Over the past while we have been talking with a number of people looking something like our frame accurate video review and approval, but for audio.
For some it was a result of a need to review voice-overs. Others were working with audio special effects. And still others were working with longer form content such as background music or podcasts. We wanted to create a solution that would well for all of these use cases and to work as well on everything from mobile phones all the way to the beefiest of desktops — just like the rest of ScreenLight does.
As of last week, ScreenLight supports pinpoint accurate audio review and approval.
Upload audio files and watch as they are automatically encoded for preview on mobile phones, tablets and desktops without requiring your users to install additional applications or plugins.
Thumbnails for audio files show the rendered wave form to provide a visual reference to more easily differentiate your audio files.
For people with more exacting needs, it is possible to disable the proxy file from being generated. In this case, the uploaded file itself will be used for playback. While this does allow for more control of the playback experience, not all browsers can play all audio file formats. In general, audio proxy generation should be left on unless you are more interested in reviewing the quality of the file rather than its content.
Recommended audio encoding specifications
For those people who do want to generate their own file for playback, there are a number of options to consider. Which is best will depend on the particular circumstances of your workflow and the capabilities of your reviewers. The key thing to remember with doing your own encoding is that just because a particular file plays back one browser does not mean it will playback in another.
Lossy formats
For broad browser support, lossy audio files are the only way to go. If you stick to these specifications, pretty much any browser that is capable of playing audio should be able to play the resulting file.
- MP3 or M4A file
- 44.1 KHz sample rate
- 16-bit sample resolution
- mono or stereo
When proxy generation is enabled, we will create an M4A/44.1KHz/16-bit file with at most two channels.
Lossless formats
While lossy formats are great for their broad support, the compression process can color the resulting file at some frequencies. For people reviewing the content of an audio file rather than its quality (ie. most people), a lossless format offers no benefit over a lossy format. To complicate matters further, there is no single lossless format that is supported by all of the major browsers. The best one can do is shown below.
- WAV file
- 44.1 KHz sample rate
- 16-bit sample resolution
- mono or stereo
Unfortunately WAV files are not supported by any version of Internet Explorer that we have tested. Somewhat perplexing in that WAV files are used throughout Windows going back decades. Nonetheless, that is where it stands today. So, if you need high fidelity playback for your reviewers, you need to ensure they have a browser other than Internet Explorer available to them if you want to use WAV. Naturally they can always be given permission to download the clip and can listen to it using Windows Media Player, but that then makes is cumbersome to add timecoded annotations.
Multi-channel
Multi-channel playback is possible in many browsers with M4A or WAV files. If you know the people playing back your audio files have a multi-channel system and you need to review files with more than two channels, you can. Generally most people will only have stereo playback capabilities in which case uploading multi-channel files is wasting storage space and means giving up control of the mix being heard in playback.
When proxy generation is enabled, files will be down mixed to stereo.
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