Audio Recording

If you like to know how to master your own tracks properly at home without asking for professional assistance; then some of the guides here are definitely helpful to you. This talks about how to use dithering and sample rate conversion application properly during your audio mastering stage. Tools alone (such as discussed below) cannot solve all the mastering issues; you need to have a good studio monitoring system and studio room acoustics.

The input to mastering stage is the product or output of the audio mix down (done by the mixing engineer). To optimize the quality of your final audio mastering output, you need to ensure that your audio mix down complies with the rules discussed in this tutorial: “How to Prepare and Submit the Mix to Audio CD Mastering Studio“

Assuming you have the correct audio format for mastering that complies with the above requirements; then you are working with the recommended audio resolution format which is 24 bits/96Khz. If you need to know if you are doing the mastering process correctly, examine the flow chart below:

As an overview (especially for beginners):

1.) It all starts with the audio mix down (as discussed previously).
2.) “Trimming” means that you will cut unnecessary portions in the start and end of the audio (such as long silence) so that it will have a reasonable length.

3.) EQ means to shape the quality of the audio by cutting and boosting important frequencies for best results. The next step is to apply compression. Or, you can combine the EQ and Compression adjustments simultaneously are using a multi-band compressor. Read this multiband compression tutorial for details.

4.) After this, you can now use limiter to maximize the volume of your mastered track. Common tools are L1 waves.

5.) Finally this is where you can start using Sample rate conversion and Dithering techniques to complete the mastering. It is important that sample rate conversion (SRC) should come first before Dithering because dithering reduces the bit depth to 16-bit and during SRC it is important to retain the bit depth at highest resolution for quality reasons.

To implement sample rate conversion:

1.) You can use Voxengo R8brain. This is one of the best sample rate converters for audio mastering and it’s free. You can download it here: www.voxengo.com/product/r8brain/

2.) Use this tool to ONLY convert a higher sample rate (example 96 KHz) to 44.1 KHz when mastering. It is recommended not to use its dithering feature so just set the output bit depth to be same with the input audio (“unaltered” bit depth). Also set quality to “very high”.

To implement dithering correctly:

1.) The input audio in the dithering (last stage) is the output of the sample rate conversion. You can use a lot of quality dithering tools such as Waves IDR, iZotope Ozone, Pow-R, MegaBitMax Ultra. See these in Google if you like to add it to your DAW mastering software.
2.) The job of the dithering is to convert a higher bit depth (e.g. 24 bit) to lower bit depth such as 16 bits. Using the quality tools mentioned previously ensures that the dithering system employs some noise shaping features that will retain the original dynamic range and quality. This makes the 16 bit output quality to be the same as it was a 24 bit audio (before dithering). Poor dithering software does not use noise shaping or does employ optimized dithering algorithm, as a result the converted audio does not exactly sound its best after conversion. Unfortunately, there are no really “free” quality dithering plug-in (which are accepted by professional mastering engineers) as of the time as I wrote this tutorial. If you know, kindly correct me and post a comment.

So why you need to use dithering and sample rate conversion? The audio format during the mastering process is around 24-bits/96Khz, so you need to employ dithering and sample rate conversion to convert that resolution to 16 bit/44.1Khz which is the standard audio format used in CD and MP3 players.