What does FPSden mean in AVISynth?

[seanmcnally]

Trying to render out a DVD compliant video using AVStoDVD. The resulting video is very choppy, and I'm thinking maybe it has something to do with the parameter FPSden. Taking a look at the auto generated AVISynth script, I see this

LoadCPlugin("C:\Program Files (x86)\AVStoDVD\Lib\ffms2.dll")

Audio = FFAudioSource("C:\path\file.mkv", track=-1)
Video = FFVideoSource("C:\path\file.mkv", track=-1, fpsnum=2997, fpsden=125, colorspace="YV12", seekmode=0)

Video = Video.ConvertToYV12()
Video = Video.Spline16Resize(720,480)
#PullDown: using DGPulldown/HCenc to upsize FPS

AudioDub(Video, Audio)

Now, the source is actually 23.976, and AVStoDVD reports it as "VFR" (even though it is actually CFR).

What does FPSden do, exactly? What is "den" short for? Lowering the value in AVSPmod seems to fix the choppiness, but changes the speed. Anyone have any ideas?

[poisondeathray]

fpsnum = fps numerator
fpsden = fps denominator

Technically "23.976" should be fpsnum=24000 , fpsden=1001 . "23.976" is a 3 decimal approximation

[seanmcnally]

Thanks for the info!! So, how does the whole denominator thing work? What’s the math?

[poisondeathray]

Thanks for the info!! So, how does the whole denominator thing work? What’s the math?

It's just a fraction

fps numerator / fps denominator

24000/1001 =~ 23.976024...


eg. If you had 25 FPS :

25/1 = 25


But you have fpsnum=2997, fpsden=125 . Which is 23.976 exactly. That's usually just an approximation and can cause you to go out of sync. 24000/1001 is the accurate value

[seanmcnally]

Ah, I get it now 29997 / 125 = 23.976, whereas 24000/1001 = 23.97602397602398, a more accurate value. Thanks for the info!

Unfortunately, it doesn't solve my problem, but perhaps it's a start. Thanks.

[poisondeathray]

Post in the avs2dvd thread for help

But I'd check file.mkv first to see if it was ok; then ffms2.dll - maybe some problem with that version ; check to see if script output is ok (preview in vdub2, go frame by frame)

(Technically all "23.976p" MKV's are VFR, because the timebase is 1ms. This is part of the MKV container spec. It might have nothing to do with your choppiness)

[seanmcnally]

Post in the avs2dvd thread for help
But I'd check file.mkv first to see if it was ok;[...]check to see if script output is ok (preview in vdub2, go frame by frame)

So, I did this, and it wasn't okay. In fact, even when opening file.mkv directly in Virtualdub 2 with no script or anything, playback is choppy, whereas opening in VLC media player, it's fine. Going frame by frame on both, Vdub2 reveals a lot of repeated frames (and what looks like skipped frames as well), whereas VLC does not. Why is Vdub2 reading the file so differently? Vdub is showing I-frames, B-frames, and + frames...I assume the + means repeated?

If it helps, here's the MediaInfo output for my file

General
Unique ID                                : 253814439383215743484232656925853782868 (0xBEF2E2068F63B5E24B18F530767C9354)
Complete name                            : file.mkv (edited for privacy)
Format                                   : Matroska
Format version                           : Version 4
File size                                : 2.53 GiB
Duration                                 : 44 min 18 s
Overall bit rate                         : 8 173 kb/s
Writing application                      : Lavf58.7.100
Writing library                          : Lavf58.7.100
ErrorDetectionType                       : Per level 1

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 44 min 18 s
Nominal bit rate                         : 8 000 kb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Writing library                          : x264 core 164 r3065 ae03d92
Encoding settings                        : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=10 / psy=1 / psy_rd=1.00:0.15 / mixed_ref=1 / me_range=32 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=-3 / threads=18 / lookahead_threads=4 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=11 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=480 / keyint_min=3 / scenecut=40 / intra_refresh=0 / rc_lookahead=180 / rc=abr / mbtree=1 / bitrate=8000 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=33 / qpstep=4 / ip_ratio=1.40 / aq=2:0.70
Default                                  : Yes
Forced                                   : No

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : A_AAC-2
Duration                                 : 44 min 18 s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 SPF)
Compression mode                         : Lossy
Default                                  : Yes
Forced                                   : No

Text #1
ID                                       : 3
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 42 min 55 s
Writing library                          : Lavc58.9.100 srt
Language                                 : English
Default                                  : No
Forced                                   : No

Text #2
ID                                       : 4
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 42 min 55 s
Title                                    : SDH
Writing library                          : Lavc58.9.100 srt
Language                                 : English
Default                                  : No
Forced                                   : No

Text #3
ID                                       : 5
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Danish
Default                                  : No
Forced                                   : No

Text #4
ID                                       : 6
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 42 min 54 s
Writing library                          : Lavc58.9.100 srt
Language                                 : German
Default                                  : No
Forced                                   : No

Text #5
ID                                       : 7
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 42 min 55 s
Title                                    : Spanish
Writing library                          : Lavc58.9.100 srt
Language                                 : Spanish
Default                                  : No
Forced                                   : No

Text #6
ID                                       : 8
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Title                                    : European
Writing library                          : Lavc58.9.100 srt
Language                                 : Spanish
Default                                  : No
Forced                                   : No

Text #7
ID                                       : 9
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Finnish
Default                                  : No
Forced                                   : No

Text #8
ID                                       : 10
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Writing library                          : Lavc58.9.100 srt
Language                                 : French
Default                                  : No
Forced                                   : No

Text #9
ID                                       : 11
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Italian
Default                                  : No
Forced                                   : No

Text #10
ID                                       : 12
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Norwegian Bokmal
Default                                  : No
Forced                                   : No

Text #11
ID                                       : 13
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Dutch
Default                                  : No
Forced                                   : No

Text #12
ID                                       : 14
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Polish
Default                                  : No
Forced                                   : No

Text #13
ID                                       : 15
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 42 min 54 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Portuguese
Default                                  : No
Forced                                   : No

Text #14
ID                                       : 16
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 42 min 55 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Russian
Default                                  : No
Forced                                   : No

Text #15
ID                                       : 17
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 44 min 14 s
Writing library                          : Lavc58.9.100 srt
Language                                 : Swedish
Default                                  : No
Forced                                   : No

Menu
00:00:00.000                             : :Teaser
00:04:08.248                             : :Act 1
00:15:33.182                             : :Act 2
00:27:28.229                             : :Act 3
00:35:25.164                             : :Act 4

[poisondeathray]

vdub2 is using an older ffmpeg library version , but it should have no problems with AVC . That ffms2.dll version with avs2dvd might be old too, but it should have no problems with AVC.

There might be some issues with the timestamps in that MKV causing other problems such as duplicates and skips in vdub2 and that version of ffms2. "normal" VFR jitter from MKV container should not cause that problem you describe

If you go frame by frame in VLC, are you sure it's ok ? What about other players, MPCHC, or MPV ?


You can try another source filter, like a modern LSmash version, or DGIndexNV to replace your avs2dvd script . Preview the avs in vdub2 or mpchc. If it's ok there, it will be ok in avs2dvd

[seanmcnally]

If you go frame by frame in VLC, are you sure it's ok ? What about other players, MPCHC, or MPV ?

Definitely, just double-checked. Works fine in MPCHC as well, even stepping frame by frame.

This is definitely some sort of muxing issue. My process looks like this:

Edit in Adobe Premiere > Export to MP4 > Add Subtitles and Chapters with FFmpeg > Copy Stream to MKV

If I take that original MP4 file and play it in VirtualDub, those (+) frames don't appear, and playback is smooth. Works fine in AVStoDVD as well. But the MKV file at the end of the pipeline (which is what I posted the MediaInfo output for) has these issues. VLC and MPCHC play the MKV just fine, but VDub2 and A2d have issues with it.

There might be some issues with the timestamps in that MKV causing other problems such as duplicates and skips in vdub2 and that version of ffms2.

If this is the case, is there a way to fix these timestamps? Thanks!

[poisondeathray]

First, try mkvmerge (mkvtoolnix) instead of the ffmpeg step

[seanmcnally]

I can try that. For reference, this was my FFMpeg script:

ffmpeg.exe -i file.mp4 -f ffmetadata FFMETADATAFILE -loglevel error
python "prpro_ffmpeg_chap.py" file_chapters.txt
ffmpeg.exe -i file.mp4 -sn -i FFMETADATAFILE -map_metadata 1 -codec copy "file_chapters.mkv" -loglevel warning -stats
del FFMETADATAFILE
del file.mp4
ffmpeg.exe -i file_chapters.mkv ^
-i DCTLHD_subs\!episode!_eng.srt -sn ^
-i DCTLHD_subs\!episode!_eng-sdh.srt ^
-i DCTLHD_subs\!episode!_dan.srt ^
-i DCTLHD_subs\!episode!_ger.srt ^
-i DCTLHD_subs\!episode!_spa-spanish.srt ^
-i DCTLHD_subs\!episode!_spa-european.srt ^
-i DCTLHD_subs\!episode!_fin.srt ^
-i DCTLHD_subs\!episode!_fre.srt ^
-i DCTLHD_subs\!episode!_ita.srt ^
-i DCTLHD_subs\!episode!_nob.srt ^
-i DCTLHD_subs\!episode!_dut.srt ^
-i DCTLHD_subs\!episode!_pol.srt ^
-i DCTLHD_subs\!episode!_por.srt ^
-i DCTLHD_subs\!episode!_rus.srt ^
-i DCTLHD_subs\!episode!_swe.srt ^
-map 0:v -map 0:a -map 1 -map 2 -map 3 -map 4 -map 5 -map 6 -map 7 -map 8 -map 9 -map 10 ^
-map 11 -map 12 -map 13 -map 14 -map 15 ^
-metadata:s:s:0 language=eng -metadata:s:s:1 language=eng -metadata:s:s:1 title="SDH" ^
-metadata:s:s:2 language=dan -metadata:s:s:3 language=ger ^
-metadata:s:s:4 language=spa -metadata:s:s:4 title="Spanish" ^
-metadata:s:s:5 language=spa -metadata:s:s:5 title="European" ^
-metadata:s:s:6 language=fin -metadata:s:s:7 language=fre -metadata:s:s:8 language=ita ^
-metadata:s:s:9 language=nob ^ -metadata:s:s:10 language=dut -metadata:s:s:11 language=pol ^
-metadata:s:s:12 language=por -metadata:s:s:13 language=rus -metadata:s:s:14 language=swe ^
-max_interleave_delta 0 -vcodec copy -acodec copy -scodec srt file_chapters_subs.mkv ^
-loglevel warning -stats
del file_chapters.mkv

[seanmcnally]

Update: Mission success, taking the MP4 and adding subs and chapters with MKVToolNix works in both VDub2 and AVStoDVD! No more choppiness!

Also, I know you said it shouldn't matter, but I want to note that the MKV file that MKVToolnix produces is reported as Constant Frame Rate in MediaInfo as well as A2D, whereas the MKV from FFMpeg is reported as Variable Frame Rate.

So my next question is, is there any way to fix the FFMPeg MKV files, rather than having to start from scratch with the MP4s? I kept 90% of the original MP4s, but unfortunately not all of them, and re-rendering would be a huge pain.

[poisondeathray]

Also, I know you said it shouldn't matter, but I want to note that the MKV file that MKVToolnix produces is reported as Constant Frame Rate in MediaInfo as well as A2D, whereas the MKV from FFMpeg is reported as Variable Frame Rate.

According to mediainfo; but technically it's still variable if you extract the timestamps

So my next question is, is there any way to fix the FFMPeg MKV files, rather than having to start from scratch with the MP4s? I kept 90% of the original MP4s, but unfortunately not all of them, and re-rendering would be a huge pain.

You should be able to just remux them with mkvmerge to "fix" them (and if you needed to, replace the timestamps with CFR ones. It's just a text file, read the section "external timestamp files" in the mkvmerge documentation) . It's really 2 lines. More decimal places or precision doesn't matter, because MKV only has a timebase of 1/1000s anyway

# timestamp format v1
assume 23.976

But there might be some other issues with the other files caused by ffmpeg ... You can try a few and see if they work

[poisondeathray]

If there were no other issues introduced by ffmpeg , you could probably use --default-duration 0:24000/1001p in a mkvmerge remux without using external timestamp file . It says in the documentation for default-duration you can

--default-duration TID
.
.

This option can also be used to change the FPS of video tracks without having to use an external timestamp file.

[seanmcnally]

According to mediainfo; but technically it's still variable if you extract the timestamps

Yeah, I get that. But the fact that the reporting was different means that *something* was different about the timestamps. I don't know exactly what, but something must have been, or else they would've both been reported as VFR.

You should be able to just remux them with mkvmerge to "fix" them (and if you needed to, replace the timestamps with CFR ones. It's just a text file, read the section "external timestamp files" in the mkvmerge documentation) . It's really 2 lines. More decimal places or precision doesn't matter, because MKV only has a timebase of 1/1000s anyway

# timestamp format v1
assume 23.976

This actually works! Thanks so much for the info! For those who find this thread in the future, this text file can be specified in the GUI when you click on the video stream, and find the "Timestamp File" selector on the right hand side. I didn't need to check "Fix bitstream timing info" in my case.

[...]you could probably use --default-duration 0:24000/1001p in a mkvmerge remux without using external timestamp file

This works great too from the command line! Here's the code I used:

"C:\Program Files\MKVToolNix\mkvmerge.exe" --output ^"C:\file_fixed.mkv" --language 0:eng --default-track 0:yes --display-dimensions 0:1920x1080 --default-duration 0:24000/1001p --language 1:eng --default-track 1:yes ^"^(^" ^"C:\original_file.mkv^" ^"^)^" --track-order 0:0,0:1

Thanks once again for all your help And to your point about FFMpeg possibly causing other issues in the MP4 > MKV conversion, I'll keep a lookout, but for now everything seems fine. In the future, I'll definitely opt for MKVToolnix vs FFMpeg.