I-Frame Interval - DevApi Builds

[octapus]

I noticed that all latest builds, (Koepis 04102002-12102002,Nics 13102002) do not respect i frame MAX intervals.

I use of course b-frames. After all, bframes made me encode with dev-api builds. So b-frames is what these builds all have in common. I faintly remember reading somewhere else about it. I suspect that b-frames are not taken into account when numbered, only iframes and pframes. Remember also that bframes are dynamic.

Maybe an xvid developer could say when will this be fixed. It's not something very important but there are some occasions when for exmaple seeking that it's useful to have iframes be put at least every 300 frames.

On the latest encode i did, searching manually the first 5000 frames, i found on extreme occasion two i-frames and between them 800 (bframes and pframes).

As statistics have a look at final results after inspecting second pass log taken from dbg.

Number Of Intra-Frames (Key-Frames) : 1088
Number Of Inter-Frames (P-Frames) : 251007
Total Number Of Frames : 252095

0.43% of the Movie is Intra-Frames (Key-Frames)
99.57% of the Movie is Inter-Frames (P-Frames)

PS I put MAX I-Frame Interval 300 and Min 4, and B-frames Number 2 with quality 150 (Divx5 Compatibility).

[iago]

@octapus

First, Koepi's 04102002-1 build is a (very ;)) stable one without B-frames (and without QPel).

Second, yes, this issue is one of the current problems with B-frames.

regards,
iago

[octapus]

Maybe i'm wrong with koepi's 04102002(about it containing enabled b-frame code), cause it's fifteen days ago. But i'm talking about all latest b-frame enabled code, from wherever they come from(even from umanics though i haven't tested it)

[wing1]

@octapus

Look 8-> here (http://forum.doom9.org/showthread.php?threadid=34956&perpage=20&pagenumber=6) . iago is correct regarding Koepi's 4102002-1 (stable build): The B-frame is all dev-builds. Try reduce your I-frame interval by (max I-frame interval/max-bframe) and see if that helps. It works for me.

[octapus]

wing1:
I tried to find a solution like the one you mentioned for all b-frame enabled builds. But since b-frames are dynamic(that's what they say) we can't really be sure if maximum b-frame number will be put everytime.

For example in order to get iframe every 300 b,p-frames you should norammly put 100 max iframe interval if max number of b-frames is 2.
But what if encoder decides it's not best to always put 2 bframe( You know IPBBPBBPBBP for Divx5 Compatib Mode)

[wing1]

@octapus

This is what the codes are supposed to do. However, it is still in development and it may be a bug that is messing with I-frame interval during B-frame encoding. I look at the video tab in vdub during encoding to see how the I-frame are being placed and how the scene changes are being utilized. for B-frame encoding, the RED line (I-frame i supposed) are far few in between when Max I-frame interval are at the normal 300(NTSC 29.97->10secs). The far/few in between can be up to 2 minutes sometime! This is also reflecting on seek time during playback (reminds me of ASF/VKI seek time :D ). However, if I set Max I-frame interval to 150, then I start to see the RED line at the normal position as if I had set it to 300 in the first place (weird). Seek time during playback is also back to normal(300).

[octapus]

@wing1

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I look at the video tab in vdub during encoding to see how the I-frame are being placed and how the scene changes are being utilized. for B-frame encoding, the RED line (I-frame i supposed) are far few in between when Max I-frame interval are at the normal 300(NTSC 29.97->10secs). The far/few in between can be up to 2 minutes sometime!
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Hey , that's 3000 frames with only pframes and bframes. It's a really big number indeed. Your B-Frames max number must have been >=5.Anyway I would suggest to view Debgview results so as to be as accurate as possible.

Anyway, i expected that -h, koepi, Nic (or any other Xvid developers i can't remember) which hang around Doom9 forum would post on this subject. Or should i post this at xvid.org also(which by the way is one day down and one day up).