imported MP4 Twitch video asynchronous: early audio (late video)

DanTheMan wrote on 7/23/2017, 4:50 AM

Downloaded my kids stream from Twitch (about 1,5h) and imported the MP4 file into Magix Movie Edit Pro (2016 version 15.0.0.107).

On playback in Movie Edit Pro, there's a noticeable video lag, i.e., audio is too early or video is too late. It's only two seconds but it's annoying.

Playing back the MP4 file in VLC or the Windows 10 Movie app, audio and video a synchronous.

Mediainfo reports:

Complete name                            : test.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom
File size                                : 2.45 GiB
Duration                                 : 1h 26mn
Overall bit rate                         : 4 065 Kbps
Writing application                      : Lavf55.43.100

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L3.1
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 2 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 1h 26mn
Bit rate                                 : 3 922 Kbps
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 29.893 fps
Original frame rate                      : 30.000 fps
Minimum frame rate                       : 0.350 fps
Maximum frame rate                       : 90 000.000 fps
Standard                                 : PAL
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.142
Stream size                              : 2.36 GiB (96%)
Color primaries                          : BT.601 NTSC
Transfer characteristics                 : BT.470 System M
Matrix coefficients                      : BT.601

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : 40
Duration                                 : 1h 26mn
Bit rate mode                            : Constant
Bit rate                                 : 132 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 44.1 KHz
Compression mode                         : Lossy
Stream size                              : 81.6 MiB (3%)

How do I fix this issue and get video and audio back in sync?

Comments

DanTheMan wrote on 7/23/2017, 5:56 AM

The original video data from Twitch can be downloaded from

https://www.dropbox.com/s/1gy5vvy55y0wa66/test.mp4?dl=0

johnebaker wrote on 7/23/2017, 7:43 AM

From the MediaInfo:-

Frame rate mode : Variable
Frame rate : 29.893 fps
Original frame rate : 30.000 fps

The variable frame rate of the video is the most likely cause of the issue, this needs to be fixed rate for MEP. You can try using a video converter, however the 2 I have tried (MovAvi and AVS) can not fix the issue.

Assuming this video was captured then uploaded to Twitch, then the screen capture software used should be set to fixed framerate, however we do not know if Twitch is converting the video as Youtube does, I suspect it is.

HTH

John EB

DanTheMan wrote on 7/23/2017, 8:10 AM

Thanks johnebaker, your comment was very helpful.

I understand that I have to convert my Twitch footage to constant framerate prior to importing, for example using converters as "ffmpeg" or "avconv" as described here:

https://video.stackexchange.com/questions/20598/convert-variable-framerate-60-fps-to-constant-60-fps-losslessly

I don't know why my footage is of variable framerate and, frankly, I don't care because I can not control it. Additionally, I learned that it's not uncommon for iPhone footage to have variable framerate. It's just something that exists and that video editing software should handle in one way or another, e.g. "repair" the footage or at least issue a warning.

However, I see that Magix does not address this problem as there's no mentioning of variable bitrate issues on the Magix website. Instead, you and other users have to come to my rescue. Well, that's great but let's not forget that this is a paid product that I'm using and not any free open source software. So to answer FredW's question he raised in the German version of this forum (which I can not answer there as the topic is locked down now): This is a paid product that I'm using an I'd like to see the documentation and user experience live up to this.

Scenestealer wrote on 7/23/2017, 6:25 PM

Considering the video fps in the captured file varies from 0.35 to 90fps i am surprised the audio inaccuracy is only 2 seconds over 1.5 hours.

Is it possible to capture with a different bit and sample rate when you record the play?

If the audio drift is accumulative over the recording, the only possible way to fix your file's sync problem would be to disconnect the Audio from the Video in MEP and Timestretch the Audio or video, then export the timeline and drag the new file back into an empty timeline.

emmrecs wrote on 7/24/2017, 3:28 AM

@Scenestealer

Considering the video fps in the captured file varies from 0.35 to 90fps i am surprised the audio inaccuracy is only 2 seconds over 1.5 hours.

Me too. If I had a loss of audio/video sync of that order over the length of more than 1 hour, given the video recording parameters listed by MediaInfo, I'd be pretty pleased!

johnebaker wrote on 7/24/2017, 4:15 AM

. . . . it's not uncommon for iPhone footage to have variable framerate. It's just something that exists and that video editing software should handle in one way or another, . . . .

The argument about video editing software handling variable frame rate has been going on for a very long while at least 5 - 6 years.

With one very well known professional NLE I used to use, it still cannot handle variable frame rate video directly, you have to do some prep work with an add-on program first.

The problem should not exist, because variable frame rate for video is technically non standard, however it does in mobile devices and screen capture for several reasons.

limited storage space available
to maintain quality due to 1.
dropping frames due to the inability of capture encoding being able to keep up with the actual capture, especially at high frame rates

HTH

John EB

DanTheMan wrote on 12/21/2017, 2:55 PM

...
With one very well known professional NLE I used to use, it still cannot handle variable frame rate video directly, you have to do some prep work with an add-on program first.

Can you name this NLE which handles variable frame rate?

The problem should not exist, because variable frame rate for video is technically non standard, however it does in mobile devices and screen capture for several reasons.
...

What is currently the best practice to fix this issue with variable frame rate footage?

Thanks!

johnebaker wrote on 12/21/2017, 3:31 PM

. . . . Can you name this NLE which handles variable frame rate? . . . .

I could, however I won't because, as I said before, it still cannot handle variable framerate directly, it has to run through a 'converter' first.

. . . . What is currently the best practice to fix this issue with variable frame rate footage? . . . .

Convert the video to fixed framerate - I and several other members here use MovAvi Video Converter, there are also many others available, make sure they support specifying a fixed framerate for the video output.

HTH

John EB

Dackenkinkg wrote on 10/15/2021, 5:58 AM

Hallo, können Sie einen guten Videokonverter empfehlen?

emmrecs wrote on 10/15/2021, 6:07 AM

@Dackenkinkg

Welcome to the Magix user to user forums.

You have posted to a thread from 2017, asking about a problem with a now old version of Movie Edit Pro! Please do not resurrect such old threads but rather start a new thread with your question, including giving details of the version of whichever Magix program you have.

Fundamentally, the advice given in the replies above is still the same.

This thread will be closed.

Jeff
Forum Moderator

Willkommen in den Magix User-to-User-Foren.

Sie haben in einem Thread aus dem Jahr 2017 nach einem Problem mit einer inzwischen alten Version von Movie Edit Pro gefragt! Bitte lasse solche alten Threads nicht wieder auf, sondern starte lieber einen neuen Thread mit deiner Frage, einschließlich der Angabe der Version deines Magix-Programms.

Im Grunde sind die Ratschläge in den obigen Antworten immer noch die gleichen.

Dieser Thread wird geschlossen.

Jeff
Forumsmoderator