Measuring the DR of a multi-channel track

[ev666il]

Hello everyone.

I would like to measure the dynamic range on my DVD and Bluray concerts but I wouldn't know where to start from.

First thing first, what do I need to rip the audio track from a DVD or Bluray?

Once the audio track is ripped, I gather I should either downmix it to stereo, or measure the front channels (FL/FR) alone. I would rather do the latter, as it seems to be making the most sense. How would I go about separating the FL/FR channels from the rest of the track to measure them?

I'll also need to downsample most tracks to 16bit/44.1khz when ripping from Bluray. What software does a good job with this?

Thanks in advance.

[soulburner]

I don't think there is a one, easy method to do all this.

If you have DVD-Audio, try googling DVDAExplorer. It can extract the audio stuff very quickly and put them into multichannel wave files - with no sampling rate changes and stuff. Some audio processing programs, like Adobe Audition, will open each channel as separate track. Sound Forge does it better, because it supports surround audio. No idea about Audacity.

If you want to extract a DVD-Video's audio... it's quite problematic, unless... you can use DVD Audio Extractor. It's commercial software, but the trial version should work with no limits for 30 days.

As for free software, I think I'd use MeGUI (http://sourceforge.net/projects/megui/). It's a video conversion utility, a rather complex one too First, copy the DVD contents to your hard drive. Might need to use some ripping software if the disc is copy protected.

Then, in MeGUI, go to Tools, then File Indexer and pick the first largest vob file - that should be the main video track. The window should show you the audio tracks detected. Make sure the option to demux audio is selected. Click queue and go to the main window's queue tab and click start. This will give you the ac3 or dts file in the video_ts folder.

Now, depending on whether your audio editor supports it, open the files directly or convert them to wave files. To convert ac3, any of these should do it: http://www.videohelp.com/tools?convert=AC3%20to%20WAV
As for dts, I have no idea.

To use the two front channels for dynamic range analysis, it depends on the audio editor you use. In Adobe Audition, each channel is a separate track. It should be easy to sort them all in the multitrack view - just leave the two front left and front right channels there and downmix it. In Sound Forge, just select the front channels and copy them to a new stereo wave file. Again, no idea about Audacity

I hope anything I wrote helps. If there are easier (freeware!) methods, I would also be happy to learn about them


edit -- edited the post quite a lot!

[Hancoque]

Converting the files (once you have extracted them) is easy with foobar2000, which is actually an audio player. There are input plug-ins for AC3 and DTS available and you can also easily downmix or extract channels with it using another plug-in called Matrix Mixer. The good thing is that you are in full control. Processing is done in 32-bit floating point and you can specify your own downmixing coefficients.

If you want to extract the two front channels, use this matrix:

Code: Select all

   FL FR FC LFE BL BR
FL  1  0  0   0  0  0
FR  0  1  0   0  0  0


If you want to downmix 5.1 to stereo, use this matrix:

Code: Select all

   FL FR    FC LFE    BL    BR
FL  1  0 0.707   0 0.707     0
FR  0  1 0.707   0     0 0.707


To convert a track you have to use the converter interface, which you can access by selecting the files you want to convert in the playlist and then open the context menu and choose "Convert". If you need any advice on how to get through all those options, feel free to ask.

Links:
foobar2000
AC3 decoder
DTS decoder
Matrix Mixer

P.S.: There's also a VST host plug-in available here, so you can use VST plug-ins like Dominion and Stereo Tool with it, too. All DSP plug-ins can not only be used by the converter but also in real time during playback.

[soulburner]

Ah, totally forgot you can convert files with Foobar
Matrix Mixer is new to me, though. Seems interesting. Thanks

[ev666il]

Thank you both very much for the info! I will try these on some of my DVD-V and DVD-A in these days and report back here with my findings. Hopefully these tools will also support Bluray