[Xperia Arc Q&A, Help & Troubleshooting] paulinodf:
I instaled MediaInfo and compared two videos... One of them run in HW mode (runs like a dream, even without overclock) and the other only in SW (runs awful).

The properties of the one that works:

General

Complete name : C:\Users\Israel\Desktop\The.Big.Bang.Theory.S05E05.720p.HDTV.x264-IMMERSE.mkv

Format : Matroska

Format version : Version 2

File size : 455 MiB

Duration : 21mn 1s

Overall bit rate : 3 026 Kbps

Writing application : x264.exe

Writing library : mkv2rls x264-tv version built on 2011. febr. 17

Video

ID : 1

Format : AVC

Format/Info : Advanced Video Codec

Format profile : High@L3.1

Format settings, CABAC : Yes

Format settings, ReFrames : 5 frames

Codec ID : V_MPEG4/ISO/AVC

Duration : 21mn 1s

Bit rate : 2 838 Kbps

Width : 1 280 pixels

Height : 720 pixels

Display aspect ratio : 16:9

Frame rate : 23.976 fps

Color space : YUV

Chroma subsampling : 4:2:0

Bit depth : 8 bits

Scan type : Progressive

Bits/(Pixel*Frame) : 0.128

Stream size : 427 MiB (94%)

Writing library : x264 core 118 r2085 8a62835

Encoding settings : cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=8 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=18 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / 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=50 / rc=crf / mbtree=1 / crf=18.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00

Language : English

Default : Yes

Forced : No

Audio

ID : 2

Format : AC-3

Format/Info : Audio Coding 3

Mode extension : CM (complete main)

Codec ID : A_AC3

Duration : 21mn 1s

Bit rate mode : Constant

Bit rate : 128 Kbps

Channel(s) : 2 channels

Channel positions : Front: L R

Sampling rate : 48.0 KHz

Bit depth : 16 bits

Compression mode : Lossy

Stream size : 19.2 MiB (4%)

Language : English

Default : Yes

Forced : No

The one that doesn't run fine:

General

Unique ID : 187155380279623684204582013841221980954 (0x8CCCD0AB4515F47C91628E7A2295931A)

Complete name : C:\Users\Israel\Desktop\The.Big.Bang.Theory.S05E17.720p.HDTV.X264-DIMENSION.mkv

Format : Matroska

Format version : Version 2

File size : 542 MiB

Duration : 21mn 28s

Overall bit rate : 3 526 Kbps

Encoded date : UTC 2012-02-16 14:26:19

Writing application : mkvmerge v3.1.0 ('Happy up here') built on Jan 19 2010 12:09:24

Writing library : libebml v0.7.9 + libmatroska v0.8.1

Video

ID : 1

Format : AVC

Format/Info : Advanced Video Codec

Format profile : High@L3.1

Format settings, CABAC : Yes

Format settings, ReFrames : 8 frames

Codec ID : V_MPEG4/ISO/AVC

Duration : 21mn 28s

Bit rate : 3 072 Kbps

Width : 1 280 pixels

Height : 720 pixels

Display aspect ratio : 16:9

Frame rate : 23.976 fps

Color space : YUV

Chroma subsampling : 4:2:0

Bit depth : 8 bits

Scan type : Progressive

Bits/(Pixel*Frame) : 0.139

Stream size : 472 MiB (87%)

Writing library : x264 core 120 r2164 da19765

Encoding settings : cabac=1 / ref=8 / deblock=1:-2:-2 / analyse=0x3:0x113 / me=umh / subme=9 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=24 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=-2 / threads=12 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=5 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=18.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00

Language : English

Default : No

Forced : No

Audio

ID : 2

Format : AC-3

Format/Info : Audio Coding 3

Mode extension : CM (complete main)

Codec ID : A_AC3

Duration : 21mn 28s

Bit rate mode : Constant

Bit rate : 384 Kbps

Channel(s) : 2 channels

Channel positions : Front: L R

Sampling rate : 48.0 KHz

Bit depth : 16 bits

Compression mode : Lossy

Stream size : 59.0 MiB (11%)

Default : Yes

Forced : No