644a refuses to jump forwards

#1
This is not a 644a specific problem as I've seen it with prior versions.

I have VR set to force I frame seeks for jumps of two seconds or more. Occasionally VR refuses to move off the initial frame in a recording when a jump of 2 or more seconds is attempted. It will move forward frame by frame or at one second jumps. If I then attempt to move forward 2 seconds or more VR snaps back to the start.

If I reset the force I frame seek to 0 it will jump forward correctly. QSFing the file allows VR to jump forward correctly too.

The source file is tv scheduler pro's 'ts-mux' format, ie transport packets and only the PIDs mapped relevant to the program by the PAT and contains MPEG-2 with 12 frame GOPs. Running the file through project-x shows it is squeaky clean with no bad or missing transport packets etc.
 
#3
project-x doesn't list any timestamp issues nor does the ancient pvastrumento.

A 'trim and copy' of the entire file produces the same problem. A trim and copy of the file less 1Mb permits correct navigation again. A trim and copy of the last ~5Mb of the file produces the problem. A QSF of all does not seem to show any time stamps issues, at least any significant difference between the three, and project-x / pvastrumento show no issues with all three.
 

Dan203

Senior Developer
Staff member
#5
project-x doesn't list any timestamp issues nor does the ancient pvastrumento.

A 'trim and copy' of the entire file produces the same problem. A trim and copy of the file less 1Mb permits correct navigation again. A trim and copy of the last ~5Mb of the file produces the problem. A QSF of all does not seem to show any time stamps issues, at least any significant difference between the three, and project-x / pvastrumento show no issues with all three.
We'll look at it, but from a logical perspective it pretty much has to be a time stamp issue. All QSF really does is it remuxes the file while recalculating all the time stamps based on the video frame rate and the audio sampling rate. (there is some syncing logic applied as well, but if that actually effected anything you'd see resync frames listed in the output dialog)

The other reason I think it's a time stamp issue is because of the way our navigation works. Basically we divide the file up based on the average data rate of the file. When you seek to a specific position we guess where, in bytes, that frame might be and then seek to that position. We then read the time stamp of the video frame at that position and adjust forward or backward based on that time stamp and where we expected to land. The only time it goes completely wonky like you describe is when the time stamps are messed up and the one we land on is way off from what we expected. And the fact that a QSF fixes the issue further proves that point because after the QSF the time stamps are all correct and we can thus navigate correctly.

But like I said we'll look at it to be sure. However if I'm right then you may need to get into the habit of QSFing your files before editing them. Time stamp errors can not only cause navigation errors in the UI but they can also cause navigation errors in the editing logic which could result in cuts ending up in the wrong place or the output stalling or failing completely.

Dan
 
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#6
I have seen this issue before with files that have been through qsf. It happens both on mpeg and mp4 files. It only happens when the iframe skip is being used. It is like it gets stuck. I thought that is was due to the age of my old machine. I just upgraded last month to a new core i5 and it does the same think. It does not happen all the time. I have a small section 5 min 80 mb that has been processed through the gui that can reproduce. Sometimes the navigation in reverse is worse.

Karl
 
#8
Trim of last ~6Mb of file as produced by trim and copy uploaded as /DrP_Seek_Problem.zip. The segment can be stepped through frame by frame without problem, but pressing end returns to the beginning.
 

Danr

Administrator
Staff member
#9
Thanks, will look at it. Please don't forget to send an email to support so we can log it into our database.
 
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