HEVC Audio
More efficiency, more channels, more functions.
When we talk about video compression standards, such as MPEG-2 and H.264, most of us prefer to think only about the video aspects, without really thinking about the sound. Sound is certainly important too, but it just … is.
Today, with the world striving to offer something better than the current MPEG-4 / H.264 compression used on Blu-ray discs and most digital camcorders, it is worth spending a little more time learning the features of audio from next-generation video compression standards. The most likely contender for the number one next generation video compression codec is HEVC (High Efficiency Video Coding), also known as H.265 in the ITU rankings. , but remember this is a video compression codec, not sound. The development of the audio compression system that accompanies the video in the HEVC standard is being carried out by a completely different team, not the one that works in the HEVC / H.265 codec.
Google is also developing a competitive compression standard called VP9 that will be integrated into many web browsers. The use of the VP9 codec is royalty-free and Google believes that the codec will provide better performance than HEVC / H.265 in terms of compression efficiency and image quality. However, it appears that H.265 will be used in professional TV and video broadcasts, despite the need to pay royalties when using the standard.
Don’t forget about another video compression standard: the newly released Daala codec, jointly developed by the Xiph.Org Foundation and Mozilla Corp. The founder of Xiph.Org claims that the Daala codec will perform better than HEVC and VP9. , But this standard will not be ready this year. It’s funny that the Xiph.Org Foundation ever developed the FLAC (Free Codec for Lossless Audio Compression) standard, which has earned an excellent reputation for performance.
TWICE MORE EFFICIENT
In terms of video parameters, the efficiency of the H.265 codec is roughly twice that of H.264, which in turn was about twice as efficient as the MPEG-2 codec. In other words, a video stream compressed at 20 megabits per second using the MPEG-2 codec can be compressed to 10 megabits per second when using the H.264 codec and 5 megabits per second using the H.265 codec. Of course, this is a very simplified approach, but it’s fine as a practical example.
MP3 Logo The MPEG-2 codec gave most of us an idea of the MP3 standard used for audio encoding. The term MP3, first introduced with MPEG-1 compression, refers to the MPEG Audio Layer III codec. It has become a popular audio compression standard, but other standards are used in parallel. As in the case of the main video compression standard, the MP3 standard provides lossy compression, which means that this codec changes the audio during the compression process and these changes are irreversible.
The MP3 standard has a wide range of settings that affect the final audio quality, including the sample rate and bit rate settings. In most cases, MP3 audio is sampled at sample rates of 32, 44.1, and 48 kHz and compressed at 56 to 384 kilobits per second. At a bit rate of 128 kilobits per second and a sample rate of 44.1 kHz, the resulting MP3 is approximately 9.1% of the uncompressed CD file. Compressing MP3 at a bit rate of 320 kilobits per second creates a bit stream that is approximately 23% the size of an uncompressed CD file.
The AAC (Advanced Audio Coding) codec was developed on the basis of MP3, taking into account the experience gained during the development and operation of the initially popular format. In general, using the AAC codec offers better sound quality compared to MP3 at the same bit rate. The AAC codec also has a kind of “fork” known as the High Efficiency Advanced Audio Coding (HE-AAC) codec, which is used in mobile TV standards such as DVB-H and ATSC-M / H. Just like MP3, the AAC codec is a lossy compression format with a number of MP3-like settings.
