Capturing 24-bit audio in VirtualDub?
 

Hi!

So, we'll have a client that's hell-bent into getting 24-bit audio from basically everything. Our capture softwares only do 16-bit: be it with our ATI All-In-One Wonder AGP GPU setup under XP or our ATI TV Wonder 600 with the Win7 machine.

The Win7 machine is fitted with a dedicated sound card that can easily record at 24-bit 192kHz. Seeing that the client will want RGB capture, I'll have to use VirtualDub. But VirtualDub 1.9.11 only allows me to capture 16-bit audio with the sound card (I don't capture through the capture card itself because I have no control over the recording volume... apparently... and this unfortunate workaround introduce roughly 10 frames delay in sync between audio and video but easily correctable in post, thankfully).

So, I'm wondering... is there a solution to getting 24-bit audio in VirtualDub? I really don't want to either record the audio elsewhere in parallel or use OBS...

Cheers.

Only pro capture devices can capture 24bit audio, If you want to capture audio only with your 24bit sound card you will have to do it separately using an audio capture app like Audacity in 24bit and then merge the sound track to the video in an editing software, Note that audio for video is maxed at 48Khz, any higher sampling frequency will not be compliant and may give you problems later on.

As to vdub, I'm not sure if vdub can capture 24bit audio but I believe it can process videos with 24bit or 32bit float audio.

As to the most likely "weakest link" in a less than optimal result, my guess is the limitations in the audio recording itself and/or in the analog audio playback while digitising are far stronger candidates than the limitations of 16 bit audio. I've seen (heard) this so many times in members' uploads here on this forum alone.

VHS/Beta HiFi and 8mm audio are much more demanding in dynamic range than linear (normal)audio but with careful level setting even they can be digitised very well using "only" 16 bits.

I've thought of recording audio separately overnight... but thinking of my workflow, it'll be a pain in the ass to sync mainly because of Premiere Pro.

Mind sharing the "pro capture cards" that can do 24-bit audio?

I agree. They want RGB recordings even though my named capture cards can only do 4:2:0 and 4:2:2 respectively. Sure, you make absolutely sure that no extra conversion happens. But then, getting good video info from the devices is more important than getting 24-bit audio for sure.

Sometimes you have to educate your customers when they are wrong, and that is, RGB and 24bit are not really needed for consumer tapes, If they have Betacam SP that might make some sense.

Professional capture cards and devices are not easy to come by and prices are usually very high, at least the ones that work well with consumer formats and built in some TBC correction.

If you still want to see if you can get one, call Ensemble Designs to see if they are still making the BE75 on special order, Last time I checked was 2 years ago you can still order one for $1450.

RGB is quite image damaging, too, on capture usage.

The 24-bit can be faked with a re-conversion/re-compress. (The audio quality off VHS tapes is already less than 16-bit fidelity.)

24-bit 192kHz is obviously compressed. In fact, very compressed, even for AAC/AC3/MP2. The compression alone is inferior to a 16-bit uncompressed. So, that's silly. Was thinking 192kbps.

Just capture it normal 4:2:2 Huffyuv with 16-bit uncompressed audio, then up-process it to the ridiculous specs. We had to do this quite often for submissions to iTunes/Netflix/etc. The ingest standards were beyond stupid for the source, so it's just upconverted.

The client is dumb/silly, and demanded you play games. Well, post-capture conversion is playing that pointless game.

FYI, the ATI 600 USB audio levels are correctable in the registry, but require reboot. The internal chips actually support audio control, but ATI did not hook into it for the drivers. So you can manually adjust (numeric value, 0-255), then reboot. Obviously, not ideal. Anybody good at coding can, potentially, whip up a standalone audio adjustment program, but nobody has to date.

24bit/192KHz can either be compressed or lossless (PCM/WAV/FLAC), But 192KHz is overkill for video, the standard is 48KHz, where 44.1KHz is for audio only formats.

I was referring to 192 kbps, not 192 kHz. Too tired + too many letters = oops. :smack:

And agreed, 192kHz is nuts.

Hey LordSmurf, sorry for the late reply.

The client is........ a national level client that has the name of a country in its name. This is not some random Joe specs. Changing their mind will most likely not happen and having them as a client insures the long term survival of my paycheck.

Since my initial post, I've actually received teh actual specs for VHS and, discovered that the unompressed AVI done in VDub is actual interlaced but AVI does not inherently support the interlaced flag... at least in VDub. At least, that's what this person here on VideoHelp here says.

I just said "RGB capture" because that's what Virtual Dub 1.9.11's files are detected as in various players, MediaInfo, etc. But, in the end, they want a v210 AVI with 24-bit / 48khz audio track.

I've used Huffyuv with Virtual Dub but I found out that Adobe Premiere fucks up the footage by inserting glitched frames and the encode later keeps those glitched frames and they're not only on the timeline. So, what I've been doing is, once I have the uncompressed capture, I put that in Media Encoder, wait an eternity for it to add the files, and then convert it to MXF OP1A Jpeg2000 which plays nice and quick in Premiere. (EDIT: In the end, I might not want to do that...?)

I'm not someone that fakes stuff. When you are expecting 24-bit audio and then, later, you decide to check your files with Schwa's Bitter VST to check for the validity of your bit depth just to find out that they're all upscaled... I'd be pissed. I know 99.9999% of the general populace won't give a flying F about it and I know where the 24-bit argument comes from but still... I'll have to see if I'll be able to capture the sound in Audition at the same time the tape is being captured to see if that could work. And I'll have to do that anyway because VDub will most likely desync the audio slightly - or at least as the chance to. Even does that when you are recording on a SSD. That's something I'll have to test and upsampling should be my absolute last thing after everything has been tried and couldn't find a solution.

As for your last comment on the volume mixer, a shame really. And changing the registry, reboot, still too loud, change the registry again, reboot, now too low, change the registry, reboot...... I don't have time for that. I have to capture and have the files ready to go in a certain amount of time so, you know, my salary to do the job passes the money we got for the job, y'know.

Cheers.

Yep, I get it. :laugh:

Correct, AVI has no flags.
MPEG does, MKV, some others.

I'm think you should capture Huffyuv AVI + 16-bit uncompressed audio.
- bloat the audio to the desired specs
- place both in MKV container (Huffyuv video + bloated audio)

I've never tried Huffyuv inside MKV, but that's probably the only way to get the container flags for interlacing.

Premiere makes a mess of most things. All NLEs do. They work really well as designed, and extremely poorly at anything not in the direct shoot/edit/output workflow. You're converting, not shooting, so it never ends well. You always have to prep sources, a pre-NLE step.

I hate MXF files, and JPEG2000 is just compounding problems later on.

But the source quality isn't even 16-bit. I'm anti-fake myself, but not when the source is this low. It's not much different than asking for HD/4K files from a progressive DVD. It's literally 100% bloat.

Odds are you'll need to buy a new needlessly fancy USB audio capture card. I forget the current "in" name brands (it's changed since the 00s/10s), but it may work.

There are ways to hardware-delay video (or audio), so you can capture in sync (when the capture is out of phase, due to capturing separate audio and video cards). If you have a volume of work, worth investigating. More black boxes, probably not cheap. Those items are the normal brands, Extron and the like. Maybe some of the audio mixer boards.

I set audio at a 66% input level, and then route through a $100 Mackie mixer. Rarely issues, and those files get Sound Forge processing.

Hopefully I've given you some ideas. I hate to see project get more complex than needed.

That explains a lot of things as to why I couldn't find a way to get the file to show up as interlaced and I thought I was recording progressive but I was really recording interlaced and I just needed the final format to be a format that's compatible with the flag.

Normally, under our normal output for any other client that just wants a video file, our output is a deinterlaced MOV H264 file with 16-bit PCM audio track with 2500kbps vbr video bitrate at 4:2:0 chroma (and overscanning artifact cropped and image centered in standard resolution, they can refuse it ofc but, normally, I do it). If it's just an average Joe job, then the container changes to MP4 with a AAC 320kbps audio track (just to say "see bigger number means it's better!" if they ask but, they won't care between the difference in "quality").

Agreed. If it's not in their "expected workflow", it's bound to break. Especially with Huffyuv where to install the codec first for the AVI file to get added at all in Premiere. And we know how not straight-forward it is to install on Windows 11...

I work in preservation and this format is in the recommanded format for US Congress, Government of Canada and other preservation bodies. The thing I discovered after I posted my original reply above is that this format CANNOT be interlaced. At least, the only software I know that can easily encode the format, Adobe Premiere and Adobe Media Encoder, unchecking the tick box next to "Progressive" does nothing. So, if I know my end result needs to be my format, I need to add a deinterlaced filter at capture.

That's where I kinda disagree. Analogue sound is a pure wave versus a digital one that's kind of a stair that looks like a wave zoomed out. To capture most of that detail, the more bits you have, the better. That's where the 24-bit argument comes from. However, the problem here is that the audio quality on most tapes does NOT justify it. Most sound tops at 16khz with everything above it being some kind of mirrorring of what's below (in the spectograms at least). If anything, it's the sampling that's too high: 32khz could be well enough, funnily enough. Alas standards are at 48khz.

For me sticking to 16-bit for this particular format's analogue audio is just a matter of "it's easier" and "nobody usually give a flying F about sound quality as long as it's not dead obvious (if it's not the actual tape's quality).

The capture computer has a dedicated audio card (Creative Sound Blaster Audigy II I think on PCI) that can capture up-to 24-bit 192khz. That's why I'm really bummed that VDub doesn't allow me to choose any kind of 24-bit option especially when the quality drop down in Windows shows the resolution I just said and recording in parralel in Audition in 32-bit float then saving it as 24-bit FLAC (or PCM - whatever, the same).

The problem is money and experience here. I don't have experience in any kind of mixer and the issue with VDub seems to be random. It does not happen all the time.

And, of course, most of the projects I've done were simple enough and the places were grateful enough to have a file and finally see what was on that old defunct format.

24bit is for post editing and restoration, If none is planned 16bit is still overkill for analog video tape formats even the pro Betacam, also 192KHz makes no sense for video. If you still insist on 24bit audio for video you have to get a pro capture device/card.

Audio-wise, these are terrible card. It's low-end "better" (and higher-priced) consumer fodder, mass produced schlock. Creative (aka Sound Blaster) cards are known to be very tinny. In general, even a "24-bit" from these cards will underperform 16-bit from a quality card.

Once upon a time, Creative had better-quality consumer-level competition, such as Turtle Beach, Roland and Pro Audio (a terribly generic name for a company). In the end, Creative "won" the consumer computer sound wars, largely due to cheaping out, but also due to suing competitors (and while Creative "lost", they bankrupted the smaller competitors in the process).

The main reason is that it wasn't the standard. However, there's (probably) no reason that VirtualDub cannot be patched for it. I've been trying, for years, to get somebody to get with me, so we can overhaul VirtualDub into two separate tools, massively upgrading each.

It's really easy. A child can operate a mixer. It's just sliders and dials, inputs and outputs. And for only $100, too.

Yep, and I try (and apparently you try) to also give them a modicum of high-end quality. But then there are those "other clients" (often with "credentials" that aren't worth the paper they're printed on).

Vdub would not output 24bit if the card does not support it, You have to have native 24bit sampling at the hardware level and a compatible driver.

Yes and that has been available on even prosumer audio cards for over 20 years. My first card in 2002 was a M Audio 2496 and there were others just as good or better. Since then the specs for AD/DA audio converters has only got better and prices generally lower. The problem is the other way around: it's Vdub which cant do 24 bit.

Having said that, for most analog to digital audio transfers I've done over that time I've mostly used 16 bit because it was more than adequate for most of the material I digitised. I once was directed to transfer some film soundtrack tapes to 24 bit, not because the material or the customer required it, but because the national government archive in which the files were to be deposited required it. So I used 24 bit. It wouldnt have made any difference to the audio quality but the taxpayer would pay for the extra data storage.

Yes, that is a given. The hardware has to support recording allowed. But most cards allow 24-bit, even cards from 25 years ago.

The issue is that VirtualDub is encoded to the standards of the era. That was DVD-Video, which called for 16-bit. Even that was "high" relative to others at the time.

Which video capture card the OP tried that has native 24bit audio support in the driver and vdub did not accept it? If he is using a stand alone audio capture card with a non 24bit video capture card and expect vdub to mashup 24bit audio to a video card that doesn't support it, then that's probably the issue.

I'm not entirely sure how vdub works, as I said previously I processed 24bit files with it and worked, I will try one of my devices with it and see if it can capture 24bit, I will report back later.

Can it really tell the difference between a 16-bit recording of a 90 dB (15-bit) audio source upscaled to 24 bits and the same source recorded directly in 24 bits?

The noise floor of any analog audio source, even a 15 ips studio master tape, is going to be way, way higher than either 16-bit or 24-bit digital -- especially with noise shaping, which became nearly universal on digital recording equipment 20+ years ago, and pushes down the noise floor even further across most of the human range of hearing (up to about 15 kHz).

I can attest to what LordSmurf said, from what I've read in the audio world it's fairly common practice to upconvert to meet client demands (for instance, I've read examples of engineers with clients who demand 192Khz, but their equipment doesn't support it. So they simply convert it 192Khz for the client.)

There are definitely ways to tell what you did, but 99.9% of clients will be happy and will not care one bit. Lord Smurf mentioned Netflix. I guarantee they did not care one bit, as this is pretty common practice (for instance music services like Spotify and Apple Music require 44.1Khz, but most producers will record in something like 48Khz, they simply downconvert.) Are there downside? Minor. Not anything anyone will notice in 99.9% of cases.