MP4 file has video speed up part of the way through but audio does not

[the_steve_randolph]

**************************************************
To see the solution to this problem along with a recap, see post #37
**************************************************


I have a streaming MP4 file (for this post I will call it orig.mp4) that I have downloaded that is 2:51:54 long. At about the 1:57:07 mark, using VLC or Zoom Player, the video speeds up but the audio does not. This continues to the end, where the video has stopped minutes earlier but the audio continues. I have downloaded this file multiple times and the exact thing happens at the same time mark each time. When I view the streaming video in a browser, the video never speeds up in relationship to the audio.

I understand that a possible solution is to find another video downloader and see if the same thing occurs. I have tried multiple apps but I have not found any others that will download from that site.

When I play this orig.mp4 in VLC, it shows that it is using the H264 codec and the frame rate is 94.126760. In another MP4 that I have downloaded from that site where the video and audio is out of sync, the frame rate is 33.056366. Those two seem like really weird rates - which is probably an indication that something is wrong. Except for these two MP4s, when I use my Adobe Premiere Elements 14 to edit the MP4s from that site, I see a value of 30 fps and VLC shows a frame rate for 29.969922 for those MP4s.

When I use Premier Elements to look at orig.mp4, the counter shows that I can only see 30 frames per second. It shows the file to be 2:24:31 long but nothing is cut off at the end. And, the place in orig.mp4 in VLC where it speeds up is at 1:38:38 in Premier Elements and the video does not speed up at that point.

I can't figure out what is going on here, what to look for to fix, and, how to fix it. In addition to fixing this MP4, I want to understand more about how the problem happened and how to figure out what needs to change. So, I have several questions:

• first, is "frames per second" and "frame rate" the same thing and, if not, how are they different?
• what tool can I use to see exactly where this change is happening?
• what is the name of the setting(s) that I am looking for to see the change?
• other than trying to concatenating two files with different fps, is it really possible to have an MP4 that has a fps change within an MP4?
• I know that speeding up the video (a la Benny Hill) is desirable in some situations, but, how /why would a video downloader want to, or be able to, do that?
• if I decide to use the ffmpeg "setpts" switch to fix this, how can I figure out exactly what value to use?
• is there a tool other than ffmpeg that can fix this problem?

[davexnet]

Open the file in mediainfo, put it in text view, and post the output here

[the_steve_randolph]

Open the file in mediainfo, put it in text view, and post the output here

General
Complete name                            : C:\out.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/avc1/mp41)
File size                                : 7.82 GiB
Duration                                 : 2 h 51 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 6 512 kb/s

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                                 : 54 min 44 s
Source duration                          : 2 h 24 min
Bit rate                                 : 7 620 kb/s
Width                                    : 1 912 pixels
Original width                           : 1 920 pixels
Height                                   : 1 088 pixels
Original height                          : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 35.648 FPS
Minimum frame rate                       : 5.994 FPS
Maximum frame rate                       : 120.000 FPS
Original frame rate                      : 29.970 (30000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.103
Stream size                              : 2.45 GiB (31%)
Source stream size                       : 7.70 GiB (98%)
mdhd_Duration                            : 3284125
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 2 h 51 min
Bit rate mode                            : Variable
Bit rate                                 : 93.6 kb/s
Maximum bit rate                         : 424 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 44.1 kHz
Frame rate                               : 43.066 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 115 MiB (1%)

Text #1
ID                                       : 1-CC1
Format                                   : EIA-608
Muxing mode                              : SCTE 128 / DTVCC Transport
Muxing mode, more info                   : Muxed in Video #1
Duration                                 : 54 min 44 s
Bit rate mode                            : Constant
Stream size                              : 0.00 Byte (0%)
CaptionServiceName                       : CC1

Text #2
ID                                       : 1-CC3
Format                                   : EIA-608
Muxing mode                              : SCTE 128 / DTVCC Transport
Muxing mode, more info                   : Muxed in Video #1
Duration                                 : 54 min 44 s
Bit rate mode                            : Constant
Stream size                              : 0.00 Byte (0%)
CaptionServiceName                       : CC3

[ProWo]

Try

ffmpeg -r 29.970 -i out.mp4 -map 0 -c copy newout.mp4

[the_steve_randolph]

Try

ffmpeg -r 29.970 -i out.mp4 -map 0 -c copy newout.mp4

After executing this command, I play the newout.mp4 in both VLC and Zoom Player. The video track stops at 54:44 (this end is before the actual end of the MP4 file) but the audio track continues to the end at 2:51:54. The original out.mp4 has the size of 8199 MB in Windows Explorer but the newout.mp4 has the size of 2691 MB. This is the Mediainfo output of outnew.mp4:

General
Complete name                            : C:\newout.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/avc1/mp41)
File size                                : 2.57 GiB
Duration                                 : 2 h 51 min
Overall bit rate                         : 2 137 kb/s
Writing application                      : Lavf58.78.100

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                                 : 54 min 45 s
Source duration                          : 54 min 45 s
Bit rate                                 : 6 405 kb/s
Maximum bit rate                         : 20.1 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 29.970 (30000/1001) FPS
Minimum frame rate                       : 5.994 FPS
Maximum frame rate                       : 121.091 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.103
Stream size                              : 2.45 GiB (95%)
Source stream size                       : 2.45 GiB (95%)
mdhd_Duration                            : 3285870
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 2 h 51 min
Bit rate mode                            : Constant
Bit rate                                 : 93.6 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 44.1 kHz
Frame rate                               : 43.066 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 115 MiB (4%)
Default                                  : Yes
Alternate group                          : 1

Text #1
ID                                       : 1-CC1
Format                                   : EIA-608
Muxing mode                              : SCTE 128 / DTVCC Transport
Muxing mode, more info                   : Muxed in Video #1
Duration                                 : 54 min 45 s
Bit rate mode                            : Constant
Stream size                              : 0.00 Byte (0%)
CaptionServiceName                       : CC1

Text #2
ID                                       : 1-CC3
Format                                   : EIA-608
Muxing mode                              : SCTE 128 / DTVCC Transport
Muxing mode, more info                   : Muxed in Video #1
Duration                                 : 54 min 45 s
Bit rate mode                            : Constant
Stream size                              : 0.00 Byte (0%)
CaptionServiceName                       : CC3

[ProWo]

And with

ffmpeg -i out.mp4 -map 0 -c copy newout.mp4

?

[the_steve_randolph]

And with

ffmpeg -i out.mp4 -map 0 -c copy newout.mp4

?

After running this command, I see no difference in the output from your previous command suggestion.

[davexnet]

Perhaps something like this to force the 29.97 constant frame rate. It's going to re-encode the file

ffmpeg -r 29.970 -vsync 1 -i in.mp4 -c:v libx264 out29.mp4

[Budman1]

Sounds like someone joined 2 segments together that had different encoding parameters. I've had this happen to me and I've always had to split at the mismatch point and reencode the failing half. If you use ffprobe you will probably see some wild swings in PTS and DTS times, especially at the join point.

[ProWo]

Sounds like someone joined 2 segments together that had different encoding parameters. I've had this happen to me and I've always had to split at the mismatch point and reencode the failing half. If you use ffprobe you will probably see some wild swings in PTS and DTS times, especially at the join point.

Agree.
Another try

ffmpeg -i out.mp4 -map 0 -c copy newout.ts

[the_steve_randolph]

Perhaps something like this to force the 29.97 constant frame rate. It's going to re-encode the file

ffmpeg -r 29.970 -vsync 1 -i in.mp4 -c:v libx264 out29.mp4

When running this command, ffmpeg generated the message "More than 1000 frames duplicated" at the 00:34:09.53 mark while continuing. It also displayed the "q=29.0" information during the re-encoding. The resulting output file showed an O/S size of 2068 MB and a time of 2:51:54. When I clicked on the output file to view it in VLCl], a panel displayed that said:

VLC crash reporting
Ooops: VLC media player just crashed.
Would you like to send a bug report to the developers team?
Yes No

My computer then automatically opened VLC with the MP4 that showed a length of 2:51:54. The video was in sync with the audio, but, stopped at 54:44 while the audio continued until the end. VLC shows a fps of 29.970000

[the_steve_randolph]

Sounds like someone joined 2 segments together that had different encoding parameters. I've had this happen to me and I've always had to split at the mismatch point and reencode the failing half. If you use ffprobe you will probably see some wild swings in PTS and DTS times, especially at the join point.

First, why would a streaming service do that? Second, I don't see that "speeding up" effect when viewing the streaming file in real time. Third, when I run ffprobe on the file, I get the same output as from ffmpeg - so I am not sure what you are claiming I will see. Please clarify.

[the_steve_randolph]

Sounds like someone joined 2 segments together that had different encoding parameters. I've had this happen to me and I've always had to split at the mismatch point and reencode the failing half. If you use ffprobe you will probably see some wild swings in PTS and DTS times, especially at the join point.

Agree.
Another try

ffmpeg -i out.mp4 -map 0 -c copy newout.ts

When I run that command, ffmpeg displays the "q=31.0" information during the re-encoding. After it is finished, the O/S information shows the file to be 1829 MB in size and 54:44 in length. VLC shows the file to be 54:44 in length, the fps is 29.970030, and, the video quality is greatly reduced. In VLC the video and audio are in sync, and, everything ends at 54:44.

[ProWo]

Another one

ffmpeg -i out.mp4 -map 0 -c:v copy -c:s copy -c:a ac3 -b:a 256k newout.mp4

Maybe the correct video length is 54min 44 sec, and there is only a problem with the aac timing.

[the_steve_randolph]

Another one

ffmpeg -i out.mp4 -map 0 -c:v copy -c:s copy -c:a ac3 -b:a 256k newout.mp4

Maybe the correct video length is 54min 44 sec, and there is only a problem with the aac timing.

That command creates a file that is 2:51:54 long according to Windows Explorer. VLC plays the audio for the full 2:51:54 but the video stops at 54:44.

I *KNOW* that this video lasts 2:51:54 because when I stream it in a browser, it lasts that long without any problems.

[ProWo]

The best way would be to download the video again

[ProWo]

The best way would be to download the video again.
Another idea: cut the first 1min with Avidemux and use this cutted part as reference file in untrunc (see software section) to repair your out.mp4.

[the_steve_randolph]

The best way would be to download the video again.
Another idea: cut the first 1min with Avidemux and use this cutted part as reference file in untrunc (see software section) to repair your out.mp4.

I have downloaded this MP4 at least 5 times and it has the same problem every time.

I cannot find a "software section". But, searching the entire site, it seems that "untrunc" is a Linux utility and I am running Windows.

[ProWo]

https://github.com/anthwlock/untrunc/releases/download/latest/untrunc_x64.zip

[ProWo]

I cannot find a "software section".

https://www.videohelp.com/software

[the_steve_randolph]

https://github.com/anthwlock/untrunc/releases/download/latest/untrunc_x64.zip

I don't know what untrunc is, what it is for, or, how to use it. How would it help me with this problem?

[ProWo]

It's a portable program to repair truncated avc videos.
Unpack the archive and start untrunc-gui.
In the left field search for the reference file (read above), in the right field for your out.mp4.
Then click on untrunc (bottom right).
That's all.

[the_steve_randolph]

It's a portable program to repair truncated avc videos.
Unpack the archive and start untrunc-gui.
In the left field search for the reference file (read above), in the right field for your out.mp4.
Then click on untrunc (bottom right).
That's all.

OK, several issues. I have Avidemux but don't know how to use it. So, I don't know what you mean by "cut the first 1min with Avidemux". If you mean, create a 1 minute file from the first minute of the MP4, I can do that with my Premiere Elements. But, I don't know if Avidemux is doing something special other than just taking the first minute. Plus, again, I don't know how to use Avidemux, so, I don't know how to use it to get just the first minute. But, I ran it and opened my MP4 and it generated this error:

This video contains B-frames, but presentation time stamps (PTS) are either missing or monotonically increasing. Avidemux can try to reconstruct correct PTS by decoding the entire video. This may take a lot of time. Proceed?

Can you tell me what Avidemux and untrunc are doing according to what you want me to do? And, why do you think that the video is "truncated" when it seems that part of it is sped up?

[Budman1]

My suspicion, FWIW, is that the download was in 2 pieces with different formats, sampling rates, etc. During a scrne change the second part began streaming behind the first. You streaming device accepts different formats so it play fine. Capturing as one file does not play well during the second half.

My suggestion is to cut the final third of the video and see if that plays ok.

[the_steve_randolph]

My suspicion, FWIW, is that the download was in 2 pieces with different formats, sampling rates, etc. During a scrne change the second part began streaming behind the first. You streaming device accepts different formats so it play fine. Capturing as one file does not play well during the second half.

I used the same video downloader (Video DownloadHelper) to download multiple MP4s from the same site that are larger/longer than my problem MP4 and those other MP4s do not have the same problem. Also, what is "a scrne change"? Video DownloadHelper does not give me any information or options that indicate this particular file is in two parts, although the fact that I have downloaded this file multiple times and the problem starts at the same timestamp every time lends itself to the idea that it may be in two parts at some point in my process. But, why would the streaming site create two parts that have "different formats, sampling rates, etc."? My "streaming device" is my PC and I am viewing it in Firefox and using Video DownloadHelper in the same browser window.

My suggestion is to cut the final third of the video and see if that plays ok.

I don't understand what this would accomplish. The MP4 plays fine in VLC and Zoom Player until 1:57:07. I want the entire MP4, so, chopping off the end would be useless for me.

[Budman1]

If the final third (past the beginning of bad start) plays ok then it is being affected by the first part. You can also check it mediainfo output against the complete video.

[the_steve_randolph]

If the final third (past the beginning of bad start) plays ok then it is being affected by the first part. You can also check it mediainfo output against the complete video.

Oh, OK, I thought you meant to get rid of the end part.

So, I ran this command to get the part after the video starts to speed up:

ffmpeg -ss 01:57:10.000 -in.mp4 -c copy out2.mp4

This resulted in a file that Windows Explorer says is 54:44 long, which is interesting since that is the exact same length of the resulting TS file from post #13. When I run this MP4 in VLC, there is no video and it just shows the orange cone, the audio goes all of the way to the end but goes in and out. Interestingly, it shows a frame rate of 0.000022. Zoom Player opens the MP4 but plays nothing. Windows Media Player is so confused that I can't even describe what it is doing. And Nero Showtime is also very confused.

So, this would prove that the first part is not causing problems for the second part.

The MediaInfo for the original MP4 is in post #3. And, here is the MediaInfo for this MP4:

General
Complete name                            : C:out2.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/avc1/mp41)
File size                                : 79.7 MiB
Overall bit rate                         : 156 b/s
Writing application                      : Lavf58.78.100

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
Source duration                          : 17 ms
Bit rate                                 : 61.1 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 59.940 (59940/1000) FPS
Original frame rate                      : 29.970 (30000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.492
Stream size                              : 29.8 TiB
Source stream size                       : 124 KiB (0%)
mdhd_Duration                            : 43977728
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 54 min 44 s
Source duration                          : 1 h 57 min
Bit rate mode                            : Constant
Bit rate                                 : 93.6 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 44.1 kHz
Frame rate                               : 43.066 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 36.6 MiB (46%)
Source stream size                       : 78.4 MiB (98%)
Default                                  : Yes
Alternate group                          : 1
mdhd_Duration                            : 3284536

[ProWo]

why do you think that the video is "truncated" when it seems that part of it is sped up?

The videostream is messed up after 54:44.
Untrunc could find this compromised frames and repair the whole videostream.

[the_steve_randolph]

why do you think that the video is "truncated" when it seems that part of it is sped up?

The videostream is messed up after 54:44.
Untrunc could find this compromised frames and repair the whole videostream.

See post #23

[ProWo]

I gave you some hints and you answer with questions instead of working off the hints.
I am out