Category: Audio and video

320 kbps audio bit rate, ideal for streaming.

The triumphant march of the MPEG-1 Layer 3 audio recording format (colloquially called MP3) is explained by the fact that a simple and effective method of compressing an audio file was proposed, allowing to store up to 12 hours of quality music acceptable on a standard CD-ROM disc.

Simply put, the MPEG-1 Layer 3 algorithm is based on the so-called “psychoacoustic” compression method, when frequencies and loudness levels that are not perceptible to the ear are excluded from the sounds in the spectrum. The spectrum “cleaned” in this way is divided into separate blocks (frames) of the same duration and compressed according to specified requirements. When played back, the signal is formed from a sequence of decoded frames.

The compression ratio depends on the parameters of the audio stream, which must be output after decoding the file.

The main parameter that determines the sound quality and the degree of compression is the so-called (what is) bit rate, the bandwidth measured in bits per second.

The higher the number, the better the sound quality and the lower the compression ratio. Since almost all MP3 files are recorded in stereo with a 44 kHz encoding rate and 16-bit depth, the determining factors for clear sound are: the source of the recording, the codec used, and the selected bit rate. .

The word codec is formed by combining the words encoder + decoder. This is a software module that allows you to encode or decode audio or video files according to your own algorithm.

The average value of the stream of 256 kbps provides a compression ratio of approximately 6: 1, for other values, the compression ratio changes proportionally. So, with 256Kbps stream, you can record music from six regular audio CDs to one CD, and with 128Kbps stream, you can record from twelve regular music discs.

There is a never-ending controversy between amateurs and professionals about the bit rate that provides good sound quality that matches the playback quality of an audio CD.

Some consider the level of 128 Kbps sufficient, others are satisfied only with the maximum value of the transmission: 320 Kbps. In all probability, both are right: the only difference is what is recorded and under what conditions it is played.

The bit rate at which digitized audio was encoded is usually indicated on the CD cover. For example, the entire Beatles collection can be purchased on three 128Kbps discs or six 256Kbps discs.

It is clear that in the second case the purchase price will be twice as expensive, but the quality is also better.

If the music is played in a home car, the 192Kbps transmission will provide sufficient sound quality, the best that you still won’t hear due to the strange noise. For listening on a computer or standalone player (MP3 player), a 256 Kbps stream is accepted.

But if the signal is sent unchanged to an external device and output to high-quality speakers, the maximum possible stream is desirable: 320 Kbps. Based on the above considerations, a stream of 256 Kbps can be considered universal: with a good recording quality, it will provide adequate playback in most cases.

INFLUENCE OF THE BIT RATE ON THE SOUND QUALITY OF AN MP3 FILE

The term bit rate means how much information was transmitted per unit of time. Encoding in MP3 files can be done with constant and variable bitrate. Usually it determines the sound quality and consequently the file size.

In normal practice, the bit rate for high-quality recording starts at 128 kbps. Although this is a purely subjective opinion and for everyone it can have its own value. It is undeniable that the higher the bit rate, the better the sound quality.

At a value of 320 kbps, the sound of an MP3 file is already difficult to distinguish from the original by the human ear.
The following table shows the comparative characteristics of the sound quality of a certain bitrate value with equivalents that are understandable to everyone. Although, we repeat, this is a subjective opinion.

Bitrate value comparison:

Bitrate (kbps) —– Mono / Stereo Equivalent
8 mono —– Telephone conversation
16 mono —– shortwave radio
32 monkey
—– Medium Wave Radio 64 Stereo FM Radio
96 stereo —– Nearly CD quality
128 stereo —– CD quality

Now let’s try to do a little quality comparative analysis of MP3 files of a certain bit rate with originals:
• 112 kbps: the sound is unnatural, the sound is far from the original. Almost any listener will notice the difference. Encoding with these parameters is ideal for listening to melodies through mobile phones (although progress has come a long way and 112 kbps is no longer sufficient on some devices). It is also very attractive for broadcasting live broadcasts over long distances.
• 128 kbit / s: many manufacturers consider this value as the standard for encoding (this is highly debatable). The quality is more or less acceptable here. Many music lovers will note that the recording is not original. Although, thanks to the many “manufacturers” of CDs, users will soon accept this quality as a source. The records can be comfortably listened to on jarring plastic office speakers, cheap headphones and iPods, and of course cell phones. If you need to recode this recording to WAV format, you will lose your sense of taste forever.
• 160 kbps – here the situation is much better than before. Many will no longer understand the difference, and those who notice slight discrepancies with the original, put 192 kbps. This bit rate suits you 100%.
• 256 or 360 kbps: For many people it will be impossible to tell the difference in sound. Recommended for fans of high quality sound, owners of hi-fi equipment, large flash players, etc.

In the following table, we will consider the effect of bitrate size on the amount of disk space occupied and the number of files that can be placed on a certain amount of media. As a comparative value, we take a sound file with a duration of four minutes, which corresponds to the average composition.
This table does not include heavier discs like DVD or the latest standards like HD DVD and Blu-Ray. But even from the last column, you can imagine how much information, even with the best quality, can be put into the new media formats.
File and disk size dependency on bit rate
Bit rate (kbit / s) 4 minute files in 64MB RAM 4 minute files on CD (650MB) Hours on CD (650MB) 4 minute files on 1GB
64 34355 24543
80 28 284 19 437
96 22237 16364128
18177
12273160
14142 9218192 12118
8182256 8 89 6137

Perhaps the greatest amount of software has been written for the MP3 format.
Not a single self-respecting software player developer, and even home gamers, will dare today not to provide support for the famous format for their creation. He’s at the top of his form, experiencing a real boom. All computers likely contain files of this type, while others have thousands of them (downloaded from the Internet or copied from discs). People are buying turntables that have become outrageously cheaper. Stores are packed with MP3-tagged CDs. People already know this word as “CD” before.
However, despite all this apparent lack of clouds, the format also has disadvantages. This is imperfect stereo encoding, problems with gapped files, multi-channel sound, high frequencies and others. Many formats are already on their heels. This is the ubiquitous Microsoft with its WM A, OGG Vorbis and others.
But the most competitive now is probably the AAC format, which Apple actively and successfully supports and promotes on its iPods and the iTunes Internet service. There is also support from Dolby, Nokia (on new phones) and many other companies.