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  #1  
08-31-2019, 02:42 PM
ELinder ELinder is offline
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Several months ago I mentioned not being able to change the audio levels on my VC500 during capture. I've recently been looking closer at the audio, and I'm finding a lot of clipped audio in my captures. This happens with both my Diamond VC500 USB and Pinnacle 510-USB in Windows 10. I thought the 510 may be doing it because everyone recommends Windows XP instead of the Windows 10 I'm using, but the VC500 has current official Win10 drivers. I decided to try my Blackmagic Shuttle Thunderbolt, and also get clipped audio capturing with it under both Windows and MacOS even with its gain turned down. Same result capturing on my laptop. Same result with both JVC C101US and HR-S7800U VCRs. Same result whether I'm passing the audio thru a Pioneer ES15 or not.

On a whim, I decided to see if the ES15 DVD recorder still recorded, so I burned a DVD straight from VCR-->ES15. After ripping the disk, I was amazed to see no clipping!

Is there something about the audio signal that the VCRs output to a television that is too strong for the capture devices but that the ES15 knows to change before recording? What are you all seeing with the audio you are capturing?

Top waveform is the ripped DVD recording, bottom is the captured file.

Erich


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  #2  
08-31-2019, 03:55 PM
hodgey hodgey is offline
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I've encountered the same issue with capture cards. The VC500, Blackmagic Intensity, and empia cards all have the gain too high for what comes out of VHS decks for whatever reason. At least on the empia cards it's possible to turn the volume down with a registry setting, the blackmagic and VC500 windows drivers don't have any working way of doing this that I've found. Blackmagic card level settings, both for video and audio seem to apply after the signal is digitized last time I tried.

On our panasonic decks and 8mm cameras using the headphone out and turning down the volume a bit solves it, but otherwise one would need something external to lower the volume or use a different devce for audio capture.

Also noticed as you, that it doesn't seem to be an issue with DVD-Recorders. No audio issues whatsoever when capturing from my Sony DVDR, (or JVC one) with the blackmagic over HDMI.

I thought the pinnacle 510 had a bit more advanced drivers, maybe it has some audio setting somewhere?
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  #3  
08-31-2019, 05:18 PM
ELinder ELinder is offline
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Yes, it looks like the Blackmagic Shuttle Thunderbolt applies the slider settings after digitizing, which is why it doesn't help with clipping. It's too bad the ES15 only passes thru the audio instead if treating it as it does when it's writing the DVDs.

Looking thru the docs for the Mac version of the Diamond VC500 shows a gain control in their capture software, but I suspect it's the same kind of thing as the Blackmagic and is done after capture. Since I already have the Windows version getting the Mac version probably won't be any different.

I wouldn't mind getting a separate USB audio box if it provides high quality audio. Synching the audio to video afterward is easy. Anyone have a recommendation?

Erich
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  #4  
08-31-2019, 06:02 PM
hodgey hodgey is offline
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The Diamond VC500 Mac has completely different hardware to the black non-Mac one, the two ones we got here are empia-based, so it's possible to adjust the volume on them with the registry setting in windows. Wouldn't recommend them though, the newer ones are pretty mediocre as far as I know.

You can technically digitize the audio with the ES15, it, like most DVD-recorders has digital (SPDIF) audio outputs, though you would probably need a end card to capture that in any case.

Alternatively, you can get, or make an RCA volume control to bring down the volume a bit.
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  #5  
08-31-2019, 06:23 PM
ELinder ELinder is offline
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Something like this should work without affecting the sound quality, shouldn't it?

https://www.amazon.com/PAC-LC-1-Remo...s%2C161&sr=1-1
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  #6  
09-02-2019, 08:07 PM
dpalomaki dpalomaki is offline
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What is the clipped audio source?

The ES15 probably has AGC on the analog audio input to the recorder, but not on the pass-thru. This would reduce the chance of clipping if the audio input is hot. But it could also mess with the dynamic range of the audio.

BM Intensity documentation (page 19) indicates that it contains an audio proc amp (with about +/- 12 DB of gain) that can be adjusted using the BM Desktop Video Setup app. It also has a check box for "Use HiFi Audio Levels" if the RCA audio inputs are selected, in which case the level controls are not active. The proc amp woudl be in the analog audio path.
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  #7  
09-02-2019, 08:26 PM
ELinder ELinder is offline
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The source is as I said, both my listed VCRs. I also already tried setting the audio level control with the Desktop Video Setup program and trying the hi-fi setting and it still clips. I'm going to try an RCA volume control and see what that does to the signal.
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  #8  
09-03-2019, 08:47 AM
dpalomaki dpalomaki is offline
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Interesting.

I ran a quick test using bars and tone composite output from a Canon XA20 with the 1 kHz tone set to -12 dB. -12 dB corresponded to 0.30 volt rms measured by a high impedance multitester (or -10 dBV). It has the ~12 dB of headroom typical of consumer audio.

I captured the NTSC SD bars and tone with a BM Intensity Pro 4K card.
Used Desktop Video Setup input audio gain settings of 0 dB, +12 dB, -12dB, and HiFi.
I captured the XA20 output using BM's Media Express.

The audio levels in the captured files were -13 dB, -1dB, -25dB, and -1 dB relative to max allowable digital record levels as measured with Audition. (IMO this provides an adequate range of control for material that was recorded with close to proper audio levels, both consumer and professional.)

The HiFi setting corresponded to maximum gain in the internal audio proc amp and that may be excessive for material recorded or played back at a high audio level, as may be common with many VCR and camcorders using AGC for the audio input. (Material played back at level exceeding 0.30 volts might clip.)

The audio gain settings provided by the Intensity Pro 4K card and Desktop Video Setup worked as expected.

Sounds like your system is not functioning as expected, The simplest issue might be not saving the new setting (which in case of the internal card means allowing accepting to the computer).

Depending on its impedance the simple level control you linked to should work. However, using a simple external mixer provides metering that can help the workflow.
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  #9  
09-03-2019, 08:58 AM
ELinder ELinder is offline
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If something's not working right on my system, it's not working right across 2 VCRs, 3 different capture devices, and 2 operating systems. Hodgey has also seen this behavior. Your test is interesting, but is that signal large enough that it would be clipped before it gets to the gain control, as seems to be happening here?

I know basically diddly and squat about audio signals, so I have no idea what the culprit could be, but I ordered a simple level control from Amazon that should arrive today.
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  #10  
09-03-2019, 10:32 AM
hodgey hodgey is offline
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I will have to check with the intensity shuttle again, but from what I remember I had level issues with it. I didn't use the audio in much anyhow as I had issues with it creating random clicking sounds.

The VC500 and empia cards I've used have all had issues though, no matter what VCR I used.

As for levels, the Ag1980P specifies https://www.manualslib.com/manual/30...page=37#manual specifies -8 dBV output level. This consumer panasonic specifies -6dBV. The VR1100 we got specifies –8 dBs, 1k ohms (0dBs=0.775).
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  #11  
09-03-2019, 11:22 AM
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Slight chance it could be the VCR. (If the VCR is from me, then no, not it, because I check audio carefully.)

ATI 600 USB also have audio input levels problems, must use the registry hack to properly normalize at 50% (128 value). This hack is covered in various forum posts, for anybody needing it.

Audio quality is a main reason I use Turtle Beach Santa Cruz + ATI AIW desktops builds for capture. The ATI 600 clones strangely don't have the problem, nor do some of the specific model/revision Pinnacle cards I use.

- Apparently yet another reason not to like the VC500.
- And another reason that Blackmagic cards are craptastic for SD input.

Since talking about audio, and ES15, sometimes ES15 creates sync delays not found on ES10. Depends on signal quality, apparently buffers ramps up on bad input. So when using ES15, to be safe, I now route audio into it as well. Better than sync delay in VirtualDub later, quicker, less work.

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  #12  
09-03-2019, 03:00 PM
ELinder ELinder is offline
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LS, yes, it's with both the VCRs I got from you. When I use the ES15 for the video pass-thru I always route the audio thru it too just in case.

The audio level controller arrived, it works great. Interestingly with it in the audio signal path even with the level set to 0 (it has a +/- 8dB range) it helps. When I dial in a bit of reduction the audio levels are perfect with no clipping. Definitely worth $8.25.

Erich
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  #13  
09-04-2019, 06:39 AM
dpalomaki dpalomaki is offline
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Ran some more tests on audio recordign in the Instnsity pro 4K.

With SD analog audio selected:
- With the HiFi setting: it will not clip if the input remains at/under 0.22 Volts RMS. By 0.25 volts RMS it is clipping. This can be seen in the attached waveform graphic.

- with audio gain set to 0 dB: it will not clip if the input remains under about 0.98 volts RMS IN this case the captured digital audio is at -0.5 dB, essentially max record level.

- With audio gain set to -12 dB: it will clip when the input exceeds reaches about 1 volt RMS.

Bottom line is keep peak audio inputs below 1 volt RMS with the Intensity Pro.
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  #14  
09-04-2019, 08:36 AM
ELinder ELinder is offline
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Is that all stuff you can control with that Intensity 4K card? I don't know what most of that means, but at least I know I'm not the only one who was seeing clipping at times with multiple hardware. I captured a half hour tape last night with the level control and the waveform looks great in Audacity and Resolve.
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  #15  
09-04-2019, 12:03 PM
dpalomaki dpalomaki is offline
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The missing graphic.

Avoiding clipping requires understanding the capabilities of your gear and adjusting accordingly. If the purchased device works for you that is what counts.

There are a number of things you can control with the card's included software such as:
- Output type (HDMI, S-VIDEO, component, composite)
- Input (HDMI, S-VIDEO, component, composite)
- Analog video levels: Y, C, setup, Cb, Cr
- Audio levels (within ranges stated above)
- input/output conversions (SD to/from HD)
- Video format
- Capture file format
- And a number of operating parameters

If not set properly you can get garbage or perhaps no capture. If the user does not understand what these mean it is not the card for them.

I mainly use the Intensity Pro cards for ingesting HDMI signals and occasionally as a monitor connection point for output from my non-linear editor. The IP4K card has had significant issues with SD component capture levels.


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  #16  
09-05-2019, 08:41 AM
ELinder ELinder is offline
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That's basically the same adjustments available with the Shuttle Thunderbolt, which makes sense since they use the same setup and capture programs.
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  #17  
09-22-2019, 12:32 AM
VideoTechMan VideoTechMan is offline
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Basically in most cases, its just better to incorporate an analog mixer for proper sound levels. I always incorporate a mixer in my setup, as I use the Kona LHi to capture.
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  #18  
09-22-2019, 09:49 AM
ELinder ELinder is offline
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The RCA level control did the trick for me. However, I did file a bug report with Blackmagic about the Intensity Shuttle Thunderbolt and sent them a few test captures. They're taking it serious enough that they're going to have me send them my Shuttle to test to see if it's my unit, a software problem, or a design hardware problem.

Erich
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  #19  
01-31-2020, 09:12 AM
ELinder ELinder is offline
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I forgot to update this. Blackmagic returned my Shuttle Thunderbolt unable to recreate the problem, so I have no idea if it's their hardware or software, but either way, the level control takes care of it.

Erich
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  #20  
02-03-2020, 01:04 PM
traal traal is offline
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What's a reliable way to determine, during and then after capture, whether any audio clipping occurred?

The Panasonic AG-1980 has an audio level display. Will that help?
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