Subscriber Discussion

Bitrate And Camera Quality

UI
Undisclosed Integrator #1
•Jan 15, 2017

Hey folks,

I noticed that you can set multiple parameters that effect camera performance.

Bitrate, compression, quality

For bitrate, just to confirm, you are setting the maximum bitrate, lets say 8Mbps, that's going to basically say the file size for the recordings are going to be no larger than 8Mbps no matter what. If you need to drop frames, or compression then that will be done in order to retain the 8Mbps file size -- Correct? 

I've noticed you can set Bitrate when it's H.264, but that option seems to go away when it's MJPEG -- Why? 

Does quality setting generally mean the amount of compression that is going to be applied? If so, why don't manufactures just say compression/quantization or whatever it's actually using instead of using the term quality? 

Thanks!!!

 

 

JH
John Honovich
•Jan 15, 2017
IPVM

Great questions, thanks for asking them!

If you need to drop frames, or compression then that will be done in order to retain the 8Mbps file size -- Correct? 

Yes, some manufacturers even provide a user configurable option to prioritize between dropping frames or increasing compression. That noted, one or both will need to be sacrificed when the max is reached.

I've noticed you can set Bitrate when it's H.264, but that option seems to go away when it's MJPEG -- Why? 

With MJPEG, by definition, there is no compression across frames, so that reduces the amount of variability. However, because the scene complexity can change over time, some frames may need more bandwidth for a given compression level. It has been some time since I have looked at MJPEG options but I do recall some cameras allow setting max bit rates / caps for MJPEG.

Does quality setting generally mean the amount of compression that is going to be applied?

Typically, yes. 

If so, why don't manufactures just say compression/quantization or whatever it's actually using instead of using the term quality? 

Technically for H.264 / H.265, the parameter is the quantization level. I suspect manufacturers rightfully are concerned that most users will not know what a quantization level is, therefore they use a less precise but easier to understand term like quality.

We have a number of reports that cover this, including:

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UI
Undisclosed Integrator #1
•Jan 15, 2017

Thanks John. Ive seen different manufactures have diff max bit rates. Does that basically mean a camera, lets say Hikvision caps it at 12288Kbps, will be able to 30Fps at no compression? Meaning full 100 pct quality? And different manufactures have diff max bit rates because they can handle more fps/resolution?

JH
John Honovich
•Jan 16, 2017
IPVM
In reply to Undisclosed Integrator #1

caps it at 12288Kbps, will be able to 30Fps at no compression?

No, there will still be compression. H.264 / H.265 / MJPEG, etc. all are compressed. The only difference is the amount of compression applied.

At some point, though, a user cannot tell the difference in lower compression levels, so bandwidth is just effectively wasted.

As for a cap of 12.28Mbs, with most cameras under 4K resolution, you are unlikely to visibly see a difference.

Related, one of the reasons manufacturers set a hard cap is to limit computing resource consumption, which could overload the device while not providing material image quality benefits.

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UI
Undisclosed Integrator #1
•Jan 16, 2017

So even at a 51 quantization level there is still some compression?

JH
John Honovich
•Jan 16, 2017
IPVM
In reply to Undisclosed Integrator #1

51 is the highest compression level on the scale:

As for 0, there would still be some compression. However, from our testing, few if any IP cameras / encoders allow anywhere close to 0 quantization level anyway, since the bandwidth requirements would skyrocket with minimal to no visible increase in quality.

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