Audio clipping occurs regardless of file format

hi, i've been capturing video/audio from VHS and digital camera without too much of a problem, except no matter what i try i cannot get rid of some clipping or clicking sounds in the recording. Regardless of the format (AVI, MPEG1, MPEG2), the quality (bit rate, frame rate, sample rate), or the program i use (VirtualDub, AVI_IO, PowerDirector 2.5, WinDVR 3.0) the audio quality is poor. Yet the audio is still in sync with the video and if i change the settings to just record audio, it sounds great. I tryed an external analog-to-digital converter and used optical inputs but there was no improvement. So i am convinced the input to the sound card is fine. There must be something happening during the capture of the video that interferes with the audio capture...but i'm not sure, and that's why i'm writting to you guys.

Specs:
Dual Pentium III 1000Mhz
512 MB RAM
Gigabye Radeon 9200 VIVO
Chaintech CMI8738 PCI Sound (w/optical I/O)
Highpoint ATA100 PCI RAID
(and much much more...)

I would really appreciate any thoughts/ideas, thanks.

 

What it sounds Like to Me is you have the Capture Volume Far too High...I know On My Sound Card when captureing I have to have the recording Volume on about 35% or I get Really Loud distorted Audio that Clips out all the Time....It is Better to capture audio that is too Quiet than audio that is too Loud because you can allways Boost the audio Later if you have to useing an audio editor....Cheers

 

thanks minion, but i just tried lowering the capture volume and it was still clipping. i had the volume down to 9% useing WinDVR and i could still tell it was bad. however, i've been trying all kinds of things and i've noticed some video problems. at times there is some lagginess in the frame rate, and once in a while a short sequence will repeat, for a second while the audio continues normally, then the video catches up with no loss of sync. it seems like it could be a drop frame issue, except that i can change the video and audio settings to the lowest possible quality and still get clipping. could there be some sort of problem with the interaction between the audio and video? either the video capture is interfereing with the audio or the audio capture is interfereing with the video....but, once again, i'm not sure.

 

Have you tried a Lower Sample Rate Like 44100hz or lower?? I don"t think it would be your sound card because I use a Crappy Sound Blaster card and get Good audio Quality...

 

yep, i already tried 44100hz sample rate settings for both mpeg1 and mpeg2 and down to 11025hz with AVI; no luck. when the sample rate is that low though, i get terrible sync problems. is there an even more raw file format that i should try to record with? and if so what program does it? there are some settings in windows control panel for sample rate conversion quality, i played around with them alittle, i don't know if they make much difference.

i'm not sure what to say about the hardware. if nothing else works to fix it then i'm going to have to at least try a different sound card just so i can say for sure that that is not it. i know that with the card i have, most of the processing operations are off loaded to the CPU, is there a possiblility that could cause problems? have you ever heard of problems with sound when both analog output and optical output are running at the same time?

 

When Captureing to AVI I find it best to use LPCM or Wav as the Audio format but when captureing to Mpeg you don"t have much Choice aceept Mpeg1 layer 1 or Layer 2 and some Programs Like WinDVR have the Option of Captureing to Dolby AC3...Have you tried the Microphone Input as opposed to the Line in Input?? It might be worth a Try as the Microphone Jack seems to usually be Quieter than the Others..I suppose as a Last resort you can Try a Different Sound Card you Motherboard might even have integrated sound which you can try to use, I know Mine does but I get better Quality with the Sound Blaster which you can pick up for about $10 on EBay (Used)...Does you capture card have a Audio Line in/Out that you are useing?? if it has one that you are useing then Try just going into the Sound Card and if you aren"t useing then try useing it..I"m just throwing things up in the air hopeing there is something you haven"t tried that might work...well good luck....Cheers

 

thanks for all the ideas Minion. i'm still having trouble thou. i tried the mic jack a while ago; no help, and my video capture card does not have audio capabilities. i'm using virtualdub when i try AVI capture, but it doesn't list LPCM or wav as one of the compression options... WinDVR indeed does have a LPCM option but was no help, of course. if i hadn't been working with computers most of my adult life, i would say this is starting to get frustrating. i'm headed out the door to find another sound card, if i buy it local and it don't work, i can just take it back... but i did come across something on the web about dual processor setups not being tested with most sound cards because generally dualies are for servers that don't need sound. if there were a problem with it then it would be very "sound card specific", but it is something to think about.

 

Hi, Virtual dub does have a Wav and LPCM capture format But it is Probably just Listed as "Uncompressed" which is what Wav and LPCM are Just uncompressed Audio...well Let us know how the new sound card works...Cheers

 

Minion, it's a no go with the new sound card...
i installed a sound blaster live 5.1 and it was still clipping like crazy! but i started playing around with VDub again, since you mentioned it, and i found a few things that seem curious. first, VDub simply does not list LPCM, Wav, or Uncompressed (not even anything like it) in the "Capture AVI" mode. i saw these settings listed for the conversion mode but not for capture, which is where i need them. also, VDub's little volume meter box has been showing a lot of peak level audio (big red bars after the blue bars), and when i reduce the input volume level both bars get smaller but there is always just as much red bar as blue bar. -i hope this is making sence- anyway, i think you were on to it from the very begining, that the input volume is too high and is causeing distortion. except that reducing the input volume decreases the sound but it does not decrease the distortion... and i know it is not a simple matter of turning down the volume on the VCR, those output levels are preset and cannot be changed. a pre-amplifier would do the trick here, but i keep thinking to myself, why in the world has no one else had this problem???

 

I found this on the VirtualDub website, what do you think??? http://www.virtualdub.org/docs_capture

Q: I get sound, but it has cracks and pops in it.
My video has greenish lines in it.
Occasionally, I see thin horizontal strips in the captured video that looks like they came from the last frame???

A: No one has a rock-solid answer for why these problems occur, but it appears to be caused by contention on the PCI bus, which then prevents the sound card and video capture devices from emptying their buffers in time. This problem is reported more frequently on motherboards that have a VIA chipset, or in systems that have a SoundBlaster Live! sound card. In the former case, try upgrading your VIA 4-in-1 drivers first, and if that is not sufficient, check for a motherboard BIOS update that specifically addresses your problem. As for the Live!, the Creative driver is known to cause problems by lowering the latency timer of the PCI bus. (The result is similar that of making the red lights appear every ten seconds at a four-way intersection.) In that case, try installing the Microsoft drivers instead.

Also, check the websites for the hardware manufacturers to see if they have utilities which may help. For instance, Pinnacle has a PCI adjustment utility for some of their cards.

If you are using RGB24 for your raw capture format, switch to YUY2 to drop your raw datarate by 33% (see below), which may be enough to lower PCI bus load to workable levels.

 

That is strange because I have a Via Chipset and a Sound blaster card and don"t have any Problems Like that but that doesn"t mean That it isn"t the Problem..
Do you have a Via Chipset?? And have you tried different capture Programs Like Virtual-VCR or IU_VCR??

 

i do have a Via chip, the Apollo pro133a, which is an older chip but i have the latest bios update and 4-in-1 drivers. it's interesting that i happened to buy the sound blaster live card as it is mentioned in the artical from VDub, the problems with sound and video do indeed seem worse with it installed. even though i have the original sound card reinstalled all of the programs i use are haveing this problem. i have not tried Virtual-VCR or IU_VCR, so i'll try them, but to be honest i am not as interested in capturing AVI as i am in capturing MPEG2. but at this point i'll try anything. of course, i still think the problem is with the hardware, do you have any tips for improving PCI latency???

 

Well You could make sure that your PCI Slot that you are useing for your Audio/Video are not shareing the Same IRQ ,They should each have there own IRQ ,And Overclocking your FSB Changes your PCI Latency which should allways be set at the default 33mhz ,Some Motherboards have the Option to Overclock without changeing the PCI Latency but you Probably don"t have this Option..I guess you could allways Upgrade your Motherboard to a Newer Model, You can get One with a Via KT333 or KT400 Chipset for Under $50...Cheers

 

well, my cards are not sharing IRQ's, i'm not overclocking, and i cannot upgrade my motherboard...so i am kind of stuck. it is wierd that my video, audio, RAID, and network cards have IRQ's 16,17,18, and 19 respectively. should they be on the regular IRQ's that are below 15??? i did try Virtual-VCR and i have actually experienced some improvement, i think because i am able to leave the capture uncompressed. however, the sound is still not at a level of quality that i would expect. and now i am having a bit more trouble with video quality in Virtual-VCR.

anyway, i've been holding off reinstalling windows (win2k) until i got this thing worked out, but now maybe it would be good to start from scratch. let me know if you think of anything else...otherwise i'll get back to you when i am up and running again.

 

well don't assume that no news is good news, because i still haven't got it to work yet...

i've seen captured footage from a VCR before and i know that it shouldn't look and sound as crappy as mine does. typically i am getting better sound quality when i drop the video quality to the 354x240 @ 1800 kbps range, but even then the sound is not that good. there is every indication that the program and the settings have very little effect on solving the issue. could it be the video card or some other device is sucking up resources on the PCI bus, or is it that the ageing Via chipset is simply unable to handle the load?????? i just don't know...

at the moment i am looking into trying to record the video and the audio separatly. i've heard of others haveing to do so, do you have recommendations as to the most efficient method???

 

Well I have never heard of Poeple captureing the audio and Video seperately unless they were dubbing in original audio tracks like when they produce movies..It would be allmost impossible to sync up the 2 Streams if Captured seperately and you would never know if you started the audio capture at the exact same moment as you Started the Video Capture at ,and VCR"s have a Terrorable Habbit of not being very Consistant when it comes to the Playback speed of the tape especially if the tape is old which would make syncing up the streams even More problematic...I guess you Probably want to Hold off upgradeing your system to a Newer faster PC unless it is a Last resort but you Might be able to do it for free or close to it as you could probably sell your Present motherboard with the 2 P-3 proscessors for as much as you could pick up a new Motherboard with a 2.0ghz-3.0ghz chip ,I actually have 2 2.5ghz chips and Motherboards Combos here that I picked up for $115 US each..well I hope you get it worked out...Cheers

 

Minion, would you agree that the issue is most likely hardware performance related? and that MB, Proc, and Mem upgrade would most likely resolve the issue? do you see any other alternative?

sorry to put you on the spot....

 

I think i have experianced some of the problems you have pointed out, but when i capture i always capture a few seconds BEHIND the actuall begining beacause, the hardware and software need some time to "settle in" its the only way i can explain it, then i just chop that bit off when editing, i'm not sure why your audio is clipping, you say it works fine with audio only?

here is a cheesy way round why not connect your audio to a laptop and record it using whatever audio software you like and then just lay that audio file backinto the video file? OK OK, its not the best solution but give it a try!

tell us how you get on.


----Anhar Miah

 

Well It sounds Like either a PCI Bandwidth problem or a sound card problem..The reason I say PCI Bandwidth problem is that you can capture Good Video and audio if you capture them seperately but not at the same time which seems to say that there could be a Problem with the PCI bandwidth Not being High enough to Transfer Both the Audio and Video at the same time ,But if this were the case you should be able to capture Good audio and video if you Just Lowered the Video resolution and the audio sample rate which you say you do get a Little better audio Quality when useing a Lower Resolution?? The thing is that the PCI Standard hasn"t changed in the Last 5 years and we still use the PCI 2.1 Specification so the There will not be any PCI Bandwidth improovement on a New Motherboard unless your Present Motherboard uses a Older PCI Standard ..There has been a Lot of Improovement on the AGP Bandwidth though so that could be were the Bandwidth Limit is because your Captureing through your AGP Video card ,Unless you are useing a PCI version of your Card which would severely limit you PCI Bandwidth...So yes I would Think that a CPU/Motherboard/Ram upgrade would Greatly increase the available Bandwidth to make Captureing Less Problematic...If you want I can Hook you up with the Guy I buy all My CPU"s and Motherboards from ,He Gives Pretty Good Deals ,Like I mentioned before I picked up a couple Intel 2.5ghz CPU/ECS Motherboard Combo"s of him for $115 US each combo which is Pretty cheap as it would cost more than that Just for the CPU if you got it retail and all Parts are Brand new ..He also Carries Athlon Combo"s also if you would rater have an Athlon...well anyways Good Luck....Cheers

 

hey Minion........
is it possible that the clipping is a form of copyright protection?????????
i had always gotten such good video that it never occured to me that the sound may be copy protected. there are still some things that would make me think that it is not copy protection but let me know what you think.

and yes i would still be interested in getting a hold of your dealer, but i won't be buying anything real soon. i think you are right about the bandwidth issues. right now i am fairly sure that there won't be a way to tell what the problem is until i can hook both my sound and video card up to a new mobo. (unless it's copy protected, so let me know...)

again, thanks for all the help