Help! bitrate shoots up after pulldown -prog_frames p?

[wfn1]

i'm trying to author with maestro and i've done a fair share of projects but this one has me stumped.

I sometimes get warning messages when compiling about exceeded bitrate but usually everything works out just fine.

However, this time I got "Please reduce stream bitrate or number of streams to be multiplexed" and maestro cancels the build after about 30% through.

So I went ahead and re-encoded the movie with max bitrate set at 9000 instead of the usual 9800 in CCE. Same problem in maestro during compile. So what I did was, I ran bitrate viewer on the encoded .mpv and it was well within the norm (high 8942, avg 5526) then I ran bitrate viewer on the same .mpv but after i telecined it using pulldown.exe with "-prog_frames p" set. The bitrate shoots up to 12000something.. no wonder maestro is bitching.

So, what I'm trying to find out is this behavior normal for pulldown (btw i use .99d)? What should I do? re-encode with an even lower maximum bitrate? Should I skip the prog_frames p flag?

Thank you!

[slk001]

Did you set the frame rate with pulldown? If anything, bitrate viewer should show you a lower bitrate than the actual, because it doesn't handle the pulldown flag properly (ie, if you encoded at 23.976 and applied a 2:3 pulldown, then your file will appear as a 29.97 fps file, but it really is a 23.976 file - BRV makes its calculations based on the 29.97 instead of the proper 23.976). Take your total .M2V file size (in BITS) and divide it by the total time (in secs) to find out exactly what your average bitrate should be.

For Masetro, you should use in your PULLDOWN options:
-framerate(29.97)
-prog_frames p
-drop_frame true (check my syntax)

NEVER use -prog_seq p (on most encodes, anyway).

Maestro has an option to show the bitrate profile in the video timeline - does this show unusual high peaks? I would try running PULLDOWN again (although I have never had it fail to work properly).

[wfn1]

thank you for your suggestions, I was not specifying the frame rate in pulldown, so I'll give that a try tonight.

In fact I tried pulldown last night without the -prog_frames p and the peak bitrate went down to 10800 which would still be too much since I also have an audio track and subs. Strange behavior. Also, judging by my file size my average bitrate should be 5928 and some change.

Thanks!

[wfn1]

I've just been told by some people in #doom9 to try and uncheck the "DVD Compliant" checkbox in video properties in CCE. I will also give it a shot after I try the framerate suggestion. If you have any more insights into the issue, please reply.

[wfn1]

unfortunately manually specifying the frame rate does not solve the problem. The peak bitrate is still too high to be authored by Maestro. I will try to uncheck "DVD Compliant" in CCE and re-encode with 9000 set as the max bitrate. Will report later.

[wfn1]

I regret to inform you that unchecking the "DVD Compliant" checkbox in CCE did not solve the problem. I'm at a loss here, before pulldown BitrateViewer reports peak at 8859 and after pulldown the peak is 11223? Allthewhile the spec window shows nominal bitrate at 9000. What wrong with this picture, obviously pulldown is doing something not right. Any ideas?

[auenf]

what exact switches are you using in pulldown.exe and what version of pulldown are you using?

Enf...

[wfn1]

auenf,

i'm using pulldown.exe by Hardcode v.99d.

using the following switches:

-prog_frames p
-framerate 29.97
-drop_frame true

I tried omitting these one by one till i had just pulldown with no options and that did not help. I've read somewhere that there is a bug in BV when scanning telecined material so my thinking is there must be something happening during VBR encoding in CCE.

I was also advised to try and check "Close all GOPs" in CCE GOP settings and lower the max bitrate further. Right now I have an encode going with "DVD Compliant" unchecked, "Close all GOPs" checked and max bitrate set at 8000. I will report later on tonight if the issue is resolved.

[wfn1]

re-transcoded with settings mentioned in the previous post, bitrate should be well within the spec, checked with BV looks good (max ~8600 on the 24fps film and around 9800 on the telecined .m2v) Tried to author in Maestro again, same problem as before. Decided to remove the subtitles and magicaly the compile went through without a hitch!

this is really strange because i though the subtitles only take up like 15kbps? the subtitles were created using Trilight's method described in DVD9 to DVD5 FAQ utilizing SubRip 1.09.

Any ideas?

[wfn1]

I was recommender to try and transcode the audio track (.ac3) which I just did in BeSweet and as I expected that did not do anything. We can chalk off another trick.

[Inwards]

Okay, just a couple of things...

First of all, pulldown.exe doesn't change the bitrate, regardless of what settings you use. What happens is that dumb MPEG analyzers don't take into account the fact that telecine is present when the report the framerate. BitrateViewer sees the new framerate of 29.97fps and assumes that all the progressive frames are going to be played back at that rate - ie; it's adding 6 phyisically encoded frames into the equation, dramatically pushing up the reported bitrate. Basically, you can ignore the bitrate that these programs report.

The only two programs that actually report the true bitrates of telecined streams are pulldown.exe itself (which displays the results at the end) or ReMPEG.

Second, as you've probably guessed by now, your problem is simply that you've set your max bitrate too high. The problem with subtitle streams is that it's often impossible to accurately guess their size. The reason for this is that they're not encoded at a constant or average bitrate. A 90 minute movie with 2000 sub pictures will produce a sub stream twice as large as a 90 minute movie with 1000 sub pictures.

One thing you can do is to demux the original subpicture stream with a program like VobSub (honestly, since VobSub will convert to Scenarist or Maestro and preserves all the colours correctly, I don't know why anyone even bothers with the Subrip method) and examine the size of the file that VobSub outputs. Add the size of the subpicture stream to the size of the rest of the DVD assets that you plan to keep, otherwise you might run out space, even if you don't exceed the maximum bitrate. And remember to deduct this from your maximum bitrate as well...

[wfn1]

Thanks!


Second, as you've probably guessed by now, your problem is simply that you've set your max bitrate too high.


So, in essense you think that my reading of max bitrate is incorrect using BV on a 23.970 fps .mpv ?

As I mentioned in my previous post it's at 8600, I have 1 soundtrack at 96K and about 1200 subtitles. So do you mean to say that the subtitles can actually occupy 1104k of bandwidth?

There has got to be a glitch in one of the programs I'm using. I'm gonna try Scenarist tonight and see if it gives me the same issue.

On another note, what do you think I should set my max bitrate to in CCE? I never had a problem with a default setting of 9800 in there and I've done close to 200 transcodes. Right now I'm using 9000 as the max and for that one problematic encode I lowered it to 8000.

I admit that most of my encodes did not have subtitles and sometimes Maestro would give me a high max bitrate warning, but everything would work fine after that. This is the first time I'm having it cancel the compile because of the max bitrate.

[Inwards]

Yes, I'm basically saying the BitrateViewer is broken when it comes to analyzing streams with pulldown applied. BitrateViewer will always report a telecined stream as having 1.25x it's true bitrate.

A lot of folks don't really understand how max bitrate works or is calculated. I'm really surprised that none of the DVD bitrate calculators out there seem to take this into the equation (which is why I wrote my own ages ago).

For DVD authoring, a bitrate calculator needs to tell you two things:

1) What the average or constant bitrate needs to be in order to best utilize all the space on the DVD, and...

2) Given all the audio and subpicture streams that you'll be muxing with the video stream, what is the max bitrate that can be reached without incurring a buffer underrun.

Remember that the max TOTAL bitrate that your DVD player can support (ie; how fast you player can read data off the disc) is only around 10 megabits. Total. So... m2v @ 9600kbits + ac3 @ 96kbits + subs @ 100kbits, plus miscellaneous padding stream information makes things very tight. If you have a scene with a whole mess of subs, you can spike over the legal max.

Personally, I always start off with 9000kbits for video and deduct the ac3 bitrates from it. Then I add the size of the original subs into the other assets that I'm keeping from the original disc.

I'd leave that DVD Compliant box in CCESP unchecked as it forces the max bitrate stamp up to 9800k.

[wfn1]

So... m2v @ 9600kbits + ac3 @ 96kbits + subs @ 100kbits, plus miscellaneous padding stream information makes things very tight. If you have a scene with a whole mess of subs, you can spike over the legal max.


well, but the m2v is 8600kbps, that's what's strange.

[Inwards]

Load the m2v into ReMPEG. It will give you a real min, max average reading. CCESP may have accidentally spiked. I used v2.50 exclusively and have never had this kind of problem. I'm not sure if other versions have max bitrate issues or not.

[wfn1]

checked the .m2v file in rempeg and the bitrate is 8600 so there should be no problem. Just authored the whole project in Scenarist 2.6 and it went through without a hickup. So all in all I think I found a bug in Maestro. I'm burning the DVD right now.

An unrelated question, what does the highlight stream do in scenarist after you import the subtitles? I looked at the screenshots in the guide and didn't see it.