ntsc film to ntsc

[joshuaindi169]

sorry if this has been answered before but i am really struggling
i have a .avi @ 23.976 and am trying to convert it to a dvd compliant file using tmpgenc.
i use the ntsc template my dvd player will accept both types however i get lip synch always i have removed any bad frames but am at the stage where i am about to give up on the whole thing as i am getting no where.
any help anbody can give would be apreciated.

[adam]

If your source is NTSCfilm, then you always want to keep it that way. Converting to NTSC decreases quality substantially and can lead to sync problems if not done right. Using TMPGenc, set the output to 23.976fps and enable the 3:2 pulldown while playback option on the video tab. Your video will be stored at 23.976fps and converted to 29.97fps during playback by your dvd player. This is by far the best way to encode NTSC material and it is fully DVD compliant. In fact, the vast majority of commercial NTSC DVDs are made in this exact way.

[FOO]

Adam,
That brings up a (sorta) interesting question.
Can you Telecine 24 fps NTSC FILM the hard way ?
That is actually store the 5th frame instead of using the
rff tff flags. I know it's legal but are there any programs
to do that ? (without encoding )

[adam]

Well if you want to do a hard telecine then you'd have to re-encode, there's no other way. But yes, TMPGenc has a 3:2 pulldown filter on the advanced tab which does just that, interlaces every frame and repeats fields in a 3:2 pattern giving you telecined NTSC output, of course this only works if your source origintes as film. Again, I can't really think of any reason why anyone would want to do this unless they were planning on transfering it to an analogue medium.

[FOO]

I'm still working on my favorite problem - editing MPEG2
video. I'm still having trouble when it has soft pulldown.
Was thinking about making a test case with hard pulldown.
Theoretically this could be done without encoding. The required
fields already exist.

[adam]

I dont see why a progressive 23.976fps w/ pulldown flag mpeg2 file could be difficult to edit. If the program is parsing the pulldown flags then just remove them prior to editing, then add them afterwards. The last thing you would want to do before editing the footage would be to telecine it. Then you would have to worry about your edit points falling on an interlaced frame.

No, there is absolutely no way to hard telecine 23.976fps footage to 29.97fps without re-encoding it. Mpeg is a particular type of ENCODING. The frames are put into groups (GOPs) and then they are decoded in pieces per say. Its like a code. You can't rearrange things without rewriting the code. If you wanted the extra frames without having the decoder create them at playback, then they would have to be stored somewhere. Bits would have to be allocated to them. This is what encoding is. Yes you are right, with an NTSCfilm source all the information needed to create the new frames is present. That's why there is no reason to duplicate the fields prior to encoding. You store it once, then let the decoder create the new frames.

You can still edit an NTSCfilm encoded mpeg2 file with pulldown flags as if it were hard telecined. It all depends on the decoder your editing software uses. For instance TMPGenc uses 3rd party decoders, and pretty much any one you will use will parse the pulldown flags. So as you edit the footage, you will get all 29.97 frames per sec, if that is what you want.

When it comes to Mpeg NTSC material, your footage is either 23.976fps (internal 29.97fps) or its 29.97fps. To go from one to the other requires a re-encode.

[FOO]

You're rightI It is more complicated than I was thinking.
For some reason my mind was on I frame only encodes.
In that case (only) the 5th frame would be easy to reconstruct
and insert.

You are also right in that it shouldn't be much harder to edit Telecined
MPEG2 but it seems to be. In other words, programs that work perfectly
on CAPTURED NTSC Film which ends up Hard Telecined because all the
frames are really there, fail on soft telecined video.
I have observed this whether I IVTC a capture with TMPGENC or
IVTC on the fly.

My test editors are TMPGenc cut & merge , womble MPEG2VCR, and
VS7.

What do you suppose an editor does when you tell it to cut immediately
after a frame containing a RepeatFirstField flag ? How does the sequence after the cut know to add a field ? It can't, so now we are missing
a frame and are out of sync by 34 ms.

Of course the editor could construct a real frame to replace the
missing virtual frame. After all a frame accurate MPEG2 editor has to
re-encode up to a whole GOP if the cut is in the GOP.

I didn't intend to bore you to death,

[adam]

Again, TMPGenc uses 3rd party decoders to access the footage. It is given what the decoder spits out. So if your decoder is parsing the pulldown flags, then once it reaches TMPGenc it is really no longer progressive 23.976fps. You are editing the result of the telecine. What you see is what you get, so edit how you like.

If you were to remove those flags or bypass them via something like DVD2AVI's forced film, than you are dealing with 24fps material. There is no such thing as a frame containing a rff flag. The flag is in the file header, it tells the decoder to repeat the fields in a sequence. So you can cut the file into as many pieces as you like, at any point you like, and if you go back and add pulldown flags to each piece, they will all be telecined by the decoder separately, in the same way. All the rff flag says is to, repeat these fields skip these fields, repeat these fields, skip these fields, etc... You can take frames out in between or do whatever you like, and the process is still the same. Its not a matter of designating a particular frame that gets repeated, its a matter of designating a particular frame number that gets repeated. So if you take out the 5th frame in the sequence, well the next frame you keep becomes the 5th frame, so it makes no difference to the decoder doing the telecine.

[joshuaindi169]

thanks for the replies.
i have converted the file using tmpgenc as suggested however when i then convert to dvd with tmpgeauthor and played the file on my pc before burning i get lip synch are you suggesting that my standalone dvd player will correct this but the dvd player on my pc will not if that is the case i am ok.

[Craig Tucker]

If you are getting problems with audio sync it is probrably the fact that the audio is encoded with a variable bitrate which TMPGEnc cannot handle properly. Open the file in virtual dub, if it has vbr audio a warning dialog box should pop up notifying you of this. You need to save the audio as an uncompressed wav file and use this wav file as your audio source in TMPGenc. Under audio in vdub select full processinbg mode and select no compression. Then save the wav file. The resulting file will be large, approx 10Mb/min.

[joshuaindi169]

thanks for your reply craig but i have already sorted the avi to wav.
the problem appears to be the 23.976fps
but people have advised that tmpgenc will sort this however when i try and play the dvd from my hard drive it synchs does the 3:2 pulldown only work once burned and played on a standalone dvd player ?

[FOO]

Well Adam that's a revelation. I thought the flags were in each
frame.
Now I'm really confused. I now don't understand how
mixed video works.
Say I capture a movie from tuner. DVD2AVI reports NTSC during
commercials and FILM during the movie. Vdub reports somewhere
between 24 and 30 fps -( total frames / total time )

Now I run IVTC on this.
So there is a header everytime the mode changes in the stream ?
Maybe the flags are in the GOP headers ?

If I now try to cut the result, I get A/V desync.

I think I need to get a definition of the MPEG2 stream. I want to figure this
out. Anybody know where one is ?

[FOO]

Adam,
Sorry, your guesses are incorrect.
I have managed to obtain ISO 13818-2
EVERY frame or field in an MPEG2 stream has
a Picture Header Extension which contains among other things
the famous RFF TFF flags.


And.... I don't think TMPGenc uses the same MPEG decoder
for MPEG tools as it does on the main encoding function
I spoze I gotta prove that too....

[adam]

Now I'm really confused. I now don't understand how
mixed video works.
Say I capture a movie from tuner. DVD2AVI reports NTSC during
commercials and FILM during the movie. Vdub reports somewhere
between 24 and 30 fps -( total frames / total time )

Well now I'm confused. If you captured it then how the heck can any portion of it be FILM and how the heck can there be any pulldown flags? Portions of it may have originated as FILM, but that's different. There should be no RFF/TFF flags anywhere in the stream, it is now simply a 29.97fps interlaced source. Its hybrid in the sense that some portions originated as FILM and some didn't, so it did not all undergo a typical telecine but its still simply an interlaced 29.97fps stream and must be treated as such. If you want to edit this footage you should cut out the commercials, then run an IVTC filter on it. The jump from one part to another should not be a problem for a decent IVTC filter, that's what pattern guidance is for. I'm sorry, I still don't understand what the problem is. Exactly what is your source, exactly how are you processing it, and exactly what problems are you running into? Sync problems? motion problems? If you are talking about an analogue capture than pulldown flags have absolutely nothing to do with this.

Sorry, your guesses are incorrect.
I have managed to obtain ISO 13818-2
EVERY frame or field in an MPEG2 stream has
a Picture Header Extension which contains among other things
the famous RFF TFF flags

Well then I guess I stand corrected. I still don't see what difference it makes though in regards to your problem. Assuming you even have material with RFF/TFF flags, which in your previous example I don't see how you could, then you either leave them intact and edit the telecined interlaced 29.97fps output, or you remove them first and edit them progressively. If the only portions which are NTSC are ones that you are editing out, then this should not be a problem. A frame is a frame. As long as the source frames in your material follow the same temporal pattern, ie: are supposed to go in that order and with no missing frames, then the telecined output should look fine too. Your going back and re-adding the RFF/TFF flags to the new output, so it doesn't matter that prior to editing that a field from that particular frame may or may not have gotten repeated.

And.... I don't think TMPGenc uses the same MPEG decoder
for MPEG tools as it does on the main encoding function
I spoze I gotta prove that too....

No it doesn't, but I don't see what this matters. Either way, it is easy to verify whether your pulldown flags are being parsed or not. If you want to either edit or encode the telecined output resulting from the pulldown flags, then this is easily done.

[FOO]

I'll start from the beginning..
I got tired of encoding on TV captures, so I started capturing MPEG2 on the fly. Editing commercials out was do-able with TMPGenc but as you know it has problems and you have to cut on GOp boundaries.

.. so I went looking for a way to edit MPEG2 captures frame accurately.
I found Womble MPEG2VCR - it worked perfectly. My life was complete.

Then I got greedy and wanted to capture large movies. So I captured
with-on- the-fly IVTC to buy 20% more effective bitrate.
After that edits usually caused various degrees of A/V desync.


I've been doing experiments and asking stupid questions ever since.
I believe the editing programs are broken.

[adam]

Ok, but just to get this straight, after the initial capture its still in sync correct? That would elimate dropped frames or a bad IVTC as the culprit.

Now I think you may have just stumbled onto one of the inherant limitations of mpeg2. As you know, you can only cut on an I-Frame. If you are willing to only cut to about the second, then this is fine. If you want to have frame accurate cuts then the only way is for the editor to insert an I-Frame on the specified frame, and then essentially re-encode the previous frames up to the next I-Frame, thus making a new GOP. The problem is that alot of editing programs cannot do this well, and result in desync. I know for a fact that TMPGEnc has serious issues with this, and perhaps mpeg2vcr does too. I don't know why you seem to only get this problem after IVTC'ing the capture. I guess this is a problem with the editing software, but I'm almost certain it is because of the nature of mpeg2. I have done similar editing with avi's and it is never a problem. In any case, if you are capping to mpeg2 you can rest assured that your mpg does not have an RFF/TFF flags, you'd have to insert those yourself.

[FOO]

Well I also captured an AVI and did the IVTC with TMPGenc.
It also would not edit right.
The AVI was definitely in sync and so was the encoded MPEG2.

Womble is most certainly re-encoding the whole GOP where
a cut occurs. I have made extensive tests with video containing
its own frame number.

No indeed, the captures have no flags (unless IVTC is run)
DVD2AVI is doing adjacent field comparisons to determine
possible pulldown.

Beats me so far. I'm still working on it.