by re-doing the bad portion with the same settings and it works fine. I am presently redoing the whole movie using 2 Pass VBR without the Peak limitation to see if this helps.

Has anyone else had this problem or have any ideas what causes it?

Cheers, Beastie.

[nFury8]

I also experienced dropped frames on an encode I did a while back, using peak vbr. Although I used WME 9 for encoding. I searched the forum back then for some clues, but found none. I believe that only the 2 guys from M$ can provide some answers, but it seems they've been MIA here for quite some time. Anyhow I'm not using peak vbr anymore, just straight unconstrained and no more dropped frames. Still the resulting file size is acceptable to me.:)

[Beastie Boy]

Thanks for the reply nFury8.
I re-did the encode using plain 2 Pass VBR and I don't have any dropped frames, so from what you say, it seems certain that the cause is the Peak VBR setting.
This is not really a problem unless you are using really high bitrates and the peak goes above what your PC (or other device) can decode without dropping frames.

It's a shame that the MS guys don't post here anymore, I think WMV9 is a good codec and it would be nice to be able to ask the odd question and provide feedback.

Cheers, Beastie.

(I like yor sig :D )

[nFury8]

Cool.
I have switched to this codec for my current encodes now and I'm quite satisfied with the quality. My bitrates never go below 2K, I just crop the black bars and let zoomplayer resize during playback. And I'm not using AVI anymore, just wmv or asf that's why I use WME 9 for encoding. That's how I found out back then about the dropped frames because the encoder indicated how many frames were dropped along the encode session. Which takes a loooong time to finish on my ageing 1Ghz Tbird.:) If only those 2 guy$ were still around, we could keep bugging them :).

[Beastie Boy]

I have just finished a 22 hour encode of Matrix Reloaded with just the black bars cropped. I used 3436 kb/s and needless to say, the quality is superb.
I used the WMV9 VCM codec via VDubMod as this allows me to keep the original ac3 audio track. At the moment it is in the Matroska container and what I need to do is get it to resize automatically at playback. I have yet to find out if Matroska supports resizing of WMV9 streams. I'm about to post in the container forum.

Cheers, Beastie.

[Atamido]

I don't know if there's any encoding difference between using the VCM codec, or WME, but if you wanted to use WME and the original AC3, then it just takes a few more steps. Encode the video without the audio to a WMV file. Open the file in Graphedit and connect it to the the Matroska Muxer, then connect it the file writer filter. Once the file is muxed, use MKVMerge to mux the AC3 with the WM9 file.

[Beastie Boy]

Excellent. Thanks for the tip Pamel. I assumed that if you used WME then you were stuck with WMA for the audio.

Cheers, Beastie.

[nFury8]

originally posted by Beastie Boy
I have just finished a 22 hour encode of Matrix Reloaded with just the black bars cropped. I used 3436 kb/s and needless to say, the quality is superb.
Mind if I ask you what your rig setup is? 22 hours for a 2hr-plus movie sounds like you're just two or three notches up from my primitive Thunderbird. :)
Cheers.

[Beastie Boy]

It's a P4 2.53Ghz @ 2.64. 512MB of 333Mhz RAM (Dual Channel).

The video was encoded at 704x424 with no resizing (cropped only) using 2 Pass VBR, one notch down from Slowest setting, Complex mode.

I used Avisynth 2.5* with Fast Recompress in VDubMod.

Does this sound slow given the highish resolution?

Cheers, Beastie.

[nFury8]

Drat, this codec is really slow, you have more than twice as much firepower as I have and it still takes that long. I also don't resize, just crop the black bars, 2-pass and complex decoder settings as well. I assumed wmv would be very fast on P4's. Well, maybe on 3Ghz with HT? Dunno, I wish I could afford it. I'll try and encode the same movie using WME 9 and see how long it takes on my rig. How did you arrive at that particular bitrate? Did you use GKnot?

Cheers

[Beastie Boy]

On disc 2, there is an extra showing the making of the freeway scene which is about 990MB. I deducted this from the size of a dvdr and encoded at the bitrate given by GKnot.
WMV9 is not so good at file size prediction as say DivX and so I always leave a bit of space.
The encoding is a little slow, but this one is probably the best quality encodings I have ever seen. Doing frame comparisons at full screen using Media Player Classic, there is no difference between the WMV and original avs file, except that WMV actually looks a little sharper. Even the colours are accurate which is a problem with WMV that I noticed during some tests I did (link above if you're interested). Well worth the wait.