Ogg

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Ogg
Vorbis logo
File extension : .ogg, .oga, .ogv, .ogx
MIME type : audio / ogg, video / ogg, application / ogg
Magic number : 4f67.6753 hex
OggS

( ASCII )

Developed by: Xiph.Org Foundation
Type: Container format
Container for: Vorbis , Theora , Speex , FLAC , Dirac , Opus and others
Standard (s) : RFC 3533
Website : xiph.org/ogg

Ogg is a container - file format for multimedia files, so it can simultaneously contain audio, video and text data. Ogg was designed with the aim of offering a free and unrestricted software patent alternative to proprietary formats for efficient storage and streaming of multimedia content . The ability to stream is the decisive design feature: Everything that is packed in an Ogg container can be streamed without additional adjustments. This distinguishes Ogg from formats that are either only capable of streaming in certain forms (such as Matroska ) or are not capable of live streaming at all (such as MP4 ). Ogg streams can be bundled and chained without having to adjust the individual stream.

The development of the container format is led by the Xiph.Org Foundation , which is also responsible for some codecs that compress the content in an Ogg container.

The best-known codec is the Vorbis audio codec , which is often simplified (or erroneously) referred to as Ogg, although Ogg is actually only the container format for the Vorbis-encoded content. Since 2012, the Vorbis successor format, Opus , has also been gaining ground , particularly in the professional broadcast environment in hardware audio codecs.

history

The development of the container format began in 1993 under the name "Squish", which however infringed trademark rights. Therefore the name was replaced by an expression from the computer game Netrek , which means something like to ogg: "to do anything forcefully, possibly without consideration of the drain on future resources" (for example: "to tackle something very energetically, possibly without considering the stress on future resources ”).

In the fall of 1998, Christopher Montgomery began developing the Vorbis audio codec after the Fraunhofer-Gesellschaft had begun enforcing license fees for its popular MP3 format. The Ogg container format experienced an upswing due to the increasing popularity of Vorbis. On July 12, 2002, Ogg version 1.0 was released, which was also intended as the first stable version for end users. The definition by RFCs followed in May 2003 : RFC 3533 defines the encapsulating data stream, while RFC 3534 defines the Internet Media Type of Ogg files, application / ogg .

In September 2008, RFC 3534 was replaced by RFC 5334 . The Internet Media Type application / ogg was redefined and the Internet Media Types audio / ogg for audio data and video / ogg for video data were added. The filename extensions were .ogx for application / ogg , .ogv for video / ogg and .oga , .ogg and .spx for audio / ogg . The seldom used media type application / x-ogg, on the other hand, comes from earlier times when the official type was not yet specified. The extension .ogm is not part of the Ogg specifications , it belongs to the Ogg-related (but not identical) format Ogg Media , which split off from Ogg to support additional video playback functions.

File format

The Ogg file format is a container bitstream format. The container contains data that are in turn compressed with different codecs. The text codec Writ , the voice data codec Speex , the audio codecs Vorbis or FLAC and the video codec Theora are usually used for compression . These data are then grouped into logical bit streams (i.e. text, audio, video image) depending on their properties. Each logical bit stream is only processed further with the appropriate codec. Several logical bit streams can be "stored" in a container. Several logical bit streams of the same type (that is, for example three logical video streams) can also be contained in one container. These can also overlap during playback. In order to store or transmit the data over the network, these logical bit streams are converted into a physical bit stream (so-called data stream ). This is then sent over the network. On the receiving end, a decoder recovers the various logical streams (e.g. text, audio, video image) from this data stream.

Codecs

Ogg is a container format that can hold video, audio, and other elements (e.g. Dirac , MNG , CELT , MPEG-4 , MP3, and others), but Ogg was designed primarily for the free Xiph.org codecs. Here is a list of some of the codecs:

  • Audio
    • lossy
      • Speex : audio codec for speech with low bit rates (~ 2.1–32 kbit / s per channel);
      • Vorbis : covers music and speech for medium to high bit rates and also with variable bit rates (~ 16–500 kbit / s per channel);
      • Opus : deals with speech or music with a low or high bit rate (≈6–510 kbit / s per channel);
    • lossless
      • FLAC for lossless compressed audio;
    • uncompressed
      • OggPCM: uncompressed music or speech in PCM audio, comparable to WAV ;
  • Video
    • lossy
      • Theora : based on On2 's VP3 and strives for high compatibility with MPEG-4 video (for example encoded with DivX or Xvid , RealVideo or Windows Media Video );
      • Daala : a video format that is currently still in development;
      • Tarkin: an experimental and obsolete video codec, developed from 2000 to 2002; it was dropped in August 2002 in favor of Theora.
      • Dirac : a free video codec from the BBC , uses wavelet encoding;
    • lossless
      • Dirac: as part of the specification for lossless video compression in Dirac;
      • Daala: The codec is still under development.
  • text
    • Writ: incomplete draft, development stopped in 2007;
    • Continuous Media Markup Language : a text codec for timed metadata, headings, and formatting;
    • Annodex : a free codec for footnotes and indexing;
    • OggKate : a subtitle codec suitable for karaoke and text; can be multiplexed in Ogg.

distribution

Audio

Ogg has meanwhile established itself in the IT sector, in the audio sector Ogg Vorbis is supported by many software and hardware products. The major breakthrough in private use has not yet materialized, but it is used in many web audio players due to its license-free nature in some browsers (particularly Mozilla Firefox and Google Chrome, but not Microsoft Edge or Apple Safari).

In this area, but also in the professional studio environment, the Vorbis successor format, Opus, is becoming more and more popular. It offers a much higher quality than Vorbis and works due to its hybrid architecture (two codec technologies in one codec) for both low bit rates (voice) and higher bit rates.

Video

In the video sector, Ogg Theora is not widespread outside of the open source scene. There are Ogg versions of the short films Big Buck Bunny (2008) and Sintel (2010), for example . Both films were created exclusively with free software and are under the Creative Commons Attribution License (CC-BY).

For HD videos, the Matroska container format , which is also free, is establishing itself outside of the open source scene.

Trademark law

The name Ogg was registered as a trademark for a while from 2001 . During this time, a company based in London, according to its own statements, was able to use this brand for warnings in the medium term; So if you used the name Ogg on a homepage, for example, you might have been asked to make high payments by warning . However, this type of branding has always violated German trademark law, so it had no legal relevance. The term of protection ended on December 31, 2011 , the trademark was not renewed and has therefore expired.

criticism

In March 2010, an FFmpeg developer assessed the qualities of Ogg as a container format critically. Among other things, he states that the file size overhead of 1% is at least eight times larger than the ISO-MP4 format and that Ogg is not suitable for applications that require short latency times. As an alternative with supposedly better properties in this regard, he recommends the Matroska container format .

The Ogg developer, however, described his claims as largely irrelevant and false. Among other things, MP4 and Matroska are just as unsuitable for applications with short latencies as Ogg, in particular because the MP4 container cannot be streamed live at all, and in order to achieve the other stream properties of Ogg, a higher proportion of administrative data is required accept. If Matroska is to be streamed, the proportion even increases over that of the Ogg container. In general, he accused the critic of picking out a certain different container for comparison for each individual property and forgetting that each container had to be adapted for certain purposes and could necessarily only be suboptimal in other cases.

Web links

Individual evidence

  1. ↑ a b RFC 5334 . - Ogg Media Types . September 2008. (Replaces RFC 3534 - Updated by RFC 7845  - English).
  2. ^ Ogg bitstream overview. Retrieved March 3, 2011 .
  3. ↑ Nico Jurran: Free audio format Ogg Vorbis shines golden . on Heise online, July 12, 2002.
  4. ↑ MIME Types and File Extensions. In: XiphWiki. October 4, 2009, accessed October 24, 2009 .
  5. ↑ OggPCM. In: wiki.xiph.org. Retrieved July 29, 2012 .
  6. ↑ Michael Smith: Tarkin. August 29, 2005; accessed on September 6, 2009.
  7. ↑ Dirac specification - integration of Dirac encoded video into commonly used container formats ( Memento from January 10, 2011 in the Internet Archive )
  8. ↑ OggWrit. In: Xiph.org . November 10, 2007, accessed on April 13, 2015 (English): “at best incomplete and at worst completely broken. In any case, it is not an "official" Xiph spec / codec "
  9. ↑ Wolf-Dieter Roth: Will “Ogg” soon no longer be open source? in Telepolis , October 2, 2005.
  10. ↑ Information on the "Ogg" trademark  in the register of the German Patent and Trademark Office (DPMA)
  11. ^ Mans Rullgard: Ogg objections. hardwarebug.org, March 3, 2010, accessed May 2, 2010 .
  12. ↑ Chris Montgomery: Monty - In Defense of Ogg's Good Name. people.xiph.org/~xiphmont, April 27, 2010, accessed May 2, 2010 .