difference between bit rate and bit depth Archives

Why can the difference in bitrate make it sound great (high, medium, low)?

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Why can the difference in bitrate make it sound great (high, medium, low)?

Bit Depth vs. Bit Rate

Reply:
Just to make sure this is clear, let’s differentiate

BIT RATE BIT DEPTH

sample rate vs bit depth

as much as

Bit rate

how they relate to audio in the digital domain …

Sampling frequency:

The sample rate is specified as a frequency (samples per second), for example, 44.1 kHz for CD. Other common values are 48, 88.2, 96, 176.4, and 196 kHz, although some formats (such as DSD) have sample rates greater than 2.8 MHz. The sample rate indicates

how often the audio signal is measured

While some people view lower readings as a tiered bar graph, I prefer to view them as a child bitmap. If you take the outline of a horse and simplify it to 20 points so the child can connect, it’s not so much that you end up with steps (using straight and curved lines to connect 20 correctly spaced points can lead to a decent figure), but there won’t be without subtlety. Whereas with 200 (or 2000) points, you could approximate the wavy strands along the horse’s mane.

In audio, a lower sample rate does not make the sound “bad” (eg, fuzzy, fuzzy, or distorted), but rather limits the maximum frequency (pitch) that can be recorded / played back as intended.

Nyquist theorem formula

, The 44.1 kHz sampling rate was chosen for CD because it can record and play back frequencies up to 20 kHz. To record a spoken word (such as a speech, a sermon, or an audiobook), it would be difficult to detect a much lower sample rate, as the human voice has less and less harmonic information above 10 kHz.

Depth bits:

Considering that the sampling frequency determines how

often

audio signal is measured, bit depth indicates

scale accuracy

Since we are talking about digital audio, we describe this measurement scale in bits, where each bit is 0 or 1, and we concatenate a certain number of them to represent the value. When we have 8 bits, there are 256 possible numerical values, including zero. With 16 bits, there are 65,536 possible values. A 24-bit register can use 16,777,216 values.

When we convert analog audio to digital representation (A-to-D) and vice versa (D-to-A), we find interesting mathematical relationships. Each bit (digital) doubles the number of possible values … And doubling the amplitude (approximately 4 times the power) of the sound wave (analog) corresponds to + 6 dB of loudness. Therefore, we can estimate the maximum dynamic range * of a digital recording at 6 dB / bit. Therefore, 8-bit recording has ~ 48 dB of dynamic range, 16-bit recording (such as a CD) has ~ 96 dB, and 24-bit recording has ~ 144 dB.

* For those of you unfamiliar with this term, dynamic range basically describes the difference between the quietest and loudest sound waves that can be recorded / played back. The CD has a difference of approximately 96 dB, which can be used to represent the most subtle pause compared to the incredibly loud burst of the cannon at Tchaikovsky’s climax.

1812 Overture

Three quick notes for those interested in delving into the rhythm …

There is a formula for the actual dynamic range of a digital recording that may differ slightly from the previous estimate, but it is a fairly minimal deviation, so an estimate of 6 dB / bit is what you normally see in quotes.
The latest 32-bit floating point representations combine a 24-bit number and an 8-bit exponent to represent many more possible values than 24-bit registers. The dynamic range estimate is getting a bit dubious, but suffice it to say it’s well above 144 dB.
Using a lower bit depth, while you might think in terms of warp plugins with names like “bit-grinder”, doesn’t have to sound “bad” (eg fuzzy, fuzzy, or distorted), but just represents a reduced dynamic range. But since a 16-bit recording with a dynamic range of 96 dB (65,536 numerical values) cannot be represented in 8 bits (48 dB and 256 numerical values), to reduce the bit depth of the already digitized audio, a mathematical correction of the numbers down. (for example, 65535 becomes 255) using a compressor or limiter, which can cause the quietest recording bits to be lost so that the difference between soft and loud parts is <48 dB. Without such scheme, the transformation will cause clipping (numerical values above the maximum),
Bit rate:

In digital audio, the bit rate is a measure of

how many bits are transmitted / processed per second

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Bit rate in DVR. What is it and what does it affect?

Bit rate in DVR. What is it and what does it affect?

When talking about digital video recording, the term bit rate will surely ring a bell. This is an important parameter that affects image quality. Including recording to a DVR.

video playback [(000152) 2019-07-13-15-20-56] .png

If you are intimidated by foreign words, the bit rate can otherwise be called the recording speed or compression ratio. Because that’s exactly what happens: the compression of the video stream. How? Let’s take a look.

After the light strikes the matrix and subsequent digitization of the image, a very dense stream of digital video signal is obtained at the output. Also, the higher the video recording resolution and frame rate, the bulkier this stream will be. You cannot write it directly to a memory card; It will fill up very quickly with huge video files and you may just not be able to cope with such a flow of information. This is why the original video stream is compressed to an acceptable bit rate. This parameter is just the output data rate. Basically it reflects the speed at which the video is written to the memory card.

Bit rate can be calculated in bits, kilobits and megabits per second – (bit / s, bps, b / s), (kbps, kbit / s, kbps) (Mbps, Mbit / s, Mbps). Most of the time, in megabits. The bit rate of the recorded video can be checked on a computer with a video editor or via the file properties menu. By dividing the number by 8, you can determine it roughly in megabytes per second; it will be more convenient to compare it with the speed of your memory card.

The bit rate indicator depends, as you might guess, on the processor and the software and hardware that is properly optimized to process the video stream. If all conditions are met, the video stream will be compressed with high quality and with minimal loss. Otherwise, the video will have noise, blurred images, artifacts, and other nasty distortions.

The bit rate also affects the size of the file. For example, at a relatively low bit rate (less than 10 megabits per second) more clips can fit on the memory card and cheap low speed cards can be used, but the video quality and details will be low. At a higher bit rate (10-20 begabits per second and more), the image will be of higher quality and more detailed. But the file size will also increase, so you need a memory card of the appropriate size and speed (16GB and above, class 10).

Manufacturers rarely indicate the bitrate on the box, therefore it is almost impossible to find out this indicator before buying. However, sometimes on the packaging you can see promises, for example, “8 hours of video in maximum quality at 32 GB”. And in this case, the bit rate can be roughly calculated. The formula is not complicated:
We took 32 gigabytes and, using the school’s computer skills, we converted them to megabits by multiplying them by eight and by 1024. Then we divided the resulting number by the number of seconds in eight hours.
– (32x8x1024) / (8×3600) – We get the result of 9.1 megabits per second.

Let’s clarify that the result will be conditional. First, because the actual volume of any card is always less than indicated. Second, the promises in the box can be just promises. Therefore, before buying, it is better to carefully study the selected model, having learned the speed of writing in the reviews.
So what bit rate should I be aiming for?

Given the adequate quality of the filling of the recorder (matrix + processor + lens + software), according to our practice, let’s say that this figure is in the region of 15 to 45 megabits per second. This bit rate allows you to get a fairly adequate video quality during the day. Again, only during the day, because night recording, as we all know, is still a weak point of many recorders due to insufficient lens aperture and small matrix pixel size.

Note that currently the maximum bit rate for recorders has been reached: 45 megabits per second, but only when working with a card with a capacity of 32 gigabytes or more. Some companies, notably Datakam and BlackVUE, are introducing bit rate selection options in settings. We find this option controversial. In our opinion, all drivers are initially interested in the highest quality videos, and it is easier to set the maximum bit rate for the recorder right away and just choose the right memory card in terms of speed and volume.