With the release of Blackmagic’s new 7.3 camera update, more options are available for BRAW in the bitrate settings for all of the pocket cameras. We had previously discussed this topic in videos last year, but with this new update I decided to revisit the topic and talk about how the bitrate settings work. We will be taking a look at this in the new BMPCC6K Pro and I’ll go through a couple of scenarios that I would use certain bitrate settings over another. I’ll also explain constant quality and constant bitrate.
Before we begin, I do want to offer a helpful resource that can show you all of the settings and features on the BMPCC6K Pro. Check out my full Video Manual Masterclass.
Defining Constant Bitrate and Constant Quality
Blackmagic Design’s RAW codecs give a ton of flexibility when it comes to bitrate and data limits. Blackmagic RAW give you two different bitrate settings – Constant Bitrate and Constant Quality.
First, let’s look at a really quick explanation as to what these settings do.
Constant bitrate gives you a predictable file size when recording and won’t encode past the bitrate you chose. This is because it records at the same bitrate during recording and doesn’t alter the bitrate.
Constant quality detects what’s going on in the image you are filming and will jack the bitrate up to compensate for complex movements. However, it will drop the bitrate when it isn’t a complex image. While this ensures quality, it keeps you from knowing how large your file sizes will be. This is essentially a variable bitrate option that has a minimum and maximum bitrate that it fluctuates between.
While it’s great to have options, it does make it more complicated for you to decide on which setting to use.
A lot of people use each one differently depending on what they are filming. As always, experiment for yourself to see what works best for you!
The Constant Bitrate Parameters on the BMPCC6K Pro
Now let’s take a look at how these settings work on the BMPCC6K Pro.
Constant Bitrate gives you displays your options in ratios to uncompressed files. These options are 3:1, 5:1, 8:1 and 12:1.
Because this is the BMPCC6K Pro, I will be showing you the bitrate settings when filming at it’s highest resolution setting: 6144×3456. I’ve included the link if you’re interested in seeing what the bitrate is for different resolutions.
- 3:1, the highest setting in constant bitrate, give you a constant bitrate of 323 MB/s – about 20 GB per minute.
- 5:1 give you a constant bitrate of 194 MB per second – about 12 GB of footage per minute.
- 8:1 gives you a constant bitrate of 121 MB per second – about 7 GB of footage per minute.
- 12:1 the lowest setting, gives you a constant bitrate of 81 MB per second – about 4 GB of footage per minute.
The Constant Quality Parameters on the BMPCC6K Pro
Next, let’s look at constant quality.
Constant quality gives you four different options. Originally, the only options you could choose were Q0 and Q3, but with the new 7.3 update, Blackmagic added both Q1 and Q5.
- Q0 is the highest setting for constant quality. This gives you a fluctuating bitrate between 242-483 MB’s – giving you a potential file size range of 14.5 GB to 30 GB per minute
- Q1 gives you a fluctuating bitrate of 162 MB to 387 MB. This gives you a potential file size range of 9 GB to 23 GB per minute.
- Q3 gives you a fluctuating bitrate of 108 MB to 277 MB. This gives you a potential file size range of 6 GB to 17 GB per minute.
- Q5 gives you a fluctuating bitrate of 65 MB to 162 MB. This gives you a potential file size range of 4 GB to 10 GB per minute.
The Importance of Bitrate
So why does bitrate matter anyway?
A lot of people confuse bitrate and resolution, but they are not the same thing. Resolution is the pixel size of your video. However, it does not ensure quality. While you may have more pixels, the reason it looks as good as it does is because of bitrate. As a video gets larger it must spread information across all of the pixels in the image. In filming at 6K, you have a lot of information to cover. Therefore, the more information your camera ingests, the better the footage.
Now, as an extreme example, here is that same video from above rendered at 1MB per second.
You can immediately see the difference. The higher the bitrate, the better the quality and clarity of the video.
Which Setting Should I Choose?
So when should you use constant quality or constant bitrate?
For me, I look at it this way. If I’m filming in an environment like this video, where I know not much is going to change in this shot and it really doesn’t matter too much because I can control almost every element, I leave it at the lowest or second lowest constant bitrate setting. And it looks great, because not much is going on other than me talking to you.
Now, let’s say, you bring your camera out to film underwater while scuba diving. I will use the highest constant quality possible, typically because of all the complex movements going on like bubbles and changing light conditions.
I find that using a higher bitrate in poorly-lit situations will keep the image from being too noisy and keep post-production clean. When time-lapsing before sunset or sunrise, I use a higher bitrate get a better image in the varying lighting conditions.
The Choice is Yours
Finally, take from what I do and the information I gave you in this video and article and apply it to how you film. My goal is to give you all the available information and my experience to help you determine what fits your needs.
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