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 ...

This is the first entry out of a series of posts, where I compare various aspects of popular podcasts. Part 1 is about file formats, bitrates, samplerates, channels, size, length and filenames.

The selection is based on Flattr podcast charts (mostly german), iTunes Store Top 10 Podcasts (english, german), podcasts by public radios (english, german) and some random ones to get more diversity.

List of Analyzed Podcasts

Here is the list of podcasts with links to the analyzed episodes, the available file formats and filenames (only for one format):

Last weekend, 15. + 16. October 2011, the first austrian podcast barcamp (#pccvie) took place in the charming sektor5 coworking space in Vienna. We had really inspiring discussions with many local podcasters and technicians, for some detailed reports in german see Podcastcamp 2001 by Nico Grienauer and Podcast Barcamp: Ein tweetiger und booiger Rückblick by Robert Lender.
I just want to add some thoughts to the discussion about enhanced podcasts and will list some practical tools.

Enhanced Podcasts

It seems that more and more podcasters try to create enhanced podcasts, where additional metadata like chapter marks, hyperlinks or images, ...

After a long, nice summer and few blog posts, it is time to present the current team behind auphonic. At the moment we are two core developers and maintain strong collaborations with three institutions here in Graz.

UPDATE: please see About Us for the latest version!

Core Team

Georg Holzmann

Georg is an audio engineer with passion for machine learning, signal processing, everything related to audio and computer music, open source software, web development and much more.

Discussions and repeating questions from podcasters led him to the idea of an automatic audio post production web service, this was the birth ...

After recording a podcast or speech audio, it is usually necessary to modify the recorded levels. This post illustrates how to normalize the subjective loudness and how to compress the dynamic range (= difference between the loudest and softest sounds) of an audio file.

Loudness normalization is one of the most common misunderstandings in audio post production. Many people use peak normalization, which ensures that the maximum peak (= the maximum value of the audio data) reaches a specific level. However, the human perception of loudness does NOT depend on peak levels, therefore peak normalization is mostly useless. Recordings should ...

Many different audio file formats exist for storing recorded audio data on a computer system. This post compares multiple file types and gives suggestions on which formats and bitrates one should use, especially when producing podcasts or other online audio.

We also added two listening examples to compare MP3, AAC and Opus files at various bitrates.

If you just want to see some practical tips, skip the description and read the conclusion.

UPDATE 2017:
The original article was updated to include the new Opus audio codec, concrete bitrate suggestions, audio examples at various bitrates and other recent developments!

Types ...

Some weeks ago I presented auphonic to the advisory board of the Science Park Graz, the local version of the Austrian incubator network AplusB.
Fortunately I am happy to announce, that the jury enjoyed the project and therefore auphonic is now part of the Science Park.

What are incubators?

AplusB (Academia plus Business) is the Austrian hightech incubator network. These incubators are linked to academic institutions, in my case the universities in Graz, and they support the development of technology-based projects for a period of 1.5 years.

Here a more detailed (and little bit cryptic) self-definition from the ...

As a Python or Django developer, various WSGI and webservers are available to deploy an application. A very fast, lightweight and relatively easy-to-install solution is the combination of Nginx, the high-performance HTTP server, and uWSGI (see benchmark of python WSGI servers). Furthermore, virtualenv and Fabric are invaluable tools to handle Python dependencies and to automate deployments.

This tutorial describes how to setup a Django 1.3, Nginx and uWSGI stack. My OS at the time of this writing was Ubuntu 10.04 LTS.

Installing all requirements

First install all the handy python tools, if you don't have them already (maybe ...