What's an acceptable frame drop percent?

[pcarver]

I just got an ATI All In Wonder Radeon. It was crashing Windows 2000 constantly, so I did a fresh install of Windows ME. So far, no crashes, so it's stable enough for me to start wondering about dropped frames.

Athlon 1.4GHz
K7S5A Motherboard
512MB RAM
30GB IBM Deskstar HD
VirtualDub
Divx 4.11 Codec

Frames Captured 99509
Total Time 55:21
Frames Dropped 128
CPU utilization 25-40% with rare spikes to high 40's

With Win2K the ATI software didn't give me errors, other than locking up or crashing. With WinME the ATI software tells me DMA is not enabled on the hard disk. The boot up screen clearly shows Ultra DMA-2. The motherboard supports UltraDMA 33/66/100. VirtualDub doesn't give any errors.

So, is 0.1286% frame drop normal? Is there anyplace in Windows to verify the BIOS report of UltraDMA-2?

[pcarver]

Update:

I've been doing some more captures and it looks like that first one was the lowest frame drop rate. Oddly, every subsequent capture is running lower CPU 5-30%, but higher frame drop rates. Capturing Divx 4.11 video and CD quality PCM audio it's dropping 2-2.5 frames per thousand.

Is this typical?

[ngnr]

It's pretty typical for me, and probably OK and likely VDub's way of keeping your audio in synch with your video because of your sound card timing. Check your video at or near the end and notice if the sound is in synch or not. If it is, forget about it because you won't see the frame drops unless they all happen at once, and this doesn't seem to be your problem.

As for the UDMA, open your device manager and check the properties of your IDE channels and it will tell you if DMA is enabled.

[stanwebber]

as someone else pointed out it is more critical how the framedrops occur as opposed to how many. dropping more than a single frame at a given momment is usually an indication of a hardware bottleneck rather than virtualdub compensating for variances in video/soundcard clock frequencies. 2-2.5 dropped frames per 1000 is borderline high....if you are planning to capture extensively i'd consider a new soundcard. to give you a mark for comparison i drop 1 frame per 8000(aiw pro 8mb agp & soundblaster awe64 isa), but anything less than 1 frame per 3000 is cream. people who boast absolutely no dropped frames are morons who trade 0 drops for progressive audio async

[pcarver]

Ok, you're implying something I haven't read anywhere. Are you saying that my frame drops probably have nothing to do with the video capture per se, but are actually related to the audio capture?

My ATI AIW has sound input jacks and a sound output cable that goes to the line in on my soundcard (SiS sound chipset on the motherboard). I had assumed that the AIW captured both video and audio and that the connector to the sound line in was for playback.

It sounds like you're saying that the AIW is capturing video only and acting as a passive passthrough for audio. Thus, VirtualDub is using the onboard sound chipset to capture the audio and deliberately dropping video frames to compensate for some sort of timing drift in the sound hardware.

Is this correct? Is there any way to verify that this is definitely the cause? The ATI System Compatibility Check says the sound card has a Clock Stability of 0.17%. It lists this under "Passed", not under "Failed" or "Warnings"

[ngnr]

I suppose one way to verify if it's the sound card is to capture without audio and see if any frames are dropped. If not that would at least suggest that the sound card is the problem. Not sure what it means if you still get drops without audio capture...

[stanwebber]

the aiw is only a passthru(only high-end professional equipment captures both video/audio & locks it). ngnr's suggestion will tell you instantly if your soundcard is the sole culprit(not hardware bottleneck), but i will tell you now .17 clock stability is consistant with 2 or more dropped frames per 1000. if you replace your soundcard aim for .05 or less. incidently, i'll sell you a soundcard with .03 clock stability if you have a free isa slot

[pcarver]

Here's the result of a capture without audio. (VirtualDub, DivX4.11)

121830 frames
35 dropped frames

That's 0.29 frames dropped per thousand. It's not zero, but it's drastically lower than the 2-3 per thousand that are dropped in a capture with audio.

When capturing with audio, I can't see any AV sync problems at the end of an hour recording, so I'm just going to consider 3 frames per thousand an acceptable drop percentage.

Here's a brain teaser though, when capturing video only without audio the CPU utilization is pegged at 60-61% constantly. This is substantially higher than the 20-30% utilization I see when capturing video with uncompressed PCM audio. No other settings were changed. So how is it that doing less requires double the CPU?

[doobster]

Well I must say, you are getting more frame drops by compressing your capture "on the fly". You are better off capping to a loseless or uncompressed Avi. As for when I cap, I use Huffy 2.1 and I get about 1 frame drop over 20,000 frames, sometimes even more without a frame drop.

So the reason I would assume for your high frame drop is the "on the fly" compression. Do a comparison and see for yourself if there is a difference.

[Torontonian]

What I found yestarday (win2000):
if I capture something simple with VDub (320x240xYUY2, sound PCM) I lose abot 5 frames per 1000.
if I capture the same format with iuVCR - I lose nothing, no dropped frames.

(did I forget to tell it's P-III/866/UDMA-66?)

I don't think it's a VDub's problem. Probably hardware & drivers (I use ATI TV Wonder). But, if I go thru that wrapper it defenetly rises something weird things than if I go directly thru WDM drivers.

PS. I tried 352x240, DivX, audio mp3 on the fly - still no dropped frames (iuVCR). just for test.

[ngnr]

Torontonian, if VDub is dropping frames to keep the sound in synch, and iuVCR is not dropping frames, it may also be that you will eventually get out of synch sound with iuVCR. Have you tried a long capture with both to confirm? I'd be interested in the result.

[stanwebber]

if you drop fewer than 1frame per 10000 under ANY circumstances whatsoever it's safe to assume video/audio clocks are not being synchronized & you will experience progressive audio async. if you do drop single frames past the 1 per 10000 mark it's most likely a momentary hardware glitch(pc, vcr, broadcast signal etc...)

[Torontonian]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-11-27 10:43:32, ngnr wrote:
Torontonian, if VDub is dropping frames to keep the sound in synch, and iuVCR is not dropping frames, it may also be that you will eventually get out of synch sound with iuVCR. Have you tried a long capture with both to confirm? I'd be interested in the result.
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>

It wasn't long capture, just for about 20-25 min (testing one), but I noticed that VDub's avi was defenetly out of sync even in this small clip. iuVcr's one wasn't.
("lock video to audio" was disabled for both; source - TVtuner, the same channel).
But I'm gonna check again, more carefully.

[stanwebber]

'lock video to audio' is irrelevant unless you are capturing in compatibility mode. the applicable virtualdub switch for internal mode capture is 'adjust video clock dynamically to match audio clock'

[Torontonian]

Ok, yesterday I checked iuVCR again. Source: TV program.

Video: 352x240, YUY2, 29.97 fps, Divx 4.02 (952 KB/s),
Audio: PCM, 22 KHz, 16 bit, mono
Capture time: 1h04m, 115224 frames captured, 0 dropped.

The same video, audio: mp-3 on the fly, 22 KHz, 32 KB/s, mono
Capture time: 35min (couldn't wait more - was too sleepy), 62941 frames captured, 0 dropped.

In both cases audio & video were completely synchronized.

[ngnr]

So, you cap with iuVCR, no lost frames and in-synch but with VDub, lost frames and out of synch. That's puzzling to me. I have had lost frames in VDub but perfectly synched audio (and just assuming it's sound card timing) but it sounds like something different is going on with you. Did you have the audio/video time clock setting turned on that stanwebber mentions? Mine is.

I may have to re-try iuVCR. I tried it a few times a couple of weeks ago but it seemed to cause my display to go out of video synch and resulted in a totally corrupt picture. I'm not sure what caused it but I couldn't find a setting to fix it so I took it off again. I just thought it was crappy s/w but maybe it was something I screwed up myself - wouldn't be the first time. Did you experience any problem with it?

[Torontonian]

'adjust video clock dynamically to match audio clock'

Maybe I'm doing something wrong but I couldn't find this option in VDub...

I've just done VDub test: 122677 frames, 896 dropped; video is a little bit ahead of audio.

So, I don't know how iuVCR manages capturing without dropping frames and keeping a/v in sync, and actually I don't care, but it is a fact on my computer.

Did you experience any problem with it?

I did not. But I installed DirectX 8 & capturing patch for DirectX-8 from microsoft - did you?
Or it can be a problem of WDM drivers.

[ngnr]

'adjust video clock dynamically to match audio clock'

In Capture mode, it's under Capture and then Timing. This is in VDub 1.4.7 so if you're using another version it may not be there.

So you're losing about 7 frames per 1000 which is pretty high. I know I said earlier 2 - 2.5 per 1000 was typical for me but I was mistaken. I just did another cap from satellite, albeit a short one and lost only one frame in about 8000 at 480x480 and CPU was below 40% the whole time (Cel 600). Actually that frame was lost right when I started the cap.

AS for iuVCR, DirectX 8.1 comes with XP, which I don't think I mentioned earlier is what I am using (sorry if that's caused any confusion). That being the case, it was already there when I installed iuCVR. Maybe it has some compatibility problems with XP?

[Torontonian]

I'm using 1.4.7, so I'll try timing.

About XP. It looks to me that it's a little bit "crude" O/S for I came across different reports from different people having some problems with it. And I have no plan to move into it. At least in nearest future.

Did you try native capturing application from Microsoft? (I mean AMcap). If doesn't work properly either it can be problem wit WDM drivers under XP.