Dropped fps when changing clip position (mp4)

[redhawk]

I have a camera app on my Android phone which encodes mp4 files as h.264 / aac.
When playing in VLC 2.0.2 it works however when the clip position is manually changed the frame rate drops to 1 fps.
There are no error message (verb 2.0) CPU load is normal, I can pause / unpause and it continues to play with dropped frames.
My mp4 files from other sources play without frame drops although I have noticed 2.0.2 does have a tendency to drop / recover frames more often when the CPU is pegged.
VLC 1.1.11 play my camera files without drops so it would appear to be a bug with 2.0.2.

I have uploaded "timebar_fps_problem.mp4" using the VideoLAN upload tool I hope this would prove useful for the developers.

Richard S.

[Lotesdelere]

This video is using variable frame rate but I can't reproduce the issue.

Please open Tools -> Messages (set Verbosity to 2) before you start the playback and then paste the full resulting log here or on Pastebin.com if it's too long.

You can also try another video output module:
http://wiki.videolan.org/WindowsFAQ-2.0 ... _output.3F

and enable or disable some video options such as Overlay and/or Hardware YUV -> RGB conversions, if needed.

[redhawk]

I had messages enabled (set Verbosity to 2) but no errors reported.
This is the same problem as indicated by another poster - viewtopic.php?f=14&t=102027 the frame rate drops when you change the position of the clip the only time VLC would recover if you move the time bar back to the start or Stop / Play.
The poster also quotes: "Problem seems to be with MPEG-4 files that have 1 reference frame." this is exactly the same way my camera clips are encoded: 1 I-Frame at the start followed by all P-Frames (as confirmed with Avidemux).
An mp4 with only 1 Intra frame isn't particularly cleaver unfortunately I have no control over the way the camera encodes my videos given the choice I would have a GOP sequence of 300 frames.
I don't know what the decoder library looks like but I am guessing that for VLC to jump to a position in a clip it must parse all the P-Frames right from the first I-Frame at the start of the file.
For whatever reason it probably discarded or lost the first I-Frame or a P-Frame and as a consequence cannot generate full fps, this would probably explain why MP4 files which contain I-Frames per GOP are unaffected by this frame dropping problem.
This doesn't explain why your machine cannot reproduce the problem perhaps your PC is more powerful than mine all I know is it's happening to me using VLC 2.0.2 but not VLC 1.1.11.

My Spec: P4 1.60Ghz, 1.25GB RAM, NVIDIA 6200 (with latest drivers), Windows XP SP3.

Richard S.

[Lotesdelere]

I had messages enabled (set Verbosity to 2) but no errors reported.

I'm sorry but I've asked for the full messages log and that's exactly what I want.

[redhawk]

Hi, I have the report you requested for some reason VLC wasn't showing debugging information before even though Verbosity was already set to 2, it starts working when you toggled the Verbosity levels.

Is this a bug or expected behaviour for VLC??

I've done logs for VLC 2.0.2 and 1.1.11 although to be honest I can't see any difference - http://pastebin.com/zDatddyb

I've also noticed VLC misreports statistics it claims to have lost 1 frame for the whole duration of the clip while the playback looks more like 1fps.
VLC is probably rendering the frames as normal but they're mostly duplicates the CPU load would confirm this because it has remains pretty constant while playing normal or playing badly.

Richard S.

[redhawk]

I've added another report with a video of my desktop demonstrating the problem "timebar_fps_problem_more.mp4" I wasn't sure how to merge this with the one I had already posted.

Richard S.

[VLC_help]

This is prolly something that might not be easily fixable in VLC.