Iframe interval on Dahua cameras

[rado stefano]

Hi Guys,
I read somewhere to match the FPS to the Iframe interval on Dahua cameras.
When I change the frame rate to lets say 15 the Iframe interval is automatically adjusted to double that value 30.
Which one is better?
Thanks

 

[Cesare]

Can someone explain me exactly what is the iframe ?

 

[bigredfish]

Some debate but I have found matching the I frame to FPS to work well..

I Frame is a complete image in the video, a full JPG if you will. Other frames in the video, P and B frames, contain partial image information, just the parts of the image that have changed from the previous frame.
Video compression picture types - Wikipedia

 

[beingaware]

Higher the iframe the less bandwidth used/brighter image BUT you will get motion blur.

Lower the iframe, more bandwidth is used but motion won't blur.

Lower iframes can cause refresh stutter/strobing of grassy areas etc.

Depends on your visual requirements really.

 

[NoloC]

Higher the iframe the less bandwidth used/brighter image BUT you will get motion blur.

Lower the iframe, more bandwidth is used but motion won't blur.

Lower iframes can cause refresh stutter/strobing of grassy areas etc.

Depends on your visual requirements really.

Not

 

[beingaware]

Not

What I've observed with my cameras.

I get more motion blur with higher iframe intervals at night, while lower numbers strobe grass in the day.

Also noted the image was ever slightly darker with lower iframes intervals.

This is based of direct observation with 5 different Dahua models.

 

[Semper Gumby]

Higher the iframe the less bandwidth used/brighter image BUT you will get motion blur.

Lower the iframe, more bandwidth is used but motion won't blur.

Lower iframes can cause refresh stutter/strobing of grassy areas etc.

Depends on your visual requirements really.

The I frame is a complete stand alone frame (like a jpeg) it contains the most bits of the other frames (P and B if used). The other frames usually just contain bits that changed from the I frame. Increasing the I frame will increase the bit rate.

 

[beingaware]

The I frame is a complete stand alone frame (like a jpeg) it contains the most bits of the other frames (P and B if used). The other frames usually just contain bits that changed from the I frame. Increasing the I frame will increase the bit rate.

iFrame rate vs interval.

1 iFrame every 50-100 frames vs every 25 etc.
One iFrame every 25 frames will take more bandwidth then one every 100 frames.

 

[Semper Gumby]

iFrame rate vs interval.

1 iFrame every 50-100 frames vs every 25 etc.
One iFrame every 25 frames will take more bandwidth then one every 100 frames.

Thanks for the clarification. My 3 year old Hikvison 2032s set "I Frame Rate" my new Dahua's use "I frame interval". I missed the word Interval. I have my Dahua's I frame interval set too high (50). I'm going to reset them to 25 and see what happens.

 

[NoloC]

What I've observed with my cameras.

I get more motion blur with higher iframe intervals at night, while lower numbers strobe grass in the day.

Also noted the image was ever slightly darker with lower iframes intervals.

This is based of direct observation with 5 different Dahua models.

Of course that is anecdotal and not what I observe. But more importantly can you point to a citation anywhere supporting your statement?
I see the logic in it, but not sure there aren't additional factors influencing what you see.

 

[suddenstop]

As stated above, the iframe is a complete picture and the other frames are just the changes.

The downside to increasing the iframe is more bandwidth / storage.

If your camera kicks on for event recording (and you are not recording continuously) the screen will be black until the first iframe is reached.

I find this a very good basic explanation of how it works:

Video compression picture types - Wikipedia

 

[bp2008]

Higher iframe intervals (fewer iframes) yields a better compression ratio. Higher quality at less bandwidth/storage space.

Lower iframe intervals (more iframes) yields poorer compression but has the benefit of allowing more efficient seeking through clips, motion-triggered recording can start more promptly, and in some cases it will help make an unstable video stream become more stable.

If you see differences in brightness, motion blur, or that strobing effect, then your bit rate/quality is probably set too low, or the firmware is glitchy.

I personally run most of my iframe intervals at 2x the frame rate.

 

[rmalbers]

It looks like in H264 it gets even more complicated and Iframes have even less meaning, amazing what these video encoders are doing and how they are progressing.

 

[aristobrat]

It looks like in H264 it gets even more complicated and Iframes have even less meaning, amazing what these video encoders are doing and how they are progressing.

IMO, it is amazing how the encoders are progressing, but iFrames can still have a of of meaning.

With Dahua NVRs, they'll create a separate recording for Motion Detection or IVS events. My experience has been that these separate videos almost never start with an iFrame, so when you go to play them back, it will display a black screen for every frame from the start of the clip until it hits the first iFrame. If you have your cameras iFrame interval set to the Dahua suggested default of 2x your frame rate, that can be up two seconds of the recording that you miss.

 

[Crows]

Hey guys interesting topic , I noticed my I Frame Inerval was set to a default 2seconds , my FPS is 20 , so as old as previous posts are ....are you still using I Frame Interval should be double FPS ...or have thing's changed?

 

[mikeynags]

I still run my fps and iframe at the same value of 20. After reading the post from @bp2008 I think I will try the 2X on some cams and see what it yields.


Sent from my iPhone using Tapatalk

 

[sebastiantombs]

Just remember that if you're running BI the sub and main streams need the same iframe settings and that Ken recommends matching iframe and frame rates to begin with. It can be important with motion detection and alerts.

 

[mikeynags]

Just remember that if you're running BI the sub and main streams need the same iframe settings and that Ken recommends matching iframe and frame rates to begin with. It can be important with motion detection and alerts.

Yes - you are correct - I recall that now. Standing down .

 

[Robertomcat]

Higher iframe intervals (fewer iframes) yields a better compression ratio. Higher quality at less bandwidth/storage space.

Lower iframe intervals (more iframes) yields poorer compression but has the benefit of allowing more efficient seeking through clips, motion-triggered recording can start more promptly, and in some cases it will help make an unstable video stream become more stable.

If you see differences in brightness, motion blur, or that strobing effect, then your bit rate/quality is probably set too low, or the firmware is glitchy.

I personally run most of my iframe intervals at 2x the frame rate.

But when there is a lot of movement in the scene, I understand that a lower i-frame rate will be better, right? Currently in my cameras I run the same rate of FPS as i-frames, but in one I have a lot of movement in the scene, and I don't know what would be better.

 

[adamg]

But when there is a lot of movement in the scene, I understand that a lower i-frame rate will be better, right? Currently in my cameras I run the same rate of FPS as i-frames, but in one I have a lot of movement in the scene, and I don't know what would be better.

Setting i-frame rate to 1 per second is not optimal. It is inefficient and results in larger bitrate than is necessary.