Question
I uploaded a video delivered (exported) with DaVinci Resolve to YouTube, but the volume is low or the sound is distorted. There is enough volume to play the file before uploading. Is there any way to adjust the sound appropriately for YouTube videos?
Answer
If you look at YouTube, etc., you may see (or hear?) similar problems not only with works uploaded by individuals, but also with works uploaded by professional artists.
reason
The concept of loudness and the inconvenience caused by it
Web service specifications such as YouTube
Volume limit for web services such as YouTube
How to quantify problems on YouTube
What you can do with DaVinci Resolve
The reason, how to confirm the problem numerically, and countermeasures are as follows.
reason
It happens for 3 reasons.
In addition, I have written in easy-to-understand words without using technical terms as much as possible, but please point out if there are places where you would like to correct the expression.
The concept of loudness and the inconvenience caused by it
It is a method that was born with the aim of maintaining a moderate volume even when watching multiple works (programs, commercials, other channels) on TV and other services in succession. Before the concept of loudness, there was also the concept of maximum volume, but there was also the problem of always using sounds near the maximum volume, so loudness was born.
Loudness refers to the average loudness in the work, not the loudest.
A combination of soft and loud sounds can cause problems such as the soft sound being too quiet, even if the loudness is fine.
Also, even if the loudness is maintained, the volume may sound loud. This is also related to the characteristics of the human ear.
Reference: Even if the loudness is kept, the fact that the R-mobile commercial felt extremely large is firmly considered.
Web service specifications such as YouTube
Depending on the specifications of web services such as YouTube, the volume may be lowered, resulting in crackling or thinning of the sound.
Many web services that handle video and audio limit the volume in order to keep the volume consistent with other works. However, if the volume is below the limit, it will not be processed to increase the volume. This results in the following situations, depending on the work you uploaded:
- If the volume is higher than the limit,
the volume is reduced to match the other works
→ The volume is the same as the other works, but it is smaller than expected, and the sound is crackling and thin - If the volume is less than the limit,
keep the upload volume
→ keep it smaller than other works
Volume limit for web services such as YouTube
There are variations in volume limits handled by each Web service. In addition, although there are cases where the restrictions are officially disclosed, there are services such as YouTube that are not disclosed.
The meaning as a unit is different, but if you are talking about a video like this, LUFS can be read as dB.
TV -23LUFS ~ -25LUFS
Nico Nico Douga -15 LUFS
YouTube -13LUFS or -14LUFS (Information not disclosed)
Since YouTube is private, various people are investigating.
I think it depends on the time of year, but as far as I have researched, I think it is -14 LUFS. As will be described later, DaVinci Resolve has a setting that determines the loudness target during editing, but it is set to "-23LUFS" by default. (TV is the default.)
It is preferable to upload data at a volume below the limits supported by the service. The ideal is the very limit. However, the WEB service side is designed to handle even when the volume exceeds the limit, and the WEB service side lowers the volume when the volume exceeds the limit. (As far as I checked on the web, it seems that the volume of Twitter videos is not restricted by loudness.(Unverified))
How to quantify problems on YouTube
Depending on the web service used, the method of checking how much volume the original data has been published differs depending on the service.
Here, the most common YouTube is used as an example.
Open YouTube in your PC's browser and play the relevant video.
Right-click the video window during playback and select "Detailed Statistics".
We will focus specifically on the "content loundness" of "Volume / Normalized", but briefly explain the other values as well.
I will explain with an example. In the example below, it is "100% / 56% (content loundness 5.1db)".
The first "100%" is the volume position of the screen playing Youtube. It changes with the volume at the bottom left of the playback screen. At maximum volume, it will be 100%.
The second "56%" means how much the volume is lowered relative to the original data. In this example it means 56% from the uploaded data. Since the volume is "100%", you can see that the volume has been lowered to 56% as the original data. Also, if you change the volume of the Youtube screen, you can see that the value "56%" in this example changes.
The third, "content loundness 5.1dB", means that the original data is delivered 5.1dB lower. This means that it will always be played with this value lowered regardless of his volume on the screen like "2.".
If the original volume is above YouTube's limit in this way, it will be served at a reduced volume. During this process of lowering the volume, the sound will be smaller than expected, and the sound will be distorted or thin .
Also, in the following example, "-14.9dB" means that the volume of the original data is 14.9dB lower.
Note that the Volume and Normalized values match. This means that even though the volume of the original data is low, the volume at the time of distribution is not increased and distributed. This is according to the specification described in If the volume is less than the limit In other words, it can be seen that the volume and sound quality are lost by 14.9dB.
The following are rare and perfect. This is the best, but very rare. (I saw it for the first time.)
What you can do with DaVinci Resolve
A workaround is currently being developed.
Please check the following video for reference.
How to suppress loud sounds Compressors and limiters
////////////// Under construction ///////////////////////////
Set "Target Loudness Level" of "Audio Meter" in "Fairlight" in project settings to "-14". ("-23" by default)
As a result of uploading, it is desirable to create videos so that the "content roundness" is about "-3dB to 0". In addition, even if the loudness is 0 on the editing software, including DaVinci Resolve, the volume may be lowered slightly at the upload destination. Even if it is lowered a little, there will be no significant deterioration, but it is recommended to check only the minimum and maximum volume once.
Normalize
Normalize the audio level of the range to be exported on Fairlight.
Select all applicable audio, right click and select "Normalize Audio Levels"
Select "ITU-R BS.1770-4" for normalization mode,
Check with a loudness meter. Numerical display of loudness during playback.
When the volume difference is large
When there is a large difference in volume, the loudness is evaluated by the average value, so the result may be that the quiet sound is too quiet.
You may need to adjust the volume up for quieter areas or lower the volume for louder areas.
Also, as mentioned above, this is the overall average value, so it is only a guideline. You don't necessarily have to stick to the loudness value.
Of course, it is also possible to increase only a specific frequency band to match the frequency characteristics of the human ear, but it may require skill.