Clip duration doesn't match after multiplexing

[arturo83]

I've two MP4 files. The video tracks of the two MP4 files are the same, while the audio tracks differ for what concerns the language: one is Italian and the other one is English.
However the duration of the two audio tracks is identical, as the duration of the two video tracks.
The two MP4 files contain even the subtitle tracks for every language.
I've tried to multiplex the video track of one of the MP4 files together with the audio and subtitle tracks of the two MP4 files.
So I obtained a new MP4 file with one video track, two audio tracks and two subtitle tracks for every language.
To multiplex the tracks together I used FFmpeg, MP4Box and MP4.tool (a GUI of MP4Box).
Everything worked fine. I checked the timeline of the new MP4 file with TMPGEnc MPEG Smart Renderer, and I found that both the audio tracks are in sync with the video track exactly as they are in the original MP4 files.
More over the duration of the single tracks is still the same.
However the clip duration of the new MP4 file differs from the ones of the original MP4 files.
The new MP4 file results longer than the original ones of about three seconds.
I really can't understand why, given that the video and the audio tracks of the three MP4 files are identical.
I even tried with other couples of files, and the result is the same in most times, even if sometime the duration matches.
When using FFmpeg I tried to use the "shortest" option to make the clip duration match the shortest track, but FFmpeg didn't recognize the "shortest" option.
Does anyone have any idea about what could be the problem? Thanks.

[ProWo]

Post the full ffmpeg commandline used to mux the streams and a mediainfo report (text mode) from the two original mp4 files.

[arturo83]

Thanks for your reply, MediaInfo has been useful to me.
I found why sometime the clip duration matches and sometime doesn't.
Using the latest versions of FFmpeg and MP4Box, everything works fine.
The problem occurs using MP4.tool that includes an old version of MP4Box.

[hello_hello]

Check the very last subtitle. Sometimes it's duration can cause it to extend past the end of the video, or it may not begin until after the video has ended, either of which might change the over-all length reported by media players etc. It probably wouldn't hurt to check any chapter files being muxed too.

Failing that, I'd start with an MP4 of just the video, then another with video and a single audio stream, then with a second audio stream etc. Maybe that'll help you work out which stream is the culprit, but it's probably the subtitles.....

[arturo83]

To multiplex the streams now I'm using the latest version of MP4Box with the following commandline:

mp4box.exe -add "D:\InputFile1.mp4"#1:name="":fps=25.000 -add "D:\InputFile1.mp4"#2:lang=ita:name="" -add "D:\InputFile2.mp4"#2:lang=eng:name="" -add "D:\InputFile2.mp4"#4:lang=ita:name="Italian" -add "D:\InputFile2.mp4"#3:lang=eng:name="English (assistive)" -new "D:\OutputFile.mp4"

Here is the MediaInfo report (text mode) of the 1st input file:

General
Complete name                            : D:\InputFile1.mp4
Format                                   : MPEG-4
Format profile                           : Base Media / Version 2
Codec ID                                 : mp42 (mp42/iso6)
File size                                : 305 MiB
Duration                                 : 23 min 6 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 1 845 kb/s
Encoded date                             : UTC 2022-06-16 15:36:41
Tagged date                              : UTC 2022-06-16 15:36:41

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                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 23 min 6 s
Bit rate mode                            : Variable
Bit rate                                 : 1 711 kb/s
Maximum bit rate                         : 20.0 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.033
Stream size                              : 283 MiB (93%)
Writing library                          : x264 core 148 r2727 7d026e8
Encoding settings                        : cabac=1 / ref=4 / deblock=1:0:0 / analyse=0x3:0x111 / me=umh / subme=10 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=120 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=8 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / stitchable=1 / constrained_intra=0 / bframes=16 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=126 / scenecut=0 / intra_refresh=0 / rc_lookahead=250 / rc=crf / mbtree=1 / crf=21.0 / qcomp=0.50 / qpmin=6 / qpmax=51 / qpstep=4 / vbv_maxrate=20000 / vbv_bufsize=25000 / crf_max=0.0 / nal_hrd=vbr / filler=0 / ip_ratio=1.40 / aq=1:0.80
Encoded date                             : UTC 2022-06-16 15:36:41
Tagged date                              : UTC 2022-06-16 15:36:41
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : E-AC-3
Format/Info                              : Enhanced AC-3
Commercial name                          : Dolby Digital Plus
Codec ID                                 : ec-3
Duration                                 : 23 min 6 s
Bit rate mode                            : Constant
Bit rate                                 : 128 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 21.2 MiB (7%)
Language                                 : Italian
Service kind                             : Complete Main
Encoded date                             : UTC 2022-06-16 15:36:41
Tagged date                              : UTC 2022-06-16 15:36:41

Text
ID                                       : 3
Format                                   : Timed Text
Muxing mode                              : sbtl
Codec ID                                 : tx3g
Duration                                 : 23 min 0 s
Bit rate mode                            : Variable
Bit rate                                 : 73 b/s
Frame rate                               : 0.363 FPS
Stream size                              : 12.3 KiB (0%)
Title                                    : Italian / Italian
Language                                 : Italian
Forced                                   : No
Encoded date                             : UTC 2022-06-16 15:36:41
Tagged date                              : UTC 2022-06-16 15:36:41

Here is the MediaInfo report (text mode) of the 2nd input file:

General
Complete name                            : D:\InputFile2.mp4
Format                                   : MPEG-4
Format profile                           : Base Media / Version 2
Codec ID                                 : mp42 (mp42/iso6)
File size                                : 35.6 MiB
Duration                                 : 23 min 6 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 215 kb/s
Encoded date                             : UTC 2022-06-16 16:06:18
Tagged date                              : UTC 2022-06-16 16:06:18

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L2.2
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 23 min 6 s
Bit rate mode                            : Variable
Bit rate                                 : 81.3 kb/s
Maximum bit rate                         : 4 000 kb/s
Width                                    : 480 pixels
Height                                   : 270 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.025
Stream size                              : 13.4 MiB (38%)
Writing library                          : x264 core 148 r2727 7d026e8
Encoding settings                        : cabac=1 / ref=4 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=10 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=120 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=8 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / stitchable=1 / constrained_intra=0 / bframes=16 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=126 / scenecut=0 / intra_refresh=0 / rc_lookahead=250 / rc=crf / mbtree=1 / crf=38.0 / qcomp=0.50 / qpmin=6 / qpmax=51 / qpstep=4 / vbv_maxrate=4000 / vbv_bufsize=4000 / crf_max=0.0 / nal_hrd=vbr / filler=0 / ip_ratio=1.40 / aq=1:0.80
Encoded date                             : UTC 2022-06-16 16:06:18
Tagged date                              : UTC 2022-06-16 16:06:18
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : E-AC-3
Format/Info                              : Enhanced AC-3
Commercial name                          : Dolby Digital Plus
Codec ID                                 : ec-3
Duration                                 : 23 min 6 s
Bit rate mode                            : Constant
Bit rate                                 : 128 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 21.2 MiB (59%)
Language                                 : English
Service kind                             : Complete Main
Encoded date                             : UTC 2022-06-16 16:06:18
Tagged date                              : UTC 2022-06-16 16:06:18

Text #1
ID                                       : 3
Format                                   : Timed Text
Muxing mode                              : sbtl
Codec ID                                 : tx3g
Duration                                 : 22 min 33 s
Bit rate mode                            : Variable
Bit rate                                 : 82 b/s
Frame rate                               : 0.500 FPS
Stream size                              : 13.6 KiB (0%)
Title                                    : English (assistive) / English (assistive)
Language                                 : English
Forced                                   : No
Encoded date                             : UTC 2022-06-16 16:06:18
Tagged date                              : UTC 2022-06-16 16:06:18

Text #2
ID                                       : 4
Format                                   : Timed Text
Muxing mode                              : sbtl
Codec ID                                 : tx3g
Duration                                 : 23 min 0 s
Bit rate mode                            : Variable
Bit rate                                 : 73 b/s
Frame rate                               : 0.363 FPS
Stream size                              : 12.3 KiB (0%)
Title                                    : Italian / Italian
Language                                 : Italian
Forced                                   : No
Encoded date                             : UTC 2022-06-16 16:06:18
Tagged date                              : UTC 2022-06-16 16:06:18

And here is the MediaInfo report (text mode) of the output file:

General
Complete name                            : D:\OutputFile.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom)
File size                                : 325 MiB
Duration                                 : 23 min 6 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 1 969 kb/s
Encoded date                             : UTC 2022-11-16 14:45:47
Tagged date                              : UTC 2022-11-16 14:45:47

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                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 23 min 6 s
Source duration                          : 23 min 6 s
Bit rate mode                            : Variable
Bit rate                                 : 1 621 kb/s
Maximum bit rate                         : 20.0 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.031
Stream size                              : 268 MiB (82%)
Source stream size                       : 283 MiB (87%)
Writing library                          : x264 core 148 r2727 7d026e8
Encoding settings                        : cabac=1 / ref=4 / deblock=1:0:0 / analyse=0x3:0x111 / me=umh / subme=10 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=120 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=8 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / stitchable=1 / constrained_intra=0 / bframes=16 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=126 / scenecut=0 / intra_refresh=0 / rc_lookahead=250 / rc=crf / mbtree=1 / crf=21.0 / qcomp=0.50 / qpmin=6 / qpmax=51 / qpstep=4 / vbv_maxrate=20000 / vbv_bufsize=25000 / crf_max=0.0 / nal_hrd=vbr / filler=0 / ip_ratio=1.40 / aq=1:0.80
Encoded date                             : UTC 2022-06-16 15:36:41
Tagged date                              : UTC 2022-11-16 14:46:00
mdhd_Duration                            : 1386160
Codec configuration box                  : avcC

Audio #1
ID                                       : 2
Format                                   : E-AC-3
Format/Info                              : Enhanced AC-3
Commercial name                          : Dolby Digital Plus
Codec ID                                 : ec-3
Duration                                 : 23 min 6 s
Bit rate mode                            : Constant
Bit rate                                 : 128 kb/s
Maximum bit rate                         : 135 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 21.2 MiB (6%)
Language                                 : Italian
Service kind                             : Complete Main
Encoded date                             : UTC 2022-06-16 15:36:41
Tagged date                              : UTC 2022-11-16 14:46:00

Audio #2
ID                                       : 3
Format                                   : E-AC-3
Format/Info                              : Enhanced AC-3
Commercial name                          : Dolby Digital Plus
Codec ID                                 : ec-3
Duration                                 : 23 min 6 s
Bit rate mode                            : Constant
Bit rate                                 : 128 kb/s
Maximum bit rate                         : 135 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 21.2 MiB (6%)
Language                                 : English
Service kind                             : Complete Main
Encoded date                             : UTC 2022-06-16 16:06:18
Tagged date                              : UTC 2022-11-16 14:46:00

Text #1
ID                                       : 4
Format                                   : Timed Text
Muxing mode                              : sbtl
Codec ID                                 : tx3g
Duration                                 : 23 min 0 s
Bit rate mode                            : Variable
Bit rate                                 : 73 b/s
Frame rate                               : 0.363 FPS
Stream size                              : 12.3 KiB (0%)
Title                                    : Italian / Italian
Language                                 : Italian
Forced                                   : No
Encoded date                             : UTC 2022-06-16 16:06:18
Tagged date                              : UTC 2022-11-16 14:46:00

Text #2
ID                                       : 5
Format                                   : Timed Text
Muxing mode                              : sbtl
Codec ID                                 : tx3g
Duration                                 : 22 min 33 s
Bit rate mode                            : Variable
Bit rate                                 : 82 b/s
Frame rate                               : 0.500 FPS
Stream size                              : 13.6 KiB (0%)
Title                                    : English (assistive) / English (assistive)
Language                                 : English
Forced                                   : No
Encoded date                             : UTC 2022-06-16 16:06:18
Tagged date                              : UTC 2022-11-16 14:46:00

Regarding the MediaInfo reports:
In the input files the "General Codec ID" is "mp42 (mp42/iso6)", while in the output file the "General Codec ID" is "isom (isom)".
In the 1st input file the "Video Stream size" is "283 MiB (93%)", while in the output file there are two fields:
- "Video Stream size" that is "268 MiB (82%)"
- "Video Source stream size" that is "283 MiB (87%)", like in the 1st input file.
What does this mean? Has the video somehow been lossless compressed in the output file?
I extracted the video tracks of the 1st input file and of the output file, then I compared them with "Beyond Compare" (binary comparison) and they're identical, and obviously they have the same size.

[arturo83]

Regarding the MediaInfo reports:
In the input files the "General Codec ID" is "mp42 (mp42/iso6)", while in the output file the "General Codec ID" is "isom (isom)".
In the 1st input file the "Video Stream size" is "283 MiB (93%)", while in the output file there are two fields:
- "Video Stream size" that is "268 MiB (82%)"
- "Video Source stream size" that is "283 MiB (87%)", like in the 1st input file.
What does this mean? Has the video somehow been lossless compressed in the output file?
I extracted the video tracks of the 1st input file and of the output file, then I compared them with "Beyond Compare" (binary comparison) and they're identical, and obviously they have the same size.

I tried to multiplex again the tracks with FFmpeg, and analyzing the resulting MP4 file with MediaInfo, this still shows me two fields:
"Video Stream Size" that is 270 MiB, and "Video Source stream size" that is 283 MiB.
But when I extract the video stream, from the resulting MP4 file to the H.264 elementary stream, this is around 283 MiB.
So I can't understand why MediaInfo gives me two different values.
Please excuse me if my question is too elementary, but I can't find an answer.
Could you help me please?

[ProWo]

@ arturo83.
Elementare. Ti dice che il video sorgente ha 283MB, mentre il video nuovo (recompresso) ha solo 270MB.
Un risultato del tutto normale, visto la recodifica.
Se vuoi eliminare i dati/tags del video sorgente fai un nuovo remux con ffmpeg, senza - map 0 (che riporta tutti i tags del video sorgente), usando solo i maps richiesti.
Oppure, per semplificare, fai un remux con clever Ffmpeg-GUI, invece di mp4box.

[arturo83]

@ arturo83.
Elementare. Ti dice che il video sorgente ha 283MB, mentre il video nuovo (recompresso) ha solo 270MB.
Un risultato del tutto normale, visto la recodifica.
Se vuoi eliminare i dati/tags del video sorgente fai un nuovo remux con ffmpeg, senza - map 0 (che riporta tutti i tags del video sorgente), usando solo i maps richiesti.
Oppure, per semplificare, fai un remux con clever Ffmpeg-GUI, invece di mp4box.

Ti ringrazio per le informazioni.
Tuttavia il video non è stato ricodificato, è stato semplicemente remuxato.
Infatti, una volta estratti, gli elementary streams del video sorgente e del video risultante, risultano identici ad un confronto bit a bit, o tramite checksum.
Inoltre il procedimento di remux è durato solo un paio di minuti, un tempo troppo limitato per una ricodifica totale del video.
Spero di aver capito bene quanto intendevi dire.

[arturo83]

Se vuoi eliminare i dati/tags del video sorgente fai un nuovo remux con ffmpeg, senza - map 0 (che riporta tutti i tags del video sorgente), usando solo i maps richiesti.
Oppure, per semplificare, fai un remux con clever Ffmpeg-GUI, invece di mp4box.

Utilizzando clever FFmpeg-GUI sono riuscito a eliminare il campo "Video Source stream size".
Ora compare solo il campo "Video Stream Size" che indica la dimensione corretta del video, che è 283 MiB.
Però se vado a riprocessare il file risulatante con MP4Box, nonostante l'operazione vada a buon fine, ottengo il seguente errore:

[iso file] Found stts entry with sample_delta=0 - forbidden ! Fixing to 1

Sapresti dirmi cosa significa, per favore?