Those subtitles are .srt files originally, in UTF-8 encoding. I use handbrake/vidcoder to mix them into MP4.
General
Complete name : E:\avTemp\Adele.Live.at.the.Royal.Albert.Hall.2011.BluRay.640p.AAC.x264.mp4
Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42
File size : 1.94 GiB
Duration : 1h 39mn
Overall bit rate mode : Variable
Overall bit rate : 2 791 Kbps
Movie name : Live at the Royal Albert Hall
Performer : Adele
Recorded date : 2011
Encoded date : UTC 2013-07-17 13:54:48
Tagged date : UTC 2013-07-17 14:54:16
Cover : Yes
hdvd : 1
stik : 9
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1h 39mn
Bit rate mode : Variable
Bit rate : 2 560 Kbps
Width : 1 136 pixels
Height : 480 pixels
Display aspect ratio : 2.35:1
Original display aspect ratio : 2.35:1
Frame rate mode : Constant
Frame rate : 29.970 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.157
Stream size : 1.78 GiB (92%)
Writing library : x264 core 133 r2334 a3ac64b
Encoding settings : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / 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=6 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=300 / keyint_min=30 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=2pass / mbtree=1 / bitrate=2560 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / vbv_maxrate=62500 / vbv_bufsize=78125 / nal_hrd=none / ip_ratio=1.40 / aq=1:1.00
Encoded date : UTC 2013-07-17 13:54:48
Tagged date : UTC 2013-07-17 14:51:18
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 1h 39mn
Bit rate mode : Variable
Bit rate : 224 Kbps
Maximum bit rate : 256 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz
Compression mode : Lossy
Delay relative to video : 67ms
Stream size : 159 MiB (8%)
Language : English
Encoded date : UTC 2013-07-17 13:54:48
Tagged date : UTC 2013-07-17 14:51:17
Text
ID : 3
Format : Timed Text
Muxing mode : sbtl
Codec ID : tx3g
Duration : 1h 38mn
Bit rate mode : Variable
Bit rate : 61 bps
Delay relative to video : 67ms
Stream size : 43.8 KiB (0%)
Language : English
Encoded date : UTC 2013-07-17 13:54:48
Tagged date : UTC 2013-07-17 14:51:17
Menu
ID : 5
Codec ID : text
Duration : 1h 39mn
Encoded date : UTC 2013-07-17 14:54:16
Tagged date : UTC 2013-07-17 14:54:16
Bit rate mode : VBR