The Sonnox Fraunhofer Pro-Codec is a real-time mp3/AAC encoder/decoder for mix and mastering engineers to audition and compare the differences in the sound of music mixes when played through up to five different, simultaneously running perceptual audio codecs. With the goal of speeding download and/or streaming times by drastically reducing (data compression) music file sizes, perceptual coding by definition, removes audio that is otherwise masked by louder sounds in the same frequency range(s). Real-time A/B auditioning enables engineers to switch seamlessly between a codecs' output stream (the engines that do the compression) and the original audio input glitch-free and without latency.

Working this way eliminates the time-consuming cycle of encoding a mix to mp3/AAC, previewing, tweaking and re-rendering. You also now have control over encoding parameters such as codec type, constant bit rate or variable, quality and some ID3 metadata tags such as bit rate, codec type and settings, date and time, and manufacturer messaging. This is far and beyond basic mp3 encoders that come with most DAW software suites.

The Pro-Codec encoding process is applied after the last stage of mixing or mastering when the mix file is now at CD-quality--44.1kHz sample rate and dithered to 16-bit. But there are provisions to directly encode from sample rates up to 192kHz and 24-bit depths with appropriate warning messages shown in red to indicate Pro-Codec's internal processing such as re-sampling or dithering to 16-bit that will be required before encoding.

All major codecs, including: mp3, mp3 Surround, AAC-LC and HE-AAC are included along with the lossless codecs mp3 HD and HD-AAC.

Since Pro-Codec is real-time, you are free to optimize and make compensating adjustments to your mix and then trim bit stream levels in the software to prevent internal codec clipping--a common source of bad-sounding mp3s--there are bit stream level meters that clearly display the possibility of decode overloads. A clever feature is the ability to "drag" and copy the indicated over level (in dB) from these meters directly to the trim faders. In this way you have easily and quickly maximized the codec's headroom exactly--awesome!

Once you're happy with your codec setup, store all the settings just like any user-modified plug-in preset and start rendering. Rendering is real-time and as simple as arming a codec channel, pushing the record button and playing the song in your DAW. Pro-Codec will simultaneous render up to five different data compressed files at the same time--even the same codec set to different bit rates for multiple formats--such as the different requirements of iTunes, game audio or streaming Internet radio feeds.

Pro-Codec also has an off-line mode where stored presets can be reused and applied to its batch encode processor. Lastly, Pro-Codec has a full decoder mode where any data compressed file is converted to standard non-compressed audio formats such as .wav or .aiff and 16 or 24-bit depths. This feature is great for importing songs in compressed formats that are not supported by your DAW. Both off-line encode and decode are "drag and drop" easy--drag the file right onto the plug-in GUI and it happens!

I especially like Pro-Codec's large FFT display where you can see the original input signal (in yellow) and also the Diff or difference signal (in red) between the encoded output and the original. The green Noise-To-Mask Ratio or NMR indicator shows when there is a possibility that encoder noise may be heard in the audio after encoding (changes to red)--more common for low bit rate audio streams. You can listen to what will be removed and ascertain its affect on the finished sound. With certain perceptual codecs and settings, this Diff signal's constituents and level compared to the source is NOT necessarily indicative of final quality--even when the audio file undergoes a huge file size reduction!