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IDProjectCategoryView StatusDate SubmittedLast Update
0001842KdenliveMLTpublic2010-10-12 14:442011-03-03 19:41
ReporterWolf_the_Grey 
Assigned Toddennedy 
PriorityhighSeverityminorReproducibilityalways
StatusfeedbackResolutionopen 
Platform64 bitOSUbuntu LinuxOS Version10.04
Product Version0.7.8 
Target VersionFixed in Version 
Summary0001842: DNxHD a/v out of sync
DescriptionAudio/video out of sync when playing DNxHD (transcoded by ffmpeg) in source and project monitors. The problem occurs only during video editing in kdenlive — a/v syncronization in rendered project file is ok. Also, waveform thumbnail on the timeline corresponds to the video.
Steps To Reproduce1. Import files to kdenlive
2. Transcode (by right-click menu) to any DNxHD profile
3. Put it on the timeline and play (or play it in the source monitor).
Additional InformationI used the following ffmpeg commands to transcode DNxHD in kdenlive interface and in the system terminal

-i <input_file> -vcodec dnxhd -b <bitrate> -an output.mov
-s 1920x1080 -r 25 -b 185000k -threads 2 -vcodec dnxhd -acodec copy %1.mov
-s 1920x1080 aspect=@16/9 -b=220000k -vcodec dnxhd -acodec pcm_s16le

with different parameters from ffmpeg DNxHD specification (http://www.itbroadcastanddigitalcinema.com/ffmpeg_howto.html [^]).
My source video — H.264 files from Canon EOS DSLR.
TagsNo tags attached.
Build/Install Method(select)
Attached Files

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-  Notes
(0005966)
Wolf_the_Grey (reporter)
2010-10-15 07:51

I continued to experiment, and found that out of sync still appears in the output file. I think this problem is quite important because DNxHD is the best codec to work with H.264.
(0005976)
mcfrisk (reporter)
2010-10-17 07:48

I noticed this kind of bug too when transcoded one 20 minute AVCHD clip in kdenlive.
After re-transcoding with latest ffmpeg and kdenlive project restart the sync problem
was gone.
(0005978)
Wolf_the_Grey (reporter)
2010-10-17 15:25

Now the correct encoding is possible and from the interface kdenlive, and directly through the CLI. But a slight problem — ffmpeg interprets H.264 files with a vertical resolution of 1080 pixels as files with a vertical resolution of 1088 pixels. Because of this kdenlive debris fills the bottom 8 lines of the frame. To get rid of this, you must add the preset encoding parameter '-cropbottom 8'.
Eg

-cropbottom 8-s 1920x1080-r 25-b 185000k-threads 2-vcodec dnxhd-acodec copy% 1.mov

Maybe I'm wrong and it's not the best solution to this problem, so I would like to know the opinion of the developers team.

P.S. I found, a/v out of sync in the H.264 files are still there, and I think that this may also be a problem.
(0006039)
ddennedy (developer)
2010-11-12 06:03

Kdenlive 0.7.8 automatically crops last 8 lines from 1088 files, but you can use -cropbottom if you like.

I do not understand the P.S. in your last comment. Are you talking about H.264 or DNxHD?
In either case, please test if a/v sync is fine with 'ffplay' (and not any other media player please)
(0006506)
moorsey (reporter)
2011-03-01 13:30

I think this issue may have re-appeared. Have had no issues for the last few projects I have done, late last year and early this. But in my current project, I have noticed that transcoded AVCHD files are approx 15 frames out with the audio. I have tried a few DNXHD profiles but not seen any difference. I primaraly transcode to 1080p 36000k with -deinterlace option. Am running latest SVN (as of 28/02/11). Will try and get a sample sorted this week
(0006507)
ddennedy (developer)
2011-03-01 19:18

"I have noticed..."
How? Whenever reporting A/V sync problems please explain how and where you observed them.
(0006508)
moorsey (reporter)
2011-03-01 23:51

apologies, I rushed the above at work with plans of following it up later, sorry.

When playing the files back either in the timeline or from the files list(sorry, can't remember proper name) the audio is behind the video.

I seem to be unable to play the DNxHD files back outside of Kdenlive, maybe this is a codec issue and maybe where my problem stems from?! Have tried in VLC and I get video, but no audio, will get a screenshot of the error this week. I'm sure I used to be able to play back

I am planning on removing all of Kdenlive and re-installing, as this seems to have started recently, will also try on my laptop which has a different install of kdenlive, see if it makes any difference

Sorry for the lack of info, not been infront of Kdenlive, should be tomorrow evening
(0006509)
ddennedy (developer)
2011-03-02 00:25

Please try with 'ffplay' in a terminal window. Also, check if the audio output is going through PulseAudio. Run pavucontrol, and it will show which applications, if any, are currently playing through PulseAudio. PA usually adds some latency - it does on my Ubuntu system where the default package is now libsdl1.2debian-pulseaudio. If you install libsdl1.2debian-all, you can tell SDL which audio driver to use:
SDL_AUDIODRIVER=alsa ffplay ...
or
SDL_AUDIODRIVER=pulse ffplay ...
.. same for melt. Kdenlive has a settings option to choose.
Then, if you could, please place a DNxHD on a timeline by itself and render to MPEG-4 or MPEG-2 and then check the playback of that result in both ffplay and Kdenlive.
(0006514)
moorsey (reporter)
2011-03-02 22:36

thank you very much for the information!

OK, installed pavucontrol, but can't see anywhere that says pulse or otherwise. On the playback tab it says "Kdenlive : Simple DirectMedia Layer on" and then my sound device

I installed the package you suggested and ran ffplay with alsa and pulse. Can't see any difference though with the audio on either.

I ran a small test clip (30 seconds) through and exported to mpeg4 25000k, this plays back the same in ffplay/VLC/kdenlive, still out of sync.

I also removed mythtv frontend that I had installed on my PC, can't say 100% but some clips I have been messing with seem more more in sync now, but others are well out.

I will record some proper test clips I think, so I can be sure on all this, don't want to waste anyones time!

Thanks again
(0006516)
ddennedy (developer)
2011-03-02 23:33

pavucontrol is a tool specific to PulseAudio. So, that info tells me that Kdenlive audio output is using PulseAudio.

With ffplay did you test the avchd, dnxhd, or both?
Does ffplay the dnxhd in sync or not?
(0006524)
moorsey (reporter)
2011-03-03 19:41

I played the dnxhd and avchd, they all play out of sync in ffplay as well as kdenlive.

I have just recorded a fresh 7 minute ish clip and it plays perfectly everywhere, which is a bit confusing.

Just to add some info on what I am actually doing. I recorded an event at the Air Cadets where I volunteer on 2 cameras. I am syncing the two videos on the timeline using the audio track of my HD camera. In places there were videos played on the projector, here I have taken the original video and put that on the timeline, with the camera audio also over that (laughter type track).

The room isn't large, the camera was about 10 meters from the speakers, but am wondering if there is echo at play, throwing the camera audio off. Seems unlikely though.

If I use the audio track from the other SD camera, then the sync is OK with the other videos etc.

I have also tried re-encoding the dnxhd, but this didn't make any difference, just confusing why other dnxhd videos work OK, I can't see any difference, unless it needs longer than 7 minutes to show!

Thanks

- Issue History
Date Modified Username Field Change
2010-10-12 14:44 Wolf_the_Grey New Issue
2010-10-15 07:51 Wolf_the_Grey Note Added: 0005966
2010-10-17 07:48 mcfrisk Note Added: 0005976
2010-10-17 15:25 Wolf_the_Grey Note Added: 0005978
2010-11-12 06:03 ddennedy Note Added: 0006039
2011-03-01 13:30 moorsey Note Added: 0006506
2011-03-01 19:18 ddennedy Note Added: 0006507
2011-03-01 19:18 ddennedy Assigned To => ddennedy
2011-03-01 19:18 ddennedy Status new => feedback
2011-03-01 23:51 moorsey Note Added: 0006508
2011-03-02 00:25 ddennedy Note Added: 0006509
2011-03-02 22:36 moorsey Note Added: 0006514
2011-03-02 23:33 ddennedy Note Added: 0006516
2011-03-03 19:41 moorsey Note Added: 0006524


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