Quote I record TV Movies using OBS Studio. During recording, the Volume Meter in OBS shows levels just touching the red.

But when I import videos into PD, their audio isn't close to topping out on the waveform display. I always have to slide the sideways mixer control to the max for that channel.

I don't hear any clipping when I play the videos on the TV. So apparently I am not overdoing the levels.

But I don't understand the discrepency between VU indications.

Maybe this, https://forum.cyberlink.com/forum/posts/list/0/82078.page#337871

Jeff

You know how there are Color Bars for calibrating displays?

Is there a video that has a "standard" volume level (like, max allowed by spec?) in a single tone for calibrating purposes?

So I went to youtube and found a few "Test your Hearing" videos. I assume that they were recorded professionally. (Although I have no basis to assume that.) In this video, the DBFS meter in OBS showed a steady -12 dB below the red 0 dB, with the VU mark about 3 dB less, at -15.

Since ppl on the web say to set your VU to -18 dB, this particular video seems like a reasonable benchmark.

There was another similar video, which said it was recorded at "-6 dB," and the indicators in OBS seem to correlate well with that one too, being about 6 dB lower than the first video.

So I imported the first video into PD. The audio waveform showed about 50% of Full Scale in PD.

It seems to me that the horizontal slider in PD's audio settings, labled Audio Gain, is simply a Quick and Dirty way to adjust the audio level of a track. It might be that 100 (which is +50, or 2x, more than normal) correlates to +6 dB.

When I used PD's vertical VU slider instead, adding +11 dB brought me just below clipping on the waveform.

Considering that -11 is close to the -12 dB in OBS's DBFS, this behavior in PD seems believable.

And so I am going to conclude that the TV movies that I record were recorded with their levels at -18 dB on a VU scale. (Remember that these are old movies from the 40's and 50's, when all they had were real rms VU meters. (As opposed to peak meters of today.))

And then I am adding about 6 dB to them when I SVRT them.

Which I probably don't have to do, since the movies sound fine when I play them direct from the TV signal without my audio boosting when I record them for playback in PD.

You can always generate a simple tone at 0 dB in Audacity to check as you wish.

I see your linked video is:
~-9dB peak in Audacity, ~-12dB RMS
~-9dB peak in AudioDirector
~-9dB peak in OBS with OBS VU bar at ~-12dB. Keep in mind the VU bar in OBS is RMS, so for this basic simple sine waveform of increasing frequency it is essentially peak*sqrt(2) or -9*1.41=~-12dB rms. So all agree very well.

The clip in PD when played shows the two vertical stereo meters under preview window in the total green range. As I described prior, these are really high end clipping meters and highlighted the approximate dB bar color for -3, -2, -1, and 0 dB. So yes, they display very low as the audio is ~9dB from clipping.

In the PD audio room, the vertical adjustment scale shows 0 dB. Keep in mind this is adjustment, not absolute dB level. So, if I amplify by typing in 8.6 dB, I should be right near clipping, basically 0dB within the 1 dB bar scale so the PD meters under the preview window will be hitting red. That appears to agree too.

Jeff

Thanks for your research and good to see the correlation.

Yeah, I figured a simple sine wave was the easiest test to do.

I will resist the tempation to raise the audio level in my TV Movie recordings then.

Quote SAnd so I am going to conclude that the TV movies that I record were recorded with their levels at -18 dB on a VU scale. (Remember that these are old movies from the 40's and 50's, when all they had were real rms VU meters. (As opposed to peak meters of today.))

Yes, probably best doing nothing but this statement was confusing. Since one is going from old analog dBvu scale to dBfs, the way converters work, -18dBfs will be pretty darn close to the analog equivalent of 0dBVU, while 0dBfs is clipping. So your old clips are probably near analog needle 0. Additionally, one is typically not talking tracks peaking at -18dBfs, they should peak higher, as one is talking average volume (RMS).

So your sample freq sweep footage you linked is not bad at -12dB rms and peaking to -9dBfs.

Jeff