Serviio

Here is another one, this time no audio.

is it supposed to pick the right codec itself?

General
Unique ID : 172794159172083187768127089480877795446 (0x81FEF1CD246D22FB937F27EE4048E876)
Format : Matroska
Format version : Version 2
File size : 922 MiB
Duration : 2h 16mn
Overall bit rate : 946 Kbps
Encoded date : UTC 2012-10-25 08:39:29
Writing application : mkvmerge v4.0.0 ('The Stars were mine') built on Jun 6 2010 16:18:42
Writing library : libebml v1.0.0 + libmatroska v1.0.0

Video
ID : 3
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.0
Format settings, CABAC : Yes
Format settings, ReFrames : 8 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 2h 16mn
Nominal bit rate : 909 Kbps
Width : 1 280 pixels
Height : 536 pixels
Display aspect ratio : 2.40:1
Frame rate mode : Constant
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.055
Title : ==== 300mbunited.me | rpnet.biz ====
Writing library : x264 core 120 r2120 0c7dab9
Encoding settings : cabac=1 / ref=8 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=9 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=24 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=12 / 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=60 / rc=2pass / mbtree=1 / bitrate=909 / 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 : English
Default : No
Forced : No

Audio
ID : 1
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : HE-AAC / LC
Codec ID : A_AAC
Duration : 2h 16mn
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz / 24.0 KHz
Compression mode : Lossy
Title : ==== 300mbunited.me | rpnet.biz ====
Default : Yes
Forced : No

Text
ID : 2
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Title : ==== 300mbunited.me | rpnet.biz ====
Default : Yes
Forced : No

Yep, HE-AAC / LC is not supported by Sony Bravia devices, but yet serviio could not distinguish AAC to HE-AAC.

So isn't it best to just transcode all AAC to AC3 so at least audio works ?

Yes but for some syteme based on NAS, it's prefered to minimize transcoding, and sony device support AAC audio, so AAC is not transcoded. Btw you can comment all "aac match" lines on sony profile to force ac3 transcoding.