What is CQP Rate Control in OBS Studio?

This article explains the Constant QP (CQP) rate control method used for video recording in OBS Studio. You will learn how CQP works, why it is highly recommended for local recording, how to choose the ideal quality values, and how it compares to other rate control options like CBR.

Understanding CQP (Constant Quantization Parameter)

CQP stands for Constant Quantization Parameter. It is a rate control method that instructs your hardware encoder (such as NVIDIA NVENC, AMD AMF, or Intel Quick Sync) to apply a fixed amount of compression to every frame of your video.

Unlike other rate control methods that target a specific bitrate (the amount of data processed per second), CQP targets a specific, consistent level of visual quality.

How CQP Works

In video encoding, “quantization” is the process of discarding visual data that the human eye is less likely to notice in order to reduce file size.

When you use CQP, you set a fixed compression level (the QP value). * In simple scenes (like a static desktop or a paused game), the encoder needs very little data to maintain your chosen compression level, resulting in a tiny file size. * In complex scenes (like fast-paced gameplay, explosions, or moving grass), the encoder will automatically allocate more data to maintain that exact same level of visual clarity.

Because of this, CQP ensures your video never suffers from pixelation or compression artifacts during high-motion moments, but it does not waste storage space during slow or static moments.

Recommended CQP Values for OBS Studio

In OBS Studio, the CQP scale typically ranges from 0 to 51, where lower numbers represent higher quality (less compression) and higher numbers represent lower quality (more compression).

• CQP 0 (Lossless): Do not use this unless you have a specific scientific need. It results in massive file sizes that can overwhelm your storage drive and cause lagging recordings.
• CQP 14 – 16 (Near Lossless): Ideal for professional video editing where you need the absolute highest quality before rendering. File sizes will be very large.
• CQP 18 – 20 (Excellent Quality): The sweet spot for most content creators. The visual quality is virtually indistinguishable from lossless, and file sizes remain manageable.
• CQP 22 – 24 (Good Quality): A great option if you have limited storage space. The quality is still very good, but file sizes are significantly smaller.

To set this up, go to Settings > Output, set the Output Mode to Advanced, navigate to the Recording tab, choose your hardware encoder, and select CQP as your Rate Control.

Why CQP is Preferred for Recording (But Not Streaming)

Why it is great for local recording:

• Consistent Quality: You will never get blurry or pixelated footage during intense action.
• Efficiency: It only uses the exact amount of storage space required to maintain your target quality.
• Lower CPU/GPU Overhead: Because the encoder does not have to calculate how to fit the video into a strict bitrate limit, it requires less processing power.

Why it should not be used for streaming:

Streaming platforms like Twitch and YouTube require a stable, predictable flow of data (using CBR or Constant Bitrate). If you attempt to stream using CQP, a sudden high-motion scene in your game will cause your bitrate to spike massively, exceeding your upload bandwidth and causing your stream to lag or disconnect.