Why are MP3 bitrates often multiples of 32? (power of 2) part 2

Depending on the resource, VBR can be encoded by changing the bitrate between a fixed rate above each frame, or by sharing the available bits in adjacent frames (effectively producing a non-standard bitrate for the two frames combined).

the fixed frame depends on the sampling rate, 1152 samples per frame. There is no limit to the size of the frame itself, nor to the base 2 size of the frame (ie 417 bytes for a 128 kbit/s MP3 sampled at 44.1 kHz).

In the end, a file encoded at 126kbps will sound worse than a file encoded at 128kbps, and similarly a file encoded at 131kbps will sound better. However, MP3s are encoded according to the compression psychoacoustic model of a specific encoder. The amount by which a file sounds “better” or “worse” at a given bitrate largely depends on the algorithm used to implement the model, but in general higher bitrates allow for more data, presumably for rebuild a more accurate original transmission. audio signal

Audio bit rate, bit rate

Bit rate refers to the number of bits (bits) transmitted per second. The unit is bps (Bit per second) The higher the bit rate, the faster the data transmission speed.

Bitrate in sound refers to the amount of binary data per unit of time after converting an analog sound signal to a digital sound signal, which is an indirect measure of audio quality.

Bitrate refers to the sampling rate at which digital sound is converted from analog to digital format. The higher the sampling rate, the better the quality of the restored sound. As a benchmark for the efficiency of digital music compression, bit rate indicates the rate of the number of bits bps (bit per second, bits per second) transmitted per unit of time (1 second). Kbps (in layman’s terms is 1000 bits per second) is usually used as the unit. The bit rate of digital music on CD is 1411.2 kbps (that is, to burn 1 second of CD music, 1411.2 × 1024 data bits are required), the high BIT RATE of the digital music file music means that it should be processed in a unit of time (1 second) The amount of data (BIT) is large, which means that the sound quality of the music file is good. However, when the BITRATE is high, the file size increases, which will take up a lot of memory capacity. The most commonly used bitrate for music files is 128 kbps, and MP3 files can generally use 8 to 320 kbps. In the same way, most of them are 32-256 Kbps. Of course, the wider the rate, the better, but 320 Kbps is the highest level at the moment.

Bitrate calculation formula
The basic algorithm is: [Bit rate] (kbps)=[file size] (bytes) X8/[time] (seconds)/1000

Special algorithm for audio files: [bit rate] (kbps) = [quantization sample point] (kHz) × [bit depth] (bit/sampling point) × [number of channels] (typically 2)

For example, the D5 drive has a capacity of 4.3G, which takes into account different audio formats, so it is calculated as 600M (so the remaining capacity is 4.3*1000-600=3700M), so the video file should not be larger than 3.7G, in this example, take The capacity of the video file is 3.446G, and the length of the video is 100 minutes (6000 seconds). The calculation result: the bit rate is approximately equal to 4933kbps.

What is a good bitrate guide for mp3 files? Part 2

To produce high-quality MP3 files of classical and jazz music, the optimal bitrate depends on the characteristics of the song.

Smooth jazz can usually be copied at 192kbps to create a good balance between file size and diminishing returns, although 256kbps may sound better in a home entertainment center. A classical orchestra should be 256kbps for a portable player, but if you want to burn a CD at home or in your car, a 320kbps file might be a better option.

For saturated music such as hard rock, metal, arena, pop, electronic and house music, 320 kbps will provide the best results. The higher the number of bits per second, the more complex acoustic envelope will be preserved.

If possible, it’s best to create MP3 files with variable bit rates. This allows the encoding program to determine if a particular frame of music requires the full bit rate. Otherwise, the program will reduce data retention for that frame, resulting in a smaller file without sacrificing quality. Forcing the program to “oversample” frames can produce artifacts.

While this article is intended as a general guide, he or she may be equally satisfied with a lower bitrate for a particular song or songs in general. Many factors affect our ability to judge the quality of music, not only the devices we use but also our activities while listening to it. For example, for those who listen to MP3 files while exercising or taking a walk, external noise can make it more difficult to tell the difference in quality. Conversely, audiophiles may prefer to sample at 320kbps, regardless of their equipment, type of music, or listening habits.

If you create your own MP3 files, there are other settings that affect quality. LAME is an excellent MP3 encoder that is free and has many graphical interfaces as the interface for this popular command line program. LAME allows users to adjust many settings to generate high-quality MP3 files in seconds. You can also experiment with various bitrates in your source file to find the best subjective balance between quality and file size.