Stuttering Playback - Identifying Bottleneck

Hi guys.

I had a problem with stuttering video.  

I decided to do some testing with this file:

Code:

Format                                   : Matroska
Format version                           : Version 2
File size                                : 16.6 GiB
Duration                                 : 3h 2mn
Overall bit rate mode                    : Variable
Overall bit rate                         : 13.1 Mbps
Encoded date                             : UTC 2013-10-26 07:02:46
Writing application                      : mkvmerge v5.8.0 ('No Sleep / Pillow') built on Sep  2 2012 15:37:04
Writing library                          : libebml v1.2.3 + libmatroska v1.3.0

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4.1
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 5 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 3h 2mn
Bit rate                                 : 11.2 Mbps
Width                                    : 1 920 pixels
Height                                   : 800 pixels
Display aspect ratio                     : 2.40:1
Frame rate mode                          : Constant
Frame rate                               : 23.976 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.304
Stream size                              : 14.3 GiB (86%)
Language                                 : English
Default                                  : Yes
Forced                                   : No

Audio #1
ID                                       : 2
Format                                   : DTS
Format/Info                              : Digital Theater Systems
Mode                                     : 16
Format settings, Endianness              : Big
Codec ID                                 : A_DTS
Duration                                 : 3h 2mn
Bit rate mode                            : Constant
Bit rate                                 : 1 509 Kbps
Channel count                            : 6 channels
Channel positions                        : Front: L C R, Side: L R, LFE
Sampling rate                            : 48.0 KHz
Bit depth                                : 24 bits
Compression mode                         : Lossy
Stream size                              : 1.92 GiB (12%)
Language                                 : English
Default                                  : Yes
Forced                                   : No

Audio #2
ID                                       : 3
Format                                   : Vorbis
Format settings, Floor                   : 1
Codec ID                                 : A_VORBIS
Duration                                 : 3h 2mn
Bit rate mode                            : Variable
Bit rate                                 : 80.0 Kbps
Channel count                            : 2 channels
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Stream size                              : 104 MiB (1%)
Writing library                          : aoTuV 20110424 (UTC 2011-04-24)
Language                                 : English
Default                                  : No
Forced                                   : No

Text #1
ID                                       : 4
Format                                   : PGS
Muxing mode                              : zlib
Codec ID                                 : S_HDMV/PGS
Codec ID/Info                            : The same subtitle format used on BDs/HD-DVDs
Language                                 : English
Default                                  : No
Forced                                   : No

Text #2
ID                                       : 5
Format                                   : PGS
Muxing mode                              : zlib
Codec ID                                 : S_HDMV/PGS
Codec ID/Info                            : The same subtitle format used on BDs/HD-DVDs
Language                                 : French
Default                                  : No
Forced                                   : No

Text #3
ID                                       : 6
Format                                   : PGS
Muxing mode                              : zlib
Codec ID                                 : S_HDMV/PGS
Codec ID/Info                            : The same subtitle format used on BDs/HD-DVDs
Language                                 : Spanish
Default                                  : No
Forced                                   : No

Text #4
ID                                       : 7
Format                                   : PGS
Muxing mode                              : zlib
Codec ID                                 : S_HDMV/PGS
Codec ID/Info                            : The same subtitle format used on BDs/HD-DVDs
Language                                 : Portuguese
Default                                  : No
Forced                                   : No

Text #5
ID                                       : 8
Format                                   : PGS
Muxing mode                              : zlib
Codec ID                                 : S_HDMV/PGS
Codec ID/Info                            : The same subtitle format used on BDs/HD-DVDs
Language                                 : Japanese
Default                                  : No
Forced                                   : No

Win 7 x64
Nvidia Geforce GTX 460
CPU: AMD Athlon 64 X2 Dual Core Processor 6000+ 3.01 GHz
Ram 8GB
K-Lite Codec Pack

I read through the K-Lite help (which was very informative by the way).

The CPU & GPU are not maxing out while playing.

I tried each Hardware Decoder that was available.  There was no difference.

I tried reducing the screen refresh rate to 24fps.  BINGO!  I could watch the perfectly smooth video.

The trouble is the low refresh rate affects other things.  (eg Windows Media Center menu transitions are now jerky, games etc)

What is causing the stuttering?  Is it the video card or the CPU?

Thanks for looking.

In my case, stuttering occurred due to the refresh rate vs. framerate discrepancy. When I was experiencing the issue, I had more than ample hardware, too. I have madVR set to automatically change refresh rates for me when I play a given video--and change back to 60 Hz when I exit fullscreen (like to play a game, etc.). For certain content, I also use ReClock, though you *should* be able to have fluid video without it on most content. Granted, that CPU isn't the most powerful anymore, but if you aren't maxing out either it or the GPU, then it seems unlikely that either is the issue. I would recommend trying to have madVR or MPC-HC do the switching for you. You may have to tweak the former to make sure it doesn't max out your GPU, but try the default settings + refresh rate switcher first. Never have used the one in MPC-HC, so I can't comment on how good it is. Beyond that, I would wait to see what admin might say, as I may be completely overlooking something.

The easiest solution that works pretty well in most cases is to change the refresh rate to 59 Hz. That should give relatively smooth playback with most videos.

More complex solutions are:
- refresh rate changer in MPC-HC or madVR, to switch to 24 Hz refresh rate only when needed
- enabling "smooth motion" in madVR in combination with high refresh rate (60 Hz or higher if available)

Thanx for the replies guys.

@amphiprion - I'd rather not have to change my media players but I tried MPC-HC with the sync option but had no luck. I also tried it with the madVR option which didn't work. Reclock looks interesting but from the description doesn't seem to work on all video files.

@admin - I just tried it & I'm stunned that 59Hz provides smooth playback. I would have thought that 60 is a multiple of 24 at 2.5 so would have been smoother.

59Hz is the best solution for me because it fixes the problem in every media player.

@admin - Would upgrading the CPU or GPU make a difference? Like I said, they weren't maxing out so I'm still curious to know. Is graphics memory a factor (my GPU has 1GB).

23.976 fps and 24.000 fps are two different framerates! Another common framerate is 29.970

A refreshrate of 59Hz is actually 59.940Hz (it is rounded down for simplicity and to distinguish it from exactly 60 Hz). That is 2.5x 23.976 and 2.0x 29.970. So your reasoning was correct, just the numbers a tiny bit different

Upgrading your hardware won't make a difference for this refreshrate issue.

Great info.

Thanx again.