diagnosing the cause of "video/audio resync frames removed"

[music_man1352000]

Well, I guess that's that then. As disappointing as it is for me, I can totally understand optimisation for sources containing bursts of corruption being a low or zero priority scenario. With that said, I still think the design choice to decode the entire source to frame level in the previously described conditions is odd. That's probably baked into the architecture to the point that it couldn't be changed without a radical redesign.

 

[Dan203]

It's just how VRD works. Basically any time you open and save a file in VRD it's demuxed to base elements and remuxed on output.

 

[PWinger]

I'm running Quickstream Fix on most of my recordings and the log indicates where the removed video resync frames were located, but I get no indication of where the removed audio recync frames are located. Is there anyway to find out where the audio frames were removed?

 

[Dan203]

No. We really don't keep this information anywhere. With audio so many frames can be removed that we don't even log every one. You'll see in the log that when a large number are removed it says something like "...488 similar frames" or something like that, rather than having a line for every one.

 

[stuart]

They're caused by corruption in the source video. Usually some sort of transmission error in the source or possibly some sort of corruption that happens at transfer. (common for .tivo files)

Even though the number seems high it's really only about 15 seconds of content at 29.97fps or only 8 seconds at 59.94. And they're probably not consecutive. More likely they're a few short 1-2 second glitches at various places in the content. Unfortunately VideoReDo does not keep track of where exactly in the source video errors occur, so there is no easy way to track these down.

If the sole cause of the audio sync errors and the deleting of sporadic words in the dialogue were due to source video errors, would you please explain why the files play perfectly well when played on VLC , through my Media Center or VRDo. I recently acquired an editing program called idoo, and this enables me to edit without any fuss whatsoever.

When I edit the redundant start and end of an H264 movie with VRDo the result is as above. Each time I edit these files VRDo shows that > 44,000 resync frames have been removed.

I would appreciate your help.

 

[Danr]

The file you uploaded uses the telecine feature of H264 that we haven't yet fully supported.

 

[stuart]

The file you uploaded uses the telecine feature of H264 that we haven't yet fully supported.

Regrettably therefore, it would appear that ALL HD channels on Dish started to use telecine simultaneously about 6 weeks ago since prior to that date I had not experienced a suchlike happenstance.

May I ask:

1. Approximately when you estimate that you will have rectified this issue?
2. Have you addressed this problem with other clients? It does seem unusual that the issue would occur simultaneously on all HD channels.

With Thanks, Stuart

 

[tmm1]

Could someone explain what exactly an audio resync frame is? Is it one where a PTS is repeated?

 

[Danr]

Regrettably therefore, it would appear that ALL HD channels on Dish started to use telecine simultaneously about 6 weeks ago since prior to that date I had not experienced a suchlike happenstance.

May I ask:

1. Approximately when you estimate that you will have rectified this issue?
2. Have you addressed this problem with other clients? It does seem unusual that the issue would occur simultaneously on all HD channels.

Do remember the help desk ticket number for the uploaded samples? We looked into this, but I don't have good notes on how much of it we fixed.

 

[Danr]

Could someone explain what exactly an audio resync frame is? Is it one where a PTS is repeated?

An audio resync frame is either an either frame that removed or an inserted silent frame. They are used to maintain sync when there is some corruption in the original source file.

 

[stuart]

Dan the Ticket id is: UXS-47451-693

Thanx, Stuart

 

[tmm1]

An audio resync frame is either an either frame that removed or an inserted silent frame. They are used to maintain sync when there is some corruption in the original source file.

I'm hoping for a more technical explanation. I have some software that produces mpegts streams, and users are saying that when they run our files through VRD it shows "Audio resync frames removed".

What is detected as corruption that would require audio frames to be removed?

 

[Danr]

There's more information in the log file, you can email us the log (to support) after a save that has resync frames and we can give you a more detailed explanation.

 

[Dan203]

I'm hoping for a more technical explanation. I have some software that produces mpegts streams, and users are saying that when they run our files through VRD it shows "Audio resync frames removed".

What is detected as corruption that would require audio frames to be removed?

Basically during muxing we keep track of the time codes attached to every frame. If there is a big enough drift/gap between the audio and video time codes then we will insert or remove a frame to maintain sync. The vast majority of the time this is caused by some short bit of corruption in the source file. However if your source file is using variable frame rate, the frame rate of the source is picked up incorrectly, or the source has bits where the provider inserted a commercial with a different frame rate then the rest of the video it can cause major discontinuity and cause the sync operation to add/remove hundreds of frames which typically results in a bad output file.

We don't support variable frame rate video at all. For files with a frame rate change in the middle there is a feature in QSF that can deal with that. And for files where the frame rate is detected incorrectly there are alternative detection options in the H.264 section of the main options that should help there.