Introduction to MetaCorder

What is MetaCorder ?

MetaCorder is a sophisticated device for recording Location Sound for TV and Film, with lots of specialist functionality to provide the additional requirements of this demanding field. MetaCorder is also extremely useful in transfer for digitising material recorded on linear tape, but which must enter a non-linear workflow. MetaCorder offers very powerful media management, and metadata entry, yet presents a very simple interface to the production sound mixer.

Making your first recording

MetaFlow is designed to be very simple to setup and operate. It has no menus or dialog boxes, and all user parameters are presented in a series of tabbed panels in the main window.

In order to get started, you will need a sound input. This can be any coreaudio device, and you should follow the instructions for installing drivers for the device you have chosen, and ensure that it is passing audio into the Mac CPU. After launching MetaCorder, go to the SETUP tab, and select your chosen coreaudio interface with the 'Input Device' menu. If you select 'Default' it will use the device you have chosen in the OSX Sound Preferences panel. After selecting the device, you will see the window update, to reflect the number of input channels available as advertised by the Core Audio driver you have selected. Often devices will present more input channels than you can see Mic Inputs on the device. This is usually because the device includes digital inputs., for example ADAT optical inputs, which will be an additional group of 8 channels. Next, you should select the appropriate SampleRate and Bit depth from the Setup panel. CoreAudio presents all audio as floating point, so you will still be able to select 24-bit from the menu, and record 24-bit files, even if your hardware interface is 16-bit only. You must also now select the file mode and format, so let's discuss the issues you will need to consider when selecting a format.

Choosing a File Format and Mode

Most often, the format and mode you record in will be defined by the workflow to be followed through telecine and into video and audio post. Be aware that decisions made early on in production can have a significant effect on the future workflow, and using the wrong format will make you extremely unpopular with the people who ultimately receive the audio you are recording. For most modern worklows, BWF (Broadcast WAVE Files) are what you will want to record. BWF files are supported by a large variety of software and hardware systems, and carry significant metadata through the workflow. If you are working in a very old fashioned workflow with old equipment in post, you may be asked to write SD2 files instead, although there are potential compromises to be made, and you should only use SD2 files with good reason and consideration. Otherwise, select BWF.

The decision to use Mono, Poly or Dual Poly is rather more complex. First let's learn a little about each type

Monophonic
In this mode, each armed track will generate a discrete mono file. Groups of tracks are associated by common metadata - on a basic level, the filenames are similar, with just the last part of the name indicating the source input channel index. However these files also contain sophisticated iXML metadata which explicitly associates them as a family, and labels their tracks, without relying on the filename. If all your target systems support iXML, then Monophonic is a good choice. In some cases you may want to import the audio files directly into an editing system, without copying or splitting the files, and again, here Monophonic may have some benefits. However, do not be fooled into thinking that Monophonic files will always be easier to ingest to mono file software. For example, in an Avid System, all ingested media is always copied (and split), and at the time of writing it is better NOT to feed mono files into Avid, since they do not communicate the 'family' grouping of the channels as well as a polyphonic file. So, in many cases, especially for large scale movie production, Monophonic is not the best choice. This may change in the future as more systems adopt the iXML protocol which clarifies all the metadata regardless of file format.

Polyphonic
In this mode, all of the armed tracks are writted into a single Polyphonic, multichannel file which contains interleaved audio data. There are several potential benefits to this approach. In particular, there is no ambiguity about channel grouping, since all the channels are carried in a single file. However, depending on whether iXML metadata is employed, and whether you are recording consecutive channels (eg 1,2,3,4 rather than 1,2,6,7), polyphonic files can lead to ambiguity in which input is written into which interleaved channel. Once again, iXML clearly documents this, but if you are feeding non iXML systems, you need to be aware of this. Importing Polyphonic files into Avid is very smooth, since Avid will copy and split the files, and at the same time create a single multichannel Masterclip named 'scene/take' from the embedded metadata.

Dual Polyphonic
In this mode, MetaCorder will record a pair of polyphonic files, containing selected channels. Historically, Dual Polyphonic mode was created to accomodate limitations in Avid's Polyphonic file ingest, which was previously limited to four channels. In this case a recorder could prepare 2 x 4 channel files to import 8 tracks into Avid. In modern Avid systems, the 4 channel limit does not apply. There is another reason to use Dual Polyphonic, and that is where you would like a specific workflow to limit the amount of data to be ingested into Avid. For example, you may choose to record 4 channels of discreet sound into one Polyphonic file, and at the same time create a mono or stereo mix into another file. In this workflow you may choose to only ingest the mono or stereo file into the Avid, simplifying the sound for picture editorial, and limiting the ingest time, and storage requirements. If your production is using Gallery's MetaFlow, they will be able to automatically relink the other 4 files later on for Audio Post once picture cuts are turned over.

It is not possible to generalise on what your choices should be. However you must take the time to evaluate the workflow you are feeding and make the correct choice of format and file mode. If in doubt, use Polyphonic mode, limited to 4 channels, since this is a common configuration and can be handled in most fairly modern post workflows.

NOTE: Audiofiles are limited to 2GB in length, which is about 2.5hours at 24 bit / 96k mono, but much less for a polyphonic file. If you are planning very long recordings, you should use Monophonic mode, and be aware of the file size limitations. It may be a good idea to 'break' the recordings periodically when you have the opportunity.

Media and Project Setups
MetaCorder supports a very wide choice of drives, and you should make a similar judgement and decision to determine what type of drives to use. You will most likely be recording to an internal hard disc, and possibly an external, and maybe mirroring to a slower removeable media like DVD-RAM. Alternatively you may choose to record to hard disc, then burn a DVD-R or CD-R when turning over a sound roll. In any case, you need to select at least a Primary Record Drive, and optionally a secondary Record Drive (which has exactly the same data written to it in real time with the primary). See later for information on Mirroring.

MetaCorder takes care of all your file management, and essential to this function is entry of a project name. This will create a master folder on your drives, into which the soundrolls will be written in their own folders. So, enter a name for your Project in the 'Active Project' field.

Let's go for a take !
Now that the basic settings have been made, you are ready to go. You need to arm at least one track using the 'REC' buttons on the input channels, and then you can press the 'Record' button in the transport section. This will create the folder hierarchy on your drives, create the file(s) and start recording incoming sound. Press Stop and you are done. You can now switch to the SoundRoll panel in the metacorder window (click on the tab underneath the duration display), and play back your recording. At this point we have not setup the timecode reader, so it will probably have a timestamp based on the Mac clock.

Introduction to MetaData
All MetaCorder recordings are rich in metadata, which will communicate vital information throughout the workflow following your recording. Modern workflows rely on accurate and detailed metadata to provide a smooth transition through telecine, picture editorial and into audio post. It is your responsibility to enter correct metadata as you record, for the benefit of the production as a whole. Fields like Scene and Take are fundamental, and you should be very careful to enter these accurately. Entering leading zeros in the scene, take, or soundroll field will be respected when the value increments, so enter 01 for take 1 and it will automatically offer 02 when you press the up button.