Category archives: Audio

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A few days ago a discussion in the Freak Show podcast pointed to an interesting BBC research project to render audio waveforms in the browser.
We now added a new output file format (Waveform Data File), which is generated by the open source tool audiowaveform and can be used to display interactive audio waveform data using the Peaks.js java script library. Here is an example screenshot:

(image from BBC R&D blog)

The tool includes features to zoom in waveforms, to mark segments in audio files (could be interesting for chapter marks) and can be easily integrated ...

A few days ago we added audio processing statistics to Auphonic productions, which display details about what our algorithms are changing in your audio file.
Some classifier results and processing steps are also shown directly in the player audio waveform and all statistics can be exported via the Auphonic API or the new output file format Audio Processing Statistics.
This article explains how to use and interpret the Auphonic Audio Processing Statistics.

UPDATE 2017:
Some information here is outdated - please see the documentation of our new audio processing statistics and inspector instead: Auphonic Audio Inspector Help

Statistics Tables ...

Do you know what's great about text? It's really easy to find stuff! You just do a quick search on that website you bookmarked last week, and boom! – there is the name of that book that you had read about, but whose title you had forgotten. But on the downside, text is not always the best medium to consume information, for example while you are driving a car. That's why we like podcasts: you can listen to them while you are driving, walking, exercising, etc. Podcasts keep your hands free and your eyes on the environment around you.

The ...

Finally we found some time to collect a few listening examples for our audio algorithms – thanks to all the people who provided audio files!
Everything is processed automatically and you can try Auphonic yourself with the unprocessed files and will get the same results.

The official Auphonic Audio Example page is here: Audio Examples.
We will extend this page with further examples, so let us know if you have some great ones!

Listen to the following examples with headphones to hear all details.

Global Loudness Normalization

Our Global Loudness Normalization Algorithms calculate the loudness of your audio and ...

Have you ever wondered how loud your audio productions should be? So have we, because it's a quite tricky question to answer!

On the one hand, you want to make sure your productions are loud enough. For example, they should still appear at a reasonable level in noisy environments (car, airplane, etc.), and their loudness should be comparable to that of other programs, no matter whether those are produced by yourself or by others.

On the other hand, you certainly don't want to compromise sound quality for sheer loudness. We have discussed in Audio loudness measurement and normalization with ...

We are very happy that Opus, an exciting new open audio codec, is now officially standardized by the Internet Engineering Task Force (IETF). Opus is particularly interesting for podcasts, radio books and internet audio in general due to its suitability for both, music and speech, and its outstanding sound quality at also very low bitrates.
In this article, we will listen to some examples of the Opus codec in action and have a closer look at the codec and how audio producers can benefit from it.

Opus Logo

Why Opus?

Opus is a lossy audio codec that has ...

Have you ever wondered why commercials sound louder than your favorite TV shows? Or why you have to adjust the playback volume on your television when switching between channels? The answer is that until recently, there was no standard way to measure the perceived loudness of sound recordings. Instead, audio productions were (and still are) normalized to peak levels, which do in no way determine how loud a signal is.

In this article we will discuss the EBU recommendation R128, a new and open standard for balancing audio programs according to their actually perceived loudness.

EBU R128 logo

This recommendation marks ...

The last metadata format in this comparison series will be metadata for AAC audio files, which are usually included in an MP4 container (see MPEG-4 Part 14). MP4 audio files can have various file extensions, most commonly m4a, but also mp4 or m4b (for audio books).
So let the confusion continue ...

MP4, AAC and iTunes-style Metadata

The MPEG-4 container format is based on Apple's QuickTime container and each MPEG-4 file must have a major file brand. For example, an AAC audio file typically lists M4A as its major file brand. See AtomicParsley for a description of the ...

A new week - a new format: this weeks post is about metadata in Ogg Vorbis audio. The metadata container for these files is called Vorbis comment, which is also used in the FLAC, Theora and Speex file formats.
For a general introduction into audio metadata see e.g. the previous post in this comparison series: Part 2: MP3 Metadata (ID3 Tags).

The tool to analyze and create metadata for Ogg Vorbis files is called vorbiscomment.

About Vorbis Comment

Vorbis comment is a relatively simple metadata format specified by Xiph.org, similar to ID3 tags for MP3 ...

The second post of this comparison series is about metadata in MP3 files. Metadata allows information such as the title, artist, comments, cover image and other information about the audio to be stored in the file itself. MP3 files use ID3 tags and in the following I will compare common tags, image details and ID3 versions of various popular podcasts.
The analyzed files are the same as in Podcast Comparison, Part 1: File Formats and Bitrates.

Nice open source tools to analyze MP3 metadata are for instance eyeD3, soxi, mp3diags or EasyTag.

ID3 Versions and Used ...