Bit depth refers to the number of bits that are allocated to each sample. You can learn more about sampling rates and bit depth in our bit VS bit section above. Many of you will likely be familiar with this popular uncompressed format. While WAV is primarily used for high-quality audio by definition a WAV file can still contain lower quality audio bitrates. It all depends on the original source. In this case, it was developed by Apple to use on their systems. Likewise, they can also contain lower quality audio bitrates.
There are two main subcategories of compressed audio formats. Lossless audio formats and lossy audio formats. Each offers some benefits depending on their intended application.
Lossless audio formats keep all the original recording data and compress that data to reduce file sizes. Below are some of the most common lossless audio formats. They say the best things in life are free. Without licensing restrictions, it has grown in popularity as the main way to offer compressed lossless audio. Apple also threw its hat into the compressed audio format space with its own file format ALAC. Offering compression similar but not as great as FLAC it is still widely used today.
While this may sound restrictive you can convert between the two formats with free tools available online. This method allows for the file to be uncompressed back to its original state without any degradation of quality or loss of data.
It can also support hi-resolution bit audio. While this lossless format was designed for archival applications it is supported by a range of consumer devices. Lossy formats aim to reduce the file sizes of audio files as much as possible.
To achieve this the data is consolidated and some data discarded. Depending on the level of compression this can result is a noticeable decline in quality. Below are some of the most common lossy audio formats.
The most well known of lossy formats is MP3. A format that revolutionized the music industry and the way we listen to music. Anything outside of the normal human hearing range is discarded. On top of that, it degrades the quality of difficult to hear frequencies and then consolidates as much of the remaining data as possible.
Offering flexibility to compress at various bitrates made it a good choice at the start of the internet boom. The smaller file sizes also allowed the files to be quickly transferred across the internet. This led to a massive spike in music piracy. It is still one of the most widely supported audio file formats. But with the increase in internet speeds and hard drive capacities, its popularity is on the decline.
Streaming and downloading higher quality files is now a viable alternative. Portable MP3 players helped drive the popularity of the MP3 file format. Ogg Vorbis is an open source compression format.
This format is actually made up of two components. The Vorbis side is actually the compression component while the Ogg side is a container to hold that data.
While an effective compression method it has not been adopted or supported by as many devices as its competitors. Designed as a better alternative to MP3 it achieves better sound quality compared to MP3 at the same bitrates.
It achieves this by offering greater sampling rates 8 to 96 kHz compared to MP3 16 to 48 kHz. It can also handle up to 48 channels compared to 2 for MP3.
As a result, it is widely used by Youtube, Nintendo and Apple to name a few. Audio compression has one primary goal, to reduce the file size of the source material. This is like how image files are compressed into.
This makes the files quicker to download. This was especially important in the early days of the internet. Speeds were as low as 56K meaning CD-quality audio files would take hours to download. All compressed audio formats take advantage of the limitations of human hearing to help determine how to compress the file. This type of compression algorithm is called perceptual noise shaping.
It uses the discoveries in Psychoacoustics the study of human hearing to make changes to the source material. It also aims to minimize the impact on what is perceived by the listener. The end result is near CD quality sounding audio without the bulky file size. Like image compression, audio compression aims to retain as much data as possible in a smaller file size.
The first one applies to the minimum audition threshold of the human ear. Our ears are most sensitive to frequencies in the kHz range.
The further you stray beyond this range the less sensitive we are to the sound. While most people can hear up to about 20 kHz it is only remotely perceptible. The rough cut off is about 16 kHz. Audio compression uses this information to eliminate any content deemed outside of the human hearing range. The second step involves Temporal Masking.
This takes advantage of another trait of human hearing to remove even more data from the source material. There can be many sounds playing at the same time, or very close to each other. In this situation, we will naturally hear the louder sound and often disregard the softer sound.
The greater the difference between volume levels the more this takes place. Audio compression uses this to find sections of softer sound data located near louder sounds. It then removes the softer sounds as it is likely the human ear will not perceive them. The next step is another form of masking known as Simultaneous Masking. How we hear sound is split into distinct critical bands.
Each band is made up of a certain frequency range. If there happens to be a loud sound within one of those ranges it can spill over into other frequencies. This will make soft sounds in those frequencies far less distinct. Once again audio compression algorithms aim to identify these sections and eliminate that data. These steps allow the file size to be reduced by up to 10 times but there are drawbacks. The lower the bitrate of the file the more aggressive the algorithm is in trying to find components to remove.
This can result in loss of audio quality, especially among lower bitrates like kbps and below. Unfortunately, many streaming services deliver audio at these levels which is equal to what you would hear on the radio. The end result can lead to some common issues and changes that were not intended by the artists creating the music.
Most notable is the lack of definition and oomph in the lower frequencies where bass tends to live. Clarity and definition can also be lost at other frequencies. For example, a hi-hat that is meant to play a prominent role may sound flat and fall behind other components of the song like vocals.
There is no denying that audio compression is a testament to human ingenuity. It helped pave the way for the internet to handle audio in a reliable and efficient way.
But likewise, there is no denying that there are issues with the end result, especially at lower bitrate levels. While there are benefits for all audio formats FLAC is one of the best audio formats currently available. It offers high-quality audio without the burden of large file sizes.
Orchestral classical should do well at kbps for portable players, but files of kbps might be a better choice if you'll be burning to CD for the home or car. For saturated music such as hard rock, metal, arena, pop, electronic and house music, kbps will give the best results. The greater number of bits per second will preserve more of the complex acoustic envelope. When possible it is preferable that MP3 files be created using a variable bitrate.
This allows the encoding program to determine if a particular frame of music requires the full bitrate. If not, the program reduces data retention for that frame resulting in a smaller file without sacrificing quality. Forcing a program to "over-sample" a frame can produce artifacts. While this article is intended as a general guideline, one might find that he or she is just as happy with lower bitrates for specific songs or in general. Many factors affect our ability to judge the quality of music, including not just the equipment we use, but our activity when listening.
For those who listen to MP3 files when exercising or walking outside, for example, exterior noise will make it more difficult to pick out qualitative differences. Conversely, audiophiles might prefer to sample everything at kbps, regardless of their equipment, the music's genre, or listening habits.
If making your own MP3 files, there are also other settings that affect quality. Use the suggestions listed below as a general starting point. In most cases, these settings will work perfectly well, but if you prefer to use higher or lower quality according to your needs, you can change them accordingly. View full-size matrix in a new tab. Triton Digital Support Center. Content Delivery. Choosing Audio Bitrate Settings. Your choice depends on how you want to balance audio quality with bandwidth expense.
Sample Rate Sample rate is similar to bitrate in that the higher numbers generally produce better sound. Enhanced Music Classical music, premium service, etc.
0コメント