File Formats for Voice Over Audio Explained
6 Tips on using audio file formats when adding Voice Over to your project
When it comes to using audio, do you know your ‘lossy’ from your ‘lossless’? Do you know whether a voice over file should be in mono or stereo? Based on my experience as a Voice Over, I thought that it might be helpful to provide some tips on audio formatting, when you’re adding Voice Over to your projects, some of which you’ll already be familiar with, others you may find useful.
Rob Bee of Bee Productive audio services has also very kindly contributed his specialist audio engineer knowledge, in this Q&A style blog…
Q1: What are the most commonly audio file formats used on Voiceover projects?
A: Lindsay – This depends on what it’s being used for (covered later in this blog), but the most requested file types are wav, mp3 and aiff.
Rob – At it’s simplest these are the 3 main file types. But there are more details that you may need, covered later.
Q2: Does it make any difference to the file types needed whether using a Windows PC or Apple Mac?
A: Rob – It used to be that PCs wouldn’t play aiffs and Macs wouldn’t play wavs, but this is no longer true, so wavs and aiffs become interchangeable. Most people will ask for wavs as the file size is slightly smaller than aiffs.
Q3: What’s the difference between these different file types?
A: Lindsay – A wav is ‘lossless’, which means that the quality is preserved. An mp3 is ‘lossy’, meaning it’s been compressed to reduce the file size (to make for faster loading online, for example).
Rob – The difference between wavs and aiffs is down to the way the audio is encoded. Think of the difference between DVDs and Blu Ray and you’re somewhere in the right ballpark. Wavs and Aiffs both capture audio information as it’s presented to them whereas mp3 ‘interprets’ what it’s given. As Lindsay says mp3 is lossy. It takes the audio information that it’s presented with and them loses the bits that the human ear can’t hear (and some other bits) and then applies some algorithms to hugely reduce the size of the file.
Q4: So, which file type should I ask the Voice Over for then?
A: Lindsay – If you or your videographer/producer/editor are planning to edit the audio in any way, either by separating clips, or adding background music for example, then it’s probably best to ask for a lossless file such as a wav or aiff, as otherwise you may lose some of the audio quality. Once you’re happy with your edit you can then re-save it as an mp3.
I often tend to send my clients an mp3 as well anyway, for ease in them being able to quickly take a listen to the file/s before signing off, as a wav can take longer to download.
Rob –Yep. Wavs and mp3s are safe bets. The VO or producer will have saved your audio as a high quality file, so converting to another format should you need it will be quick and painless.
Q5: Does a particular form of media change the file type needed from my Voiceover?
A: Lindsay – Yes, which is why I always ask this question before we record:
Online Corporate Video:
Generally your finished edit is likely to be mp3, but you may want a .wav from the VoiceOver if you need to edit it at your end too (see above). Standard recording settings: 44100Khz (44100Hz or 44.1 KHz) 16bit mono. Don’t worry about this latter bit – I just need to know that your project is needed for online video.
DVD or Broadcast (such as a commercial or documentary):
wav or aiff – but the Voiceover’s recording settings will need to be set to higher quality 48Khz 16bit mono.
Online podcast, or anything else online:
As Online Corporate or Commercial above…
Requirements can be hugely varied but generally these are much smaller files. Check with whoever is responsible for uploading the audio onto your system – engineer, IT or facilities department, telecoms provider etcetera – or your system manual.
Rob: It can get a bit complicated. As Lindsay has explained there are different requirements for different types of jobs, so simply saying wav/aiff/mp3 may not be enough. Most VOs and producers who have been at it a while will be able to take an educated guess as to exactly what format they should send but with IVR/on-hold stuff it’s difficult to guess.
With Wavs and Aiffs there are 2 other numbers needed – the sample rate and bit depth (48KHz 16 bit for example) and with mp3 there’s one number – Bit rate (320kbps is a high resolution bit rate) With all these the bigger the number the better the quality.
If your project is IVR/on-hold and you need wavs there are further complications. Lots of telephony companies use a different encoding for wav files. They may ask you for a-law or u-law (mu-law) encoded wavs. Just pass this information along to your VO or producer and let them worry about getting it right! You may also be asked for .vox files, ogg files or one of many other file types. But please bear in mind when you listen to the files that have been produced for your telephone system that these low-resolution files are designed for use over the telephone. They may not sound very good if you listen to them with your computer speakers, but they will sound fine over the phone.
Q6: Should the Voice Over file be in stereo or mono?
A: Lindsay – There are a lot of misconceptions about this one, but a Voice Over file is recorded with one voice usually, so it should be a mono file.
Rob: 98% right! I do remember a long time ago having to supply a VO on an audio CD. So the VO was recorded as a mono file, but produced as a stereo file to burn straight to CD. That never happens any more.
Q: I’m not sure about any of this – help?!!!
A: Lindsay – No worries…just ask!
Thanks very much to Rob Bee for providing his extra special audio expertise. You can find Bee Productive by visiting his website here: http://beeproductive.co.uk