Full HD videos crawling ugly

[VPupkin]

Hello!
I'm using SMPlayer with mplayer chosen in Windows 7 and I encountered a problem recently when I tried to play a video in Full HD. I usually watch videos in HD and it makes no problem, but with Full HD it slowed down to a crawl, both video and audio. The computing power is definitely enough, the CPU is 50% loaded at most and there's plenty of free memiory and also it runs on GeForce GT630M, but somewhy the playback turns into a mess. I've tried playing with options of codecs and video output in the settings, but it didn't help.
What could be the problem? And is there a tool for a diagnosis?

[VPupkin]

Question update:
I examined this Full HD video and discovered a parameter I've not met before. Media Info shows a string
Muxing mode: Header stripping
I suspect this might be the point, if so, why does it cause problems?

[VPupkin]

This topic definitely needs developer's attention.
Hey, developer, are you here?

[rvm]

Can you provide a small sample file with this problem?

[VPupkin]

Will, the file itself is 18 GiB, so I'll have to cut a piece out of it somehow. I don't know how to do this without changing compression options. And doesn't this strange mode tell you anything? By the way, when I open this file and run mplayer log, here's a part of what it shows:

Too many video packets in the buffer: (200 in 33656968 bytes).
Maybe badly- or non-interleaved stream/file or the codec failed?
Fix the file or try the -ni option (can cause high memory usage).

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)

AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)


************************************************
**** Your system is too SLOW to play this! ****
************************************************

[VPupkin]

I tried cutting a piece out using Avidemux, but it won't save that mode, although I copied audio and video streams as they were. After cutting this piece out MediaInfo and mkvinfo won't show this mode anymore.

[rvm]

Is the problem still happening if you play the video directly with mpv or mplayer?

[VPupkin]

You mean running in console? Yes, it is. And it shows the same message about buffer.

[rvm]

Do you have this problem with other videos or only this one?

[VPupkin]

I checked another Full HD video and it's running fine.