The VideoLAN Forums

Hi all,

I ve noticed that when playing an MKV file where the video track is encoded with real video codec (at least in rv10 or rv40) that the video is most of the time jerky or have a kind of slow motion on rapid movement scene.
I've noticed it from the version where real video where introduced to the 1.05 version.
I used to have a quite old pc (pentium IV 2.4 GHZ with an ati radeon X850) so I thought it was due to a performance problem from my machine, but now i have a modern pc (core I5 570 2.66 GHZ, ATI HD 5800 series, windows seven 64 bits...) and the problem is still present while the CPU usage is at max 5% when playing this kind of file, so it is not due to performance.

sorry if this problem is already known but i couldn't find any information about it on the forum.

Thnaks for your help

Cheers

Touco

Try 1.1.0 nightly builds, they should work a bit better.

I've just tried nighty build, the problem seems to be exactly the same when playing MKV file with real video.

I used to play this kind of file with Media Player Classic (using the codec real alternative) but I'd prefer not having to reinstall it on my new machine (it is not a comestic bug to me it is nearly impossible to watch a movie in that conditions)

is there an open ticket for this issue ? strange that I can find mention of this problem

Can you share a sample?

Honestly I can not without causing a copyright problem

but what I could do is to find a public domain video, encode it using real video codec and put it in an MKV container, then post it on a web page for you, unless I can find that free right stuff directly on the web.

I keep you up date, (that would be great if that bug could be corrected since I would not have to use another player)

Touco

I add the fact that the problem is also visible on the MacOSX version, tested on a recent macbook with the current VLC release.
I'm trying to find a way to provide a sample...

Great, I found a sample on the web (a short sample from the movie Abyss) and I've tested it over MPC with real alternative and VLC.

Apparently It doesn't have to be in a MKV container since the problem occurs with an .rmvb file with a video track encoded with realvideo.

when looking at it you will see that in VLC the movement are not fluid, look at the beginning when the title "Abyss" is becoming bigger and bigger, it is jerky ("saccadé" in french, hope that it is the right translation)
you can also notice that in the "20th century fox" introduction by looking the way the light are moving.
everyting is fluid with MPC.

here is the sample :
http://samples.mplayerhq.hu/real/VC-RV4 ... V9_FR.rmvb

I've investigated a bit further on the different samples on the website.
the problem doesn't seem to occur when the frame rate of the video is 30 fps but always occur when the frame rate is 25fps.

I haven't noticed that before since all the movies I own are made from cinema (24 fs to 25 fps in the video conversion process) and this website also provides videos from an NTSC source (29.997 fps)

In VLC bugtracker I found a ticket that looks related to it, it hasn't been closed but its status changed to "invalid" (?)

http://trac.videolan.org/vlc/ticket/2463
Once again I'm not sure if it is the same bug, or if another ticket should be open.

Ticket for this
http://trac.videolan.org/vlc/ticket/3738

Ticket for this
http://trac.videolan.org/vlc/ticket/3738

thanks
I had a look at the source code, since it's seem related to frame rate, I suspected something like the frame rate is not correctly read from the video data and since the default frame rate in VLC is 30 FPS that could explain why there is no problem when the vieo file is 30 fps.
In the file real.c, at line 1296 the field "frame_rate" is read from the real video data, I wanted to find real video specifications to see if it was correctly read but I coudn't find it (just found the real audio data format specifications) so i wanted to put a debug to diplay the frame rate, but I didn't feel brave enough to go in compiling VLC
maybe it is just simple as that.

Hi

I've instigated a little bit further, first, looking at the debug message, the decoding is made with FFmpeg (so the file real.c should not be concerned since it is a demuxer for real file format)
So I had a look at FFmpeg bug database.

there is a bug that it's still open and that look similar to this one

https://roundup.ffmpeg.org/issue814 (choppy playback of rv30 and rv40 video)

So the problem could be in FFmpeg and not directly in VLC code ?

Can it be confirmed by a VLC developer ?

I made a comparaison using Mplayer that also use FFmpeg for RV40 decoding, there is no problem, therefore FFmpeg must not have a real video decoding problem.
maybe the parameters passed to FFmpeg (in case of real video) are not correct ?

still to be confirmed by someone who can have a deeper look in the code than me

Hi,

I made new test. I suspected the movies in cause to not be played at the correct frame rate by VLC, I had this idea because in a lot of movie with Real Video track the framerate indicated (by VLC or MediaInfo) is often "weird" (sometimes 30 fps when I'm absolutly positive that the source is PAL and shoud be 25 fps, moreover Media Player Classic plays them correctly at 25 fps)

I also noticed that a lof frame were lost (shown in the statistic windows) when VLC plays these movies

So, I wanted to force VLC to play these movies at 25 fps.
I used MKVMerge and I remux all the movies by specifying 25 fps (in format->specific options)

and the resulats is great since that the movies are now perfectly played by VLC !

so, it is definetly a problem of playing at incorrected frame rate.

I hope it will help to localize the bug

Touco

Can you detail what VLC was detecting before (logs and such?)

Here is a what i get in the debug windows (verbosity set to 2) when playing the original MKV file (that is before changing the frame rate) I played the video for a few seconds and then stopped it, in the statistics no images were lost. the video were jerky.
Then, in the same conditions, I played a remux of the same file specifying a frame rate of 25 fps in MKVMerge, no images were lost. the video were played correctly.

Yeah, i can confirm the same problem using Debian. With Mplayer it plays just fine, but vlc does not. I have found a couple of *.rm's which just wont play correctly. I could provide a fine example, but this is not family-safe and also not copyright compliant. So download it only for enhancement reasons: http://tinyurl.com/2u6c6ga.

I hope you get things working correctly, since this bug buggs me since version 0.98.

Another thing that buggs me, is that i try to start vlc with --perfer-system-codecs, but it simply ignores them. Have you experienced similar problems?

Real Media codecs have never been system codecs in VLC. VLC only thinks DMO codecs are system codecs.

It seems, that it ignores not only RM system-codecs. Never managed to use the system ones. How could i verify, that i am using system-codecs, and not the vlc-ones?

But even that would not correct the RM-codec-playback-issue.

If you open Tools -> Messages (set Verbosity to 2) before playback, it will print some DMO messages during file opening if DMO codecs are used. But since amount of DMO codecs is very limited, VLC will in many cases use its own codecs.

Hello, any updates on how to solve this ?

I haven't seen any updates related to this. (but libav* updates in contrib might have changed something)

any updates on this issue?

* it's not a Windows specifc...

this problem is still current in VLC latest version (2.1.0)

ive got the first same working fine on my machine its a little jittery with media player classic on windows and its holding a flux between 20 and 22 fps with jitter of -30ms/+36ms

ive got the first same working fine on my machine its a little jittery with media player classic on windows and its holding a flux between 20 and 22 fps with jitter of -30ms/+36ms

Could you share your file ?

it depends of the container.
for instance if the video is contained in a MKV file where the frame rate is not specified, then you can reproduce the bug.
otherwise if you produce a MKV file where you specify the correct frame rate, then the playback is fine.

it looks like VLC can not correctly read the correct frame rate from a real video file. I'm just making assumption.