MP3 bitrate is the amount of data that is used to encode an MP3 audio file. The higher the bitrate, the higher the quality of the audio file. However, higher bitrates also result in larger file sizes.
How is MP3 Bitrate Calculated?
MP3 bitrate is calculated using a variety of factors, including the complexity of the audio signal, the desired quality of the audio file, and the target file size.
What are the Different Types of MP3 Bitrate Calculation Methods?
There are two main types of MP3 bitrate calculation methods:
Constant bitrate (CBR): This method uses a constant bitrate for the entire audio file. This results in a consistent audio quality throughout the file, but it can also result in larger file sizes for complex audio signals.
Variable bitrate (VBR): This method uses a variable bitrate, which means that the bitrate changes depending on the complexity of the audio signal. This results in smaller file sizes for complex audio signals, but it can also result in a slight variation in audio quality.
Which MP3 Bitrate Calculation Method is Best?
The best MP3 bitrate calculation method depends on your needs. If you need a consistent audio quality throughout the file, then CBR is the best option. If you are more concerned about file size, then VBR is the best option.
How to Choose the Right MP3 Bitrate for Your Needs
When choosing the right MP3 bitrate for your needs, you should consider the following factors:
The type of audio signal: Complex audio signals, such as those that contain a lot of high-frequency content, require a higher bitrate than simple audio signals.
The desired quality of the audio file: If you want the highest possible quality, then you should use a higher bitrate. If you are more concerned about file size, then you can use a lower bitrate.
The target file size: If you have a specific file size in mind, then you can use a bitrate calculator to determine the bitrate that you need.
Conclusion
MP3 bitrate is an important factor to consider when encoding audio files. By understanding the different types of MP3 bitrate calculation methods and how to choose the right bitrate for your needs, you can ensure that your audio files sound great and have a reasonable file size.
Here are some additional details about the different types of MP3 bitrate calculation methods:
Constant bitrate (CBR): This method is the simplest to understand and implement. It is also the most reliable, as it ensures that the audio quality is consistent throughout the file. However, it can result in larger file sizes for complex audio signals.
Variable bitrate (VBR): This method is more complex than CBR, but it can result in smaller file sizes for complex audio signals. This is because VBR allows the encoder to use a lower bitrate for less complex parts of the audio signal, and a higher bitrate for more complex parts of the audio signal. However, VBR can result in a slight variation in audio quality, depending on the complexity of the audio signal.
Ultimately, the best MP3 bitrate calculation method for you depends on your specific needs. If you need a consistent audio quality throughout the file, then CBR is the best option. If you are more concerned about file size, then VBR is the best option.
MP4 is a popular video format that is widely used in digital media. It uses a specific compression algorithm to compress video files to make them smaller and easier to share. The bitrate of an MP4 video refers to the amount of data that is used to represent each second of the video. It is typically measured in kilobits per second (kbps) or megabits per second (Mbps). A higher bitrate means that the video will have more data and will be of higher quality, but the file size will also be larger.
Why is MP4 Bitrate Important?
The bitrate of an MP4 video is important because it affects the quality and size of the video file. If the bitrate is too low, the video may appear pixelated or blurry. On the other hand, if the bitrate is too high, the file size will be larger, and it may take longer to upload or download the video. In addition, a higher bitrate requires more bandwidth to stream the video, which may be an issue for viewers with slower internet connections.
How to Choose the Right MP4 Bitrate
When choosing the bitrate for your MP4 video, you should consider the intended use of the video, the resolution of the video, and the file size. For example, a video that is intended to be viewed on a large screen should have a higher bitrate than a video that will be viewed on a smaller screen. Similarly, a video that has a higher resolution will require a higher bitrate to maintain the same quality as a lower resolution video.
As a general rule of thumb, a bitrate of 5-10 Mbps is suitable for 1080p HD video, while a bitrate of 2-5 Mbps is suitable for 720p HD video. For lower resolution videos, such as 480p or 360p, a bitrate of 1-2 Mbps may be sufficient. It’s also important to consider the file size of the video, as larger files will take longer to upload or download and may be more difficult to share.
How to Change MP4 Bitrate
To change the bitrate of an MP4 video, you will need to use video editing software that allows you to adjust the bitrate settings. There are many different video editing software options available, including Adobe Premiere Pro, Final Cut Pro, and Handbrake. These programs allow you to adjust the bitrate settings and other video parameters to optimize the video for your specific needs.
MP4 Bitrate FAQ
What is the maximum bitrate for MP4 videos?
The maximum bitrate for MP4 videos is 10 Mbps. However, this may vary depending on the specific device or platform where the video will be played.
What is the minimum bitrate for MP4 videos?
The minimum bitrate for MP4 videos will depend on the intended use of the video and the resolution of the video. In general, a bitrate of at least 1 Mbps is recommended for standard definition video, while a bitrate of at least 2 Mbps is recommended for high definition video.
What is the recommended bitrate for streaming MP4 videos?
The recommended bitrate for streaming MP4 videos will depend on the resolution of the video and the available bandwidth. As a general rule of thumb, a bitrate of 5-10 Mbps is suitable for 1080p HD video, while a bitrate of 2-5 Mbps is suitable for 720p HD video. For lower resolution videos, such as 480p or 360p, a bitrate of 1-2 Mbps may be sufficient.
However, it’s important to note that these are just general guidelines, and the optimal bitrate will also depend on factors such as the complexity of the video content, the encoding settings used, and the target audience’s viewing preferences.
For example, videos with fast-moving scenes or complex visual effects may require a higher bitrate to maintain a high level of image quality and avoid compression artifacts, while simpler videos with less motion may be able to use a lower bitrate without sacrificing quality.
Additionally, the target audience’s internet connection speed will also affect the recommended bitrate. For viewers with slower internet connections, a lower bitrate may be necessary to ensure that the video plays smoothly without buffering or interruptions.
What are the advantages of using a higher bitrate?
Using a higher bitrate can result in higher quality video with more detail and fewer compression artifacts. This is because a higher bitrate allows for more data to be transmitted and encoded per second, resulting in a more faithful representation of the original video source.
A higher bitrate can also be beneficial for videos with a lot of movement or detail, as it allows the encoding algorithm to capture more information and produce a more detailed image.
However, it’s important to note that using a higher bitrate will also result in larger file sizes and require more bandwidth to stream or download. This can be a disadvantage for viewers with slower internet connections or limited data plans.
What are the disadvantages of using a lower bitrate?
Using a lower bitrate can result in lower quality video with more compression artifacts, such as blurring or pixelation. This is because a lower bitrate means that less data is being transmitted and encoded per second, resulting in a loss of detail and fidelity.
Lower bitrates may also result in a lower overall resolution or frame rate, which can further degrade the quality of the video.
However, using a lower bitrate can also have benefits, such as smaller file sizes and reduced bandwidth requirements. This can be advantageous for viewers with slower internet connections or limited data plans.
Can the bitrate of an MP4 video be adjusted after it’s been encoded?
Yes, it is possible to adjust the bitrate of an MP4 video after it has been encoded. This can be done using video editing software or specialized tools designed for this purpose, such as MP4Gain.
However, it’s important to note that changing the bitrate of a video after it has been encoded can result in a loss of quality or introduce additional compression artifacts. For best results, it’s recommended to encode the video at the desired bitrate from the beginning.
Conclusion
In summary, the bitrate of an MP4 video is an important factor that can affect its quality, file size, and streaming performance. The optimal bitrate will depend on factors such as the resolution of the video, the complexity of the content, and the available bandwidth.
Using a higher bitrate can result in higher quality video with more detail and fewer compression artifacts, while using a lower bitrate can result in smaller file sizes and reduced bandwidth requirements.
If you need to adjust the bitrate of an MP4 video, it is possible to do so using specialized tools such as MP4Gain. However, it’s recommended to encode the video at the desired bitrate from the beginning for best results.
Overall, understanding how bitrate affects MP4 video quality can help you create and deliver video content that meets your needs and those of your audience.
The Differences Between 128 kbps, 256 kbps, and 320 kbps MP3s
mp3 kbps
When it comes to MP3s, bitrate is one of the most important factors to consider. Bitrate is the number of bits that are processed per second and is typically measured in kilobits per second (kbps). Common bitrates for MP3s include 128 kbps, 256 kbps, and 320 kbps, but what exactly do these numbers mean, and how do they affect the overall quality of the audio?
mp3 kbps
128 kbps
128 kbps is a standard bitrate for MP3s and is considered to be a good balance between file size and sound quality. At this bitrate, a four-minute song will take up approximately 4 megabytes of space. Audio encoded at 128 kbps will sound decent on most devices, but it may not be suitable for those who are particularly picky about sound quality. It is often used in streaming services and online platforms because of the small file size which allows for faster streaming and less data consumption.
256 kbps
Compared to 128 kbps, 256 kbps offers a significant improvement in sound quality. The increased bitrate means that more data is used to represent the audio, resulting in a more accurate representation of the original recording. A four-minute song at 256 kbps will take up approximately 8 megabytes of space. This bitrate is recommended for music enthusiasts who want to enjoy a higher quality sound without having to sacrifice too much storage space.
320 kbps
320 kbps is considered the highest quality bitrate for MP3s and offers the best representation of the original audio. The increased bitrate means that even more data is used to represent the audio, resulting in a near-perfect representation of the original recording. A four-minute song at 320 kbps will take up approximately 10 megabytes of space. This bitrate is recommended for audiophiles or professional musicians who want to ensure that their music sounds as close to the original recording as possible. However, due to the large file size, it may not be practical for streaming or online platforms.
Compression
When converting audio to an MP3, the file is compressed to make it smaller in size. However, this process can cause a loss of audio quality, especially at lower bitrates. The higher the bitrate, the less compression is applied and the better the audio quality will be. For example, a 128 kbps MP3 will have more compression than a 256 kbps MP3, resulting in a lower quality sound.
Conclusion
In conclusion, the bitrate of an MP3 can have a big impact on the overall sound quality. 128 kbps is a good balance between file size and sound quality, while 256 kbps offers a significant improvement in sound quality. 320 kbps offers the best representation of the original audio, but the large file size may not be practical for streaming or online platforms. To optimize the sound quality of your MP3s, one of the best solutions is MP4Gain, that optimizes the audio of your files, making them sound better than ever before.
When most people hear the word MP3, they usually think of songs, podcasts, and other compressed audio files. While it’s worth acknowledging the role these uncompressed files have played in the world of music, the goal of this guide is to explain in detail what’s behind these files, how they work, and what makes them so popular. Through this understanding guide, we hope to cover the core concepts behind the MP3 audio format, such as bitrate and samplerate, as well as offer some tips and tricks to ensure you’re getting the best audio quality from your MP3 files.
MP3 Audio Format
What is MP3 Format?
MP3 is a digital audio format used to compress audio files without losing quality. This is made possible by an audio compression algorithm called MPEG-1 Audio Layer 3, also known as MP3. Compression technology involves reducing the amount of data without losing the fundamental attributes of the original audio. Compressed data can be saved as a higher quality audio file in a much smaller size. This means MP3 files are easier to stream and share online.
MP3 files can be compressed at different bit rates depending on the user. Bitrate is generally in kilobits per second. For example, a 128 kbps (kilobits per second) MP3 file uses 128,000 bits to encode the audio every second. While bitrate is an important factor in determining the quality of an audio file, there are other factors as well, such as samplerate. The samplerate is the number of audio samples taken every second. An audio file recorded at a sample rate of 44.1 kHz (kilohertz) means that 44,100 audio samples were taken every second. The higher the samplerate, the better the audio quality.
The magic behind the MP3 format lies in its ability to shed unnecessary data without compromising audio quality. This is accomplished by removing inaudible components from the audio. These inaudible components are called high and low frequencies. MP3 is a lossy audio compression codec, which means that deleted data cannot be recovered. This is why an MP3 file encoded at a small size cannot recover the audio quality of a file encoded at a larger size. MP3 is an extremely popular audio format, as it allows you to compress audio files without losing quality.
How You Can Improve the Quality of MP3 Audio Files
How can you improve the quality of audio files in MP3 format? The answer to this is to use an audio conversion program like MP3gain to adjust the volume of your audio files. MP3Gain is a free and open source tool that you can use to normalize the volume of your audio and video files. This tool is not only useful for improving audio quality, but also for saving space on your hard drive, as MP3 files encoded at lower sample rate and bitrate are smaller in size.
Of course, there is a downside to MP3 audio compression. As with any type of compression, there is a chance that the audio may become distorted or lose quality. While MP3 files encoded at a small size will have lower audio quality than those encoded at a larger size, if the proper bitrate and samplerate are selected, the audio will not be excessively distorted. The key is to find the balance between file size and sound quality.
Conclusion
We hope this guide has provided you with a clear and simple explanation of the concepts behind the MP3 audio format. While this article has mainly focused on the basics and technology behind MP3 audio files, we hope we’ve also provided some helpful tips on how to get the best audio quality out of your MP3 files. Finally, it is also important to mention the importance of using an audio conversion program like MP4Gain to normalize the volume of all audio and video files.
The bitrate and its relationship with the audio quality in an MP3
The bitrate and its relationship with the audio quality in an MP3
The bitrate is a measure of the amount of audio information that is encoded per second in a compressed audio file, such as an MP3. Bit rate is measured in kilobits per second (kbps).
The bitrate and its relationship with the audio quality in an MP3
The higher the bitrate, the higher the audio quality. However, a larger file size will also be required to store the same amount of audio time. Therefore, it is important to choose a suitable bitrate to balance quality and file size.
For music files, a bitrate of at least 128 kbps is recommended for decent sound quality. However, if you want higher sound quality, you can go for a higher bitrate, such as 256 kbps or even 320 kbps.
For voice audio files, a bit rate of 64 kbps is sufficient for clear sound quality. However, if you want higher sound quality, you can go for a higher bitrate, such as 96 kbps or 128 kbps.
In short, bitrate is an important factor in the audio quality of an MP3 file. It is important to choose a suitable bitrate to balance quality and file size.
Also, it’s important to note that bitrate isn’t the only factor that affects the audio quality of an MP3. Other important factors include the sample rate and the number of channels. The sample rate refers to the number of times the sound is measured per second, while the number of channels refers to the number of audio channels in the file.
For example, an audio file with a bit rate of 128 kbps and a sample rate of 44.1 kHz and 2 audio channels will have higher sound quality than a file with the same bit rate but a sample rate of 22 kHz and 1 audio channel.
In conclusion, if you want to get the best audio quality from an MP3 file, it’s important not only to choose a suitable bitrate, but also to consider the sample rate and number of channels. It is advisable to choose an optimal combination of these factors to obtain the best sound quality.
In addition, it is important to mention that there are other audio formats, such as WAV, FLAC, AIFF, which, unlike MP3, are not compressed, which means that they do not lose audio quality to the compression process. However, these formats often have much larger file sizes than compressed formats like MP3.
So, if you want the best audio quality, it’s recommended to use uncompressed formats like WAV or FLAC, but it’s also important to consider storage space and compatibility with different devices and audio players. In case of opting for compressed formats, it is important to choose an appropriate bitrate and take into account other factors such as the sampling frequency and the number of channels.
In summary, bitrate is an important factor in the audio quality of an MP3 file, but it is not the only factor to consider. It is important to choose a suitable bitrate, as well as take into account the sample rate and the number of channels to obtain the best sound quality. In addition, there are other uncompressed audio formats that offer higher sound quality, but also have a larger file size.
What is the difference between 128k and 320k music? Part 2
Bit Rate, Sample Rate, Lossless, MP3, FLAC, APE, 320kb, 192kb, 128kb, 44.1khz, CBR, VBR. Does this bunch of various names make you both familiar and unknown?
Audio File Sizes
The higher the bitrate, the better the sound quality. Lossless music is the highest sound quality, right? So, let’s start with the sound collection.
【Audio composition】
Nowadays, when we talk about audio, everything is digital audio. Digital audio consists of three parts: sample rate, sample precision, and number of sound channels.
Sample Rate: Both the sample rate, which refers to the number of samples per second when recording the sound, expressed in Hertz (Hz).
Sampling Precision: Refers to the dynamic range of the recorded sound, measured in bits (Bit).
Sound channel: the number of channels (1-8).
In simple terms, we can think of a sound wave as a curve. We know that the curve is made up of points, and the sampling rate is the number of points in the middle of the length per second (the horizontal axis in the figure above). Sampling precision is the number of points in the dynamic range (upper vertical axis). The finer the positioning of these two dimensions, the greater the true sound restoration and the better the sound quality. Of course, the larger the audio file will be. The customer mentioned by the above colleague said that the latest Hi-Res Audio format released by SONY is a 6-channel 192kHz/24-bit recorded audio file. The size of the lossless format, of course, will be more than 200 megabytes.
The sampling frequency is approximately the following depending on the type of use (k is the thousand-bit symbol, 1khz=1000hz):
8khz – used for phones etc, is enough to record human voices.
22.05khz: transmission use frequency.
44.1kb: Audio CD.
48khz: used in DVD and digital TV.
96khz-192khz: used for DVD-Audio, Blu-ray HD, etc.
The common range of sample precision is 8 bits to 32 bits, with 16 bits generally used on CD.
Having said that, my friends are starting to get confused. It’s not the bitrate that determines the sound quality, so why is everyone saying that 320kb sound quality is better than 128kb?
What is the difference between 128k and 320k music?
Mp3 Bit Rate
192k is a turning point. Below 192K, the sound quality is relatively damaged, especially the high-frequency part above 16Khz will be cut off.
Mp3 Bit Rate
In short, mp3 above 192k, ordinary home equipment can no longer hear the difference in CD sound quality, except for golden ears and hi-fi equipment. Of course, these data are not 100% reliable. There are always people on the internet sharing fake mp3 above 192K. In fact, they are converting low bitrate music to high bitrate through software, but the sound quality will not improve. Windows Media Player compresses the resulting mp3 is absolutely wonderful. No matter how high the compressed bitrate is, it will cut perfectly at around 16K, so if you want to compress MP3 yourself, don’t use Windows Media Player.
Well, in fact, the bit rate should be said to be another dimension, it is a compression of audio files.
Nowadays, most of the audio formats that we use regularly are based on the original “WAV” file of the audio CD (44.1khz sampling rate, 16bit sampling precision, 2ch). The original recorded sound data is stored in an array, which is in PCM format, while WAV format is an encoding format developed by Microsoft, and its function is to play the PCM format data through encoding.
Since the data in WAV basically completely restores the PCM data, MP3, AAC and other lossless encoding formats are basically recompressed based on the WAV files. Therefore, we can simply think that WAV is the original audio format and other audio formats are compressed formats.
When it comes to compression, storage and transmission are inseparable. The purpose of compression is to improve storage and transmission. Therefore, before we talk about compression, we need to understand the basic units of computers.
We all know that the computer is a binary number system, and the files stored by the computer are made up of two numbers, 0 and 1. Therefore, the computer’s transmission is based on each number, and each number is called 1 ” bit”. For example, for an audio piece, its basic data is “0,1,1,1,0,1, 1 ,0”, and when transmitting, these numbers are transmitted one by one. The sampling precision mentioned above is this unit.
Why are MP3 bitrates often multiples of 32? Part 2
MP3 bitrate
Technically, there is nothing to limit the MP3 bitrate to a multiple of 2, as variable bitrate encoding can be used, or a custom bitrate can be achieved using some flags not used in the MPEG specification (although it must be implemented manually).
MP3 bitrate
For MP3 to be MPEG-compliant, and therefore compatible with most MP3 decoders, it must have a bitrate defined by the specification, so all CBR-encoded MP3 files must have a bitrate that is a multiple of two.
Depending on the resource, VBR can be encoded by changing the bitrate between a fixed rate above each frame, or it can be encoded by sharing the available bits in adjacent frames (effectively generating a non-standard bitrate for the two frames combined). The length of a given frame depends on the sampling rate, there are 1152 samples per frame. There is nothing to limit the size of the frame itself, nor is there any limit to making the frame size base 2 (i.e. a 128 kbit/s MP3 with a 44.1 kHz sample rate would have a frame size of 417 bytes).
In the end, a file encoded at 126 kbps sounds worse than a file encoded at 128 kbps, and likewise a file encoded at 131 kbps sounds better. However, MP3s are encoded for compression according to the psychoacoustic model of a specific encoder. The amount by which a file sounds “better” or “worse” at a given bitrate depends largely on the algorithm used to implement the model; however, in general, higher bit rates can hold more data, likely reproducing Build a more accurate raw stream audio signal
I strongly suspect that the reason the MPEG standard specifies multiples of 2 is because binary computers can often optimize math involving both themselves and programmers.
This is a begging question. Don’t you think there is a mathematical/arithmetic reason for the chosen bitrate value? Or doesn’t the mere presence of VBR justify any limits on possible bitrates?
@slhck I’ve just updated my answer to provide more relevant details, please let me know if this answers all questions.
MPEG 1 Layer-III (mp3) files are streams of frames.
This web page details the data structure of the framework.
As you can see, only 4 bits are allocated to determine the bitrate. When designing a format for live streaming, you don’t want to waste more space than describing the stream.
I’m not sure exactly why 4 bits was determined to be a good compromise between space footprint and “bitrate resolution” – for the particular bitrate chosen, they were probably chosen based on the lowest and highest quality range that the engineer considered acceptable. mp3 algorithm.
Probably most MP3 players read one frame at a time, probably trying to “early” buffer at least one frame when decoding/playing the current frame.
The size of the frame and possibly the RAM allocated to it is as follows:
FrameSize = 144 * BitRate / SampleRate when the padding bit is cleared.
FrameSize = (144 * BitRate / SampleRate) + 1When the padding bit is set.
Higher bit rate/sample rate = more RAM required.
128 Kbps is probably popular as it is the default setting for many encoders.
Also, a colleague gave me insight into the discussion: 128 Kbps also roughly translates to “minutes in a minute” (unverified though), probably has something to do with that as well.
When “raw” data is logged, that data is buffered in chunks. These blocks will obviously be powers of two. It’s conceptually easier if you have an integer number of blocks per second.
I understand why multiples of 2 are often found on computers due to their binary nature, but I can’t figure out that the most common mp3 bitrates (64kbps, 128kbps, 160kbps, 192kbps, 256kbps, 320 kbps, etc.) also tend to follow this rule.
MP3 bitrate
Since MP3 is just a sequential encoding of sound waves, why does it matter that each second is represented by thousands of digits per second that are divisible by 2?
Do music players like iTunes continue to read the file and play the encoded sound regardless of where the second limit is, or will they read the file every second?
In the latter case, reading a 256kbps file requires slightly fewer memory pages than reading a 257kbps file, but the player can always read 256kbit chunks, regardless of their bitrate, and process them incrementally , it is right?
Is MP3 popular at 128kbps because it’s a generally accepted bitrate, or does it really have some advantages over 126kbps and 131kbps files? Very slight difference in quality/file size?
For constant bit rate (CBR) encoding, the MPEG-1 Audio Layer III standard specifies standard bit rates of 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256 and 320 kbit/s. There are other definitions in the MPEG-2 standard, but they’re also all multiples of 2 (actually all multiples of 8 are in the range 8 to 160 – see the table called “Bitrate Index” at the link above ).
Why are MP3 bitrates often multiples of 32? (power of 2)
MP3 Bitrate
Some people say:
MP3 Bitrate
I understand why multiples of 2 often show up on computers since they are binary, but I can’t figure out how the most common mp3 bitrates (64kbps, 128kbps, 160kbps, 192kbps, 256kbps, 320kbps, etc.) also tend to follow this rule.
Since MP3 is just a sequential encoding of sound waves, why is it important to represent each second in kilobits divisible by 2?
Does a music player like iTunes continue to read the file and play the encoded sound regardless of the second limit, or does it read the file every second?
In the latter case, reading a 256kbps file requires reading slightly fewer memory pages than a 257kbps file, but the player can always read 256KB chunks, regardless of their bitrate, and just process them automatically. incremental, right, Bar?
Are 128kbps MP3 songs popular simply because it’s a generally accepted bitrate, or do they really have any advantages over 126kbps and 131kbps files, apart from a very slight difference in quality/file size?
For constant bit rate (CBR) encoding, the MPEG-1 Audio Layer III standard specifies standard bit rates of 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256 and 320 kbit/second. There are a few others defined in the MPEG-2 standard, but they are also multiples of 2 (actually all multiples of 8 in the range 8 to 160 – see the table called “Bitrate Index” in the link above) .
Technically, there is nothing that limits the MP3 bitrate to a multiple of 2, since variable bitrate encoding can be used, or a custom bitrate can be achieved using some flags not used in the MPEG specification ( although this must be implemented manually). . In order for MP3 to be MPEG-compliant, and therefore compatible with most MP3 decoders, it must have a bitrate defined by the specification, so all CBR-encoded MP3 files have a bitrate of two.
