This is just an example as it happens with all my 720p files.... All 1080p files play excellent and have no problems I've added a MediaInfo sample from both 720 & 1080p
720p file:
General
UniqueID/String : 206034767489268555529301326838081721297 (0x9B00DA530471CBAC98643085A7AB13D1)
CompleteName : \\MEDIAPC\Video\Alice in Wonderland (2010)\Alice in Wonderland.mkv
Format : Matroska
Format_Version : Version 2
FileSize/String : 4.37 GiB
Duration/String : 1h 48mn
OverallBitRate/String : 5 764 Kbps
Encoded_Date : UTC 2008-05-07 20:18:35
Encoded_Application : mkvmerge v2.9.8 ('C'est le bon') built on Aug 21 2009 13:21:42
Encoded_Library/String : libebml v0.7.7 + libmatroska v0.8.1
Video
ID/String : 1
Format : AVC
Format/Info : Advanced Video Codec
Format_Profile : High@L3.1
Format_Settings_CABAC/String : Yes
Format_Settings_RefFrames/String : 5 frames
CodecID : V_MPEG4/ISO/AVC
Duration/String : 1h 48mn
BitRate/String : 4 254 Kbps
Width/String : 1 280 pixels
Height/String : 720 pixels
DisplayAspectRatio/String : 16:9
FrameRate/String : 23.976 fps
ColorSpace : YUV
ChromaSubsampling : 4:2:0
BitDepth/String : 8 bits
ScanType/String : Progressive
Bits-(Pixel*Frame) : 0.193
StreamSize/String : 3.14 GiB (72%)
Encoded_Library/String : x264 core 94 r1583 7608d73
Encoded_Library_Settings : cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=7 / psy=1 / psy_rd=1.00:0.20 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-3 / threads=12 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=3 / weightb=1 / weightp=0 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=2pass / mbtree=1 / bitrate=4254 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / aq=1:1.00
Language/String : English
Default/String : Yes
Forced/String : No
Audio
ID/String : 2
Format : DTS
Format/Info : Digital Theater Systems
Format_Profile : ES
CodecID : A_DTS
Duration/String : 1h 48mn
BitRate_Mode/String : Constant
BitRate/String : 1 510 Kbps
Channel(s)/String : 6 channels
ChannelPositions : Front: L C R, Side: L R, LFE
SamplingRate/String : 48.0 KHz
BitDepth/String : 24 bits
Compression_Mode/String : Lossy
StreamSize/String : 1.15 GiB (26%)
Language/String : English
Default/String : Yes
Forced/String : No
Text
ID/String : 3
Format : UTF-8
CodecID : S_TEXT/UTF8
CodecID/Info : UTF-8 Plain Text
Language/String : English
Default/String : No
Forced/String : No
1080p file:
eneral
UniqueID/String : 201193189032766048143739626143896455976 (0x975C661398548260A3ECB43362664B28)
CompleteName : \\MEDIAPC\Videos2\The Adventures of Tintin (2011)\The Adventures of Tintin.mkv
Format : Matroska
Format_Version : Version 1
FileSize/String : 8.74 GiB
Duration/String : 1h 46mn
OverallBitRate/String : 11.7 Mbps
Encoded_Date : UTC 2012-02-23 14:01:42
Encoded_Application : mkvmerge v2.2.0 ('Turn It On Again') built on Mar 4 2008 12:58:26
Encoded_Library/String : libebml v0.7.7 + libmatroska v0.8.1
Video
ID/String : 1
Format : AVC
Format/Info : Advanced Video Codec
Format_Profile : High@L4.1
Format_Settings_CABAC/String : Yes
Format_Settings_RefFrames/String : 4 frame2
CodecID : V_MPEG4/ISO/AVC
Duration/String : 1h 46mn
BitRate/String : 10.2 Mbps
Width/String : 1920 pixel3
Height/String : 816 pixel3
DisplayAspectRatio/String : 2.35:1
FrameRate/String : 23.976 fps2
ColorSpace : YUV
ChromaSubsampling : 4:2:0
BitDepth/String : 8 bit3
ScanType/String : Progressive
Bits-(Pixel*Frame) : 0.272
StreamSize/String : 7.44 GiB (85%)
Encoded_Library/String : x264 core 120 r2164 da19765
Encoded_Library_Settings : cabac=1 / ref=4 / deblock=1:1:1 / analyse=0x3:0x113 / me=umh / subme=10 / psy=1 / psy_rd=0.85:0.00 / mixed_ref=1 / me_range=48 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=-4 / threads=36 / sliced_threads=0 / nr=0 / decimate=0 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=8 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=2pass / mbtree=1 / bitrate=10205 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / aq=2:1.20
Language/String : en
Default/String : Yes
Forced/String : No
Audio
ID/String : 2
Format : DTS
Format/Info : Digital Theater Systems
CodecID : A_DTS
Duration/String : 1h 46mn
BitRate_Mode/String : CBR
BitRate/String : 1510 Kbps
Channel(s)/String : 6 channel3
ChannelPositions : Front: L C R, Side: L R, LFE
SamplingRate/String : 48.0 KHz
BitDepth/String : 16 bit3
Compression_Mode/String : Lossy
StreamSize/String : 1.13 GiB (13%)
Default/String : Yes
Forced/String : No