How are you capturing? You should post a log file.
Here.
20:06:07: Open Broadcaster Software v0.625b - 64bit ( ^ω^)
20:06:07: -------------------------------
20:06:07: CPU Name: AMD FX(tm)-4100 Quad-Core Processor
20:06:07: CPU Speed: 3624MHz
20:06:07: Physical Memory: 3581MB Total, 1564MB Free
20:06:07: stepping id: 2, model 1, family 21, type 0, extmodel 0, extfamily 3, HTT 1, logical cores 4, total cores 2
20:06:07: monitor 1: pos={0, 0}, size={1360, 768}
20:06:07: Windows Version: 6.1 Build 7601 S
20:06:07: Aero is Disabled
20:06:07: -------------------------------
20:06:07: OBS Modules:
20:06:07: Base Address Module
20:06:07: 000000003F0B0000 OBS.exe
20:06:07: 00000000EF4C0000 OBSApi.dll
20:06:07: 00000000FA480000 DShowPlugin.dll
20:06:07: 00000000FA5C0000 GraphicsCapture.dll
20:06:07: 00000000FA450000 NoiseGate.dll
20:06:07: 00000000FA3D0000 PSVPlugin.dll
20:06:07: ------------------------------------------
20:06:07: Adapter 1
20:06:07: Video Adapter: ATI Radeon 3000 Graphics
20:06:07: Video Adapter Dedicated Video Memory: 533237760
20:06:07: Video Adapter Shared System Memory: 1609330688
20:06:07: Video Adapter Output 1: pos={0, 0}, size={1360, 768}, attached=true
20:06:07: =====Stream Start: 2014-08-14, 20:06:07===============================================
20:06:07: Multithreaded optimizations: On
20:06:07: Base resolution: 1360x768
20:06:07: Output resolution: 680x384
20:06:07: ------------------------------------------
20:06:07: Loading up D3D10 on ATI Radeon 3000 Graphics (Adapter 1)...
20:06:07: D3D10CreateDeviceAndSwapChain1: Failed on ATI Radeon 3000 Graphics: 0x80004002. Trying compatibility mode
20:06:07: ------------------------------------------
20:06:07: Audio Format: 48000 Hz
20:06:07: ------------------------------------------
20:06:07: Audio Channels: 2 Ch
20:06:07: Playback device {0.0.0.00000000}.{021b1728-a3db-4fc8-be81-53c68e914ffc}
20:06:07: ------------------------------------------
20:06:07: Using desktop audio input: Realtek HD Audio 2nd output (Realtek High Definition Audio)
20:06:07: Global Audio time adjust: 0
20:06:07: ------------------------------------------
20:06:07: Audio Encoding: AAC
20:06:07: bitrate: 128
20:06:07: Using Monitor Capture
20:06:07: Scene buffering time set to 700
20:06:07: ------------------------------------------
20:06:07: Video Encoding: x264
20:06:07: fps: 30
20:06:07: width: 680, height: 384
20:06:07: preset: veryfast
20:06:07: profile: high
20:06:07: keyint: 250
20:06:07: CBR: yes
20:06:07: CFR: yes
20:06:07: max bitrate: 1000
20:06:07: buffer size: 1000
20:06:07: ------------------------------------------
20:07:16: Total frames encoded: 2062, total frames duplicated: 80 (3.88%)
20:07:16: Total frames rendered: 2058, number of late frames: 16 (0.78%) (it's okay for some frames to be late)
20:07:17:
20:07:17: Profiler time results:
20:07:17:
20:07:17: ==============================================================
20:07:17: video thread frame - [100%] [avg time: 17.34 ms] [children: 97.2%] [unaccounted: 2.75%]
20:07:17: | scene->Preprocess - [55.7%] [avg time: 9.65 ms]
20:07:17: | GPU download and conversion - [41.6%] [avg time: 7.213 ms] [children: 42%] [unaccounted: -0.386%]
20:07:17: | | flush - [0.0115%] [avg time: 0.002 ms]
20:07:17: | | CopyResource - [41.9%] [avg time: 7.272 ms]
20:07:17: | | conversion to 4:2:0 - [0.0346%] [avg time: 0.006 ms]
20:07:17: Convert444Thread - [100%] [avg time: 0.238 ms] [children: 98.7%] [unaccounted: 1.26%]
20:07:17: | Convert444toNV12 - [98.7%] [avg time: 0.235 ms]
20:07:17: encoder thread frame - [100%] [avg time: 0.657 ms] [children: 2.74%] [unaccounted: 97.3%]
20:07:17: | sending stuff out - [2.74%] [avg time: 0.018 ms]
20:07:17: ==============================================================
20:07:17:
20:07:17:
20:07:17: Profiler CPU results:
20:07:17:
20:07:17: ==============================================================
20:07:17: video thread frame - [cpu time: avg 5.632 ms, total 11590.9 ms] [avg calls per frame: 1]
20:07:17: | scene->Preprocess - [cpu time: avg 4.752 ms, total 9781.27 ms] [avg calls per frame: 1]
20:07:17: | GPU download and conversion - [cpu time: avg 0.227 ms, total 468.002 ms] [avg calls per frame: 1]
20:07:17: | | flush - [cpu time: avg 0 ms, total 0 ms] [avg calls per frame: 1]
20:07:17: | | CopyResource - [cpu time: avg 0.214 ms, total 436.802 ms] [avg calls per frame: 1]
20:07:17: | | conversion to 4:2:0 - [cpu time: avg 0 ms, total 0 ms] [avg calls per frame: 1]
20:07:17: Convert444Thread - [cpu time: avg 0.161 ms, total 327.602 ms] [avg calls per frame: 1]
20:07:17: | Convert444toNV12 - [cpu time: avg 0.161 ms, total 327.602 ms] [avg calls per frame: 1]
20:07:17: encoder thread frame - [cpu time: avg 0.045 ms, total 93.6 ms] [avg calls per frame: 1]
20:07:17: | sending stuff out - [cpu time: avg 0.007 ms, total 15.6 ms] [avg calls per frame: 1]
20:07:17: ==============================================================
20:07:17:
20:07:17: =====Stream End: 2014-08-14, 20:07:17=================================================