Problem No1.
I tried to convert a DivX movie from AVI to MKV.
The movie was previously as AVI normaly streamed from my PC to TV (Panasonic G30), but when I remuxed it with MKVmerge GUI to MKV container, it was not possible to stream it to TV. I've got a message that file is not supported on TV screen. This is crazy since in both cases there are the same audio and video files (and used codecs), the difference is only file container.

Bellow I am posting the info about the both AV files:

AVI
General
CompleteName : J:\Everybody's Fine[2009]DvDrip[Eng]-FXG.avi
Format : AVI
Format/Info : Audio Video Interleave
FileSize/String : 700 MiB
Duration/String : 1h 39mn
OverallBitRate/String : 982 Kbps
Encoded_Application : VirtualDubMod 1.5.10.2 (build 2540/release)
Encoded_Library/String : VirtualDubMod build 2540/release

Video
ID/String : 0
Format : MPEG-4 Visual
Format_Profile : Advanced Simple@L5
Format_Settings_BVOP/String : 2
Format_Settings_QPel/String : No
Format_Settings_GMC/String : No warppoints
Format_Settings_Matrix/String : Default (H.263)
MuxingMode : Packed bitstream
CodecID : DX50
CodecID/Hint : DivX 5
Duration/String : 1h 39mn
BitRate/String : 845 Kbps
Width/String : 704 pixels
Height/String : 288 pixels
DisplayAspectRatio/String : 2.40:1
FrameRate/String : 23.976 fps
ColorSpace : YUV
ChromaSubsampling : 4:2:0
BitDepth/String : 8 bits
ScanType/String : Progressive
Compression_Mode/String : Lossy
Bits-(Pixel*Frame) : 0.174
StreamSize/String : 602 MiB (86%)
Encoded_Library/String : XviD 1.0.3 (UTC 2004-12-20)

Audio
ID/String : 1
Format : MPEG Audio
Format_Version : Version 1
Format_Profile : Layer 3
Format_Settings_Mode : Joint stereo
Format_Settings_ModeExtension : MS Stereo
CodecID : 55
CodecID/Hint : MP3
Duration/String : 1h 39mn
BitRate_Mode/String : Constant
BitRate/String : 128 Kbps
Channel(s)/String : 2 channels
SamplingRate/String : 48.0 KHz
Compression_Mode/String : Lossy
StreamSize/String : 91.2 MiB (13%)
Alignment/String : Aligned on interleaves
Interleave_Duration/String : 42 ms (1.00 video frame)
Interleave_Preload/String : 504 ms

MKV
General
Unique ID : 208709661691110793108736231014982813238 (0x9D0404CA667C33219E42DBF8FA7D0636)
Complete name : J:\Everybody's Fine[2009]DvDrip[Eng]-FXG.mkv
Format : Matroska
Format version : Version 2
File size : 694 MiB
Duration : 1h 39mn
Overall bit rate : 975 Kbps
Encoded date : UTC 2011-10-28 20:08:01
Writing application : mkvmerge v5.0.1 ('Es ist Sommer') built on Oct 9 2011 11:55:43
Writing library : libebml v1.2.2 + libmatroska v1.3.0

Video
ID : 1
Format : MPEG-4 Visual
Format profile : Advanced Simple@L5
Format settings, BVOP : Yes
Format settings, QPel : No
Format settings, GMC : No warppoints
Format settings, Matrix : Default (H.263)
Codec ID : DX50
Codec ID/Hint : DivX 5
Duration : 1h 39mn
Bit rate : 827 Kbps
Width : 704 pixels
Height : 288 pixels
Display aspect ratio : 2.40:1
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.170
Stream size : 589 MiB (85%)
Writing library : XviD 1.0.3 (UTC 2004-12-20)

Audio
ID : 2
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 3
Mode : Joint stereo
Mode extension : MS Stereo
Muxing mode : Header stripping
Codec ID : A_MPEG/L3
Codec ID/Hint : MP3
Duration : 1h 39mn
Bit rate mode : Constant
Bit rate : 128 Kbps
Channel(s) : 2 channels
Sampling rate : 48.0 KHz
Compression mode : Lossy
Stream size : 91.2 MiB (13%)

Text #1
ID : 3
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text

Text #2
ID : 4
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text

Problem No 2.
I noticed that at some MKV files the subtitles are presented on TV in the way that TV does it when movie is played from local USB port (quite small font and no support for east Europen letters). On the other hand, sometimes the subtitles are shown with full support for east european letters (bigger font similar to BS player with east European letters supported).
It seems that subtitles were transcoded in Mezmo?! I would like to force such transcoding every time since I like bigger font.