REDCINE-X build_454 - problem with 96.000KHz 24bit audio

[Daniele Mercanti]

Hi there,

I'm the DIT on a feature over in London, I think I just bumped onto a bug with REDCINE-X

- REDCINE-X_build_454 - Audio Match function doesn't work with 96.000KHz 24bit audio.
- Also the waveform does not render correctly making manual synching impossible.

Files are coming from a TASCAM recorder. They are .WAV multitrack files.

Application worked fine with audio recorded at 48.000KHz. on a Sound Devices recorder.
Also worked fine when I downsampled the TASCAM 96.000KHz to 48.000KHz.

Anybody else having this issue?
Is there a fix?

And by the way,
does someone has a detailed explanation of the 'Rate Override' feature?


thank you,

any help appreciated.

Daniele M.

 

[Matthew Yaeger]

You probably need to set the rate override before matching.

Some sound recorders set their bitrate to a False rate for drop frame modes designed for workflows where they need the audio slowed down 1% less than realtime, the rate override settings are there to account for that.

 

[Philipp Straehl]

It is not a bug. Not all audio cards support 96 kHz/24 bit. What audio card do you use? Built-in or professional? Are you on a Mac (Core audio) or on a PC (ASIO)? The same with software. Not every software supports 24 bit and high sampling rates, because it's only used in professional sequencer applications like Protools (internally it uses 48 bit), Cubase, Logic, Sonar, etc. There may be some video editors/colour grading/compositing applications that can read 24 bit audio, but it does not make much sense anyway. Because when you do serious mixing, you will have to switch to these sequencer applications anyway, they are made for that purpose. There's no feature film without Protools/Cubase/Logic. These applications can display a proxy video, and you can create a 5.1 until 11.2 mix.

But before going into details, here's a quick fix: convert your audio to 48 kHz/16 bit, the problems will be gone. Use WaveLab or similar application for the conversion. And I highly recommend to record in that format from now on, you save recording space and there is no quality loss at all. I understand that you want to capture most of the real world as possible, but you are perfectly fine with 44.1 kHz and 16 bit, it's the CD standard. 48 kHz/16 bit is the DVD standard, that's why it is recommended when you record for film/video.

24 bit audio is only relevant in an audio mixing application. It allows you to decrease the audio level without losing information. With 16 bit you will lose high frequency information when you drop the level significantly (- 40 dB and more). Minor adjustments around +/- 12 dB are alright with 16 bit. It's fine to record with 24 bit, for the sake of keeping the best possible audio file. But if there are problems with importing, render to 16 bit, without losing audio quality (this has to be emphasised again and again):rolleyes5:.

Sampling rates above 44.1 or 48 kHz are only relevant if you apply software effects, although this is still a topic of debate, because many professional audio plugins utilise oversampling anyway, so there's no need to have the project at higher sampling rates. Many N#1 music top chart hits are produced at 44.1 kHz (read Sound On Sound magazine where top chart producers reveal their workflow). But 24 bit is a must for them because they have to use low levels for certain elements. If they could leave every channel at 0 dB, they would not need 24 bit. This has to do with the Nyquist theorem and other facts from the digital audio recording/reproduction science, if you are interested in the theory behind it.

Field recorders have the option to record higher sampling rates than 48 kHz, but it only makes sense if you really need it. If not, record at 48 kHz/16 bit to prevent problems in video applications. Be assured, you won't lose any audio quality. If you're still unsure, go to an audiophile shop and play back your 96 kHz audio and the converted 48 kHz audio. You won't hear a difference (because you can't).