1 What are the most common file formats used in audio?

· The first type of files are audio media only files, containing only the recorded audio clips.

These formats include AIFF and AIFC (Developed by Apple), WAV (Developed by Microsoft), Broadcast WAV and a number of proprietary formats.

· The second type of file contains audio media and can include video, EDL, editing information and additional meta data. These formats include OMF1, OMF2, AAF, and AES31. Audio file formats commonly contained in the OMF format include AIFF or WAV. In future formats such as AAF there is mention of including extra complex picture information such as telecine "Pan & Scan", colour grading notes, etc.

2 Why do we need a common interchange format?

· Saving of time and money, by removing the need for EDL conforms.

· Double handling of audio material and editing time.

· Transfer flexibility of product between different workstations.

· Ensure authenticity of authorship by receiving a project that is identical to the final cut created by the picture editor and director.

· Preserves quality by using all digital transfers.

· Saves time in having to dub all source material to time coded formats.

· Mixing facilities can receive audio from multi-platform workstations.

All these points are very beneficial in postproduction, if it all works! Credit should be given to Avid for initiating the file interchange process with the OMF format.

3 What is required to interchange file formats?

File exchange between platforms relies on three completely independent pieces of technology.

· The first aspect is the disk or the format that contains the media. You can't exchange with some body unless both parties can read common media. A number of different disk file systems currently exists. Examples of disk file systems are Fat16, Fat32, NTFS, HFS (Mac), and a dozen or so proprietary systems that are out there on the market including Fairlight, Akai, etc. If you want to read a file created by some body else the first thing you have to do is be able to read the disk that they put it on. Then if you want to be able to send media to them you have to be able to write it to a disk that they can read.

· The second aspect is the audio file format, that is to say the file in which the audio is stored. Common examples of these are WAV, Broadcast Wav, AIFF, AIFC, and again lots of proprietary ones. For example Fairlight is able to read Akai's file format because they provided information about their file format and Akai can read Fairlight files because Fairlight provided them with information about their file format. AES31 uses the broadcast wave audio file format and uses Fat32 as its disk file format. OMF doesn't mandate either of those things. It allows you to use any disk file system and any audio file format. This is one of the reasons why it becomes so complicated.

· The third aspect is the audio EDL format: the Edit Decision List format. In digital audio workstations these are proprietary files in each companies case. In Protools it is called a session file, in Akai's case it is called an AKL file, in AES31 it's called an ADL, in OMF it's all part of the OMF file. These three areas must be examined and adhered to very closely.

4 Where are we at currently?

Even in the OMF format, there is not one confirmed standard. At present, across Sydney studios, there is a mixture of OMF1 and OMF2 files being used. For Protools, with the release of the Digidesign's Digitranslator, more and more OMF2 files are being utilised.

Currently the ABC, Beyond, and Tracks Television all use OMF1 file transfers.

Trackdown, Philmsound and Soundfirm (Farscape) have been using OMF2 with a good success rate. Simon mentioned for the last 4 years Yoram Gross Studios has used OMF1 and OMF2 on all of their television series projects: transfers from Avid to Protools.

Whether OMF1 or 2, the use of these formats seems to be growing and gaining supporters along the way. In the list below are projects that recently have utilised OMF1 and 2 transfers. Provided by Trackdown and Tracks Television:

5 What are the problems reported with the OMF process?

Where do we begin? Both manufacturers and operators have experienced a number of problems.

Manufacturers problems: One of the problems experienced, centres around the varying versions of software release. As most OMF files are currently created on Avids, independent sound facilities are now expected to handle OMF files created on multiple versions of Avid software. Ranging from version 6, 7, 8, and now 9, either Mac or NT. Fairlight, DSP, Protools and AMS all at one time or another have been able to open OMF files successfully, then all of a sudden files won't open. A new Avid software version release! It is then the job of the DAW manufacturers to play catch up with this new software release by modifying their software.

Comments: Digby: - DSP "When Avid were running Version 6.5 we were a 100% compatible and every one thought it was wonderful. Then Avid Version 7 came out. We didn't change our software we didn't change a thing, but all of a sudden the files didn't go across for various reasons. It's easy to point the finger and say, it's not our fault, but…. I understand both AMS and Fairlight also experienced similar problems. We think we are doing everything right. We have the published spec for OMF, we follow it completely, then some thing changes from some one else and it doesn't work. This has been the story with OMF and why there have been problems with the format. I was at an OMF developers conference two years ago and the highlight of the week was a report from a feature film editor. He was to come in and tell us about his success with OMF. When he got up to speak, he eventually said OMF transfer was full of problems. "

Andrew: - Fairlight "I think what they've really changed are the bits of OMF that they're implementing. OMF contains features that are not universal to the audio industry. So if a particular company uses those features they may not be able to translate their audio into another format, or rather somebody else may not be able to get it out of the OMF format, as in group clips and sub clips. OMF also allows you to use any sort of processing you like. In theory you're supposed to define what this is, but that's not really possible. This is processing that takes place in real time on the audio. For example there is a thing called a group object and you can specify any algorithm you would like to operate on that group. So the algorithm might mix them all together or it might play only the one with the most recent date on it. There are options and they are not specified by OMF, OMF just says you can add your own effect here. That is one of the biggest problems."

TM: Should the specifications for OMF be more stringent?

AB: Well there are arguments on both sides. You could say, lets reduce it to the most reasonable common denominator of features that most workstations have. This would result in a better success rate, but you would have people saying, well I want to do more on my workstation before I transfer it across. I don't want to render all that to the audio because I want the next guy down the line to have the ability to unpick it if he wants to. This precise argument was expounded in great detail during the AES31 development. Now that's the other side of the coin in most respects. It's not sponsored or owned by one company. It's not subject to anybody's contractual control. It's simply a standard that's been created now and ratified.

6 Why does all source material have to be stripped with time code?

The importance of time code referenced source material can't be emphasised enough. OMF file transfer is a thing of beauty when it works, but when it doesn't work it can be a disaster with both editors and sound post crew pulling their hair out. There must always be a fallback position of the EDL and referenced source material for use in a conform session. With more documentaries and projects using multi-format non-time coded source material, DVC Pro, DVCAM, if the OMF doesn't work this requires the audio post facility to have access to mulit-format playback decks, which many don't have, and if they obtain a machine, the audio has to be manually re-sunk.

Comments: Philip: - Tracks

"It is very important that you have a reference EDL to fall back on if the OMF does not work. All source material must have been striped with time code. I would like to see the day when it isn't necessary but at present you must have an EDL to fall back on if there are problems.

The practice in a lot of boutique editing cottages of digitising material off DV tapes with out time code can create real problems if the OMF doesn't work.

The same goes for material digitised directly off CD. This is really not a good idea at the moment as it means you are totally dependent on your OMF file and if it doesn't work you are really up the creek. You can't even go back to the EDL because there isn't one.

These are the very jobs that have booked one day in the studio to do their mix and if you spend the first half of the day trying to open an OMF file with out success you've really blown it.

You need to know that there is an EDL somewhere, there are time coded source reels somewhere, and if the OMF really doesn't work you can make the decision to go back to the EDL and re-conform the project.

The other point to mention is that the EDL also has to be readable. Today a lot people don't spend any time sorting out their EDL because they assume the OMF will work. So you ring the picture edit suite for an EDL and you receive a disk that is unreadable, or the wrong format or missing half the edits you require.

There was a time when EDLs were important and people would spend time to make sure that they would work."

Simon: - Trackdown

"Before you even talk about the translations issues, you must discuss the day one issues. The procedures that are going to happen in the edit room. I want to use a piece of music.

Don't take it straight off a CD. First dub it to a DAT with time code, it now at least has a reference.

If you are doing digital transfers they are all to be done at set sample rate and stick to it, 44.1kHz or 48kHz. My preference is 44.1 kHz. The amount of time that can be wasted in sample rate conversion can be a real pain. "

7 What are some of the problems originated in the picture editing facility?

Comments: SimonLeadley: - Trackdown

"I have visited a lot of assistant editors digitising stations. They have twenty drives running right next to them, a pair of speakers about an inch tall, and one of the speakers doesn't work or is blown.

I recently visited a facility from where I had received an OMF. The visit was to confirm the audio quality out of the Avid. The audio on the workstation was completely distorted. Both tweeters in the speakers were blown. There was no option other than to go back and re-digitise all the audio.

There has to be some one who has to say, if you go this route you cannot expect some one with little or no experience to deal with this. For the simple reason that this is stage one and you're potentially carrying this audio to the end, being the final mix.

What is worse is you receive the program right at the very end, you discover that there is a major problem that been there since day one and you have five minutes to solve it before it is to be delivered to SBS, Channel 9 or who ever.

You can throw up your hands and say it is not my problem, and of course you know that never happens. It is your problem and you have to deal with it. In the past we had full time transfer people who would look after the audio and transfers. That role has become part of the editing assistant's duties. They should be given the tools to do their job properly.

The assistant editors role is crucial. They can save you time, money and grief."

Phillip Purcell: - Tracks

"We tend to build up a relationship with the editor who digitises all material, edits, and creates the OMF file. Quite often we will go over to the edit suites and sit in with them while they create the OMF file.

The role of the editing assistant is really important. As we don't use charts any more with DAWS, the naming and logging information on the audio clips that's done by the assistant editor is extremely helpful. As these same clips are transferred across through the OMF process. It's incredibly useful as you can see what is coming up while you are mixing. When you go through EQing clips on the Fairlight and you see a clip, Joe Blogs at a certain location, and then discover you have just mixed and EQed the same guy two scenes earlier. It is very easy for the mixer to copy that EQ curve on to all clips of the same name in that project.

These picture workstations almost have to be audio mastering machines as the digitised audio created by them is used in final mix."

8 How important will networks and the internet be in the future?

The ever-increasing use of networks and the Internet can be seen daily. Tele-streaming is currently being used by Cutting Edge in Brisbane to send program material for Beastmasters to Canada.

Mathew Wood, supervising sound editor for Phantom Menace recorded 1,500 lines of ADR on set in the UK into Protools on a modified G3 Powerbook, then sent the Protools session file over the Internet to Skywalker in the US.

As bandwidth increases it is becoming more and more practical to send files across networks.

Digby: - DSP

"The future with file transfer will be networks where you can read the files straight off a server. Networks are going to be vital in the future. Not just local networks, with the expansion of bandwidth, you will be networking between buildings, cities, even internationally.

You will also be networking between multi-platform machine. You will be pulling data live off a server and read it natively or translate it."

Andrew Bell: - Fairlight

"In future you will see more workstations being online in regards to both the Internet and internal networks and that is where the real benefits of file transfer capability will be seen.

Networking between multi platform workstations is being used today and will become an accepted practice, between audio and video. Turner Network Television in Hong Kong have a Fairlight Media Link server where different Avids export OMF1 files to the server and the Fairlight transfers the OMF1 file from the server directly onto it's hard drives.

Star TV in India also is networking Lightworks with Fairlights. Digital Post in Auckland, New Zealand have a PC sitting beside them in the studio which is networked with the Fairlight. With this PC they receive wave files from clients saying can you use this music or can you email me that voice take to me we recorded last week."

Phillip Purcell: - Tracks

"I would like to see it happen, but I imagine it would need everyone to have ISDN or fibre optical cabling. The idea of permanently moving hard drives and backup tapes around the place as we do now, is like the old 24 track tape days. With the advances in technology you would hope a faster way of file transfer would be possible. It would make sense to download OMF files over the net, even if it were over night. They would appear on your hard drive in the morning and you could open them straight away."

Simon Leadley: - Trackdown

"Networking will be very important. For the past four years at Yoram Gross's studio all of the projects have been done OMF over a network. The picture editors consolidate to a drive on the network somewhere away from the edit suite. The sound editor picks it up off the server on the network and translates the OMF file. It all works fine.

Even here at Soundfirm they have two servers on the network to transfer files. The other day I was working with one of the music editors on Bootmen. He needed access to a video clip. I went into the guys next door who are on the network, cut 50 second clip from their material, created a new QuickTime file, sent it over the network, and he then imported it into his session here. It was done with no hassle with in ten minutes.

If you had to go and get a dub of the scene or bring in a Beta SP it would have been a nightmare. Even in a mix session a director will want to change some thing, I will go to the edit suite change some thing and send the new file back across the network to the mix theatre. Simple.

We also have a hard drive on the network which is dedicated specifically for sound effects. This just hangs off the server.

I think you will see more and more networking between multi-platform machines. In regards to Internet when I was working on Mission Impossible 2 we were sending video files across to America. These were compressed files, about 80 meg, and sent across via a cable modem.

With Yoram Gross we send audio files back and forth to Canada via the net. With these dialogue files we usually compress them using MPEG and we can get something like 80 meg down to 10 meg."

9 How could the OMF process be simplified?

As OMF files are usually created by the editor at the end of a 12 to 13 hour day, the last thing they want to worry about is the extra work. Consolidation, stripping of audiosuite effects, EQ, level, time compression, etc.

This may be wishful thinking, but if the in the next Avid software release they could place another button on their "Create OMF" page which just says "export without audio effects". It would save a lot of time for the editors and reduce problems in sound post. Another idea would be to establish a practice of including an OMF technical cover sheet to be filled out by the editors and delivered with the HDD or Jaz drives that hold the OMF files and contain the following information:

· Type of machine created on.

· Software version.

· NT or MAC.

· Type of OMF 1 or 2.

· Sample rate.

· Exact name of the OMF file.

· Number of audio tracks in the OMF.

· T/C of first and last frame of audio, or T/C of Head and tail 2 pip.

· Name of operator who created the OMF and contact number.

The same procedure could take place my including a text only file on the same hard drive that the OMF file is delivered on.

Comments: Phillip Purcell: - Tracks

"The last thing an editor does at the end of his long day is to export the OMF files. Probably he or she really isn't in the frame of mind to be worried about the fine details of exactly how to create the OMF file. Which buttons to click and which options to select.

I think the more automated and more user friendly all that can be made, the better. Ideally this probably could be achieved through communication between both the picture and audio workstations manufacturers. Similar to a word processor, where you export as WordPerfect, Word7, etc.

In the Avid or Lightworks export menu you could have export as Protools, MFX, DSP, etc. The computer just does it. The picture editor doesn't have to think about it. All the editor would have to do is click the name of the audio workstation, turn the lights off and walk out.

At the moment the editor has to sits there agonising has he named it the right way, or has he put too many dots or commas in the name, or has he selected the wrong audio format. If he is buggered at the end of the day, these issues are the last thing he wants to worry about.

We often then come in the next morning and expect an OMF to open and it doesn't because one of these parameters is wrong. What's needed is a simple export software package that wraps up the OMF file. "

 

12 Will transfer of non-linear video file to sound post become standard?

The general consensus is that this is way off yet. The reasons why can be seen in the comments below.

Digby: - DSP "Video is far more difficult to transfer than audio, as with video you are almost always dealing with compressed formats. Once you are dealing with compressed formats you are not dealing with software but rather hardware and chipsets that compressed it into that format.

You can have JPEG cards that come from two different manufacturers and they won't generate the same JPEG format. This is because some boards will only read a subset of the standard. There are a lot of parameters you can also change. You are also dealing with a lot more data. We have had a number of requests to offer the ability to both import and export video files."

Phillip: - Tracks

"It would be nice to able to get a non-linear video file with the OMF to work with since a lot of post people are already using non-linear pictures. At the end of a project you would be able to back up the video file with the project as with automation. Particularly because we are about to enter new Digital TV formats, wide screen, 16:9, HDTV, etc. If a project is originated in a set format it would be good to follow this format through to audio post. Maybe non-linear video is a practical way of doing sound mixes in the future. Rather than having to get a reduction dub from high definition down to PAL standard television, as we most likely won't be running high definition in sound post. "

Simon: - Trackdown

"The new version of Protools 5 can use the ABVB board, which the Avids use and can do up to AVR75.

The idea is when they give you an OMF they will give you a drive with all the media on it and the OMF would play back the vision that has been cut as well. Theoretically it means down the track if changes are made to the vision you just get an EDL and that conforms the program to the latest version including the audio.

Personally, with most facilities in this country I can't see it being a convincing thing to do yet. It is quite expensive.

I think we are a way off from being able to have a standard video file format. At present an old Avid can't even read a new Avid file. This is due to different file formats, resolutions, chipsets and compression.

We are having enough problems with audio."

TM: And we haven't even mentioned digital television video standards and MPEG2 video.

Conclusion:

I was planning on writing a summary paragraph but I think Simon best summed it up:

"I think the problem has been in the past that a lot the manufacturers were terrified of the opposition and consequently, close relationships and communication between them in regards to standards did not take place.

They really need to look at how the MIDI standard was developed. If you bought a MIDI device at the back of every manual it had the MIDI spec and told you what all the controllers did. Every body benefited from that. There were no down sides.

This is what all the manufacturers need to understand. By making varied workstations open to communicate with one another it means that suddenly there is true competition and you can talk about why our system is better than some one else's. You are able to discuss the benefits like, this is a better editor because of this function. The end result is that you're not locked in.

You are able to work on some body else's project created in another format. If I am working on Protools and some body else is doing their dialogue editing on a Fairlight, that should be of no consequence what so ever.

We should easily be able to interchange our files. Manufacturers have too much to loose if they don't get involved in being able to freely exchange files. We are starting to get to that momentum point now where enough of them have jumped on board with this and are willing to release their computer codes that are required.

It will be a case of, if you don't jump on the bandwagon, you will be the one that misses out. We've seen this with open source code for computers.

Microsoft has rigidly stood by and said we are not interested in doing that. Apple opened their code for many things. Linux is doing exceptionally well.

People are saying, because we know what the source code can do we can add on to these systems and create far more powerful applications. Through this process we are able to develop standards.

The only way to develop a standard is if every body knows what that standard is. The moment you close ranks it is going to be a mess.

What might be beneficial is to establish a page on the ASSG website for sound post personal and sound post facilities to post their own comments on this topic.

Open lines of communication."

Tony Murtagh - tmurtagh@zip.com.au

Thanks again to:

Digby Richards from DSP

Andrew Bell from Fairlight

Simon Leadley from Trackdown Studios

Phillip Purcell from Tracks Television

Information Sources: Brett Chambers - Fairlight | Charles Tetaz - Digidesign | David Richards - DSP | John Marsh - Aus. AMS Beta Test site.

With the increasing trend of stand alone software packages (DSP OMF Connect, *Digitranslator, AMS Media Tool Box, Waveframe) expect to see a wider range of formats supported