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The Truth About High Bitrate Lossy Compression Part 3

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The Truth About High Bitrate Lossy Compression Part 3

BITRATE

For most users of the MP3 format, the problem of high quality sound is usually phrased as follows: “256 or 320? Or maybe try VBR?”

Bitrate

And this question haunts them day after day. Not all recordings sound good at 256; there is a strong audible and visible (measured) loss in the high frequency range. When using VBR mode (the so-called variable bit rate stream), it often happens that music sounds better by ear than 256, but this should not be taken as a general rule of thumb. Encode low-value or poor-quality records – you can’t go wrong. I have selected the VBR parameters to get the highest quality for VBR.

For the commercial LQT format, there is only one encoder proprietary to the authors: Liquifier Pro. We push them. Note that the LQT format is originally based on VBR encoding, so there are simply multiple modes for it, such as “bad”, “good”, and “excellent”. Naturally, for our tests we took the “excellent” (audiophile) mode, which results in a stream of 192 to 256, most of the time 200-220 kbps. Let me remind you that the LQT format is based on the MPEG-2 AAC family of algorithms. Also, this is the highest quality AAC implementation to date (tested on analogs).

The OGG format is a relative of the MP3 format, but it contains a different psychoacoustic model and some technical innovations that MP3 does not have. For starters, OGG initially only supports VBR mode. The user sets the approximate bit rate and the encoder tries to compress as closely as possible. The range of variation is extremely wide: 8 to 512 kbps, and it is much more discreet than MP3. The top bar is up to 512 kbit / s, whereas nowadays MP3 encoders really only “pull” up to 320. You may ask “is it possible that even 320 is not enough?” Yes, it happens, but rarely.

Roxette samples
Well, we come to the most interesting part. Let’s start with my auditory sensations.

For MP3 in a 256 kbps stream, noise disturbances at high frequencies are clearly audible. Not only is a considerable part of them absent from the sound, but strong distortion, wheezing, clanging and other “charms” are also mixed in. This is a sign that 256 is clearly not enough, therefore you need to test higher. Let’s take a 320 compressed sample. The sound has changed significantly, this is a completely different matter: the upper part is in place, no differences by ear were found. For the purity of the experiment, let’s see what happens in floating flow mode. We obtain an average bit rate of 290 kbit / s, of which the conclusion suggests that 256 for the sample under study will not be enough. In fact, a sample encoded in VBR mode sounds a little better than 256, but it clearly falls short of 320. In the case of MP3, for high-quality compression, only encoding in 320 kbps mode is adequate, ie , to the maximum of opportunities.

Let’s take OGG as “modified MP3”. There are five approximate bit rates for the encoder: 128, 160, 192, 256 and 350. Well, let’s try 192 and 256. We will not take 350 bit rates, because we already know that MP3 at 320 kbps clearly transmits excellent quality, it seems that better not necessary. For 192 mode, we get an average stream of 226, and for 256 mode, up to 315 kbps. So far the precision. Such a large deviation from the reference point is a signal for sound material that is very difficult to encode; with a sample with a simpler density, the precision will be higher. To be honest, I tried to evaluate 320 MP3 and 315 OGG for a long time and came to the conclusion that they both sound almost identical to the original sound. But they are based on different psychoacoustic models and their sound coloration is different. Personally, I liked the MP3 a bit more. But, this is really a controversial issue; after all, the OGG encoder is just a beta version. When there is a release, I think it should surpass MP3 in quality. Comparing them separately to the original, I was inclined to believe that the OGG has an even closer sound to the original, but there is something wrong with the high frequencies of this encoder. Because of this, MP3 sounds a bit better. I don’t think it is necessary to say that in 350 mode (average bitrate was 365) OGG “perfectly” repeats the original.

Now we are talking about the little-known but widely advertised format as the “highest quality”: the LQT format. And most importantly, it sounds great overall, however after listening to it, I realized that I didn’t like its sound. It doesn’t distort high frequencies, like MP3 256 kbps, but it smears the sound and smears a lot. Loud sounds fade over time.

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The Truth About High Bitrate Lossy Compression Part 2

The Truth About High Bitrate Lossy Compression Part 2

Bitrate

I decided to “drop” the three specified formats to get the highest quality sound with the minimum file size.

audio bitrate

For the test, we selected several samples (here a sample is a small fragment cut from a PCM file) from two types of compositions. The first is a very dense and loud sound with amplitude normalization (compacting the sound “vertically” to fit 16-bit from a 24-bit master) and compression of the dynamic range (so that the sound of all instruments is always strong). As the first type (as in my previous tests), the composition Crush On You from the album Have A Nice Day by Roxette was chosen, three samples of 15-20 seconds each of different parts of the composition were examined. The second sample is clean and transparent (acoustic or light orchestral arrangement).

Why these particular records? Roxette samples have very strong dynamic compression (the amplitude value is very often equal to the maximum (which is bad) and leads to overload of the playback equipment and strong distortions).

Roxette sample
In such samples, the encoders have to work in extreme mode, so any distortion becomes easily audible. encoding distortions add to the existing intrinsic distortions of the original. You ask “why then take a sample as a test?” It is necessary and how. The vast majority of albums released today are recorded this way. Therefore, the encoder must adequately accept clipping sound.

With Klaiderman’s samples, the situation is diametrically opposite. The original analog recording after a very high quality digital remastering was recorded to CD and without dynamic compression.

Clayderman sample
Great sound, very nice and smooth highs. We will pay special attention to them during the analysis, we will try to preserve them. But it is these frequencies that will be the most difficult for encoders to transmit.

the truth about high bitrate lossy compression

the truth about high bitrate lossy compression

bitrate lossy

Preface

bitrate lossy

In the understanding of most people, the word music lover is most often associated with a person who not only loves and collects music, but also appreciates high-quality music, and not only in artistic and aesthetic terms. but also the quality of the recording. of the phonogram itself. Think, a few years ago, an audio CD was considered the standard of music quality, but a computer, even in dreams, could not compete with the quality of a CD. However, time is a great joker and he often likes to turn things upside down. It would seem that quite a long time passed, one or two years and … that’s it, the CD on the PC went into the background. Don’t ask “why?”, You know the answer to this question yourself. Everything is to blame for the revolution in the world of sound on a computer: audio compression (hereinafter referred to as audiolo compression which means lossy compression to reduce the size of the audio file), which made it possible to store music on the hard drive, lots of music! In addition, it was possible to exchange it over the Internet. New sound cards have been released, capable of squeezing almost studio quality out of a piece of hardware that seems useless in terms of music. Today, even having a computer that is not very smart in performance, having bought a Creative SoundBlaster Live! And remembering that since the Soviet times there is a good amplifier and good acoustics, you will get nothing but a high-quality music center, the sound of which is inferior only to very expensive audio equipment (mid-range or even high-fidelity hi-fi). ). Add to this the general availability of music files and you know you have the power at your fingertips. And then there is a revolution, and you understand that a compact disc is no longer so convenient, you are fascinated by something completely different: the magic signs of the “MP3”. He cannot eat or sleep; faces the seemingly insoluble question of the “chicken and egg”: how to “squeeze” and, more importantly, how to “squeeze” …

This is where I will help you. This article is the beginning of my new series of informational materials on music on the computer. For over a year maintaining an extensive database of MP3 files, I have accumulated a great deal of research on audio compression. It is these studies that I will try to share with you. Several respected authors have written many articles on audio compression, so I will try not to write what I can easily find in other sources of information. I would like to express my position on the subject under discussion simply and clearly. We will not consider audio compression to be as compact a tool as possible put audio information on your hard drive (so that you can record so many hours of music there). Yes, compression allows you to record music more compactly, but my goal is to minimize quality loss by converting “pure” audio to compressed. That is why only high bitrates and encoders that compress qualitatively are considered in these modes. So it is much more convenient to work with compressed audio – instant access to any track from any album, convenient software for playback. And, of course, the financial issue has not been forgotten either.

Of the audio compression formats that exist today, three deserve attention, in my opinion: MP3 (or MPEG-1 Audio Layer III), LQT (as representative of the MPEG-2 AAC / MPEG-4 family) and the completely new OGG format (Ogg Vorbis) developed by a group of enthusiasts:

MP3 is by far the most widely used of these (mainly because it is free). Let me remind you that it was thanks to the MP3 format that the victorious procession of compressed audio took place. However, as is often the case with pioneers, little by little it is losing ground and giving way to new and better formats.
The second format, LQT, is a representative of a new direction of audio coding algorithms, a representative of the AAC family. This is a fairly high quality, but commercial and highly classified format.
OGG became widely known to the public this summer and is currently developing rapidly, soon (with the release of the Encoder and Decoder) it should beat MP3 with better sound quality with smaller file size.
I will not give a detailed description of technologies and formats here, you can easily find them yourself. There will only be facts, conclusions and recommendations. I plan to present my research separately for each format in separate articles.

But what role does the bit rate play?

This term is known primarily for describing the quality of lossy compressed audio (eg MP3). Unfortunately, this makes it even more difficult than with channel-separated compression, the bit rate is split between the two channels: stereo MP3 (not to be confused with dual channel) with a 320 kBit / sec bit rate. uses only 160 kBit / sec per channel.

Bit Rate

Or different bit rates per channel: set stereo (mono signal calculated with additional stereo information), on the other hand, it works with volume differences between the two channels and therefore can use the bit rate much more efficiently .

Bitrate

DAC, bit rate

What exactly is the obviously so essential bit rate? For a CD based on the Red Book standard, the bit rate is calculated as follows: 2 channels * 44,100 Hz sample rate * 16 bit depth per sample results in 1,411,200 bits / sec., That is, 1.4112 Mbit / sec. Bit rate. Obviously, this is considerably more than what compressed formats (should) provide. You can see how the compression processes work: last but not least, they more or less cleverly reduce the bit depth per sample at a given sample rate of 44.1 kHz, for example. The amount of data decreases, and that is exactly the goal of every data compression: halving the bit rate means exactly halving the amount of data.

As an example, I have compared some common file formats for digital audio:

Format

Codec (s)

Multichannel

Sampling rate

Bit depth or resulting bit depth from bit rate

Compression
/
subject to acoustic losses

Wav

PCM et al.

yes

any

Optionally, depending on the codec, also lossless

AIFF

PCM et al.

Not

any

Not

FLAC

FLAC (Free Lossless Audio Codec)

yes

0.001 kHz-655.350 kHz

4, 8, 16, 20, 24, 32

without losses

Apple loses
less
MP4

ALAC (Apple Lossless Audio Codec)

yes

0.001 kHz-384,000 kHz

16, 20, 24, 32

without losses

MP3

MPEG I Layer 3 in various incarnations
as B. LAME

Not

8-48 kHz

8-320 kBit / sec. CBR / VBR or 640 CBR for free MP3 format

with mandatory loss

Most readers will know that lossy compression is often based on psychoacoustic models or natural limitations of human hearing: what humans cannot (should) hear is not stored in the musical signal and is irretrievably lost, apparently not. you need it. The most popular example of this is the old MP3 format already mentioned. For some audiophiles, lossy compression is by definition useless for serious music listening, regardless of whether or not they would notice the loss of compression. For others, the sound is 320 kBit / sec. MP3 encoded for pop music are identical to CDs, they are satisfied.

DAC bit rate

Lossless compression, on the other hand, has become increasingly popular since Internet bandwidths and storage capacities have steadily increased. An example is the FLAC format, which fortunately is also “open source”, which means that it can be used freely and even changed in terms of the program. Meanwhile, most of the time it is directly compatible with proprietary audio hardware, so FLAC files can be played without the help of a computer, and in some cases even created (ripped CDs). As the table above shows, FLAC supports very high sample rates and bit depths, as well as multi-channel sound.

With FLAC, the audio signal is encoded based on computable fixed-point algorithms that conserve computational power, in which blocks are formed step by step and stereo separation is converted to mid-side separation and performed the remodeling of the signal with differential storage. No information is lost, it is stored more efficiently than, for example, on a CD; Depending on the complexity of the audio signal, compression rates of up to 30% can be achieved.

FLAC

It should be clear once again that FLAC or MP3 are file formats and therefore cannot be directly compared to the PCM of the Red Book encoding of a CD or DSD (see next section). Let’s leave it at that on the subject of data compression.

What does “bit rate” mean in a video?

When downloading videos from the Internet or copying videos from disc to your computer, you may have the option of choosing a different bitrate. Even DVDs have specific bit rates. As technology has advanced, video media are able to achieve higher quality, such as high definition DVD, and this is achieved by increasing the video bit rate.

Bitrate

Definition

Bit rate, sometimes referred to as “bit rate”, is the term used to define compression of audio, video, or other multimedia compression in terms of the amount of data, measured in bits, per unit of time in the printed material. Bit rate is the ratio of quality to time. Bit rate is also often measured in kilobits or megabits per second.

Bitrate

Sense

Videos with a higher bit rate will have a larger file size. For example, it will take longer to download or stream from the Internet and upload to a device or computer, and you can burn fewer videos to DVD. However, a higher bit rate usually indicates a higher quality. In this way, your video can be clearer and sharper. When browsing for video or importing it to computer from DVD or camera, choose the highest bit rate for higher quality. However, if space is your main concern, choose the lowest bitrate when downloading or compressing video files.

bit rate factors

Programs will have different bit rates depending on different factors. For example, the output material may have more depth and quality, thus producing a higher bit rate. High definition movies have a higher bit rate than standard definition, for example. Different types of video files have different bit rates and you can also choose different bit rates for the same file. For example, iTunes allows you to compress audio files with a bit rate greater than 128 kilobytes per second to save space on your iPod.

Standard bit rates

Most standard definition DVDs have a maximum bit rate of 9.8 megabits. High definition television has a bit rate range between eight and 15 megabits per second, while the standard for 720p high definition video is approximately 19 megabits per second. At the time of publication, Blu-Ray DVDs have the highest bit rate of all consumer videos with a maximum of 40 megabits per second. This makes the content of Blu-Ray DVDs more than four times that of standard DVDs.

Understanding the bit rate

When you start to make comparisons between video cameras you are faced with a series of aspects to take into account: numbers, characteristics, options … One of the lesser known but no less important issues is the bit rate. Let’s find out what it is, once and for all.

Bit rate

What is the bit rate?

Bit rate is the amount of digital information (bits) that is transferred or recorded in the unit of time.
In the case of video, the bitrate is generally expressed in bits per second, and the amounts being played to date are Mbps (Megabit, that is, millions of bits, per second) or kbps (kilobits, thousands of bits per second).

Bit rate

Because it is important

The bit rate is a parameter to take into account because it affects many aspects of digital production, both technical and more practical (ie economic).
First of all, it affects the quality of the video and the size of the single file: obviously, the more data is transmitted in the unit of time, the higher the quality of the recording. And at the same time, it will increase the size of the recorded file.
However, this should not lead us to think that a very high bit rate is always necessary: in fact, we must bear in mind that as the bit rate increases, the difference becomes more and more marginal.
Basically, bit rate variations made from already high values to reach higher values are less visible than variations made from low values.

Then there is the question of file accessibility on the network: if the bit rate is very high, it will take a long time to download a video and watch it (for example, YouTube recommends not very high bit rates).

Finally, the bit rate also influences our portfolio: if we want to record at very high bit rates, we must first have a higher performance equipment, and then we will have to have more capable and higher performance media. Hence, larger SD, with high write speeds and consequently higher costs.

This is why you need to know what bitrate is, especially if you are serious about creating videos.

Bitrate, framerate and resolution

To get an idea of the concept of framerate you can read this article that talks about 24 fps and the cinema effect. Instead, resolution is simply the number of pixels the camera uses to “describe” the scene – more pixels means more resolution and therefore more detail (up to a certain limit).

Why are we talking about these other two concepts? Because the bit rate is a bottleneck that can make you lose part of the information we want to record.

A little math

Let’s imagine that we have our machine and we set it to 4K and choose a frame rate of 60 frames per second.
Now let’s take the same machine and set it up in HD choosing a frame rate of 30 frames per second.

How will the bit rate change?

Since the bit rate is bit / second, let’s try to calculate the bits to transfer in each case.

-In the first case we will have 4096 × 2160 pixels, all multiplied by the 60 times in one second that the frame is recorded: a total of 530841600 pixels.
In the second case, however, 1920 × 1080 pixels multiplied by 30 frames: a total of 62,208,000 pixels.

That is why the bit rate can be a bottleneck: each pixel is represented by a certain number of bits, and if we record with resolution and framerate parameters that exceed the bit rate possible with a certain machine, this will have to apply compression to the file. And we know that the more compressed a file is, the lower its quality.

What is the bit rate and how does it influence the quality of the videos?

Amid the pandemic we are facing and authorities increasingly asking people to stay home, the use of the Internet, especially broadcast services, is skyrocketing. Amazon Prime Video, Netflix, YouTube, Twitch and others have already announced measures to try to ensure everyone accesses their videos without gagging, but there are differences between the measures on some platforms.

YouTube reduces standard video quality to SD worldwide

Netflix, for example, opted for a reduction in the data rate or bit rate without lowering the resolution of the video itself. YouTube is already one of the platforms that now forces you to load at a lower resolution while maintaining the data rate, that is, the final quality, and allows you to increase the image size manually by the user.

bitrate

Oops wait! So does reducing resolution not reduce the quality and quantity of data to transfer? Not quite. Resolution is not the only thing that defines the quality of a video image, or even a JPG image, audio and the like, there are a number of factors. Among them, in addition to the image size, the bit rate that will be transferred from a server to a device, for example.

Data rate versus bandwidth

Reducing the amount of data sent to each user can help guarantee the service for everyone (Photo: Pixabay)
To understand metering on Netflix, you first need to understand the difference between the data rate of a media file and the bandwidth of the connection. Both can be called bitrate and throughput, and whether those terms are correct or not matters little. What matters is that it confuses, so it is necessary to clarify it.

The data rate of a media file refers to the maximum size of a second of the video. A video, as you may already know, is divided into frames, the most common speed is 30 fps (30 frames per second). Each table has its own set of information, and the total of 30 (or 24, 60, 120, and the like) forms the bitrate.

The bandwidth of the connection is the speed of your internet. Brazilian 4G, for example, has an average of 20 Mbps. Some fixed broadband operators offer packages of 100 Mbps, 200 Mbps or even more. This rate is the maximum amount of data that your Internet can receive from a central server.

Data volume

YouTube chose to lower the standard resolution without decreasing the volume of data (Photo: Pixabay)
The bit rate of a media file, therefore, is the amount of data it has each second. Netflix reduced this rate to decrease the amount of information that its servers need to send to each user connected to the platform. This reduces the quality of the image because it is less data, which can slightly reduce sharpness and cause noise, which some call “pixelization”, especially in very dark areas of the frame.

The resolution is not the lowest: it is that this image has less information. When loaded onto a large screen such as a TV, details are missing to display. On smaller screens, you will hardly notice the difference.

Facebook and Instagram will reduce the quality of video in Brazil
Globoplay will reduce video quality to meet demand
In short, Netflix’s decision ensures resolution, keeping sharpness a little closer than the user is used to, but reducing the amount of data transferred, resulting in images with a lower level of detail and sometimes , even more noise, even.

By sending less information to each user, Netflix, as well as Facebook, Globoplay and other services with similar measures, the platform avoids what we call server bottlenecks. This could cause suffocation and connection failures. YouTube’s measure also alleviates traffic because not everyone will manually increase the resolution, which in itself already reduces the amount of information to be transferred.

What is a video bit rate? What is mp3

The bit rate is of two types:

internal: the number of bits transmitted per second;

external: data rate and its value for real-time transmission (to watch a movie or listen to music).

Let me remind you that high bitrate usually means better quality, however this may depend on the source file.

How to find out the bit rate of a specific file?

It can usually be found right inside

And what is the difference, let’s see?

There is said to be little difference. 🙂 In my opinion)) (hearing), it is necessary to listen to music not through the speakers for 100 rubles, and certainly not through a portable speaker. C and everything fits immediately: it does not sound, but cacophony, if the bit rate is less than 120 kbps.

Bitrate

Different bit rates for people who work with sound. Well, to listen at home, any bitrate, even the lowest bitrate, will. Here it is, as the saying goes, an amateur.

Incidentally, one of the “representatives” of music with a high bit rate is the .flac format. . , the bit rate weighs less than 800-1000 kbps, however it takes up more space, such a song can weigh 30mb, and the album less than 400.

I hope this explanation of “What is the bit rate in music” has helped me a little? Please leave the comments below so I can reply to you.
Don’t be afraid of me and add

With the concept of “bit rate” we are faced with the mention of files in audio and video format. To understand the essence of this term, you must master file compression and encoding. German scientists have established the general principle of compressing files with minimal loss. Using the MP3 encoding example, the source audio file is cut into chunks lasting 50 milliseconds, each of which is analyzed separately. In the analysis, the fragment is broken down into harmonics according to the Fourier method, of which, according to the theory of sound perception, the harmonics that the person perceives worse than the rest are expelled from the human ear. These are quieter harmonics in the context of the stronger ones. As a result, sounds masked by hearing inertia are ejected (for example, if a very short beep sounds at once, with a delay of a fraction of a second, some other short-term signal is heard, then it will not be heard. ) The remaining harmonic information after filtering is recorded in an MP3 file, which results in a much smaller size than the original WAV. The WAV file stores complete information about the original sound, digitized and quantized at a frequency of 44 kHz. This information is stored on normal audio CDs. During playback, a reverse transformation is performed, in which the remaining harmonics are converted back into a sound wave. Some information about the original signal has disappeared, therefore the sound is not the same as the original. But insignificant sounds have been thrown, so the human ear cannot distinguish the signal from the original, which it was before packaging in MP3.

Bit rate is the amount of information per unit of time. Its essence: how much information about each second of the registry can we spend. Of course, the smaller it is, the smaller the files are with the same duration over time, so they have to throw more “extra” harmonics. Bit rates have units of measure: kilobits per second (Kbps) and megabits per second (Mbps). The MP3 audio compression algorithm is often used with 128 kbps compression. They are of two types: fixed and variable. So with video compression, if a constant bit rate is applied, a fixed amount of data is used to encode a second of a movie. In the case of variable bitrate, the codec sets its own bitrate value based on the scene in the movie. For example, when encoding in MPEG, in practice, the compression gain is obtained by saving only the difference between adjacent frames. With a slow scene change, the difference between the frames is small, and therefore it is possible to reduce the bit rate required to reproduce these scenes.

MP3 Bit Rate: What Does It Mean?

Meaning of bit rate and what MP3 bit rate to use

MP3 is a popular digital audio encoding format. When looking at the bit rate of an MP3, generally the higher the bit rate, the better the sound quality. A lower bit rate is only useful when space is minimal.
What does the bit rate mean

The bit rate of an MP3 file is a measure of the performance of audio data over a specified period of time. Simply put, it is the number of bits that are processed each second.
For example, audio data in an MP3 file that has been encoded with a constant bit rate (CBR) of 128 kilobits per second (kbit / s) is processed at 128,000 bits per second. For audio that has been encoded at a variable bit rate (VBR), the displayed value is an average.

The higher the bit rate, the better the sound quality will be when playing a lossy audio format tune. To put digital audio compression into perspective when it comes to bit rates, a standard audio CD, which contains uncompressed audio data, has a bit rate of 1,411 kbit / s. This is much higher than the best bit rate for MP3, which is 320 kbit / s.

Does the bit rate matter?

Unless you consider yourself an audiophile and have a top-notch pair of headphones to wear while listening to your music, the bit rate of your MP3s may not be as important.

If you use low-cost headphones with your iPod, you won’t be able to hear the difference in your music. Even with premium headphones, the difference between high and low bit rates is most noticeable in just a few areas:
Some details in low bitrate MP3 may be missing.
You may not be able to hear subtle background tracks.
You may hear a slight distortion.
Use an audio file converter to change the bit rate of an MP3.
Here are some examples of how audio quality differs as bit rate increases:
32 kbit / s: Generally used only for spoken audio
96 kbit / s: low quality voice or transmission
128 or 160 kbit / s: midrange bit rate quality
192 kbit / s: medium quality bit rate
256 kbit / s – A commonly used high quality bit rate
320 kbit / s – The highest bit rate level MP3 supports