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Intel HDe audio issue

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Kieran MatthewIntel HDe audio issue
by on Nov 6, 2007 at 6:42:09 pm

Hi All,

OK, this one has me stumped - and I'm praying that it is something simple I've missed.

A while back I posted that the analogue audio outputs of my HDe (v11.6.4) were too hot and this was throwing out the readings on my PPMs. At the time I believed that the output was stuck on the american +24db monitoring level and submitted this as a bug.

My workaround was to lower the master audio bus by 4db, balance my levels and the return to 0db for export. But a recent export to Soundtrack Pro has shown that in fact the analogue outputs are correct - the Media 100 is adding around 4db to levels.

This boost is apparent on both the analogue & firewire outputs.

Has anyone else experienced this? Or have any suggestions as to a setting I may have missed?

K


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FlohRe: Intel HDe audio issue
by on Nov 6, 2007 at 6:57:22 pm

[Kieran Matthew] "My workaround was to lower the master audio bus by 4db, balance my levels and the return to 0db for export. But a recent export to Soundtrack Pro has shown that in fact the analogue outputs are correct - the Media 100 is adding around 4db to levels. "

Hmmm, what do you mean by Media 100 is adding 4dB? Compared to what? How do you get your material into the system (your reference level)? How do you compare STP and Media 100s level?


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Kieran MatthewRe: Intel HDe audio issue
by on Nov 6, 2007 at 7:27:04 pm

Hi Floh

[Floh] "Hmmm, what do you mean by Media 100 is adding 4dB? Compared to what? How do you get your material into the system (your reference level)? How do you compare STP and Media 100s level?"

For instance I have a largely speech based programme with the Audio FX limiter set to -10db. The media 100 internal levels read that the audio is peaking at around -10db. I export the audio as an AIFF and open in STP. The levels are now showing at around -6db. If I lower the bus audio by 4db and re-export, the Media 100 shows at well below -10 but STP shows the audio now at -10.

As another test I opened the PAL -18 test tones from the Media 100i CD in STP. There it reads -18 (well -17.8 but you get the picture). Imported into Media 100 it reads -18 as you would expect. Exported out, and opened in STP it reads -14.

I did wonder if my fried brain was missing something about pan levels etc but I think I checked everything. Plus DVDs I have authored with the bus set to 0db do sound louder than usual.

K


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FlohRe: Intel HDe audio issue
by on Nov 6, 2007 at 9:05:51 pm

I am not really sure that this is an issue, since different applications do use different headrooms. So what Media 100 shows as -10dB on its level display does not represent -10dB digital level. Otherwise everything above 0dB would be digitally clipped and would sound really bad. And there is no real convention that defines where 0dB digital should be when converted tp analog, so there are various different ways to do this conversion.
I will check the Media 100 levels tomorrow (I am not in the office right now), but I don


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Kieran MatthewRe: Intel HDe audio issue
by on Nov 6, 2007 at 10:02:14 pm

Floh,

Thanks for your help on this, it is appreciated.

[Floh] "And there is no real convention that defines where 0dB digital should be when converted tp analog, so there are various different ways to do this conversion."

OK, but consider this. My PPMs read true on the output of my Media 100i. When I boot into FCP, -18db tone reads true on FCP's level meter and on my PPMs attached to the AJA outputs. Do the same in Media 100 and -18db tone and the PPMs read high.

Also if I put tone out at -18db through the firewire, my DSR 40 reads high on its level meters.

[Floh] "I am not really sure that this is an issue, since different applications do use different headrooms. So what Media 100 shows as -10dB on its level display does not represent -10dB digital level."

But aren't Media 100's audio levels locked to QT's levels? Afterall Media 100's own -18db test tone media reads correctly in both FCP and STP.

[Floh] "What version of Media 100, QuickTime and Soundtrack are you using?"

11.6.4 on Intel, QT7.2, whichever was the latest STP before FCS2 was released

Thanks again

K


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Kieran MatthewRe: Intel HDe audio issue
by on Nov 7, 2007 at 7:19:54 pm

Hi Floh,

OK, I've done some more tests and I've made a mistake on one of my claims. The -18 db tone does not read -18 in STP or other apps, so you are right in that Media 100 uses a different definition of zero db than say FCP or STP. Apologies.

That said, it does still seem to get louder when exported out of media100, plus the audio starts to clip on the media 100 timeline at lower than 0db - around 3-4 db lower (which equates to 0db in STP), so there does seem to be something amiss here.

Any further thoughts?

K


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FlohRe: Intel HDe audio issue
by on Nov 7, 2007 at 7:28:32 pm

Which analog outputs are you using? We use the XLR analog outs for testing, which are 2dB hotter than they should be (a -9dB reference level shows up at -7dB). But since we use SDI or AES audio most of the time I am not really sure what is wrong there. But our old Media 100 i audio level tone from Media 100i V4 days is still at -9dB when going out digital (and at -7dB when using the XLR analog outs). So it seems like nothing has changed there dramatically.


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Kieran MatthewRe: Intel HDe audio issue
by on Nov 7, 2007 at 7:42:36 pm

[Floh] "Which analog outputs are you using?"

The XLR outputs for testing, Phonos for monitoring. With -18 db tone running, the PPMs show +5 rather than +4. Lowering the tone (or bus) by 4db brings the PPMs to +4 again.

Also testing the Firewire audio out. about -10 tone reads at about -6 on my DSR-40 which doesn't give you control over input levels over firewire. This has to be taken with a pinch of salt as there is no common graticule between Media 100 and the DSR-40 and the 40's level meter is very crude.

Thanks again for your help

K


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