How to improve video sound quality? – Sample size, sample rate, bit rate Part 2
Parameters related to the sound quality of the audio data.
The factors that affect the sound quality of audio data are listed below.
By understanding and understanding the following and setting them properly when creating audio data, you will be able to control sound quality properly.
Sample size (bit depth)
The larger the sample size, the finer the volume of the sound, so it sounds softer. If the sample size is small, it sounds harsh to the ear.
If it’s 16-bit, it’s 2 to the power of 16, and the volume of the sound is divided by 65536 and played.
If it is 24 bits, it will be 2 to the power of 24, which is 16777216 division.
Actually, when you create a 32-bit MP3 file and an 8-bit MP3 file from the same WAV file and compare them, the 8-bit has a “sir” noise and the 32-bit has the same level of fluency. sounds like the original rice field file. (The bit rate and sample rate of the two files are the same.)
In the case of MP3 and AAC, the bit rate also greatly affects the sound quality.
Sampling rate
This is the frame rate on the video.
It is a numerical value that indicates how many times a second is divided into data, and if it is 44.1 kHz, it means that the sound is divided into 44100 times and converted into data.
The finer the cut, the higher the sound reproducibility and the better the sound quality.
CD is 44.1 kHz, and the range said to be audible to the human ear can almost be covered by this 44.1 kHz. . So even if the sampling rate is higher than that, the human ear can’t feel it.
However, many people feel that the sound is different at high sample rates, so there are audio files with higher sample rates.
44.1kHz or 48kHz is often used for the audio of Internet videos.
Since the music industry uses 44.1kHz and the video industry uses 48kHz, it is recommended to use 48kHz for audio used for video unless there is a particular problem.
When collecting audio materials with different sampling rates into one video, problems such as sound deviation will occur.
Bit rate
It is a numeric value of how much data is voice data in one second.
The unit is bps.
If the bit rate is high, the sound quality can be improved because one second’s sound can be played with a large amount of data.
For AAC and MP3 used in Internet video, the upper limit is 320 kbps. (MP3 is the upper limit of the specification. AAC may be higher depending on the software.)
resume
To briefly summarize,
・ High sampling rate
・ High bit rate
If so, the sound quality can be improved in terms of data.
However, the higher the bitrate, the greater the amount of audio data.
If it is 320 kbps, it will be 300 MB in an hour.
I wrote that there is a trade-off between image quality and capability when deciding the image quality of a video, but the same idea applies to sound quality.
If you want to stream music clearly, you may want to consider improving sound quality at the expense of picture quality.
If it’s a movie, you can look at both picture quality and sound quality, even if it reduces viewer comfort.
If you just need to broadcast how the instructor speaks alone, like in a seminar, you probably don’t need as much sound quality.
However, if the original audio data is noisy or the sound is broken, there is little point in improving the sound quality of the data.
First of all, it may be the most important thing to try to record in the best possible environment.
I’d like to write an article about the recording method at another time.
In addition to that, it should be set to high sound quality as video data.
