Audio drops out part with through HDMI capture

[nick1977]

Hi everyone
I've been using my HD PVR2 with a splitter to back up some of my programmes to my PC to free up space on my Sky Box.
Everything has been working fine for ages, but I've come across a problem today.

When trying to record 2 episodes from a show that was a download to the sky box rather than a recording. It keeps glitching about 10 mins in, afterwhich there is no sound recorded. You can hear the sound when recording but it's not there on playback afterwards.
I tried the same episode 3 times, and another episode once, always the same problem.

Subsequent captures of broadcast recordings I've done work fine, so I'm pretty sure it's linked to the fact the shows are downloaded through the catch up or on demand service.

Anyone encountered anything similar?
I might resort to capturing from actual recordings, since the show still airs regularly. Just tried to avoid that due to adverts and lots of on screen logos!

Look forward to hearing your thoughts.

[Cornucopia]

Cinavia detection?

Scott

[nick1977]

I was thinking that, since it sounds like the same symptom. Wasn't aware that it was used for things like this though...

[Brad]

Build a capture graph using GraphStudioNext, or GraphStudio, or GraphEdit (1st is most feature-filled, 3rd is most basic).

Same problem then?

[nick1977]

I'm happy to spend some time mapping out, but I don't see how that will make the problem disappear?

For now a very simple explanation:

Sky HD Box - HDMI Splitter - Hauppauge HD PVR2 Gaming edition - USB3 connection - Hauppauge Capture software (TS format maximum bitrate variable, AC3 direct stream capture

That's basically the setup. To reiterate, I have done plenty of captures before and since with no issues.

I have an alternative (less desirable) fallback which I can use, just curious if anyone has encountered something similar before I do that.

[Brad]

I would try changing the output of the Sky box to PCM.

[nick1977]

That's a good idea thanks, I'll give that a try tomorrow.
Another thing I thought to try is an older sky hd box from around 2010 - it's currently running as an extra box in the bedroom. Not sure if that would make a difference...

[nick1977]

Changed the Skybox to output "Normal" - I'm sure it used to say PCM but I could be wrong!
Seemed to work fine now, so whatever the issue it seems to be linked to the AC3 track. It works fine on another catch up service I tried had an AC3 track, plus all recorded broadcasts with AC3.

Bit of a mystery but at least I have a workaround now!

Thanks for your help.

[Brad]

The PCM output/capture is stereo only, correct?

Something that just came to mind: early in this product's life, the HDMI audio capture was only partially implemented and extremely buggy. I have no idea whether they ever tried to fix it. You might try doing an AC3 capture via optical.

Another possibility is that the AC3 track suddenly changes from 5.1 to 2.0 and freaks out the capture device. It's a normal thing for broadcasters, especially when changing from program to ads and back, but a lot of hardware and software fails to handle it appropriately.

I'm happy to spend some time mapping out, but I don't see how that will make the problem disappear?

For now a very simple explanation:

Sky HD Box - HDMI Splitter - Hauppauge HD PVR2 Gaming edition - USB3 connection - Hauppauge Capture software (TS format maximum bitrate variable, AC3 direct stream capture

That's basically the setup.

Re-reading this post, I'm wondering if you misunderstood my suggestion. Understable, if so; I didn't actually explain. Was hoping if you didn't know about GraphEdit you would search around and get the gist of my idea.

Your response sounds like you may have thought I was asking you to build me a flow chart of your connections.

GraphEdit is a utility intended for developers to test functionality of DirectShow devices without having to write code. But the important point for us is that sometimes video capture drivers include hidden settings that aren't exposed in any capture application. Sometimes GraphEdit lets you see these. Sometimes it can't, but there are registry edits you can do. Sometimes nothing so "obvious" works, and you would need a datasheet on the relevant chips and knowledge of hardware at a low level to make any changes. And so on.

[nick1977]

Yes I did indeed misunderstand your post, sorry. I did however look into what you suggested, albeit the basic version, and what I saw was exactly as you described - what looked like a process map / flow chart!

I think Hauppauge must've at least partially fixed the audio issue from what you describe. I've captured without issue a number of programs that switch between 2.0 and 5.1 AC3 - usually the ads before are 2.0 and then it switches to 5.1 as the program starts (I like to keep a short amount of pre show footage).

Another good suggestion to try the audio by Optical. I'll see if I've got a spare cable I can have a go with (the current one is tidily wired into my setup!)

Thanks again.

[nick1977]

Tried using optical and same issue. Interestingly I've notice the video also glitches slightly when the audio drops. It doesn't if I change the sky to output pcm and record to mp2.
The AC3 is recognised as 384kbps 2.0 which I also thought was odd.
Sky normally has 192kbps for 2.0 tracks.

Anyway, it seems to be fine with mp2, and 384kbps on that wit only 2 channels seems plenty to avoid any noticeable drop in quality.

I'll stick with that, but thanks all for your help.