Blackmagic audio trouble

[Mockingbird]

Hi, I am capturing Hi8 and VHS tapes through Blackmagic and its Media program on to my Mac Pro. On many of my tapes audio distortion appears as the tape progresses past around the fifteen minute mark. I can capture the entire tape only if I capture it fifteen minutes at a time. Before I started using the Blackmagic desktop program I was using Quicktime. The same problem happened but the audio dropped out intermittently instead of creating distortion.

I can monitor the tape audio through the deck's headphones and it is fine. And since I can capture the tape successfully in fifteen minute chunks I assume the tapes are fine.

This problem occurs when I capture either to an internal drive or external drive.

I have been advised to further simplify my chain. Right now the tape deck is connected to the Blackmagic and the Blackmagic is connected to a CalDigit Thunderbolt deck. The the Caldigit is connected to the MacPro using an adapter. The Blackmagic outputs via Thunderbolt 3 which the MacPro does not accept. So the converter converts to regular thunderbolt. I have tried to remove that Caldigit and just use the adapter but the Blackmagic desktop program does not recognize it.

I would appreciate any thoughts.

Thank you.

[dellsam34]

What Blackmagic device are you using? What video/audio connections used? And are you using MediExpress?
Normally Media express won't allow monitoring audio through its driver, So an external monitoring is required, It gives you a visual meter though to adjust levels but it won't allow audio into the computer system.
It is highly likely that too many devices in the chain that is causing this problem. Once you post all model # for your hardware we'll try to find you a simpler solution without having to use too many adapters.

[Mockingbird]

I am using a Mini HD. The audio cables into the blackmagic are quarter inch. The inputs to the video decks are RCA. The video is BNC into the BM and RCA to the Decks. Yes, I am using Media Express.
No, I cannot monitor the capture in real time - which makes this a bit more difficult, but this other problem is even bigger so I have ignored the monitoring issue for now.
Thank you.

[dellsam34]

Do you have technical names for the connections and the type of signal they carry? BNC could mean analog composite or digital SDI, so saying BNC won't give any details, Alternatively, post pictures of all connection on your devices so we can identify them for you.
Yes not having audio via the capture app is normal, don't worry about that, Focus on the capturing part.

[Mockingbird]

I am a complete novice at this so i can't speak to the types of signals. Here is a photo of the back of the blackmagic and its connection to the CalDigit. Then there is a photo of the two Thunderbolt cables that the white adapter is connecting in order to plug into the Mac Pro.
[Attachment 65298 - Click to enlarge]

[hdfills]

always run a seperate line in from your device to your sound card for the audio and that will fix your audio issues

[Mockingbird]

Hi, I just installed Blackmagic onto another computer, an iMac, with a thunderbolt 3 input. So the signal is going direct from the Mini HD into the Mac. And the Hi8 camcorder is plugged directly into the Mini HD. But the audio distortion began to occur about 13 minutes into the capture - just as it was doing before when I was using a thunderbolt deck as an adapter into our Mac Pro that has no thunderbolt 3 inputs. The problem happens with both Hi8 and VHS decks. And the distortion is not present if I capture in short intervals. Really strange.

[dellsam34]

What setting are you capturing to? 8bit UYV or 10bit RGB. I really need to know models numbers for those boxes so I can look up their specifications, Could you post a screenshot of the MediaExpress showing the setting?

Edit:
Is it this BM box you are using? If so, What type of 1/4" connectors you are using? Those are balanced 3 connector type (Hot, Cold, Ground), Usually to go from unbalanced consumer stuff to balanced pro connector you could just short out the cold to the ground however it is not always the case unless the manufacturer suggested so.

Thunderbolt 3 is 40Gbps, so it shouldn't be the bottle neck, There is a performance test app in the Desktop software, it analyses your system performance (CPU, HDD, Memory ...etc), Launch it and set your video parameters and post the test results here.

It sucks that it doesn't have Y-C input for Hi8 S-Video connection, just composite and component (YUV).

[Mockingbird]

Thank you for those questions. Yes. That is the exact BM box that I am using. I will check the cables when I return to the studio. But I should say that I have been successfully digitizing almost 1000 hours of DVCAM and Mini DV tapes for the past few years with this exact same set up and cables - capturing with Quicktime. I did not have these audio problems. It was only until I started capturing VHS and Hi8 tapes did these problems begin. I started using Express to capture thinking that it might work better than Quicktime. The audio problems in QT were sound cutouts - increasing as the tape progressed. Media Express creates a low end digital flutter as the tape progresses. It cannot be the tapes because they capture properly if I do them in 15 minute intervals.

[energizerfellow]

I will check the cables when I return to the studio.

Those XLR audio cables in your pic look like some hot garbage, gotta say. That's an impressive level of electrical tape, which isn't a compliment. Get some new audio cables man, seriously.

But I should say that I have been successfully digitizing almost 1000 hours of DVCAM and Mini DV tapes for the past few years with this exact same set up and cables - capturing with Quicktime.

DVCAM and DV are digital video formats (thus the "D" and "V" in their name...), so I really hope you were using the Apple Thunderbolt to FireWire Adapter with an appropriate one-piece 9-pin to 4-pin or one-peice 9-pin to 6-pin IEEE 1394 cable for an all-digital capture pipeline. Analog capture of DVCAM/DV will result in heavy quality loss, especially over composite, and not recommended.

Using a consumer Digital8 camcorder will also let you do digital DV codec captures over Firewire of analog Video8/Hi8 tapes provided you use a Digital8 camcorder with analog tape support.

I did not have these audio problems. It was only until I started capturing VHS and Hi8 tapes did these problems begin.

Since DVCAM/DV are stable digital formats without the timing jitter of analog tape, you've been able to get away without a time base corrector (TBC). Once you introduced the unstable signals from consumer analog formats like VHS/S-VHS or Video8/Hi8, that UltraStudio HD Mini and downstream hardware/software started freaking out, thus the dropouts and other issues. Unfortunately, Blackmagic as a company doesn't make any TBC-equipped devices at all, at any price, which unfortunately includes your Blackmagic UltraStudio HD Mini.

I started using Express to capture thinking that it might work better than Quicktime.

Blackmagic's Media Express is a solid capture tool (along with AJA Control Room), but dealing with the timing problems of things like VHS needs to be dealt with in the analog front-end hardware.

For something that can handle unstable analog video and work with macOS, you should be looking at a Magewell USB Capture AIO / Pro Capture HDMI / Pro Capture AIO. These cards will also let you use a YC S-video cable from a Hi8 / S-VHS deck (which will also play regular Video8 / VHS) to get notably higher quality than regular CVBS composite.

If you need a Thunderbolt 3 enclosure, I recommend sticking to Sonnet.

[dellsam34]

If you happen to have a SDI to thunderbolt or SDI to USB3 adapter try it, You do have a SDI output in the BM HD mini.

[Eric-jan]

Is fast storage used ? T5 ? looks like there is still some bottleneck…. i'm using ES35v vcr over component BMD's Analog to SDI to BMD Video Assist onto SD flash card storage, (ProRes422LT) 625i50 and is working fine. (no need to use a pc for capture)
btw audio is set to unbalanced or EBU ?
beware of differences,(with same connector) mini display port, TB2,TB3, USB C, etc… converting (or putt through) between them can be a failpoint.

max frame rates of all devices are fine ?

[dellsam34]

The test I told him to perform in post #8 will pinpoint the bottleneck.

[Mockingbird]

I borrowed a Pixie TBC unit.
https://www.markertek.com/product/burst-pxfs/burst-pixie-fs-frame-store-tbc

It seems to have worked a bit better. I was having to digitize in 10 minute chunks to avoid sound problems. Today, I tested a longer tape and it worked for longer than that. But after about 30 minutes the file stops playing in real time - at least on Quicktime. The second counter slows down and the sound stops while the image continues.

[dellsam34]

I bought that TBC before and had to return it the second day, I don't know if it was a bad unit or it just sucked, I suggest you do the test I told you, it will pinpoint your weak link.

[Mockingbird]

Thank you for your help.

[Mockingbird]

I think this is the test

[Mockingbird]

Trying again

[dellsam34]

Nope, It looks like this:

[dellsam34]

Your settings are wrong, Output should be set to SMPTE 259M-C level C, not 1080p. For audio try checking "Use HiFi Audio Levels". Your 1/4 jacks should have 3 connectors, unless the cold is in the center sleeve not the tip.

[Mockingbird]

Thank you. Those settings were on my IMac which seems to have been overwhelmed by the capture. I went back to my Mac Pro and was able to capture an hour and a half tape without trouble. Here is a photo of the test.

[dellsam34]

Glad you sort it out, So what has changed from the first time you used Mac Pro to now? Was it wrong settings? This helps other members who stumble upon this thread to find a solution if they have a similar problem.

[Mockingbird]

The Pixie TBC seems to be the key. I borrowed one. Now I will buy one. I appreciate your help.

[dellsam34]

Yes, BM analog capture cards are notorious for signal drop from consumer analog sources, We've discussed this numerous times here. They are only good in SDI bridge mode as an interface between SDI and Thunderbolt/USB3/PCIe. I personally use 2 of the BM UltraStudio SDI to connect my pro capture devices to my PC laptops, I use S&W TBS800 and ED BrightEye 75 which are SDI out only analog capture devices and they work in the SMPTE 259-C standard 12bit YUV but I let MediaExpress output 8bit for compatibility purposes in post processing.

If I was in your shoes I would get rid of that BM capture device since it's composite only, Your Hi8 tapes need S-Video connector to capture the Y and C signals separately, Basically you are downgrading your Hi8 recordings to V8 or VHS quality. Even VHS and V8 can benefit from a S-Video connector even when in fact are not S-VHS and Hi8 formats, Just reducing the interference between Y and C improves the quality of VHS and V8 quite a bit.

[Mockingbird]

Thank you.

[Eric-jan]

What are your Pro capture devices, dellsam34 ?

[dellsam34]

They are listed in the very same post.