WaveConvert Pro 2.3 and BarbaBatch 2.1

WaveConvert Pro 2.3 and BarbaBatch 2.1

Introduction Audio File Input and Processing Sample Rate Conversion and Compression Dynamics, Bit-Rate Conversion, and Extensibility File Output Performance -- How Does It Sound? Picking A Winner

Even more so than low-sample-rate files, low-bit-rate files have long been the bane of multimedia and game audio developers. Simply put, most 16-bit to 8-bit file conversions sound awful. In addition to the loss of 48 decibels of signal to noise ratio, the reduction in amplitude resolution almost always introduces quantization noise. This introduced noise is most noticeable in quiet passages of music or in the spaces between words of speech files. Both programs have many useful tools for dealing with these problems.

Both tools offer great flexibility, allowing you to limit peaks without normalizing and vice versa. For instance, suppose you have a dialog between two characters that contains both whispered and shouted lines. For clarity and ease of use, you've cut up the dialog into separate files, all of which need to be converted into 8-bit. In this situation, you'd add some gain and increase the signal-to-noise ratio prior to conversion. However, if you normalized these files, the whispers (not to mention background ambiance) would end up disproportionately loud, and the flow of the dialog would be lost. Instead, you'd want to maximize the files by adding gain and using the peak limiter to prevent clipping, but leaving the normalization off to retain the relative volumes between the lines. This approach will boost the overall perceived volume of the dialog, and thus it's post-conversion signal-to-noise ratio, while leaving the dynamics intact.

Normalization and maximization do not, however, address the issue of quantization noise in quiet passages. Fortunately, both programs have a noise gate to deal with this problem. A noise gate looks for signals that fall below a certain volume (as quantization noise typically does) and then processes these low-level signals. WaveConvert Pro provides a noise gate with two settings, hard and soft, which silence quantization noise quickly (with hard) or more gradually (with soft). WaveConvert Pro also supplies a rumble filter for removing very low-frequency noise, such as HVAC noise, from recordings. For higher sample rate files (down to 22KHz), WaveConvert Pro offers a noise shaping and dithering scheme called IDR (Increase Digital Resolution). Although I can't remember ever using 44KHz 8-bit files for anything, 22KHz 8-bit files are still a common format. BarbaBatch offers only noise gating and simple dithering features, but the noise gate has more adjustable parameters (Figure 3). This allows for greater flexibility in dealing with low-level signals that can't be altogether removed, such as room tone.

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Figure 3: The 'Define New Conversion' dialog box in Barbabatch.

As I mentioned, only WaveConvert Pro can be extended with DSP plug-ins. These external plug-ins include L1 (a high-end look-ahead peak limiter), C1 (a compressor/gate), Q10 (a multiband "para-graphic" equalizer), TruVerb (a digital reverberation and room simulation processor), S1 (a stereo enhancer) and others. WaveConvert Pro allows you to enter multiple plug-ins and even multiple instances of the same plug-in into the batch process. All settings and the order of the plug-ins are saved in both the settings files and the Joblist files.

WaveConvert Pro includes the full version of the AudioTrack plug-in (Figure 4), which contains a four-band para-graphic equalizer combined with a compressor and noise gate section. AudioTrack adds a tremendous amount of depth and control when used in conjunction with WaveConvert Pro.

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Figure 4: AudioTrack's main control surface.