H.265 vs H.264: CCTV Compression Explained

The short answer

H.265 (also called HEVC) produces a similar picture to H.264 at roughly half the bitrate. For CCTV that means about half the storage and half the network load. Almost every current IP camera and NVR supports it, so for a new system H.265 should be the default.

What compression does

A 4MP camera produces a huge amount of raw image data every second. Compression throws away what the eye will not miss and, more importantly, only stores what changes between frames. A wall that has not moved is stored once and then referenced, not stored 20 times a second.

H.265 does this more cleverly than H.264. It can use larger and more flexible blocks, which suits CCTV scenes with big areas of unchanging background — car parks, corridors, factory floors.

Side by side

Smart codecs: H.265+ and similar

Most brands add their own layer on top, such as Hikvision's H.265+. These codecs separate the still background from moving objects and spend very little data on the background. On quiet scenes — a store room at night, an empty corridor — the saving over plain H.265 can be large. On busy scenes like a road or a crowded entrance, the extra saving is small.

Smart codecs can make some analytics or third-party software unhappy, because the stream is less standard. If you use a separate video management system, check that it supports the codec, or record the main stream in plain H.265.

Settings that matter more than the codec

• Frame rate: 15 fps is enough for most security cameras. Dropping from 25 to 15 fps cuts data noticeably.
• Bitrate type: variable bitrate (VBR) with a sensible maximum saves space on quiet scenes; constant bitrate (CBR) keeps quality steady on busy ones.
• I-frame interval: longer intervals save space, but make seeking in playback slower. Twice the frame rate is a common setting.
• Sub-stream: set a low-resolution second stream for phone viewing so remote access does not choke your internet line.

When to stay on H.264

If you have an older NVR, a viewing PC or a video wall decoder that cannot handle H.265, keep H.264 on the affected streams. You can also run H.265 on the main recording stream and H.264 on the sub-stream for older viewing devices. Mixing is fine; the recorder handles each stream separately.

Getting it set up properly

Codec, frame rate and bitrate settings are usually left at factory defaults, which wastes storage or hurts picture quality. When we install or service a system we set these per camera, based on what each camera is watching and how many days you need to keep.

Example: the same disk, more days

An office with twelve 4MP cameras on H.264 was getting about 18 days of recording on its 8 TB of disks. Switching every camera to H.265, keeping the same resolution and frame rate, and enabling the brand’s smart codec on low-activity cameras such as corridors and the store room, raised retention to over 30 days without buying new disks. Picture quality at the entrance stayed the same; the busier cameras saw the smallest gain, as expected, because compression works best on static scenes.

Quick answers