trying to convert stuttering video but having problems

[billsantos]

I tried using ffmpeg today, got it to work after relearning about these types of programs, and used the code provided by Blimey in an attempt to rebuild the flv container. Although a new file was created, it made no difference as the video is still stuttering. Any more ideas?

[billsantos]

I found out the problem, but I still don't know the solution. I used Virtual Dub with a plug-in that allows working with flv files. I took one of the HD (not 1080p but standard HD) downloads from CBS (see prior message for links) and opened it in Virtual Dub. Upon examination, at irregular intervals, there appears to be duplicate video frames created, one right after another. When these duplicates occur, they seem to replace the next progressive frame that should have been there originally, so we end up with not only a doubling up of frames, but a missing frame as well because the duplicate replaces the actual frame. Since this happens irregularly and only involves two frames, we end up with the stuttering effect. Now the question is, what's causing it and what's the solution? Either all of the HD videos from CBS for this particular program have this fault upon download, or there is a glitch in GetFLV causing it. Like I said before, it only happens on CBS HD and not HD 1080p.

Just to see what would happen, I took a one minute section and removed all duplicate frames and saved it as a new AVI with Virtual Dub. The stuttering wasn't as great, but still there because now a frame is missing, the one the duplicate replaces.

Is there another program I can try with CBS to see if I get the same results?

[blimey]

Do you have "stuttering" when playing the raw flv file as downloaded?

I checked the file that you mentioned. It seems to play ok to me. I tried to look carefully, and perhaps I noticed some un-smoothness when there is a lot of fast horizontal action - but it didn't seem like stuttering. Please explain exactly when you experience the problem; is it on the raw file (as downloaded) playing on a PC? Or perhaps you are playing it on some sort of set-top media player or htpc?

It is kinda odd for a HD 720p file to use VP6 for the video. I'm not sure why they did that. The framerate does seem to be an accurate 24.000 fps.

I realize that you don't want to do any conversion - and I would agree if the video was h.264 - but in my opinion it is really not much of an advantage to keep the video in VP6. I would convert it to h.264. Have you tried converting it, and if so, does the stuttering remain?

[billsantos]

Originally Posted by blimey

Do you have "stuttering" when playing the raw flv file as downloaded?

Yes, I do.

Originally Posted by blimey

I checked the file that you mentioned. It seems to play ok to me. I tried to look carefully, and perhaps I noticed some un-smoothness when there is a lot of fast horizontal action - but it didn't seem like stuttering. Please explain exactly when you experience the problem; is it on the raw file (as downloaded) playing on a PC? Or perhaps you are playing it on some sort of set-top media player or htpc?

That's what I'm talking about. This unsmoothness is all throughout the video at random spots. It's also occurring during more stationary action, but more difficult to notice obviously. I experience the problem when I try to play it with any of the PC media players I have, it doesn't seem to matter which one. And yes it is the raw flv file download from GetFLV.

Originally Posted by blimey

It is kinda odd for a HD 720p file to use VP6 for the video. I'm not sure why they did that. The framerate does seem to be an accurate 24.000 fps.

Depending on which media player I use, I sometimes see 23.5 fps for the rate all the way up to 24 fps.

Originally Posted by blimey

I realize that you don't want to do any conversion - and I would agree if the video was h.264 - but in my opinion it is really not much of an advantage to keep the video in VP6. I would convert it to h.264. Have you tried converting it, and if so, does the stuttering remain?

I tried your conversion suggestion tonight using Super. The result still has the unsmoothness.

[blimey]

The problem is present even when downloaded by means other than GetFLV. After looking at the video further, my guess is that it is a bad encode. I can't think of any easy way to fix it.

[billsantos]

Originally Posted by blimey

The problem is present even when downloaded by means other than getflv. After looking at the video further, my guess is that it is a bad encode. I can't think of any easy way to fix it.

Thanks, that's what I was wondering about. I'm also curious about how the video appears when being streamed live- does it still show unsmoothness? I don't have fast enough of a connection to test that.

There is some discussing of this type of problem at the Doom 9 forum also, although I can't find the thread and I don't think a solution was found there either. So far, the only real progress I've had is slightly speeding up the frame rate which leaves the sound syncing issue of course. Looks like I may have to go that route with the 15 or so in HD (thank goodness the 1080p's don't have this problem!).

Thanks again for your help. Should you or anyone else continue to have suggestions, I encourage sharing of it and I'd be greatly appreciative.

[blimey]

If frames are missing, I'd think that the web flash player would have the same issue.

Most media players that work with the flv container simply parse the codecs directly. However, Sothink Flv Player uses the adobe flash decoder, so it plays flv files much like a web flash player would.

Also, most video converters parse the codecs directly, but Moyea Flv to Video Converter Pro 2 also uses an adobe decoder, and parses all of the flv container timestamps. This is why the moyea converter will often work well with livestream flv files that may have non-linear irregularities.

But if frames are missing, nothing is going to create them for you. If the content was one-of-a-kind, it might be worth the trouble to edit the flv timestamps for the duplicate frames to match the previous frame, so the audio would not advance - and then run it through the moyea converter. But this still would be a lot of work.

Does the HQ version have the same problem? Maybe they will eventually post 1080p versions. As far as the current HD version, it is just hard to take bad input (with missing information) and make it good.

Originally Posted by blimey

Sothink Flv Player uses the adobe flash decoder, so it plays flv files much like a web flash player would uses the adobe flash decoder, so it plays flv files much like a web flash player would.

Is it a DirectShow decoder?

AFAIK freeware Applian FLV player works the same way. At least it plays flv videos much like a web flash player would.

[Inception]

Encode with 23.976 or 24fps audio will perfectly sync for files which are downloaded by GetFLV.

Try Handbrake to encode.