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Audio Coding Part 9

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Audio Coding Part 9

Features: Sound quality performance at low bitrate is hard to match.

Applicable to: digital radio station setup, online listening, music appreciation with low requirements.
mp3PRO
As an enhanced version of mp3, mp3PRO shows pretty good quality, with full treble. Although mp3PRO is inserted during playback via SBR technology, the actual listening experience is quite good. Although it seems a bit thin, you are already in the world of 64 kbps. There is no rival, even more than 128kbps mp3, but unfortunately, mp3PRO’s low-frequency performance is also broken like mp3, fortunately, SBR’s high-frequency interpolation can more or less cover this shortcoming, so mp3PRO’s weakness. low frequency is not as obvious as that of WMA. You can feel it deeply when you use the PRO switch of RCA mp3PRO Audio Player to switch between PRO mode and normal mode. In general, the 64kbps mp3PRO reaches the level of sound quality of the 128kbps mp3 and wins slightly in the high frequency part.
Features: The king of sound quality at low bit rates.
Applicable to: Music appreciation with low requirements.
BUN
An emerging lossless audio encoding that can provide 50-70% compression ratio. Although it is not worth mentioning compared to lossy encoding, it is a boon for friends who are looking for perfect sound quality. APE can be truly lossless, not only without sound, but also with better compression than similar lossless formats.
Features: The sound quality is very good.
Suitable for: The appreciation and collection of music of the highest quality.
Transmission audio coding technology comparison
Classified by waveform coding, parametric coding, and hybrid coding, some typical coding methods are compared in terms of coding rate (code rate), voice quality, and application fields; see the table below for more details.
Table 1 Comparison of typical audio coding techniques
coding technology
algorithm
encoding standard
Bit rate (kbit/s)
quality
Scope
Waveform coding
PCM
G.711
64
4.3
PSTN, ISDN
ADPCM
G.721
32
4.1
–
SB-ADPCM
G.722
64/56/48
4.5
–
parameter encoding
LPC
–
2.4
2.5
confidential voice
hybrid coding
ECLAC
–
4.8
3.2
–
VSELPC
FAMILY
8
3.8
Mobile communication, voice mail
LTP-RPE
GSM
13.2
3.8
–
LD-CELP
G.728
16
4.1
ISDN
MPE
MPE
128
5.0
CD
Note: There are five levels of quality evaluation (1, 2, 3, 4, 5), of which 5.0 is the highest score.
For the full Chinese and English names of various algorithms and abbreviations in the application fields in the above table, please refer to the following description.
PCM: pulse code modulation, pulse code modulation.
ADPCM: Adaptive Differential Pulse Code Modulation, Adaptive Differential Pulse Code Modulation.
SB-ADPCM: Subband Adaptive Differential Pulse Code Modulation, Subband Adaptive Differential Pulse Code Modulation.
LPC: Linear Predictive Coding, Linear Predictive Coding.
CELPC: Code Excited Linear Predictive Coding, Code Excited Linear Predictive Coding.
VSELPC: Vector Sum Excited Linear Predictive Coding, Vector Sum Excited Linear Predictive Coding.
RPE-LTP: Regular Pulse Excited-Long Term Predictive, long-term prediction of regular pulse excitation.
LD-CELP: Low Delay Code Excited Linear Predictive, Low Delay Code Excited Linear Prediction.
MPE: Multipulse Excitation, Multipulse Excitation.
PSTN: Public Switched Telephone Network, public switched telephone network.
ISDN: Integrated Services Digital Network, Integrated Services Digital Network.

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Audio Coding Part 8

MP3

MP3 has a good compression ratio, and the medium and high bitrate mp3 encoded by LAME is very close to the source WAV file in the listening sense. With the right parameters, LAME encoded MP3 is very suitable for listening to music. Since MP3 has been around for a long time, along with its good sound quality and compression ratio, many games also use mp3 for event sound effects and background music. Almost all well-known audio editing software also support MP3, you can use mp3 as wav, but because mp3 encoding is lossy, after several edits, the sound quality will decrease drastically, mp3 is not suitable for saving material, but the demonstration as a work is actually quite excellent. The long history and good sound quality of mp3 make it one of the most widely used lossy codecs. A lot of mp3 resources can be found on the Internet, and mp3player has become a trend day by day. Many VCD players, DVD players, and even mobile phones can play mp3, and mp3 is one of the best supported encodings. MP3 is also not perfect and does not work well at lower bit rates. MP3 also has the basic features of streaming media and can be played online.
Features: good sound quality, high compression ratio, compatible with a large number of software and hardware, and widely used.
Applicable to: Suitable for music appreciation with relatively high requirements.
OGG
Ogg is a very promising codec that works surprisingly well at various bit rates, especially medium and low bit rates. In addition to good sound quality, Ogg is also a completely free codec, which lays the foundation for further compatibility with ogg. OGG has a very good algorithm which can have better sound quality with smaller bitrate, and 128kbps OGG is better than 192kbps or even higher MP3. OGG’s treble has a certain iciness to it, so the OGG flaw will be exposed when encoding some musical instruments with high-frequency requirements. OGG has the basic features of streaming media, but there is no media service software support, so ogg-based digital streaming cannot be done. Ogg’s current support situation is not good enough, either software or hardware, it can’t compare with mp3.
Features: It can achieve better sound quality than mp3 with lower bit rate than mp3 and has good performance at high, medium and low bit rates.
Suitable for: Better sound quality with less storage space (relative to MP3).
MPC
Just like OGG, MPC’s competitors are also mp3. At medium and high bit rates, MPC can achieve better sound quality than the competition. At medium bit rates, MPC’s performance is not inferior to Ogg’s. At high bit rates, MPC performance Performance is even higher Hard to beat. The sound quality advantage of MPC is mainly reflected in the high-frequency part. MPC’s high frequency is much more delicate than MP3’s, and doesn’t taste like Ogg’s ice cubes. It is currently the most suitable lossy encoding for music appreciation. Since they are all nascent code, similar to the Ogg encounter, they also lack extensive software and hardware support. MPC has good encoding efficiency and the encoding time is much shorter than OGG and LAME.
Characteristics: At medium and high bit rates, it has the best sound quality performance in lossy encoding, and at high bit rates, it has excellent high-frequency performance.
Ideal for: Listening to music with the best sound quality while saving a lot of space.
WMA
WMA developed by Microsoft is also loved by many friends. At low bit rate, it has much better sound quality than mp3. The appearance of WMA immediately eliminated the once popular VQF encoding. WMA with Microsoft background has got good software and hardware support, Windows Media Player can play WMA, and can also listen to digital radio stations based on WMA encoding technology. Because the player exists on almost every PC, more and more music sites are happy to use WMA as the first choice for online listening. In addition to the good support environment, WMA also has a very good performance under the bit rate of 64-128Kbps. Although many friends with higher requirements are not satisfied, more friends with low requirements have accepted this encoding, and WMA is very good. . Quickly popularized.

Audio Coding Part 7

WMA format

WMA is the file format encoded by Windows Media Audio, developed by Microsoft, WMA is not aimed at the standalone market, but at the network!

The competitor is the well-known Real Networks in the online media market. Microsoft claims that at a bit rate of just 64 kbps, WMA can achieve sound quality close to CD. Unlike the previous encoding, WMA supports the anti-copy function. Supports adding protection via Windows Media Rights Manager, which can limit playback time, number of playback times, and even playback machine, etc. WMA supports streaming technology, that is, play while reading, so WMA can easily realize online streaming. Because it is a Microsoft masterpiece, Microsoft has added support for WMA in Windows. WMA has excellent technical characteristics. With vigorous promotion, this format has been accepted by more and more people.
AR format
RA is the RealAudio format, which is a format that many Internet users have come into contact with. Most online audition music websites use RealAudio. This format is completely targeted at the Internet media market and supports very rich features. The biggest flickering point is that this format can control its bitrate according to the bandwidth of the audience and improve the sound quality as much as possible on the premise of ensuring fluency. RA can support a variety of audio codecs, including ATRAC3. Like WMA, RA not only supports reading and playing, but also supports the use of special protocols to hide the real network address of the file, in order to realize the online playback-only viewing method without downloading. This is very important for record companies and record sales companies. Under vigorous promotion from various parties, RA and WMA are currently the most widely used audio media formats for online listening on the Internet.
mono format
APE is a lossless compression format provided by Monkey’s Audio. Monkey’s Audio provides plugin support for Winamp, which means that the compressed file is no longer a simple compressed format, but an audio file format that can be played as MP3. The compression ratio of this format is much lower than other formats, but it can be truly lossless, so it has won favor with many enthusiasts. Among the many existing lossless compression schemes, APE is a format with outstanding performance, satisfactory compression ratio and fast compression speed, which has become the only choice for many friends to communicate with fever music in private. .
Broadcast Format Features
All types of audio coding have their technical characteristics and applicability in different occasions, we will briefly explain how to apply these audio coding flexibly.
PCM encoded WAV
As mentioned above, PCM encoded WAV file is the format with the best sound quality and on Windows platform all audio software can support it. There are many functions in WinAPI provided by Windows that can play wav directly, so when developing multimedia software, wav is often used in large numbers for event sound effects and background music. PCM encoded wav can achieve the best sound quality with the same sample rate and sample size, so it is also widely used in audio editing, non-linear editing and other fields.
Features: The sound quality is very good and it is supported by a lot of software.
Suitable for: multimedia development, saving music and sound effects.

Audio Coding Part 6

OGG encoding

An audio codec called Ogg Vorbis appeared on the Internet, known as the MP3 killer! What is the origin of Ogg Vorbis? OGG is the project name of a large multimedia development program, which will involve the development of video and audio encoding. The whole purpose of the OGG project plan is to provide a completely free media encoding solution for anyone! OGG’s belief is: OPEN! FREE! The word Vorbis is the name of a “playboy” character in the fantasy novel “Small Gods” by Terry Platjat. This term became the official name for audio encoding in the OGG project. At present, Vorbis has been successfully developed and an encoder has been developed.
Ogg Vorbis is a high quality audio coding scheme. Official data shows that Ogg Vorbis can achieve better sound quality than MP3 at relatively low data rates. Ogg Vorbis is also much more advanced than MP3, which was successfully developed in the 1990s. It can support multiple channels, what does this mean? This means that Ogg Vorbis can encode all channels with the support of SACD, DTSCD, DVD AUDIO ripping software (currently there is no such software), instead of MP3 it can only encode 2 channels. The rise of multi-channel music has brought revolutionary changes in music appreciation, especially when enjoying the symphony, it will bring more presence. This revolutionary change cannot be adapted to MP3.
Like MP3, Ogg Vorbis is a flexible and open audio codec that allows for significant sound quality adjustments and further algorithm improvements once the codec has been fixed. Therefore, your sound quality will get better and better. Like MP3, Ogg Vorbis is more like an audio coding framework, which can be continually improved by introducing new technologies. Like MP3, OGG also supports VBR.
MPC encoding
MPC is another impressive and powerful player. Its popularization process is very discreet and there is no complicated backstory. She only has one purpose for her looks, smaller size and better sound quality! MPC was previously known as MP+, and it’s obvious who it’s targeting. However, anyone who has used this code will be impressed by its excellent sound quality.
mp3PRO encoding
On June 14, 2001, Thomson Multimedia SA and Fraunhofer Institute released a new version of music format on June 14 named mp3PRO, which is an improved scheme based on mp3 encoding technology is quite attractive in features announced by the officer. According to various information, mp3PRO is not a completely new format, it is an improvement based on traditional mp3 encoding technology, and its biggest technical feature is SBR (Spectral Band Replication), which is a new audio encoding enhancement algorithm. Provides the ability to improve speech and audio encoding performance at low bit rates. This approach increases audio bandwidth or improves encoding efficiency at a specific bit rate. The biggest advantage of SBR is that it can achieve very efficient encoding at low data rates. Unlike traditional encoding technology, SBR is more like a post-processing technology, so the quality of the decoder algorithm directly affects the sound quality. . The high frequency is actually produced by the decoder (player), and the SBR encoded data is more like a set of commands that produces high frequency, or a guide signal source, which is kind of the way it works. We can see that mp3PRO is actually a mixed data stream encoding of mp3 signal stream and SBR signal stream. Relevant information shows that SBR technology can improve high-frequency sound quality with little data traffic by about 30%. We don’t care how this 30% is obtained, but it can be predicted in advance that this improvement can make the 64kbps mp3 reach 128kbps. The sound quality level of mp3 (note: under the same encoding conditions, the increase in data rate is not proportional to the increase in sound quality, at least in the human ear), which is comparable to mp3 PRO official 64kbps, which is comparable to 128kbps mp3 The propaganda is basically consistent.

“The Origin of Ogg Vorbis” Part 2

“The Origin of Ogg Vorbis” Part 2

By the way, there is an item called “stream serial number” in the header. Ogg can handle multiple data streams and OggStream on the Xiph.Org website As shown in the figure at the bottom of the explain page, you can compose a file by mixing three streams of red, light blue, and green.

In this case, it will be shuffled page by page, so it is necessary to indicate “what flow data I have” on each page. This is indicated by the serial number of the sequence.

·Table 1
item name Size Content
capture_pattern Four OggS
stream_structure_version 1 0x00
header_type_flag 1 The Bitstream type that the page stores.
absolute position of granules 8 If Bitstream leaves this page, its location
stream serial number Four Bit stream number
page sequence no Four page number
Checksum Page Four 32-bit CRC Value
page_segments 1 Size of bit stream to store (bytes)

■ Vorbis characteristics

Vorbis, on the other hand, comes from the name of the main character in Terry Pratchett’s novel “Small Gods.” Basically, it has very similar characteristics to MP3s. Specifically, it has the following characteristics, and it is a “slightly better than MP3” number.

-Uses MDCT (Modified Discrete Cosine Transform)
-The sampling rate is 8 KHz to 192 KHz
-Precision
sampling is 16/24

bits -Maximum number of channels is 255 channels Bit rate is not uniquely determined as described below. The goal is to ensure a quality that beats MP3 at the same bit rate compared to the average bit rate, and the quality is generally said to be roughly the same as AAC.

On the other hand, there are some differences. The most important point is that the bit rate is only “VBR (Variable Bit Rate)”. MP3 uses “CBR (constant bit rate)”, so in summary, the playing time and the file size are in a proportional relationship.

In Vorbis, on the other hand, both timbre and play time are related to file size, and as a result, the file size is roughly the same as MP3 for the more complicated timbre and smaller for the more complicated timbre. simple. it is one of the factors for better sound quality than MP3 if it has the same bit rate. However, on the other hand, the fact that the processing required to encode / decode is definitely more than MP3 is a disadvantage of Vorbis.

■ The future of Ogg Vorbis

Ogg Vorbis is implemented on multiple platforms and, in addition to Windows / Mac OS / UNIX / LINUX, OS / 2 and Pocket PC players are available as standard. However, the official source is limited to providing the necessary libraries (and a simple interface).

In addition to this, for example, plugins for Windows Media Player and media players like WinAMP support it as standard, and groundwork is being prepared. However, the following factors can be considered as the reasons why it has not been widely used. -Is not

much better than MP3-There is no
a lot of support in portable players

Especially for the second point, the following problems are likely to exist.

-Since both encoding and decoding have a higher load than MP3, processing with a portable player is a bit heavy, and as a result there are disadvantages such as a reduction in continuous playback time.
-It does not have a copyright protection feature (this is from Xiph.org) as it is not set as a policy), it is unlikely to be used for music distribution which is popular these days,

and although it is not recognized that it is necessary to back it up with a portable player, there are cases in which music is distributed with Ogg Vorbis little by little, I am beginning to see it and I think that little by little it will increase its power in the future. However, to become a major format, you need some kind of opportunity, but it is a bit disappointing that such a move seems not to be that particular so far.

The Origin of Ogg Vorbis

“The Origin of Ogg Vorbis”

■ What is Ogg Vorbis?

“Ogg Vorbis” is another audio format similar to the term used so far. Strictly speaking, Ogg and Vorbis are separate, Ogg refers to a container, a container for storing audio data, and Vorbis is the audio codec method.

You can think of it as the same as storing videos from video codecs like CinePak, Indeo, WMV, and DivX in a video format called AVI. However, Ogg itself is not as popular as AVI.

So far, Ogg supports “FLAC – Lossless Audio Codec”, “Speex – Specialized Audio Codec for Conversation Recording”, “Theora – Free Video Codec”, “Icecast – Streaming Audio”. Of these, is FLAC the only one that is relatively widely known during the period? For this reason, there is a section where Ogg and Vorbis are generally recognized as the same thing, and the facts support it.

■ Establishment of Ogg Vorbis

Ogg Vorbis, the container named Ogg and the Vorbis codec, was created by Xiph.Org. This is a non-profit organization whose purpose is to provide multimedia technology that anyone can use freely. Ogg Vorbis is a typical example of this, and it can be used for free even for commercial use, with no royalties or license fees, only with the following conditions.

-Specifications: Public Domain (that is, it can be modified in addition to free, there are no restrictions)
Software: The utility provided by Xiph.Org is GNU GPL (There are no restrictions on use, but there is an obligation to publish the source). Also, most libraries / SDKs have a modified BSD license (the copyright notation of Xiph.org author is not removed when distributing or modifying). From

So, PC games made in Japan often use Ogg Vorbis. However, one of the reasons is said to be that there are no royalties. Behind this movement is the fact that the popular MP3 format license is actually loaded. MP3 encoded music data is exempt from the license fee depending on certain conditions, but basically it is charged. Thomson of France obtained a patent and obtained it under license. The specific license fee is the one shown here, which has hindered the spread of free encoders / decoders.

Even in Japan, “It’s afternoon” temporarily stopped distribution (click here for details on this process) .Xiph.Org has started work to create a free format that is not subject to patents, etc., so to counteract these movements. The development work started in 1993 and the distribution of Ogg Vorbis already started in 2000 (although the version is recent).

Since then, FLAC has joined Xiph.Org (which was previously developed into its own project), and Speex and Theora have joined. Checking the current version, Icecast is 0.8.6 and Theoa is 1.0 Alpha 7 (both as of Dec 2006), which is a bit recent, but all other libraries are over 1.0 so it can be used stably by the moment. I can see that it is.

■ Ogg Features

First, let’s look at Ogg’s features. Ogg was adopted by RFC in May 2003 as “RFC3533 (The Ogg Version 0 Encapsulation Format)” and “RFC3534 (The Application Media Type / ogg)”. By the way, the name Ogg has been popular as a “strategy (tactic?) Of attacking a special attack (Kamikaze Attack) with the Orion G ship (commonly known as Og)”, and this is converted to counter the enemy’s strategy. which is called Ogg. It seems to have been converted. In this case, it seems to have the meaning of counteracting the strategy of the major licensees to earn revenue through patent licensing.

Ogg’s structure is surprisingly easy. First, the original bitstream is divided into 255-byte “packets”. This 255 bytes is the maximum value, so it can be 254 bytes or less. Then put this package on a “page”. Each page has a 27-byte header, for a maximum total page length of 282 bytes. The Ogg file is built by grouping several pages together.

The page header at the top of each page has the structure shown in Table 1. This header is interesting. For example, even if you rearrange the order after dividing it by page, you can still see the header and revert to the original order. It’s more like looking at the Ethernet or IP headers rather than the file format.

What is an Ogg (Ogg Vorbis) file?

What is an Ogg (Ogg Vorbis) file?

Ogg Vorbis

The Ogg file (Ogg Vorbis) is a kind of audio file, and it seems to be called Ogg or Odge. It mainly has the following characteristics.

Ogg vorbis

The file size can be reduced compared to uncompressed audio files.
The sound before compression cannot be fully reproduced. (Lossy compression)
It is often used for PC games due to its flexible license restrictions.
Supports gapless playback

MP3 difference
Ogg can play better than MP3s at the same bit rate, and it appears to be comparable to other lossy compression formats like AAC and WMA. Its performance is highly rated, especially at low bit rates.

Also, when distributing MP3-compatible software or hardware, you have to pay a license fee, while Ogg does not have to pay a license fee. So it seems like it is often used when handling compressed audio in PC games as described above.

Other lossy compression formats
Lossy compression formats other than Ogg Vorbis include:

MP3 (MPEG 1 Audio Layer 3)
AAC (advanced audio coding)
WMA (Windows Media Audio)
ATRAC (TRansform Adaptive Acoustic Coding)
Compared to these, it appears that there are still few Ogg-compatible portable music players due to popularity and technical factors.

Playing Ogg files with Windows Media Player [Tutorial]

An Ogg file (Ogg Vorbis) is a type of lossy compressed audio file, similar to MP3 and AAC. It is being used recently as it has few license restrictions. However, it is not currently supported as standard on Windows and Mac.

So this time I will show you how to play Ogg files with Windows Media Player.

It should be noted that the characteristics of Ogg files and Ogg files (Ogg Vorbis) refer to. Also, if you want to handle Ogg files with iTunes, please play Ogg files with iTunes, and if you want to edit Ogg files, “You can edit Ogg files with SoundEngine! Simple explanation from DLL download to setup and use